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Glandular trichomes: What comes after expressed sequence tags?
Abstract
Glandular trichomes cover the surface of many plant species. They exhibit tremendous diversity, be it in their shape or the compounds they secrete. This diversity is expressed between species but also within species or even individual plants. The industrial uses of some trichome secretions and their potential as a defense barrier, for example against arthropod pests, has spurred research into the biosynthesis pathways that lead to these specialized metabolites. Because complete biosynthesis pathways take place in the secretory cells, the establishment of trichome-specific expressed sequence tag libraries has greatly accelerated their elucidation. Glandular trichomes also have an important metabolic capacity and may be considered as true cell factories. To fully exploit the potential of glandular trichomes as breeding or engineering objects, several research areas will have to be further investigated, such as development, patterning, metabolic fluxes and transcription regulation. The purpose of this review is to provide an update on the methods and technologies which have been used to investigate glandular trichomes and to propose new avenues of research to deepen our understanding of these specialized structures.
... The trichomes of the genus Grewia are not exempted from this either, as they occur in diverse shapes and sizes such as stellate, multangulate-stellate, T-shaped, simple [19,23]. According to [26] plants have adapted varied storage techniques which depend on the type of secretion. This adaptation is responsible for the variety of trichome morphologies observed in plants. ...
... The final process involves the release of the metabolites, which could be on any side of the trichome head (Figure 2Ei,Eii). This release of metabolites around the head is in agreement with the observation of [26]; who reported that cells at the tip of the trichome secrete substances directly onto the trichome's surface. ...
... It may be proposed that the presence of more glandular trichomes on a plant's vegetative organs (stem, leaves, and roots) or reproductive organs (seeds or fruits) implies more phytometabolites will be obtained from that part of the plant [26,[60][61][62]. The four distinct parts of glandular trichomes, namely head, neck, stalk, and foot cells were also observed to be present in the glandular trichomes on the leaves and stem bark of Grewia lasiocarpa. ...
Grewia lasiocarpa E. Mey. Ex Harv., Malvaceae (forest raisin) is a tropical small tree or shrub valued for its ecological importance as well as its nutritional, antioxidant, antibacterial, and anti-cancer properties as well as its ecological and ornamental importance. Glandular and non-glandular trichomes are present on the fruits, stem bark and leaves of G. lasiocarpa and these trichomes are the first line of defense. They are important structures that plants use to combat biotic and abiotic stress. The development of G. lasiocarpa trichomes and the biomechanics of the exudates present in the glandular (capitate) trichome were investigated for the first time using advanced microscopy techniques [Scanning electron microscope (SEM) and Transmission electron microscope (TEM)]. The pressurized cuticular striations may play a role in the exudates’ biomechanics, i.e., releasing secondary metabolites present in the capitate trichome, which was observed to be multidirectional. The presence of many glandular trichomes on a plant implies an increase in the amount of phytometabolites. A common precursor for the development of trichomes (non-glandular and glandular) was observed to be DNA synthesis associated with a periclinal cell division, thus the final fate of the cell is determined by cell cycle regulation, polarity, and expansion. The glandular trichomes of G. lasiocarpa are multicellular and polyglandular, while the non-glandular (glandless) trichomes are either single-celled or multicellular. Since, trichomes ‘house’ phytocompounds of medicinal, nutritional, and agronomical benefits; the molecular and genetic study of the glandular trichomes of Grewia lasiocarpa will be beneficial to humanity.
... A crude extract of V. polyanthes was prepared by rinsing the leaves with dichloromethane. The rinsed leaves extract of V. polyanthes (Vp-LRE) was chosen for analysis since many bioactive compounds in Vernonia species (such as flavonoids and sesquiterpene lactones) are localized mainly at the glandular trichomes leaves [21][22][23]. ...
... The purity of the isolated glaucolide A was estimated to be higher than 95% via HPLC-DAD analysis ( Figure 2). analysis since many bioactive compounds in Vernonia species (such as flavonoids and sesquiterpene lactones) are localized mainly at the glandular trichomes leaves [21][22][23]. ...
... However, despite the antimicrobial potential of V. polyanthes leaves, a correlation between its chemical composition and its antibacterial activity has not been supported by any scientific evidence so far. Additionally, several studies have reported that flavonoids, sesquiterpene lactones and other potentially active compounds of Vernonia species are located in the glandular trichomes of the leaves, which are epidermal secretory structures related to the production, storage and secretion of a wide number of compounds associated with plant defense and its antimicrobial and antifeeding effects [21][22][23]. The locations of these structures on the surfaces of the plant organs allow for the extraction of these compounds by washing the leaves with organic solvents, producing a selective plant extract to obtain the stored compounds in the glandular trichomes called Vp-LRE in the present study [21][22][23]. ...
Vernonia polyanthes is a medicinal plant used to treat many disorders, including infectious diseases. This study investigated the chemical constituents and the antibacterial activity of V. polyanthes leaf rinse extract (Vp-LRE). The chemical characterization of Vp-LRE was established using ultra-high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS), and glaucolide A was identified through 1H and 13C nuclear magnetic resonance (NMR) and mass fragmentation. The cytotoxicity was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). The antibacterial activity was assessed by minimal inhibitory concentration and minimal bactericidal concentration. Interactions between ligands and beta-lactamase were evaluated via molecular docking. UHPLC/Q-TOF-MS detected acacetin, apigenin, chrysoeriol, isorhamnetin, isorhamnetin isomer, kaempferide, 3′,4′-dimethoxyluteolin, 3,7-dimethoxy-5,3′,4′-trihydroxyflavone, piptocarphin A and glaucolide A. Vp-LRE (30 µg/mL) and glaucolide A (10 and 20 μg/mL) were cytotoxic against RAW 264.7 cells. Glaucolide A was not active, but Vp-LRE inhibited the Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Escherichia coli, Salmonella Choleraesuis and Typhimurium, with a bacteriostatic effect. The compounds (glaucolide A, 3′,4′-dimethoxyluteolin, acacetin and apigenin) were able to interact with beta-lactamase, mainly through hydrogen bonding, with free energy between −6.2 to −7.5 kcal/mol. These results indicate that V. polyanthes is a potential natural source of phytochemicals with a significant antibiotic effect against MRSA strains.
... Trichomes on the leaf surface were classified as non-glandular trichomes and glandular trichomes. The non-glandular trichomes generally act as a filter to protect plant tissues against physical damage, while the glandular trichomes may act as chemical defense against external damage [35,39]. The numbers of leaf T-shaped trichome and leaf glandular trichome in wild Chrysanthemum species were generally higher than in tea Chrysanthemum cultivars (Figure 3), which could be related to the high resistance of wild Chrysanthemum accessions. ...
... In addition, it was found that the volatile terpene compound content from leaves was significantly correlated with the density of glandular trichomes, but there was no correlation with T-shaped trichome density ( Figure 6A). Our results support the hypothesis that glandular trichomes are bio-factories with unique capacities to synthesize, secrete or store many valuable secondary metabolites in plants [35,40]. Floral scents are the primary characteristic of ornamental plants and have a significant influence on plant development/reproduction and human physical/mental health [41,42]. ...
... Chrysanthemum plants synthesize diverse secondary metabolites from leaves and flowers [17,28,33,34]. Trichomes are epidermal protuberances widely present on the surfaces of plants that can assume many different shapes and sizes [31,35]. Two types of trichomes were found on the leaf surfaces in each of the six Chrysanthemum cultivars\accessions ( Figure 1C,D), including multicellular T-shaped trichomes ( Figure 2B) and biseriate peltate glandular trichomes (Figure 2A,C). ...
Chrysanthemum is a popular ornamental plant with a long history of cultivation. Both the leaf and flowerhead of Chrysanthemum are known to produce diverse secondary metabolites, particularly terpenoids. Here we aimed to determine the relationship between terpene chemistry and the trichome traits in Chrysanthemum. In our examination of three cultivars of C. morifilium and three accessions of C. indicum, all plants contained T-shaped trichomes and biseriate peltate glandular trichomes. The biseriate peltate glandular trichome contained two basal cells, two stalk cells, six secondary cells and a subcuticular space, while the non-glandular T-shaped trichome was only composed of stalk cells and elongated cells. Histochemical staining analysis indicated that the biseriate peltate glandular trichome contained terpenoids and lipid oil droplets but not the T-shaped trichome. Next, experiments were performed to determine the relationship between the accumulation and emission of the volatile terpenoids and the density of trichomes on the leaves and flowerheads in all six Chrysanthemum cultivars\accessions. A significant correlation was identified between the monoterpenoid and sesquiterpenoid content and the density of glandular trichomes on the leaves, with the correlation coefficients being 0.88, 0.86 and 0.90, respectively. In contrast, there was no significant correlation between the volatile terpenoid content and the density of T-shaped trichomes on the leaves. In flowerheads, a significant correlation was identified between the emission rate of terpenoids and the number of glandular trichomes on the disc florets, with a correlation coefficient of 0.95. Interestingly, the correlation between the density of glandular trichomes and concentrations of terpenoids was insignificant. In summary, the relationship between trichomes and terpenoid chemistry in Chrysanthemum is clearly established. Such knowledge may be helpful for breeding aromatic Chrysanthemum cultivars by modulating the trichome trait.
... Glandular trichomes (GT) have attracted considerable attention due to their potential as sources of a vast array of specialized plant metabolites [1,2]. Among such metabolites, many have industrial or medicinal value [3,4], whereas others are especially relevant for plant defense against insect pests [5,6]. ...
... Although MT-Get accumulated more AS than MT, it showed statistically significant qualitative and quantitative differences from S. galapagense. Notably, MT-Get showed reduced levels of AS harboring C10 and C12 moieties, such as S4:23 (2,4,5,12), S4:22 (2,5,5,10), and S4:24 (2,5,5,12) ( Figure 6, Table 1). The amounts of S4:23, S4:22, and S4:24 were 120-, 42-, and 18-fold lower in MT-Get than S. galapagense, respectively (Table 1). ...
... Although MT-Get accumulated more AS than MT, it showed statistically significant qualitative and quantitative differences from S. galapagense. Notably, MT-Get showed reduced levels of AS harboring C10 and C12 moieties, such as S4:23 (2,4,5,12), S4:22 (2,5,5,10), and S4:24 (2,5,5,12) ( Figure 6, Table 1). The amounts of S4:23, S4:22, and S4:24 were 120-, 42-, and 18-fold lower in MT-Get than S. galapagense, respectively (Table 1). ...
The leaves of the wild tomato Solanum galapagense harbor type-IV glandular trichomes (GT) that produce high levels of acylsugars (AS), conferring insect resistance. Conversely, domesticated tomatoes (S. lycopersicum) lack type-IV trichomes on the leaves of mature plants, preventing high AS production, thus rendering the plants more vulnerable to insect predation. We hypothesized that cultivated tomatoes engineered to harbor type-IV trichomes on the leaves of adult plants could be insect-resistant. We introgressed the genetic determinants controlling type-IV trichome development from S. galapagense into cv. Micro-Tom (MT) and created a line named “Galapagos-enhanced trichomes” (MT-Get). Mapping-by-sequencing revealed that five chromosomal regions of S. galapagense were present in MT-Get. Further genetic mapping showed that S. galapagense alleles in chromosomes 1, 2, and 3 were sufficient for the presence of type-IV trichomes on adult organs but at lower densities. Metabolic and gene expression analyses demonstrated that type-IV trichome density was not accompanied by the AS production and exudation in MT-Get. Although the plants produce a significant amount of acylsugars, those are still not enough to make them resistant to whiteflies. We demonstrate that type-IV glandular trichome development is insufficient for high AS accumulation. The results from our study provided additional insights into the steps necessary for breeding an insect-resistant tomato.
... Compared with various microbial systems, the use of a plant system that is already naturally optimized for the production of substrates for terpenoid biosynthesis could make the engineering process less complex and therefore more likely to succeed, as well as less costly since energy from sunlight and carbon (in the form of CO 2 ) will be provided by the environment (Xu et al., 2018a). Glandular trichomes are known as metabolic cell factories with the capacity to produce large quantities of specialized metabolites such as terpenoids (Huchelmann et al., 2017;Schilmiller et al., 2008;Schuurink and Tissier, 2020), and regarded as suitable targets for metabolic engineering for production of some plant high-value specialized metabolites (Huchelmann et al., 2017;Kortbeek et al., 2016;Schilmiller et al., 2008;Tissier, 2012). The carbon metabolism of glandular trichomes in Solanaceae including wild and cultivated tomatoes has evolved to support high metabolite production (Balcke et al., 2017). ...
... for plant growth under cultivated conditions (Balcke et al., 2017;Schilmiller et al., 2008). Therefore, diverting of metabolic flux of DMAPP from naturally occurring monoterpenes toward trans-chrysanthemic acid biosynthesis using trichome-type specific promoters rather than strong ubiquitous promoters will not have deleterious effects on the robust growth and photosynthetic activities of the other parts of the plant (Schilmiller et al., 2008;Tissier, 2012). In contrast, modifying the fate of isoprenoid precursors IPP and DMAPP in leaves using ubiquitous promoters can lead to severe effects on plant growth and development, as have previously been observed in tobacco (Gwak et al., 2017;Saxena et al., 2014). ...
... However, making this monoterpenoid acid in tomato glandular trichome has some general advantages over fruit. Extract of the final product from the trichomes should be easier, since the location of trichome on the surface allows for collection and recovery by simple solvent washes without extracting internal leaf metabolites (Schilmiller et al., 2008;Tissier, 2012), as well as the large amount of leaf tissue bearing trichomes. ...
Glandular trichomes, known as metabolic cell factories, have been proposed as highly suitable for metabolically engineering the production of plant high-value specialized metabolites. Natural pyrethrins, found only in Dalmatian pyrethrum (Tanacetum cinerariifolium), are insecticides with low mammalian toxicity and short environmental persistence. Type I pyrethrins are esters of the monoterpenoid trans-chrysanthemic acid with one of the three rethrolone-type alcohols. To test if glandular trichomes can be made to synthesize trans-chrysanthemic acid, we reconstructed its biosynthetic pathway in tomato type VI glandular trichomes, which produce large amounts of terpenoids that share the precursor dimethylallyl diphosphate (DMAPP) with this acid. This was achieved by coexpressing the trans-chrysanthemic acid pathway related genes including TcCDS encoding chrysanthemyl diphosphate synthase and the fusion gene of TcADH2 encoding the alcohol dehydrogenase 2 linked with TcALDH1 encoding the aldehyde dehydrogenase 1 under the control of a newly identified type VI glandular trichome-specific metallocarboxypeptidase inhibitor promoter. Whole tomato leaves harboring type VI glandular trichomes expressing all three aformentioned genes had a concentration of total trans-chrysanthemic acid that was about 1.5-fold higher (by mole number) than the levels of β-phellandrene, the dominant monoterpene present in non-transgenic leaves, while the levels of β-phellandrene and the representative sesquiterpene β-caryophyllene in transgenic leaves were reduced by 96% and 81%, respectively. These results suggest that the tomato type VI glandular trichome is an alternative platform for the biosynthesis of trans-chrysanthemic acid by metabolic engineering.
... The powerful biosynthetic secreting and accumulating capabilities of glandular trichomes for the production of plants' secondary metabolites including terpenoids, flavonoid, alkaloids, polysaccharides, polyphenols, and phenylpropanoids have made them an exciting research topic in recent years for plant metabolic engineering strategies (Wagner et al., 2004;Fridman et al., 2005;Gershenzon and Dudareva, 2007;Xie et al., 2008;Tattini et al., 2010;Weinhold and Baldwin, 2011). Many efforts have been dedicated to promoting the accumulation of secondary metabolites in plants, and it is feasible to improve secondary metabolic productivity by increasing glandular trichome density (Tissier, 2012). Unlike glandular trichomes, non-glandular trichomes are not efficient in secondary metabolism (Soetaert et al., 2013;Huchelmann et al., 2017). ...
... Glandular trichomes are special structures derived from the epidermal cells of many plants (Werker, 2000). They have the potential to be a powerful secondary metabolic factory (Tissier, 2012). Furthermore, the various compounds in glandular trichomes are potential active ingredients for many applications, including curing diseases, in fragrance, in killing pests, etc. (Dixon, 2001;Schilmiller et al., 2008;Tissier, 2012;Huchelmann et al., 2017). ...
... They have the potential to be a powerful secondary metabolic factory (Tissier, 2012). Furthermore, the various compounds in glandular trichomes are potential active ingredients for many applications, including curing diseases, in fragrance, in killing pests, etc. (Dixon, 2001;Schilmiller et al., 2008;Tissier, 2012;Huchelmann et al., 2017). In A. annua, one of the most well-known compounds is artemisinin which is synthesized in GSTs (Olofsson et al., 2011). ...
Artemisia annua L. is known for its specific product “artemisinin” which is an active ingredient for curing malaria. Artemisinin is secreted and accumulated in the glandular secretory trichomes (GSTs) on A. annua leaves. Earlier studies have shown that increasing GST density is effective in increasing artemisinin content. However, the mechanism of GST initiation is not fully understood. To this end, we isolated and characterized an R2R3-MYB gene, AaMYB17, which is expressed specifically in the GSTs of shoot tips. Overexpression of AaMYB17 in A. annua increased GST density and enhanced the artemisinin content, whereas RNA interference of AaMYB17 resulted in the reduction of GST density and artemisinin content. Additionally, neither overexpression lines nor RNAi lines showed an abnormal phenotype in plant growth and the morphology of GSTs. Our study demonstrates that AaMYB17 is a positive regulator of GSTs’ initiation, without influencing the trichome morphology.
... Glandular trichomes are often multicellular and serve as the site of biosynthesis and storage of significant amounts of VOCs in a liquid state, which are only released when trichomes are broken [11]. Many plant species have glandular trichomes, and much literature on this topic has demonstrated the enormous variation in their shape and size [12]. The number of specific metabolites generated by a plant is frequently closely connected to the density of glandular trichomes present at the epidermis's surface [13]. ...
... In this work, we used 16,341 DEGs derived from different tissues of O. vulgare 'HS' and clustered nine modules based on expression profiles. Frequently, the amount of specialized metabolites generated by a plant is strongly associated with the density of glandular trichomes present on the surface of the epidermis, and the higher EO content in oregano may be attributable to the significantly greater abundance of glandular trichomes [12,13]. Therefore, we not only observed gene modules positively correlated with carvacrol metabolite (orangered4, plum1, ivory), but also focused on the PGT-related gene modules of orangered4, plum1, and lightcyan (positive correlations) and darkgrey and skyblue3 (nagative correlations). ...
Origanum vulgare, belonging to the Lamiaceae family, is a principal culinary herb used worldwide which possesses great antioxidant and antibacterial properties corresponding to various volatile organic components (VOCs). However, the metabolite profiles and underlying biosynthesis mechanisms of elaborate tissues (stems, leaves, bracts, sepals, petals) of Origanum vulgare have seldom been reported. Here, solid-phase microextraction–gas chromatography/mass spectrometry results showed that Origanum vulgare ‘Hot and Spicy’ (O. vulgare ‘HS’) was extremely rich in carvacrol and had the tissue dependence characteristic. Moreover, a full-length transcriptome analysis revealed carvacrol biosynthesis and its tissue-specific expression patterns of ‘upstream’ MVA/MEP pathway genes and ‘downstream’ modifier genes of TPSs, CYPs, and SDRs. Furthermore, the systems biology method of modular organization analysis was applied to cluster 16,341 differently expressed genes into nine modules and to identify significant carvacrol- and peltate glandular trichome-correlated modules. In terms of these positive and negative modules, weighted gene co-expression network analysis results showed that carvacrol biosynthetic pathway genes are highly co-expressed with TF genes, such as ZIPs and bHLHs, indicating their involvement in regulating the biosynthesis of carvacrol. Our findings shed light on the tissue specificity of VOC accumulation in O. vulgare ‘HS’ and identified key candidate genes for carvacrol biosynthesis, which would allow metabolic engineering and breeding of Origanum cultivars.
... In aromatic medicinal plants, leaves are covered with special multicellular structures, trichomes, which are divided into glandular trichomes (GTs) and non-glandular trichomes (NGTs) depending on their secondary metabolism capability (Liu et al., 2019). GTs are known as cell metabolic factories due to their powerful biosynthetic secretion and accumulation capabilities (Tissier, 2012). For example, the antimalarial drug, artemisinin, is produced in A. annua GTs, and pharmaceutical essential oils of M. haplocalyx accumulate in the GTs (Tissier, 2012). ...
... GTs are known as cell metabolic factories due to their powerful biosynthetic secretion and accumulation capabilities (Tissier, 2012). For example, the antimalarial drug, artemisinin, is produced in A. annua GTs, and pharmaceutical essential oils of M. haplocalyx accumulate in the GTs (Tissier, 2012). Some genes controlling GTs initiation and development have been identified, such as AaMXITA1 AaHD1, and AaHD8 in A. annua, and SlMX, and SlMYC in tomato (Chalvin et al., 2020). ...
The peltate glandular trichomes (PGTs) on Nepeta tenuifolia leaves can secrete and store bioactive essential oils. ScRNA-seq is a powerful tool for uncovering heterogeneous cells and exploring the development and differentiation of specific cells. Due to leaves rich in PGTs, the young leaves were used to isolated protoplasts and successfully captured 33,254 protoplasts for sequencing purposes. After cell type annotation, all the cells were partitioned into six broad populations with 19 clusters. Cells from PGTs were identified based on the expression patterns of trichome-specific genes, monoterpene biosynthetic genes, and metabolic analysis of PGT secretions. The developmental trajectories of PGTs were delineated by pseudotime analysis. Integrative analysis of scRNA-seq data from N. tenuifolia leaves and Arabidopsis thaliana shoot revealed that PGTs were specific to N. tenuifolia . Thus, our results provide a promising basis for exploring cell development and differentiation in plants, especially glandular trichome initiation and development.
... These 10 cells include two stalk cells, two basal cells, four subapical cells, and two apical cells (Olsson et al. 2009). GTs can also be classified according to the type of compounds they produce: hydrophilic and lipophilic proteins, poly-or monosaccharides (Tissier 2012). ...
... We can refer to the research model of tomato GTs to study medicinal plant GTs. Moreover, Artemisia annua may also become a biological model for the study of GTs; however, thus far, all genomic information on A. annua has not been published (Tissier 2012). ...
Glandular trichomes (GTs) are one of the epidermal tissues of medicinal plants which function in the synthesis, storage, and secretion of secondary metabolites. The active ingredients of Chinese medicinal materials are mostly secondary metabolites of plants. Accordingly, it is of great research value to explore the quality of medicinal materials using the GTs of medicinal plants as the starting point. However, most of the current studies on GTs of medicinal plants are still at the simple morphological identification stage, and there are few studies on the compounds secreted by GTs and secondary metabolic processes. Here, we reviewed the literature, summarized the morphological types of medicinal plant GTs, separation and purification technology, analysis technology, and biological activities of secondary metabolites, and established a research approach to medicinal plant GTs. We hope to provide a reference for future research on GT inclusions and secondary metabolism. © 2022, Institute of Experimental Botany, ASCR. All rights reserved.
... El tabaco es una planta de ciclo corto, considerada modelo de la familia Solanaceae y muy conocida por presentar compuestos tóxicos como mecanismos de defensa lo que la hace atractiva para estos fines. La superficie de la hoja de tabaco está cubierta por tricomas, en su mayoría glandulares (Akers et al., 1978, Wagner, 1991 que están involucrados en la secreción de compuestos, principalmente diterpenos y ésteres de azúcares, seguidos de ceras y un menor número de compuestos volátiles y variados (Severson et al. 1984, Wagner, 1999Tissier, 2012). Se cree que al encontrarse un gran número de estos compuestos en la superficie foliar, estén involucrados fundamentalmente en la defensa contra insectos y otros patógenos (Reuveni et al.,1987;Wang et al., 2004;Shepherd et al., 2005;Amme et al., 2005;Seo et al., 2012). ...
... Este sistema permite la separación de diferentes componentes de una muestra y mostrar la diversidad química que presentan los extractos etanólicos obtenidos, dado por la gran diversidad química característica de la familia Solanaceae en general y la diversidad de genotipos (Wollenweber et al., 2005;Cui et al., 2011;Tissier, 2012, Sallaud et al., 2012, lo que posibilita una diversidad de aplicaciones potenciales de estos extractos. Otros métodos de cromatografía se requieren para la cuantificación e identificación de los compuestos presentes. ...
Natural products are an alternative to control microorganisms that cause diseases in crops. This work aimed to evaluate different solvents for obtaining crude extracts from tobacco leaf exudates and to determine in vitro effect of these extracts against two phytopathogenic bacteria: Xanthomonas campestris (Xc) and Pectobacterium carotovorum (Pc). Crude extracts from ten tobacco lines using solvents with polarities between 3.1 and 6.2 (dichloromethane, n-butanol, ethyl acetate, methanol and ethanol 90%) were obtained. Ethanol 90% was selected as the best solvent for obtaining extracts from tobacco leaf exudates and as a substitute of dichloromethane due to the best yield. The chemical composition diversity of the ethanolic extracts was revealed by thin-layer chromatography. The antibacterial activity was evaluated by agar disk diffusion method recording the inhibition zones. Growth inhibition was observed for all extracts against Xc, and the better activity corresponded to the lines Nic 1061"TI 1738" and Nic 1016 "Incekara" until a minimal amount of 5 μg/ disc, with higher yield in case of the line Nic1061 . Only the extract of the line Nic 1015 was able to inhibit the growth of Pc until a minimal inhibitory concentration of 5 μg/disc. These results suggest a potential use of crude extracts from lines Nic 1061 and Nic 1015 "TI 1341" as an effective agent for the crop protection against Xc and Pc respectively.
... The mature capitate trichomes look with degenerative head, because their content exudes outside. In some papers it has been mentioned [5,6] that these trichomes are involved more in the biosynthesis of polysaccharides, and less in the synthesis of terpenes. Tissier A. [5] pointed that the capitate ones predominantly produce nonvolatile or poorly volatile compounds that are directly exuded onto the surface of the trichome. ...
... In some papers it has been mentioned [5,6] that these trichomes are involved more in the biosynthesis of polysaccharides, and less in the synthesis of terpenes. Tissier A. [5] pointed that the capitate ones predominantly produce nonvolatile or poorly volatile compounds that are directly exuded onto the surface of the trichome. ...
The microscopic and citochemistry study denotes 3 types of glandular trichomes (peltate, capitates type I and type II), implicated in the synthesis of the metabolites, including volatile oils (with biological and protective role) and one type of non-glandular trichomes with the potential adaptive role to stressors in 7 new genotypes (4 cultivars – Moldoveanca 4, Vis Magic 10, Alba 7, Aroma Unica and 3 hybrids – Fr.5S8-24, Fr.8-5-15V and Cr.13S-6-7) of sp. Lavandula angustifolia Mill., spp. angustifolia. The degree of development and distribution mode of both types of trichomes (glandular and non-glandular) varies according organs (stem, leaf, bract, flower calyx and corolla) and genotype.
... Another notable example is the anti-malaria drug artemisinin, which is produced in the GSTs of Artemisia annua L. (Graham et al., 2010). The amount of such specialized metabolites that can be extracted largely depends on the density of GSTs (Paetzold et al., 2010;Tissier, 2012), and so increasing GST density represents a potential strategy to improve the yield of desired metabolites. However, there is currently a limited understanding of the molecular mechanism of GST initiation (Tissier, 2012;Huchelmann et al., 2017). ...
... The amount of such specialized metabolites that can be extracted largely depends on the density of GSTs (Paetzold et al., 2010;Tissier, 2012), and so increasing GST density represents a potential strategy to improve the yield of desired metabolites. However, there is currently a limited understanding of the molecular mechanism of GST initiation (Tissier, 2012;Huchelmann et al., 2017). ...
Plant glandular secretory trichomes (GSTs) produce various specialized metabolites. Increasing GST density represents a strategy to enhance the yield of these chemicals; however, the gene regulatory network that controls GST initiation remains unclear. In a previous study of Artemisia annua L., we found that a HD‐ZIP IV transcription factor, AaHD1, promotes GST initiation by directly regulating AaGSW2. Here, we identified two AaHD1‐interacting transcription factors, named AaMIXTA‐like 2 (AaMYB16) and AaMYB5. Through the generation and characterization of transgenic plants, we found that AaMYB16 is a positive regulator of GST initiation, while AaMYB5 has the opposite effect. Notably, neither of them regulates GST formation independently. Rather, they act competitively, by interacting and modulating AaHD1 promoter binding activity. Additionally, the phytohormone jasmonic acid (JA) was shown to be associated with the AaHD1‐AaMYB16/AaMYB5 regulatory network through transcriptional regulation via a JASMONATE‐ZIM DOMAIN (JAZ) protein repressor. These results bring new insight into the mechanism of GST initiation through regulatory complexes, which appear to have similar functions in a range of vascular plant taxa.
... To investigate the cellular mechanism of friction, the surfaces of perianth organs were examined using scanning electron microscopy. The TKS corolla formed a number of glandular secretory trichomes (GSTs) with four head secretion cells, similar to the type VI GST in Lycopersicon species (Fig. 3a, b) 21,22 . In Q513, almost no GSTs had developed on the corolla surface, and nonsecretory hair trichomes developed at the distal part of the corolla (Fig. 3c, d). ...
... Since GSTs biosynthesize and accumulate secondary metabolites, we suggest that secretions from GSTs on perianth organs act as a lubricant and reduce the friction of floral organs, enabling the corolla to elongate straight properly ( Supplementary Fig. 8). This suggests a novel function for GSTs in organogenesis, i.e., mechanical regulation to reduce the conflicting stresses between surrounding organs, in addition to acting as mechanical and chemical barriers for plant defense 21,22,34 . Genetic and physiological analyses of GSTs constitute the next step to understand the molecular function of GSTs in corolla morphogenesis. ...
In complex structures such as flowers, organ–organ interactions are critical for morphogenesis. The corolla plays a central role in attracting pollinators: thus, its proper development is important in nature, agriculture, and horticulture. Although the intraorgan mechanism of corolla development has been studied, the importance of organ–organ interactions during development remains unknown. Here, using corolla mutants of morning glory described approximately 200 years ago, we show that glandular secretory trichomes (GSTs) regulate floral organ interactions needed for corolla morphogenesis. Defects in GST development in perianth organs result in folding of the corolla tube, and release of mechanical stress by sepal removal restores corolla elongation. Computational modeling shows that the folding occurs because of buckling caused by mechanical stress from friction at the distal side of the corolla. Our results suggest a novel function of GSTs in regulating the physical interaction of floral organs for macroscopic morphogenesis of the corolla.
... In plants, trichomes can be divided into glandular and nonglandular types based on the presence or absence of glandular heads (Werker, 2000). Glandular trichomes are responsible for the synthesis, storage, and secretion of phytochemicals, and their distribution and density are linked to phytochemical production in various plants (Glas et al., 2012;Tissier, 2012;Cui et al., 2022). In contrast, non-glandular trichomes lack secretory mechanisms and YL represents young leaves, OL represents old leaves, TR represents trichomes, and ST represents trichome-removed stem. ...
Artemisia argyi (A. argyi) is a medicinal plant belonging to the Asteraceae family and Artemisia genus. Flavonoids abundant in A. argyi are associated with anti-inflammatory, anticancer, and antioxidative effects. Eupatilin and jaceosidin are representative polymethoxy flavonoids with medicinal properties significant enough to warrant the development of drugs using their components. However, the biosynthetic pathways and related genes of these compounds have not been fully explored in A. argyi. This study comprehensively analyzed the transcriptome data and flavonoids contents from four different tissues of A. argyi (young leaves, old leaves, trichomes collected from stems, and stems without trichomes) for the first time. We obtained 41,398 unigenes through the de-novo assembly of transcriptome data and mined promising candidate genes involved in the biosynthesis of eupatilin and jaceosidin using differentially expressed genes, hierarchical clustering, phylogenetic tree, and weighted gene co-expression analysis. Our analysis led to the identification of a total of 7,265 DEGs, among which 153 genes were annotated as flavonoid-related genes. In particular, we were able to identify eight putative flavone-6-hydroxylase (F6H) genes, which were responsible for providing a methyl group acceptor into flavone basic skeleton. Furthermore, five O-methyltransferases (OMTs) gene were identified, which were required for the site-specific O-methylation during the biosynthesis of eupatilin and jaceosidin. Although further validation would be necessary, our findings pave the way for the modification and mass-production of pharmacologically important polymethoxy flavonoids through genetic engineering and synthetic biological approaches.
... It is nonetheless known that the viscous secretions from trichome-bearing plants generally serve as a defense barrier against phytophagous arthropods and other organisms. [12,13] It thus seemed an excellent opportunity to study aspects of the natural history and biology of the possible interaction of a neotropical resin bug with plant species endowed with a gummy trichome secretion on its stems. We hypothesized that H. stali might collect the trichome secretion (hereafter TS) of R. cf. ...
... Typically, GTs are multicellular structures with differentiated basal, stalk and apical cells. The production and storage compartments are usually located at the tip of the hair and are part of one or more glandular cells (Tissier, 2012). GTs may release the stored exudate by physical rupture or secrete it through the tip opening, causing the plant surfaces to become sticky (Falara & Pichersky, 2012). ...
Rubus adenotrichos is an Andean blackberry plant bearing glandular trichomes which secrete an adhesive exudate. The resin bug Heniartes stali is frequently found on this plant and collects this exudate using the forelegs to enhance its preying capacity. Here, we describe the morphology of the plant's glandular trichomes with the aid of light and scanning electron microscopy, as well as the chemical components of the exudate by histochemical and gas chromatography-mass spectrometry analysis. We have also combined behavioral observations with the analysis of the insect leg morphology to identify possible morpho-functional adaptations evolved by H. stali for collecting the sticky secretions. Glandular trichomes exhibited a multicellular long stalk and a calyx-shaped head with radially aligned cells. The composition of the resinous fluid was mainly terpenes and phenolics, which may contribute to its sticky properties. Brush-like structures on the tibia of forelegs in H. stali suggests an adaptive trait for collecting the trichomes exudate. A profusely hair-covered area on metatibiae operated as a resin storage structure. Abundant pore-like openings were observed in the 2 cuticle of this area through which substances could be conceivably secreted to prevent resin hardening. These findings combine morphological and chemical features of a fascinating insect-plant interaction in the Neotropics. Resumen Rubus adenotrichos es una planta de mora andina que contiene tricomas glandulares los cuales secretan un exudado pegajoso. El chinche de las resinas Heniartes stali se encuentra con frecuencia en esta planta recogiendo el exudado con sus patas delanteras para mejorar su capacidad en la captura de las presas. En este trabajo empleamos microscopía de luz y microscopía electrónica de barrido para describir la morfología de los tricomas. Los constituyentes químicos del exudado fueron estudiados mediante técnicas histoquímicas, de cromatografía de gases y espectrometría de masas. También combinamos observaciones del comportamiento del insecto en la recolección y almacenamiento del exudado con el análisis de la morfología de sus patas, empleando microscopía de luz y microscopía electrónica de barrido para identificar las posibles adaptaciones morfo-funcionales desarrolladas para la manipulación de estas secreciones adhesivas. Los tricomas glandulares exhibieron un tallo largo multicelular y una cabeza glandular en forma de cáliz con células alineadas radialmente. El fluido resinoso estaba compuesto principalmente por terpenos y compuestos fenólicos, los cuales parecen contribuir con sus propiedades adhesivas. La presencia de estructuras tipo pincel en las puntas de las tibias de las patas delanteras sugieren un carácter adaptativo para recoger el exudado de los tricomas. También describimos un área en las patas traseras profusamente cubierta de pelos, que funcionaban como estructuras de almacenamiento de la resina. En la cutícula de éstas observamos abundantes aberturas similares a poros y sugerimos que a través de ellos se secretan sustancias que impiden el endurecimiento de la resina almacenada. Estos hallazgos aportan información sobre características morfológicas y químicas de un novedoso modelo de interacción insecto-planta en el neotrópico.
... Capitate trichomes (Figure 9.7g) are described to have one basal cell with one to several stalk cells and secretory cells at the tip of the stalk. They primarily secrete poorly to nonvolatile oils [67,68]. On the other hand, peltate trichomes (Figure 9.7h) are described to have one short stalk cell attached to one basal cell. ...
Essential oils have been known for millennia for its therapeutic uses and properties and continually expanding worldwide due to its growing interest for a rediscovery of natural remedies. The sources, methods of extraction, diversity, uses, and applications of essential oils are variable in their application to pharmaceutics and pharmaceutical industry. The oily fragrance of essential oils from different plant parts can be extracted using different techniques mostly by steam distillation and hydrodistillation. Essential oils are widely used in massage therapy and aromatherapy for physical and psychological treatment. Most essential oils possessing bioactive compounds have potential therapeutic properties such as anti-inflammatory, antidiabetic, antivirals, antimicrobial, antioxidant, wound-healing, chemopreventive, chemotherapeutic, and anxiolytic activities. The essential oils of aromatic plants could be the active ingredients of their pharmaceutical properties. The use and application of essential oils in folk herbal remedies could support the therapeutic potential of most aromatic plants used in aromatherapy.
... Interestingly, Si-mediated mechanisms have similar effects on plants above and below ground. For instance, sugarcane [48] and oilseed rape [94] both accumulate lignin in their roots, leading to stronger roots and, subsequently, increased resistance to insects [95]. The Chrysomellid beetle, Diabrotica speciose larva, was found to destroy the roots and tubers of the potato, while young adults consume the leaves. ...
Silicon (Si), an essential nutrient in the plant health system, are gaining momentum in facilitating defense mechanisms against biotic and abiotic stresses. Recently, Si has received increased attention for its role in alleviating arthropod pests. Albeit many studies focused on direct mechanisms such as physical /mechanical barrier and the biochemical and molecular mode in reinforcing defense activity, the deep insight into the tri-trophic level is obscured. Our study emphasizes the key role of Si in tri-trophic interaction (plant-herbivore-natural enemies), its accumulation in plant tissue, and its consequences on beneficial arthropods. Evidently, the accumulation of Si is greater in monocot tissues than in dicots. We summarize how soil and climatic factors influence Si upregulation in plants. Ironically, the herbivore-induced plant volatiles play a crucial role in defense action, resulting in cascading effects on the attraction of natural enemies, facilitating locating the prey, subsequently strengthening the natural biocontrol. This review explores the abundance of Si in up-regulating the defense activity in the plant by favouring natural enemies and suppressing harmful arthropods, subsequently supporting a green environment and sustainable production system. Further, the present study elucidates variable functions of stress signal hormones like jasmonic acid, salicylic acid, and ethylene in both monocots and dicots. The study also highlights the availability and mode of Si application in response to plant health and emphasizes the future research needs on the role of Si in safeguarding plant health against arthropod pests.
... Student's t-test: *P < 0.05; **P < 0.01. important tool of genetic engineering for quality improvement of varieties (Glas et al., 2012;Tissier, 2012;Wu et al., 2020). However, limited studies to date have investigated the development of tobacco trichomes, and the detailed mechanism has not been fully understood. ...
Trichomes are specialized hair-like organs found on epidermal cells of many terrestrial plants, which protect plant from excessive transpiration and numerous abiotic and biotic stresses. However, the genetic basis and underlying mechanisms are largely unknown in Nicotiana tabacum (common tobacco), an established model system for genetic engineering and plant breeding. In present study, we identified, cloned and characterized an unknown function transcription factor NtMYB306a from tobacco cultivar K326 trichomes. Results obtained from sequence phylogenetic tree analysis showed that NtMYB306a-encoded protein belonged to S1 subgroup of the plants’ R2R3-MYB transcription factors (TFs). Observation of the green fluorescent signals from NtMYB306a-GFP fusion protein construct exhibited that NtMYB306a was localized in nucleus. In yeast transactivation assays, the transformed yeast containing pGBKT7-NtMYB306a construct was able to grow on SD/-Trp-Ade+X-α-gal selection media, signifying that NtMYB306a exhibits transcriptional activation activity. Results from qRT-PCR, in-situ hybridization and GUS staining of transgenic tobacco plants revealed that NtMYB306a is primarily expressed in tobacco trichomes, especially tall glandular trichomes (TGTs) and short glandular trichomes (SGTs). RNA sequencing (RNA-seq) and qRT-PCR analysis of the NtMYB306a-overexpressing transgenic tobacco line revealed that NtMYB306a activated the expression of a set of key target genes which were associated with wax alkane biosynthesis. Gas Chromatography–Mass Spectrometry (GC-MS) exhibited that the total alkane contents and the contents of n-C28, n-C29, n-C31, and ai-C31 alkanes in leaf exudates of NtMYB306a-OE lines (OE-3, OE-13, and OE-20) were significantly greater when compared to WT. Besides, the promoter region of NtMYB306a contained numerous stress-responsive cis-acting elements, and their differential expression towards salicylic acid and cold stress treatments reflected their roles in signal transduction and cold-stress tolerance. Together, these results suggest that NtMYB306a is necessarily a positive regulator of alkane metabolism in tobacco trichomes that does not affect the number and morphology of tobacco trichomes, and that it can be used as a candidate gene for improving stress resistance and the quality of tobacco.
... Two primary mechanisms of Si-based plant defenses involve strengthening physical or mechanical barriers and inducing plant defense mechanisms via biochemical or molecular reactions. Similarly, Si-mediated mechanisms act in plants below and above ground, as Si induces the accumulation of lignin in the roots of sugarcane [17] and oilseed rape [18], increasing toughness and, eventually, the resistance to insects [19]. Despite the differences in Si accumulation among plant species, they display similar Si defense mechanisms against insects. ...
The fall armyworm (Spodoptera frugiperda) is a major economic pest in the United States and has recently become a significant concern in African and Asian countries. Due to its increased resistance to current management strategies, including pesticides and transgenic corn, alternative management techniques have become more necessary. Currently, silicon (Si) is being used in many pest control systems due to its ability to increase plant resistance to biotic and abiotic factors and promote plant growth. The current experiments were carried out at the College of Plant Protection, Gansu Agricultural University, Lanzhou, China, to test the effect of Si on lifetable parameters and lipase activity of fall armyworm and vegetative and physiological parameters of maize plants. Two sources of Si (silicon dioxide: SiO 2 and potassium silicate: K 2 SiO 3) were applied on maize plants with two application methods (foliar application and soil drenching). The experiment results revealed that foliar applications of SiO 2 and K 2 SiO 3 significantly (P�0.05) increased mortality percentage and developmental period and decreased larval and pupal biomass of fall armyworm. Similarly, both Si sources significantly (P�0.05) reduced lipase activity of larvae, and fecundity of adults, whereas prolonged longevity of adults. Among plant parameters, a significant increase in fresh and dry weight of shoot, stem length, chlorophyll content, and antioxidant activity was observed with foliar applications of Si. Root fresh and dry weight was significantly (P � 0.05) higher in plants treated with soil drenching of SiO 2 and K 2 SiO 3. Moreover, SiO 2 performed better for all parameters as compared to K 2 SiO 3 and control treatment. The study conclusively demonstrated a significant negative effect on various biological parameters of fall armyworm when plants were treated with Si, so it can be a promising strategy to control this pest.
... In addition, Si enriched trichomes in rice plants provide protection against stem borers and planthoppers. These trichomes negatively influence the oviposition and feeding behavior of insects by secreting secondary metabolites such as alkaloids, flavonoids, and terpenoids that can be poisonous and repellent to various insects thus increasing plant resistance (Tissier 2012). ...
Silicon (Si) is one of the essential and important elements that plays a vital role in the growth and productivity of crop plants by improving their nutritional status. The exogenous application of Si activates plant defense and phytohormones signaling mechanisms under biotic and abiotic stresses. Different soil factors such as soil pH, texture, organic matter, and temperature significantly influence the bioavailability and solubility of Si in the soil system. However, the uptake, transport, and accumulation of Si within the plants depend upon Si-transporters including LSi1, LSi2, and LSi6 that are present in the roots of plants. From the past few decades, the role of Si in mineral nutrient deficiencies, toxicities, biotic and abiotic stresses is being explored in cereals crops. Si improves the plant resistance against pathogenic stress, salinity, drought, heat, and heavy metals by regulating the defense system. In addition, Si facilitates the uptake of essential nutrients and restricts metal ions by making conjugates, provides mechanical strength to plant cell wall, and enhances the resistance against unwanted environmental conditions. It potentially regulates phytohormones biosynthesis, improves photosynthetic attributes, and increases the activities of antioxidant enzymes to reduce the harmful impacts of reactive oxygen species (ROS) and other toxic ions. Furthermore, the actual mechanisms behind Si-mediated alterations in plants under mineral nutrient stress are still unclear; however, a little literature is available on other abiotic stresses. Therefore, this study summarizes the findings from various investigations for better understanding the mechanism, regulation, and crosstalk among different phytohormones, micro- and macro-nutrient disorders, other biotic and abiotic stresses and their possible solutions in response to exogenous applications of Si (soil or foliar). Overall, this study suggested that Si supplementation significantly enhances the physio-biochemical attributes, defensive mechanism, hormonal regulation, and activates the regulation of expression pattern of stress responsive genes under stressful conditions.
... The trichomes have a lot of Si in them have a mechanical effect on the insects, obstructing their mobility and settlement and probably altering the oviposition preference and their eating rate (Handley et al. 2005). This is another type of trichome i.e., glandular trichomes which act as deterrents by secreting secondary metabolites (e.g., flavonoids, terpenoids, and alkaloids) that are toxic and repellant to many insect pests, resulting in increased resistance (Tissier 2012). Similarly, our SEM studies revealed a variety of silica cell shapes, including butterfly-shaped silica cells in maize and rice leaves and oval silica cells in wheat. ...
Plants can use silicon (Si) as a common element that helps plants recover from environmental stresses. Using Si helps build tolerance to many stresses, illnesses, infections and protects plants against fungus and herbivorous insects. Silica is absorbed by plant roots and then transferred to the plants above-ground components via the transpiration stream. Si deposition in plant tissues promotes stiffness and strength while decreasing water transpiration and abiotic stress. It is found in plant cell walls, lumens, trichomes, intracellular spaces and reproductive organs. Plants contain 0.1–10% silicon by weight. Concentration-based categories include accumulators, intermediates, and excluders. It increases protective chemicals (enzymes such as peroxidase, polyphenol oxidase and phenylalanine ammonia lyase) and phenolic resins (phytoantitoxins, polylactones). Silicon can regulate plant volatile emissions, which may affect herbivore insects and higher trophic levels. Si accumulation in plants modifies three major plant hormones (jasmonic acid, salicylic acid and ethylene), altering volatile organic compound (VOC) emissions. During pest infestations, soluble Si in plant tissues attracts natural predators and parasitoids and it works as a natural insect repellant and can be easily integrated with other pest management practices. Because silicon leaves no pesticide residues in food or the environment, it is a feasible component of integrated pest management, so the connection between silicon-treated plants and reduced insect damage was discussed in this review.
... It also enhances the effectiveness of the compounds against attackers that function in a spatially specic manner. 141,142 Therefore, it can be very benecial to investigate the metabolic specialization in plants at the tissue or single-cell level to understand the spatial-temporal coordination of cellular processes underlying specialized metabolic pathways. A notable example in this direction is the work done by , where metabolomics and transcriptomics data were generated from 14 plant tissues and developmental stages of Nicotiana attenuata and predictions were made about the assignment of unknown genes and metabolites to specic metabolic pathways using the principles of information theory. ...
Covering: up to 2022With the emergence of large amounts of omics data, computational approaches for the identification of plant natural product biosynthetic pathways and their genetic regulation have become increasingly important. While genomes provide clues regarding functional associations between genes based on gene clustering, metabolome mining provides a foundational technology to chart natural product structural diversity in plants, and transcriptomics has been successfully used to identify new members of their biosynthetic pathways based on coexpression. Thus far, most approaches utilizing transcriptomics and metabolomics have been targeted towards specific pathways and use one type of omics data at a time. Recent technological advances now provide new opportunities for integration of multiple omics types and untargeted pathway discovery. Here, we review advances in plant biosynthetic pathway discovery using genomics, transcriptomics, and metabolomics, as well as recent efforts towards omics integration. We highlight how transcriptomics and metabolomics provide complementary information to link genes to metabolites, by associating temporal and spatial gene expression levels with metabolite abundance levels across samples, and by matching mass-spectral features to enzyme families. Furthermore, we suggest that elucidation of gene regulatory networks using time-series data may prove useful for efforts to unwire the complexities of biosynthetic pathway components based on regulatory interactions and events.
... Glandular secretory trichome density was shown to be positively correlated with the production of terpenes (Yan et al., 2017). Consequently, increasing the density of glandular secretory trichomes could be an effective approach for improving the production of these natural metabolites (Tissier, 2012). Knowledge about genes involved in glandular secretory trichome formation comes mostly from work on Artemisia annua, Nicotiana benthamiana (tobacco), and Solanum lycopersicum (tomato) (Robert and Tissier, 2020). ...
Thyme has medicinal and aromatic value because of its potent antimicrobial and antioxidant properties. However, the absence of a fully sequenced thyme genome limits functional genomic studies in Chinese native thymes. Thymus quinquecostatus Celak., which contains large amounts of bioactive monoterpenes, such as thymol and carvacrol, is an important wild medicinal and aromatic plant in China. Monoterpenoids are abundant in glandular secretory trichomes. Here, high-fidelity and chromatin conformation capture technologies were used to assemble and annotate the T. quinquecostatus genome at the chromosome level. The 13 chromosomes of T. quinquecostatus had a total length of 528.66 megabases (Mb), a contig N50 of 8.06 Mb, and BUSCO of 97.34%. We found that T. quinquecostatus experienced two whole-genome duplications, with the most recent event occurring ∼4.34 million years ago. Deep analyses of the genome, in conjunction with comparative genomic, phylogenetic, transcriptomic, and metabonomic studies, uncovered many regulatory factors and genes related to monoterpenoids and glandular secretory trichome development. Terpene synthase (TPS)-, cytochrome P450 monooxygenases (CYP)-, short-chain dehydrogenase/reductase (SDR)-, R2R3-MYB-, and homeodomain-leucine zipper (HD-ZIP) IV-encoding genes were among those present in the T. quinquecostatus genome. Notably, Tq02G002290.1 (TqTPS1) was shown to be the gene encoding the terpene synthase responsible for catalyzing geranyl diphosphate (GPP) to produce the main monoterpene product γ-terpinene. Our study provides significant insight into the mechanism of glandular secretory trichome formation and monoterpenoid biosynthesis in thyme. Furthermore, this work will facilitate the development of molecular breeding tools to enhance the productivity of bioactive secondary metabolites in Lamiaceae.
... Secondary metabolites often present in only a few tissues, cell types, and organs [12]. In plants, defence metabolites are mostly found in specific tissues or cell types to minimize autotoxicity and/or to maximize the effectiveness of the metabolites [27,28]. In Nicotiana attenuata, for example, 63% of non-redundant metabolite spectra showed that secondary metabolites often have organ-and tissue-specific gene expression [29]. ...
Tigilanol tiglate (EBC-46) is a small-molecule natural product under development for the treatment of cancers in humans and companion animals. The drug is currently produced by purification from the Australian rainforest tree Fontainea picrosperma (Euphorbiaceae). As part of a selective-breeding program to increase EBC-46 yield from F. picrosperma plantations, we investigated potential gene biomarkers associated with biosynthesis of EBC-46. Initially, we identified individual plants that were either high (>0.039%) or low EBC-46 (<0.008%) producers, then assessed their differentially expressed genes within the leaves and roots of these two groups by quantitative RNA sequencing. Compared to low EBC-46 producers, high-EBC-46-producing plants were found to have 145 upregulated genes and 101 downregulated genes in leaves and 53 upregulated genes and 82 downregulated genes in roots. Most of these genes were functionally associated with defence, transport, and biosynthesis. Genes identified as expressed exclusively in either the high or low EBC-46-producing plants were further validated by quantitative PCR, showing that cytochrome P450 94C1 in leaves and early response dehydration 7.1 and 2-alkenal reductase in roots were consistently and significantly upregulated in high-EBC-46 producers. In summary, this study has identified biomarker genes that may be used in the selective breeding of F. picrosperma.
... To date, available evidence indicates that GTs are biofactories for terpene biosynthesis and accumulation (Yan et al., 2016), and GTs are considered true cell biofactories for producing valuable chemicals, thereby increasing GT density could be suitable targets for metabolic engineering and breeding (Tissier, 2012). The VOCs content of peppermint leaves was a positive correlation with the total number of GTs present (Turner et al., 2000;Maffei and Mucciarelli, 2003). ...
The plant hormone, methyl jasmonate (MeJA), is an orthodox elicitor of secondary metabolites, including terpenoids. Lavandula angustifolia is an important aromatic plant generating, yet few studies have been performed to evaluate the function of MeJA on the biosynthesis of terpenoids in lavender. Five treatments (with concentrations of 0, 0.4, 4, 8, and 16 mM) were set, and the physiological indicators of each group were determined after 0, 6, 12, 24, 48, and 72 h. The results illustrate that (1) MeJA could affect the diurnal rhythm of the emission of volatiles and MeJA acted in a dose-dependent and time-dependent manner; (2) 8 mM MeJA treatment increased the total content of the volatiles, and the contents of monoterpenoids and sesquiterpenoids were up-regulated 0.46– and 0.74– fold than the control at 24 h and 12 h, respectively; (3) after MeJA treatment, all the genes expression analyzed changed to varying degrees, of which 3-carene synthase (La3CARS) gene changed most significantly (7.66– to 38.02– fold than the control); (4) MeJA application was associated with a rise in glandular trichome density. The positive effects of MeJA indicate that the exogenous application of MeJA could be a beneficial mean for studies on the biosynthesis of terpenoids in lavender.
... Trichomes arise from epidermal cells and can be divided into glandular trichomes (GTs) and nonglandular trichomes (NGTs) according to their structure and function (Schuurink and Tissier 2020). GTs are often referred to a "cellular factory" for the synthesis of terpenoids, flavonoids, polysaccharides and alkaloids (Tissier 2012). NGTs are nonsecretory protuberances widely found in the epidermis of plant organs, and play a more important role than GTs in complex and changing environments. ...
Main conclusion
Glandular trichomes of Artemisia argyi H. Lév. & Vaniot are the key tissues for the production of flavonoid and terpenoid metabolites.
Abstract
Artemisia argyi H. Lév. & Vaniot is an herbaceous perennial plant that has been widely used in traditional medicine for thousands of years. Glandular trichomes (GTs) and nonglandular trichomes (NGTs) have been reported on the leaf surface of A. argyi. The aim of this study was to elucidate the morphogenetic process and to analyze the metabolites of trichomes in A. argyi. The morphogenesis of GTs and NGTs was characterized using light, scanning, and transmission electron microscopy. The constituents of GTs were analyzed using laser microdissection combined with gas and liquid chromatography–mass spectrometry. Five developmental stages of two types of GTs and four developmental stages of one type of NGTs were observed. Two types of mature GT and one type of NGT were composed of 10, 5, and 4–6 cells, respectively. A large storage cavity was detected between the cuticle and cell walls in the first type of mature GT. Large nuclei, nucleoli, and mitochondria were observed in the basal and intermediate cells of the second type of GT. In addition, large vacuoles were observed in the basal and apical cells, and large nuclei were observed in the middle cells of NGTs. One monoterpene and seven flavonoids were identified in GTs of A. argyi. We suggest that GTs are the key tissues for the production of bioactive metabolites in A. argyi. This study provides an important theoretical basis and technical approach for clarifying the regulatory mechanisms for trichome development and bioactive metabolite biosynthesis in A. argyi.
... Wild relatives of tomato are known as a source of insect resistance (Oliveira et al., 2009) and are generally associated with the presence of different trichome types and densities (Tissier, 2012). Glandular trichomes (GT) synthesize and store secondary metabolites (Schilmiller et al., 2010;McDowell et al., 2011). ...
Tuta absoluta, the pinworm on tomato has slowly become a menace to tomato growers in India. In India,
it was first reported in 2014 on tomato followed by reports on potato at Bengaluru and later in Pune. The pest
has an egg period of 4-10 days, larval period of 14-16 days, pupal period of 7-10 days and 7-15 days of adult
period depending on the temperatures. In India it was reported to cause more damage on the stem, leaves
and fruits of tomato during the rabi season than during kharif. Much work has been done on the molecular
characterization of the pest. Management practices using resistant varieties and studies on biochemical and
physical bases for resistance in plants have been discussed. Host induced plant volatiles and cues also can
help in the IPM strategies for this pest which has developed resistance to some commonly used insecticides.
An integrated approach alone can help achieve success in managing this devastating pest.
... Si induces lignin accumulation in the roots of both sugarcane (a monocot) (Frew et al. 2017) and oilseed rape (a eudicot) (Tissier 2012), increasing toughness and, eventually, resistance to insect attack (Johnson et al. 2010). Though the accumulation of Si differs among plant species, they likely display similar Si defense mechanisms against insects. ...
Priming is a phenomenon in which plants upon treatment with a resistance-inducing agent acquire an enhanced defensive capacity to respond faster and/or stronger at the moment that the plant is exposed to biotic or abiotic stresses. The priming can be found in different induced resistance systems to decrease lag time from the start of defense activation to the point when the defense is fully activated as well as to decrease the trade-off between induced resistance and the cost of defense activation. In addition, numerous chemical compounds, often of natural origin, have been found to act as priming stimuli. Priming also contributes in the existing relationship between members of a tritrophic system when plants upon damage by herbivorous arthropods release a mixture of HIPVs, green leaf volatiles (GLVs), terpenoids, and others to attract natural enemies of the herbivores. Interestingly, when there is a strong selection pressure on plants, they can evolve mechanisms by which they pass the parental memory of herbivory to their progeny for enhanced defense, known as transgenerational priming. Heavy metals and some mineral elements like silicon can lead to priming in plants. Among different priming approaches, seed priming in which seeds expose to specific compounds to enhance seed germination was found to be a promising approach because it should enable seedlings to mount a robust immune response and thereby remain disease-free (or only moderately infected) for a long time with minimal labor and expense. However, although it has been reported that priming compared to elicitation generally results in low fitness costs for the plant, it could lead to the downregulation of some resistance pathways or could sensitize plants such that they respond to false alarm signals. Overall, new findings on priming and other upcoming techniques like symbiotic control and endophytes open a new era regarding biological control concepts in which not only natural enemies and pests are important, but also other factors like microorganisms that are in association with natural enemies (endosymbionts) and plants (endophytes) have a main important contribution.
... Hence, it is not surprising that publications about glandular trichomes skyrocketed in the last decade, especially those related to -omics biology [48]. In this context, glandular trichomes of S. lycopersicum were studied intensively in the past [43,49], probably sparked by rich genetic resources and extensive sequence data available for this species [50]. For instance, S. lycopersicum type VI trichomes were subjected to transcriptomics, proteomics, metabolomics and 13 C-labelling in a single study [51] after trichome isolation with the aid of a frozen paint brush [52]. ...
Background
Rosette leaf trichomes of Arabidopsis thaliana have been broadly used to study cell development, cell differentiation and, more recently, cell wall biogenesis. However, trichome-specific biochemical or -omics analyses require a proper separation of trichomes from residual plant tissue. Thus, different strategies were proposed in the past for trichome isolation, which mostly rely on harsh conditions and suffer from low yield, thereby limiting the spectrum of downstream analyses.
Results
To take trichome-leaf separation to the next level, we revised a previously proposed method for isolating A. thaliana trichomes by optimizing the mechanical and biochemical specifications for trichome release. We additionally introduced a density gradient centrifugation step to remove residual plant debris. We found that prolonged, yet mild seedling agitation increases the overall trichome yield by more than 60% compared to the original protocol. We noticed that subsequent density gradient centrifugation further visually enhances trichome purity, which may be advantageous for downstream analyses. Gene expression analysis by quantitative reverse transcriptase-polymerase chain reaction validated a substantial enrichment upon purification of trichomes by density gradient centrifugation. Histochemical and biochemical investigation of trichome cell wall composition indicated that unlike the original protocol gentle agitation during trichome release largely preserves trichome integrity. We used enriched and density gradient-purified trichomes for proteomic analysis in comparison to trichome-depleted leaf samples and present a comprehensive reference data set of trichome-resident and -enriched proteins. Collectively we identified 223 proteins that are highly enriched in trichomes as compared to trichome-depleted leaves. We further demonstrate that the procedure can be applied to retrieve diverse glandular and non-glandular trichome types from other plant species.
Conclusions
We provide an advanced method for the isolation of A. thaliana leaf trichomes that outcompetes previous procedures regarding yield and purity. Due to the large amount of high-quality trichomes our method enabled profound insights into the so far largely unexplored A. thaliana trichome proteome. We anticipate that our protocol will be of use for a variety of downstream analyses, which are expected to shed further light on the biology of leaf trichomes in A. thaliana and possibly other plant species.
... Si induces lignin accumulation in the roots of both sugarcane (a monocot) (Frew et al. 2017) and oilseed rape (a eudicot) (Tissier 2012), increasing toughness and, eventually, resistance to insect attack (Johnson et al. 2010). Though the accumulation of Si differs among plant species, they likely display similar Si defense mechanisms against insects. ...
Priming is a phenomenon in which plants upon treatment with a resistance-inducing agent acquire an enhanced defensive capacity to respond faster and/or stronger at the moment that the plant is exposed to biotic or abiotic stresses. The priming can be found in different induced resistance systems to decrease lag time from the start of defense activation to the point when the defense is fully activated as well as to decrease the trade-off between induced resistance and the cost of defense activation. In addition, numerous chemical compounds, often of natural origin, have been found to act as priming stimuli. Priming also contributes in the existing relationship between members of a tritrophic system when plants upon damage by herbivorous arthropods release a mixture of HIPVs, green leaf volatiles (GLVs), terpenoids, and others to attract natural enemies of the herbivores. Interestingly, when there is a strong selection pressure on plants, they can evolve mechanisms by which they pass the parental memory of herbivory to their progeny for enhanced defense, known as transgenerational priming. Heavy metals and some mineral elements like silicon can lead to priming in plants. Among different priming approaches, seed priming in which seeds expose to specific compounds to enhance seed germination was found to be a promising approach because it should enable seedlings to mount a robust immune response and thereby remain disease-free (or only moderately infected) for a long time with minimal labor and expense. However, although it has been reported that priming compared to elicitation generally results in low fitness costs for the plant, it could lead to the downregulation of some resistance pathways or could sensitize plants such that they respond to false alarm signals. Overall, new findings on priming and other upcoming techniques like symbiotic control and endophytes open a new era regarding biological control concepts in which not only natural enemies and pests are important, but also other factors like microorganisms that are in association with natural enemies (endosymbionts) and plants (endophytes) have a main important contribution.
... Les trichomes sont de tailles variables et peuvent être unicellulaires ou pluricellulaires, glandulaire ou non (Payne, 1978). Les trichomes glandulaires ont des glandes pouvant synthétiser, stocker voire sécréter des métabolites secondaires (Tissier, 2012). Ce type de trichomes est peu fréquent chez les passiflores et n'a à ce jour été décrit que chez 4 espèces : P. clathrata, P. foetida, P. lepidota et P. villosa (Dhawan et al., 2004). ...
De nombreuses espèces de papillons aposématiques possèdent des défenses chimiques associées à des patrons de coloration vifs constituant un signal d’alerte visuel pour les prédateurs. En population naturelle, il est fréquemment observé des convergences évolutives de ces motifs colorés entre espèces phylogénétiquement distantes. Ainsi, des « cercles mimétiques » formés de plusieurs espèces à l’apparence similaire émergent localement. Ces interactions de mimétisme Müllerien sont positives pour les papillons. En effet, plus le nombre d’individus et/ou d’espèces partageant le même motif est grand, plus ce signal d’alerte est efficacement appris par les prédateurs qui subissent les effets des défenses chimiques. Bien que l’évolution de l’aposématisme ne soit pas totalement élucidée, l’évolution des défenses chimiques au sein des lignées de lépidoptères a probablement joué un rôle important dans l’émergence de la convergence évolutive pour le signal d’alerte coloré entre espèces mimétiques. Dans le cadre de cette thèse je m’intéresse à des papillons mimétiques, principalement de la tribu des Heliconiini mais aussi de la tribu des Ithomiini (Nymphalidae). Ces deux clades ont divergé il y a 82 millions d’années. Si des espèces de ces deux tribus ont convergé vers un même patron de coloration, elles présentent en revanche des défenses chimiques très différentes dont les voies d’acquisition sont contrastées, ce qui peut causer d’importantes variations intra et interspécifiques qui à leur tour ont des conséquences sur le comportement des prédateurs et la dynamique du mimétisme. Les Heliconiini séquestrent des glucosides cyanogènes au stade larvaire à partir des feuilles de passiflores (Passifloraceae) mais synthétisent aussi de façon endogène ces métabolites secondaires tout au long de leur vie. En revanche, chez les Ithomiini, les défenses chimiques proviennent d’alcaloïdes pyrrolizidiniques acquis principalement au stade adulte à partir de fleurs ou végétaux en décomposition de la famille des Asteraceae, des Boraginaceae et des Apocynaceae. Les origines végétales variées et la possibilité d'une voie endogène des défenses chimiques ainsi que la différence dans les stades développementaux où elles sont acquises (chenille ou adulte) suggèrent une évolution différente des défenses chimiques dans ces deux tribus. Au cours de cette thèse j’ai pu montrer que la considération du mimétisme Müllerien est cruciale pour l’implémentation de modèle théorique visant à comprendre les boucles de rétroaction entre mimétisme, aposématisme et spécialisation sur les plantes hôtes. L’analyse des variations qualitatives et quantitatives des glucosides cyanogènes d’Heliconiini sauvages a mis l’accent sur l’influence des relations phylogénétiques mais aussi de facteurs écologiques : interaction mimétique, spécialisation à la plante hôte et micro-habitat, sur l’évolution des défenses chimiques. Elever des Heliconiini en conditions contrôlées précisa les variations des défenses chimiques au cours du développement et le contrôle génétique sur les glucosides cyanogènes synthétisés. Les papillons de ces deux tribus peuvent séquestrer un très grand panel de molécules candidates aux vues de la diversité des molécules produites par les plantes. Pourtant, la diversité des molécules de défenses connues des Heliconiini est assez restreinte contrairement à celle des Ithomiini. En exploitant des techniques de chimie analytique j’ai pu explorer la diversité des glucosides cyanogènes des Heliconiini et des alcaloïdes pyrrolizidiniques des Ithomiini pour tenter de découvrir de nouvelles molécules de défenses. La combinaison d’approches méthodologiques : de modélisation, de chromatographie liquide couplée à la spectrométrie de masse en tandem, de signal phylogénétique, d’élevage de papillon, d’imagerie par spectrométrie de masse et de réseau moléculaire a permis d’explorer des questions évolutives en alliant biologie, chimie des substances naturelles et phylogénie.
... Depending on the type of secretion, plants have adopted different strategies of storage leading to various trichome morphologies (Tissier et al., 2017). Nonvolatile sticky compounds are produced by capitate trichomes and directly exuded out of the glandular cells at the tip through the cuticle which is more permeable in this zone (Tissier, 2012;Fich et al., 2020). Volatile compounds are stored either in a subcuticular storage space located above the secretory cells, as is the case for peltate and biseriate trichomes, or in between the cells, as is the case for schizogenous trichomes (Tissier et al., 2017;Schuurink & Tissier, 2020). ...
Trichomes and cuticles are key protective epidermal specializations. This review highlights the genetic interplay existing between trichome and cuticle formation in a variety of species. Controlling trichome development, the biosynthesis of trichome‐derived specialized metabolites as well as cuticle biosynthesis and deposition can be viewed as different aspects of a common defensive strategy adopted by plants to protect themselves from environmental stresses. Existence of such interplay is based on the mining of published transcriptomic data as well as on phenotypic observations in trichome or cuticle mutants where the morphology of both structures often appear to be concomitantly altered. Given the existence of several trichome developmental pathways depending on the plant species and the types of trichomes, genetic interactions between cuticle formation and trichome development are complex to decipher and not easy to generalize. Based on our review of the literature, a schematic overview of the gene network mediating this transcriptional interplay is presented for two model plant species: Arabidopsis thaliana and Solanum lycopersicum. In addition to fundamental new insights on the regulation of these processes, identifying key transcriptional switches controlling both processes could also facilitate more applied investigations aiming at improving much desired agronomical traits in plants.
... Peltate GTs accumulate metabolites under a thick cuticle that ruptures upon mechanical stimulation, for example in contact with an insect 46,48 . They are known to produce volatile monoterpenes and were previously shown to contain sclareol 25,45 . ...
Sclareol, an antifungal specialized metabolite produced by clary sage, Salvia sclarea, is the starting plant natural molecule used for the hemisynthesis of the perfume ingredient ambroxide. Sclareol is mainly produced in clary sage flower calyces; however, the cellular localization of the sclareol biosynthesis remains unknown. To elucidate the site of sclareol biosynthesis, we analyzed its spatial distribution in the clary sage calyx epidermis using laser desorption/ionization mass spectrometry imaging (LDI-FTICR-MSI) and investigated the expression profile of sclareol biosynthesis genes in isolated glandular trichomes (GTs). We showed that sclareol specifically accumulates in GTs' gland cells in which sclareol biosynthesis genes are strongly expressed. We next isolated a glabrous beardless mutant and demonstrate that more than 90% of the sclareol is produced by the large capitate GTs. Feeding experiments, using 1-13C-glucose, and specific enzyme inhibitors further revealed that the methylerythritol-phosphate (MEP) biosynthetic pathway is the main source of isopentenyl diphosphate (IPP) precursor used for the biosynthesis of sclareol. Our findings demonstrate that sclareol is an MEP-derived diterpene produced by large capitate GTs in clary sage emphasing the role of GTs as biofactories dedicated to the production of specialized metabolites.
... Domatesin yabani akrabaları, böceklere dayanıklılık için gen kaynakları olarak kullanılmıştır (Oliveira ve ark., 2009). Böcek direnci genellikle trikom (bitki üzerine kaplayan tüyler) tipleri ve yoğunluklarının varlığı ile ilişkilidir (Tissier, 2012). Trikomlar, epidermis üzerinde özelleşmiş yapılardır (Glas ve ark., 2012) ve uç kısımlarında kokulu sıvı bulunduran bir glandüler baş yapısının varlığına / yokluğuna bağlı olarak glandüler (tip I, IV, VI ve VII) veya glandüler olmayan trikomlar (tip II, III, V) olarak sınıflandırılırlar (Channarayappa ve ark., 1992). ...
Domates (Solanum lycopersicum L., syn. Lycopersicon esculentum Mill.), 12 çift kromozom içeren (2n = 24) ve kendine döllenen diploid bir türdür. Biber, patlıcan ve patates gibi dünya genelinde yüksek ölçekte tarımı yapılan diğer önemli sebze türleri ile birlikte Solanaceae familyasında yer almaktadır. Domates zengin bir vitamin (A ve C), mineral (Ca, P ve Fe) kaynağı olduğu gibi; karotenoidler ve özellikle likopen içeriği nedeniyle kanser ve kalp hastalıklarına karşı güçlü bir antioksidandır. Domatesin genel ıslah hedefleri meyve verimi, meyve kalitesi ve hastalıklara ve zararlılara dayanıklılık, farklı yetiştirme dönemlerine uyum sağlamak üzere abiyotik streslere toleranstır. Domateste tür içi melezlemelerin yanı sıra türler arası melezlemeler sayesinde genetik varyasyonun artırılması için günümüze kadar önemli aşamalar kaydedilmiştir. Geleneksel ıslah yöntemleriyle bazı biyolojik engellere takılmak söz konusu olduğundan, doku kültürü yöntemleri ve moleküler markır teknolojileri devreye sokularak ıslah çalışmalarına hız ve ivme katılmıştır. Embriyo kültürü, in vitro hücre ve bitki seçimi, somatik hibridizasyon uygulamaları birçok çözümler sunmuştur. Bununla birlikte domates, hâlâ katlanmış haploidi yönteminin etkin olarak ıslah çalışmalarına entegre edilemediği bir türdür. Bu konuda mümkün olan en kullanışlı yöntemin ıslah programlarına dahil edilmesi ve yerli çeşit ıslahında bu teknikten yararlanma yollarının geliştirilmesi gereklidir.
F1 hibrit çeşitlerin en yaygın kullanıldığı sebze türlerinin başında gelen domateste hibrit çeşitlerin geliştirilmesinde maliyeti azaltacak erkek kısırlığı gibi özelliklerin pratik ve güvenilir şekilde kullanımını geliştirmek, QTL bölgelerinin ve genlerin markırlarla ucuz ve kolaylıkla tarayabilmek, bunun için gereken yerli teknoloji/altyapıyı kurmak, ıslah sürecini kısaltacak doku kültürü yöntemlerinde olduğu gibi önem taşımaktadır.
Son yıllarda geliştirilen CRSPR/Cas9 teknolojisi, hedef odaklı, arzu edilen gen veya DNA lokuslarında in vivo olarak yüksek doğrulukla kırıklar oluşturabilen bir tekniktir. Bu teknoloji, bitki ıslahında kullanılacak etkili ve spesifik mutasyonların oluşturulmasına olanak tanımaktadır. Islah programlarını kısaltması, kolaylaştırarak maliyeti azaltması, CRSPR-Cas9 teknolojisinin avantajları arasındadır. Moleküler markırlara (belirteçlere) dayalı seleksiyon (MAS) dahil olmak üzere geleneksel ıslah ve çağdaş bitki biyoteknolojisi yöntemlerinin bir arada uygulanması durumunda domates ıslahının hız kazanacağı öngörülmektedir.
... Moreover, the ultrastructure of the cells undergoes dramatic cytological reorganization in the course of trichome development with consequences for the metabolic activity and function. These observations should help plan future experiments for the investigation of metabolic pathways in trichomes [25][26][27]. ...
Sunflower and related taxa are known to possess a characteristic type of multicellular uniseriate trichome which produces sesquiterpenes and flavonoids of yet unknown function for this plant. Contrary to the metabolic profile, the cytological development and ultrastructural rearrangements during the biosynthetic activity of the trichome have not been studied in detail so far. Light, fluorescence and transmission electron microscopy were employed to investigate the functional structure of different trichome cells and their subcellular compartmentation in the pre-secretory, secretory and post-secretory phase. It was shown that the trichome was composed of four cell types, forming the trichome basis with a basal and a stalk cell, a variable number (mostly from five to eight) of barrel-shaped glandular cells and the tip consisting of a dome-shaped apical cell. Metabolic activity started at the trichome tip sometimes accompanied by the formation of small subcuticular cavities at the apical cell. Subsequently, metabolic activity progressed downwards in the upper glandular cells. Cells involved in the secretory process showed disintegration of the subcellular compartments and lost vitality in parallel to deposition of fluorescent and brownish metabolites. The subcuticular cavities usually collapsed in the early secretory stage, whereas the colored depositions remained in cells of senescent hairs.
... Therefore, our results point at a role for additional genetic components that have not been introgressed. It has been shown that poor terpene producing genotypes also have drastically reduced transcript levels for key steps in the terpene biosynthesis pathway (Tissier 2012), suggesting that the transference of additional components enhancing zFPS and SBS expression could increase the content of sesquiterpenes in MT-Sst2 even further. So far, only a few transcription factors have been shown to be involved in the regulation of terpene pathways in tomato (Spyropoulou et al. 2014;Xu et al. 2018c), though these were not implicated as positive regulators of zFPS or SBS specifically. ...
Main conclusion
Cultivated tomatoes harboring the plastid-derived sesquiterpenes from S. habrochaites have altered type-VI trichome morphology and unveil additional genetic components necessary for piercing-sucking pest resistance.
Abstract
Arthropod resistance in the tomato wild relative Solanum habrochaites LA1777 is linked to specific sesquiterpene biosynthesis. The Sesquiterpene synthase 2 ( SsT2 ) gene cluster on LA1777 chromosome 8 controls plastid-derived sesquiterpene synthesis. The main genes at SsT2 are Z-prenyltransferase (zFPS) and Santalene and Bergamotene Synthase ( SBS ), which produce α-santalene, β-bergamotene, and α-bergamotene in LA1777 round-shaped type-VI glandular trichomes. Cultivated tomatoes have mushroom-shaped type-VI trichomes with much smaller glands that contain low levels of monoterpenes and cytosolic-derived sesquiterpenes, not presenting the same pest resistance as in LA1777. We successfully transferred zFPS and SBS from LA1777 to cultivated tomato (cv. Micro-Tom, MT) by a backcrossing approach. The trichomes of the MT- Sst2 introgressed line produced high levels of the plastid-derived sesquiterpenes. The type-VI trichome internal storage-cavity size increased in MT- Sst2 , probably as an effect of the increased amount of sesquiterpenes, although it was not enough to mimic the round-shaped LA1777 trichomes. The presence of high amounts of plastid-derived sesquiterpenes was also not sufficient to confer resistance to various tomato piercing-sucking pests, indicating that the effect of the sesquiterpenes found in the wild S. habrochaites can be insect specific. Our results provide for a better understanding of the morphology of S. habrochaites type-VI trichomes and paves the way to obtain insect-resistant tomatoes.
... Type VI glandular trichomes are the key site for the biosynthesis and storage of volatile terpenes (Tissier, 2012;Lange and Turner, 2013;Schuurink and Tissier, 2019). To address the effects of SlSCL3 on trichome development, we analyzed the density and morphology of type VI glandular trichomes on the surface of plants. ...
Tomato (Solanum lycopersicum L.) type VI glandular trichomes that occur on the surface of leaves, stems, young fruits and flowers produce and store a blend of volatile monoterpenes and sesquiterpenes. These compounds play important roles in the interaction with pathogens and herbivorous insects. Although the function of terpene synthases in the biosynthesis of volatile terpenes in tomato has been comprehensively investigated, the deciphering of their transcriptional regulation is only emerging. We selected transcription factors that are over‐expressed in trichomes based on existing transcriptome data and silenced them individually by virus induced gene silencing. Of these, SlSCL3, a scarecrow‐like (SCL) subfamily transcription factor, led to a significant decrease of volatile terpene content and expression of the corresponding TPS genes when its transcription level was down‐regulated. Overexpression of SlSCL3 increased both the volatile terpene contents and glandular trichome size dramatically, whereas its homozygous mutants showed reduced terpene biosynthesis. However, its heterozygous mutants showed significantly elevated volatile terpene contents and enlarged glandular trichomes as well, which were similar to those of the overexpression plants. SlSCL3 modulates the expression of terpene biosynthetic pathway genes by transcriptional activation, but neither direct protein‐DNA binding, nor interaction with known regulators was observed. Moreover, transcript levels of the endogenous copy of SlSCL3 were decreased in the overexpression plants but increased in the heterozygous and homozygous mutants, suggesting feed‐back repression of its own promoter. Taken together, our results provide new insights into the role of SlSCL3 in the complex regulation of volatile terpene biosynthesis and glandular trichome development in tomato.
... In C. sativa L., high THC-containing strains had a bigger resin head on their glandular trichomes than in low-THC industrial hemp (Small and Naraine, 2016). Capitatestalked glandular trichomes have more secretory disc cells than other plants and secrete specialized metabolites in the subcuticular oil storage cavity, instead of through pores formed in the cuticle (Tissier, 2012;Huchelmann et al., 2017). Excretory cells secrete a resin in a subcuticular cavity (Small and Naraine, 2016). ...
Differences in cannabis (Cannabis sativa L.) plant chemistry between strains are influenced by genetics, plant growth and development, in addition to environmental conditions such as abiotic and biotic stress. Resulting secondary metabolite profiles are further altered post-harvest by drying and extraction, all of which present sizable challenges to industrial scale producers of pharmaceutical grade products in Canada and elsewhere. Consistent quantity and quality of cannabis extracts, demonstrated by preferred cannabinoid ratios and other secondary metabolites present are important, particularly as the list of therapeutic uses for medical cannabis is expanding. As more countries contemplate the legalization and licensure of medical cannabis, the number of cannabis extraction and testing laboratories is increasing to keep up with demand. However, it is not always known what standards are adhered to, resulting in numerous non-validated methods. In this review, a summary of cannabis chemistry and biosynthesis of secondary compounds is provided, and post-harvest processing practices occurring along the cannabis product value chain that might affect cannabis phytochemistry, potency and volatility are presented. An emphasis is placed on improved drying and extraction methods for plant material suitable for the cannabis industry. Finally, new approaches to secondary metabolite profiling for cannabis products are compared.
... As most of the secondary metabolites are synthesized within trichomes, so increasing trichome density or manuplating trichome developmental genes will also play an important role in enhancing metabolite biosynthesis within planta. Much progress has been made to understand the development of non-glandular trichomes, but little is known about the mechanisms underlying the development of glandular trichomes (Tissier 2012). Different transcription factors have been found to control trichome development in different plants. ...
Trichomes are specialized structures derived from epidermal cells. Apart from providing protection to plants, trichomes are source of medicinally important compounds. Although genes involved in initiation and patterning of trichomes have been characterized in some plants like Arabidopsis thaliana, but our knowledge about the development of these trichomes is still limited. Recent studies confirm the role of different transcription factors in trichome development of plants. In model plant Arabidopsis different transcription factor families have been studied in detail. It has been found that transcription factors like bHLH, R2R3 MYB form an activation complex with TTG1 which initiate trichome formation while as R3 MYB type transcription factors inhibit the formation of activation complex. The activation complex acts as a major trigger in the regulation of trichome development. It would be interesting to know whether such activation complex occurs in other plants like Nicotiana tobaccum, Lycopersicum esculentum, Artemisia annua etc. In this review, we focus on recent updates on transcriptional regulation of trichome development and conservation of these regulators in various species of pharmacologically and economically important plants. We have briefly discussed the cross talk of transcription factors with different hormones during trichome development. Further we have elaborated fundamental research ideologies on trichome development and translation of this research from model plant to plants of industrial interest.
... In C. sativa L., high THC-containing strains had a bigger resin head on their glandular trichomes than in low-THC industrial hemp (Small and Naraine, 2016). Capitatestalked glandular trichomes have more secretory disc cells than other plants and secrete specialized metabolites in the subcuticular oil storage cavity, instead of through pores formed in the cuticle (Tissier, 2012;Huchelmann et al., 2017). Excretory cells secrete a resin in a subcuticular cavity (Small and Naraine, 2016). ...
Cannabis sativa L. is cultivated for its secondary metabolites, of which the cannabinoids have documented health benefits and growing pharmaceutical potential. Recent legal cannabis production in North America and Europe has been accompanied by an increase in reported findings for optimization of naturally occurring and synthetic cannabinoid production. Of the many environmental cues that can be manipulated during plant growth in controlled environments, cannabis cultivation with different lighting spectra indicates differential production and accumulation of medically important cannabinoids, including Δ ⁹ -tetrahydrocannabinol (Δ ⁹ -THC), cannabidiol (CBD), and cannabigerol (CBG), as well as terpenes and flavonoids. Ultraviolet (UV) radiation shows potential in stimulating cannabinoid biosynthesis in cannabis trichomes and pre-harvest or post-harvest UV treatment merits further exploration to determine if plant secondary metabolite accumulation could be enhanced in this manner. Visible LED light can augment THC and terpene accumulation, but not CBD. Well-designed experiments with light wavelengths other than blue and red light will provide more insight into light-dependent regulatory and molecular pathways in cannabis. Lighting strategies such as subcanopy lighting and varied light spectra at different developmental stages can lower energy consumption and optimize cannabis PSM production. Although evidence demonstrates that secondary metabolites in cannabis may be modulated by the light spectrum like other plant species, several questions remain for cannabinoid production pathways in this fast-paced and growing industry. In summarizing recent research progress on light spectra and secondary metabolites in cannabis, along with pertinent light responses in model plant species, future research directions are presented.
... Although trichomes may exhibit tremendous diversity between plant species and also within species or even individual plants (Tissier 2012), we found only one type of capitate glandular trichome in R. acetosella populations. The common number of four trichome head (secretory) cells in R. acetosella leaves was similar to what has been found in the congeneric species R. thyrsiflorus (Ślesak et al. 2017) and R. acetosa (personal observation). ...
The pseudometallophyte Rumex acetosella L. occupies habitats with normal and high soil concentrations of zinc (Zn), lead (Pb), and copper (Cu). It remains unclear if the plants respond to the toxic metals by altering their morphology and increasing the resilience of their cells. We compared plants growing on soils contaminated with Zn/Pb (populations Terézia, Lintich), or Cu (populations Špania Dolina, Staré Hory), with those from non-contaminated soil (Dúbravka) in Slovakia, and analysed leaf structure, physiology, and metal contents by light and electron microscopy, element localization by energy-dispersive X-ray analysis (EDX) in scanning electron microscope, and by specific fluorescence dyes. In control population, the epidermis of the amphistomatic leaves of R. acetosella contained capitate glandular trichomes, consisting of four head (secretory), two stalk, and two basal cells. The ultrastructure of secretory cells revealed fine wall ingrowths bordered by plasma membrane protruding into the cytoplasm. The metallicolous populations had higher contents of Zn and Cu in the epidermal and glandular cells, and a higher density of both stomata and trichomes. Extensive cell wall labyrinth was present in the trichome secretory cells. Their abnormal number and elevated metal contents might indicate effects of heavy metals, especially of Cu, on mitosis and cell plate formation. Differences in leaf physiology were indicated by significantly higher cytoplasmic tolerance to Zn and Cu in metallicolous populations and by structural properties of glandular heads suggesting secretion of toxic metals. Our findings are suggestive of plant reactions to metal stress, which facilitate the populations to occupy the metal-contaminated sites.
... Variation is inter-and intra-specific, but may also occur within an individual, depending on leaf position and developmental stage of the plant (Chien and Sussex, 1996;Vendemiatti et al., 2017). Glandular trichomes are characterized by the ability to synthesize, store and secrete a vast array of secondary metabolites, mostly terpenoids and phenylpropanoids, making them appealing platforms for biotechnological applications (Huchelmann et al., 2017;Tissier, 2012). ...
Trichomes are epidermal structures with a large variety of ecological functions and economic applications. Glandular trichomes produce a rich repertoire of secondary metabolites, whereas non-glandular trichomes create a physical barrier on the epidermis: both operate in tandem against biotic and abiotic stressors. A deeper understanding of trichome development and function would enable the breeding of more resilient crops. However, little is known about the impact of altered trichome density on leaf photosynthesis, gas exchange and energy balance. Previous work has compared multiple, closely related species differing in trichome density. Here, we analysed monogenic trichome mutants in the same tomato genetic background (Solanum lycopersicum cv. ‘Micro-Tom’). We determined growth parameters, leaf spectral properties, gas exchange and leaf temperature in the hairs absent (h), Lanata (Ln) and Woolly (Wo) trichome mutants. Shoot dry weight, leaf area, leaf spectral properties and cuticular conductance were not affected by the mutations. However, the Ln mutant showed increased carbon assimilation (A) associated with higher stomatal conductance (gs), with no differences in stomatal density or stomatal index between genotypes. Leaf temperature was furthermore reduced in Ln in the hottest, early hours of the afternoon. We show that a single monogenic mutation that modifies trichome density, a desirable trait for crop breeding, concomitantly improves leaf gas exchange and reduces leaf temperature.
Glandular secretory trichomes (GSTs) can secrete and store a variety of specific metabolites. By increasing GST density, valuable metabolites can be enhanced in terms of productivity. However, the comprehensive and detailed regulatory network of GST initiation still needs further investigation. By screening a complementary DNA (cDNA) library derived from young leaves of Artemisia annua, we identified a MADS-box transcription factor, AaSEPALLATA1 (AaSEP1), positively regulates GST initiation. Overexpression of AaSEP1 in A. annua substantially increased GST density and artemisinin content. The HOMEODOMAIN PROTEIN 1 (AaHD1)-AaMYB16 regulatory network regulates GST initiation via the JA signaling pathway. In this study, AaSEP1 enhanced the function of AaHD1 activation on downstream GST initiation gene GLANDULAR TRICHOME-SPECIFIC WRKY 2 (AaGSW2) through interaction with AaMYB16. Moreover, AaSEP1 interacted with the jasmonate ZIM-domain 8 (AaJAZ8) and served as an important factor in JA-mediated GST initiation. We also found that AaSEP1 interacted with CONSTITUTIVE PHOTOMORPHOGENIC 1 (AaCOP1), a major repressor of light signaling. In this study, we identified a MADS-box transcription factor that is induced by JA and light signaling and that promotes the initiation of GST in A. annua.
Hair-like structures are shared by most living organisms. The hairs on plant surfaces, commonly referred to as trichomes, form diverse types to sense and protect against various stresses. However, it is unclear how trichomes differentiate into highly variable forms. Here, we show that a homeodomain leucine zipper (HD-ZIP) transcription factor named Woolly controls the fates of distinct trichomes in tomato via a dosage-dependent mechanism. The autocatalytic reinforcement of Woolly is counteracted by an autoregulatory negative feedback loop, creating a circuit with a high or low Woolly level. This biases the transcriptional activation of separate antagonistic cascades that lead to different trichome types. Our results identify the developmental switch of trichome formation and provide mechanistic insights into the progressive fate specification in plants, as well as a path to enhancing plant stress resistance and the production of beneficial chemicals.
Coleus amboinicus Lour. is a perennial shrub frequently used in folk medicine for the treatment of cough, sore throat and other respiratory disorders. Although being one of the best chemically documented Lamiaceae species, little is known about the glandular trichomes that secrete essential oils in this species and the effects of leaf development on the volatile composition. We characterized herein the different types of glandular trichomes of C. amboinicus and, using headspace solid phase microextraction coupled to gas chromatography (HS-SPME-GC–MS), we evaluated the chemical composition of leaves in different stages of development. Two main categories of glandular trichomes were observed: short-stalked and long-stalked capitate trichomes, two types of each were described whilst no peltate trichome was observed. The chromatographic analysis showed that carvacrol was the main component of the volatile profile, followed by o-cymene, γ-terpinene, (E)-caryophyllene and α-trans-bergamotene. The proportion of mono- and sesquiterpenes changed as the leaves expanded, every volatile component varied significantly (p < 0.05) such as an increase in carvacrol area percentage and decrease in (E)-caryophyllene and γ-terpinene, suggesting that expanding leaves are chemically distinct to the fully expanded ones. These results provide new insights about C. amboinicus morphoanatomy and phytochemistry, further research is required to establish the effects of leaf developmental stage on volatile composition and glandular trichome distribution in other Lamiaceae species.
1. Herbivore densities can be regulated by bottom‐up and top‐down forces such as plant defences and natural enemies, respectively. These forces can interact with each other to increase plant protection against herbivores, however, how much complementarity exists between bottom‐up and top‐down forces still remains to be fully elucidated. Particularly, because plant defences can hinder natural enemies, how these interactions affect herbivore performance and dynamics remains elusive. 2. To address this topic, we performed laboratory and greenhouse bioassays with herbivorous mite pests and predatory mites on mutant tomato plants that lack defensive hairs on stems and leaves. Particularly, we investigated the behaviour and population dynamics of different phytophagous mite species in the absence and presence of predatory mites. 3. We show that predatory mites do not only perform better on tomatoes lacking defensive hairs but that they can also suppress herbivore densities better and faster on these hairless plants. Hence, top‐down control of herbivores by natural enemies more than compensated the reduced bottom‐up herbivore control by plant defences. 4. Our results lead to the counter‐intuitive insight that removing, instead of introducing, plant defence traits can result in superior protection against important pests through biological control.
Trichomes, which are classified as glandular or non-glandular, are hair-like epidermal structures that are present on aerial parts of most plant species. Glandular secretory trichomes (GSTs) have the capacity to secrete and store specialized metabolites, which are widely used as natural pesticides, food additives, fragrance ingredients or pharmaceuticals. Isolating individual trichomes is an essential way for identifying trichome-specific gene functions and discovering novel metabolites. However, the isolation of trichomes is difficult and time-consuming. Here, we report a method to isolate the GSTs from leaf epidermis dispense with fixation using laser capture microdissection (LCM). In this study, 150 GSTs were captured efficiently from Artemisia annua leaves and enriched for artemisinin measurement. UPLC analysis of microdissected samples indicated specific accumulation of secondary metabolites could be detected from a small number of GSTs. In addition, qRT-PCR revealed that the GST-specific structural genes involved in artemisinin biosynthesis pathway were highly expressed in GSTs. Taken together, we developed an efficient method to collect comparatively pure GSTs from unfixed leaved, so that the metabolites were relatively obtained intact. This method can be implemented in metabolomics research of purely specific plant cell populations and has the potential to discover novel secondary metabolites.
Nepeta tenuifolia is a medicinal plant rich in terpenoids and flavonoids with antiviral, immunoregulatory, and anti-inflammatory activities. The peltate glandular trichome (PGT) is a multicellular structure considered to be the primary storage organ for monoterpenes; it may serve as an ideal model for studying cell differentiation and the development of glandular trichomes (GTs). The genes that regulate the development of GTs have not yet been well studied. In this study, we identified NtMIXTA1, a GT development-associated gene from the R2R3 MYB SBG9 family. NtMIXTA1 overexpression in tobacco resulted in the production of longer and denser GTs. Virus-induced gene silencing of NtMIXTA1 resulted in lower PGT density, a significant reduction in monoterpene concentration, and the decreased expression of genes related to monoterpene biosynthesis. Comparative transcriptome and widely targeted metabolic analyses revealed that silencing NtMIXTA1 significantly influenced the expression of genes, and the production of metabolites involved in the biosynthesis of terpenoids, flavonoids, and lipids. This study provides a solid foundation describing a mechanism underlying the regulation of GT development. In addition, this study further deepens our understanding of the regulatory networks involved in GT development and GT development-associated metabolite flux, as well as provides valuable reference data for studying plants with a high medicinal value without genetic transformation.
Background
Mentha canadensis L. has important economic value for the production of essential oils, which are synthesised, secreted and stored in peltate glandular trichomes. As a typical multicellular secretory trichome, glandular trichomes are important biological factories for the synthesis of some specialised metabolites. However, little is known about the molecular mechanism of glandular trichome development in M. canadensis.
Results
In this study, the R2R3-MYB transcription factor gene McMIXTA was isolated to investigate its function in glandular trichome development. Bioinformatics analysis indicated that McMIXTA belonged to the subgroup 9 R2R3-MYB, with a R2R3 DNA-binding domain and conserved subgroup 9 motifs. A subcellular localisation assay indicated that McMIXTA was localised in the nucleus. Transactivation analysis indicated that McMIXTA was a positive regulator, with transactivation regions located between positions N253 and N307. Yeast two-hybrid and bimolecular fluorescence complementation assays showed that McMIXTA formed a complex with McHD-Zip3, a trichome development-related HD-ZIP IV transcription factor. Overexpression of McMIXTA in Mentha × piperita L. caused an increase in peltate glandular trichomes density of approximately 25% on the leaf abaxial surface.
Conclusions
Our results demonstrated that the subgroup 9 R2R3-MYB transcription factor McMIXTA has a positive effect on regulating peltate glandular trichome development and the MIXTA/HD-ZIP IV complexes might be conserved regulators for glandular trichome initiation. These results provide useful information for revealing the regulatory mechanism of multicellular glandular trichome development.
Some basil varieties are able to convert the phenylpropenes chavicol and eugenol to methylchavicol and methyleugenol, respectively. Chavicol O-methyltransferase (CVOMT) and eugenol O-methyltransferase (EOMT) cDNAs were isolated from the sweet basil variety EMX-1 using a biochemical genomics approach. These cDNAs encode proteins that are 90% identical to each other and very similar to several isoflavone O-methyltransferases such as IOMT, which catalyzes the 4′-O-methylation of 2,7,4′-trihydroxyisoflavanone. On the other hand, CVOMT1 and EOMT1 are related only distantly to (iso)eugenol OMT from Clarkia breweri, indicating that the eugenol O-methylating enzymes in basil and C. breweri evolved independently. Transcripts for CVOMT1 and EOMT1 were highly expressed in the peltate glandular trichomes on the surface of the young basil leaves. The CVOMT1 and EOMT1 cDNAs were expressed in Escherichia coli, and active proteins were produced. CVOMT1 catalyzed the O-methylation of chavicol, and EOMT1 also catalyzed the O-methylation of chavicol with equal efficiency to that of CVOMT1, but it was much more efficient in O-methylating eugenol. Molecular modeling, based on the crystal structure of IOMT, suggested that a single amino acid difference was responsible for the difference in substrate discrimination between CVOMT1 and EOMT1. This prediction was confirmed by site-directed mutagenesis, in which the appropriate mutants of CVOMT1 (F260S) and EOMT1 (S261F) were produced that exhibited the opposite substrate preference relative to the respective native enzyme.
Mentha longifolia, a wild relative of the polyploid, cultivated Mentha (mint) species, was evaluated as a potential model system for genetic research relevant to the cultivated mints. Fourteen Mentha longifolia accessions maintained by the US Department of Agriculture (USDA), Agricultural Research Service, National Clonal Germplasm Repository (NCGR), were highly diverse with respect to geographic origin, oil composition, verticillium wilt resistance, aspects of morphology, and molecular marker polymorphism. Accession CMEN 584 was the only carvone chemotype, while CMEN 682 was the only accession with high menthol content. Trans-piperitone oxide was the primary oil component of accessions CMEN 17 and CMEN 18, while pulegone was most abundant in CMEN 20, CMEN 500, CMEN 501, and CMEN 585. Four accessions - CMEN 585, CMEN 17, CMEN 501, and CMEN 81 - were consistently resistant to verticillium wilt, while CMEN 584 and CMEN 516 were highly susceptible. Pairwise similarity coefficients were calculated and a UPGMA (unweighted pair-group analysis) tree was constructed on the basis of 63 informative randomly amplified polymorphic DNA (RAPD) marker bands. CMEN 585 and CMEN 584 shared the greatest number of bands (16), and formed a distinct cluster in the UPGMA tree. Seven pairs of accessions had no bands in common, emphasizing the high degree of molecular diversity represented by these accessions. The favorable features of diploid (2n = 2x = 24) genome constitution, comparatively small genome size (400 to 500 Mb), self-fertility, fecundity, and diversity with respect to economically relevant traits, contribute to M. longifolia's potential usefulness as a model system for the cultivated mints. As a perennial species amenable to vegetative propagation, M. longifolia's spectrum of susceptibility/resistance to an important vascular wilt disease encourages its further evaluation as a system for broader studies of plant-microbe interactions and disease resistance mechanisms.
Theobjective of this work was to evaluate the feasibility of selection for higher glandular trichome densities, as an indirect criterion of selection for increasing repellence to spider mites Tetranychus urticae, in tomato populations derived from an interspecific cross between Lycopersicon esculentum x L.hirsutum var.glabratum PI134417. Trichome densities were evaluated in 19genotypes, including 12from advanced backcross populations, derived from the original cross L.esculentum x L.hirsutum var.glabratum PI134417. Counts were made both on the adaxial and abaxial leaf surfaces, and trichomes were classified into glandular types IV and VI, other glandular types (types I+VII), and nonglandular types. Mite repellence was measured by distances walked by mites onto the tomato leaf surface after 20, 40 and 60min. Spider mite repellence biotests indicated that higher densities of glandular trichomes (especially type VI) decreased the distances walked by the mites onto the tomato leaf surface. Selection of plants with higher densities of glandular trichomes can be an efficient criterion to obtain tomato genotypes with higher resistance (repellence) to spider mites.
Limitations in the supply of the antimalarial compound artemisinin from Artemisia annua L. have led to an interest in understanding its biosynthesis and enhancing its production. Recent biochemical and molecular genetic data have implicated dihydroartemisinic aldehyde as a precursor to the corresponding acid, which is then converted to artemisinin. Thus, it is important to understand the enzyme or enzymes involved in dihydroartemisinic aldehyde oxidation. Given its activity on artemisinic aldehyde, the cytochrome P450 CYP71AV1 was investigated for its ability to oxidize dihydroartemisinic aldehyde. However, no net activity was detected. In a search for alternative enzymes that could catalyze the oxidation, an expressed sequence tag (EST) collection from A. annua was investigated for relevant cDNAs. This led to the isolation of a full-length cDNA encoding an aldehyde dehydrogenase homologue, named Aldh1, which is highly expressed in trichomes. Expression of the cDNA in E. coli and characterization of the purified recombinant enzyme revealed that the gene product catalyses the NAD(P)-dependent oxidation of the putative artemisinin precursors, artemisinic and dihydroartemsinic aldehydes, and a limited range of other aldehydes. The observed enzyme activity of Aldh1 and the expression pattern of the corresponding gene suggest a role in artemisinin biosynthesis in the glandular secretory trichomes of A. annua.
Plants in many genera of Iridaceae, Krameriaceae, Malpighiaceae, Orchidaceae and Scrophulariaceae possess specialised oil-secreting organs (elaiophores), and genera of Cucurbitaceae, Melastomataceae, Solanaceae, Primulaceae and Gesneriaceae may contain oil flowers, which are found most abundantly in neotropical savannas and forests. Oil flowers are visited and pollinated by highly specialist bees (Melittidae, Ctenoplectridae, Anthophoridae, Apidae), which use energy-rich floral oils in a number of ways, eg use of lipid secretions with or in place of nectar in pollen provisions for larval development, for water-resistant cell linings, and possibly for adult nutrition. Questions of co-evolved mutualism are raised.-P.J.Jarvis
The molecular genetics of carbon–carbon double bond reduction in the plant Artemisia annua L. was studied. Expressed sequence tags from this plant were investigated for sequences with similarity to known double-bond reductases. This resulted in the isolation of a cDNA, corresponding to the gene A. annua Dbr1 (Double bond reductase1), encoding a member of the medium chain dehydrogenase/reductase protein superfamily with sequence similarity to tobacco allyl alcohol dehydrogenase. Recombinant A. annua Dbr1 protein was purified from Escherischia coli and shown to catalyze the reduction of the carbon–carbon double bond of 2-alkenals. This activity included the reduction of the double bond at C11–C13 in the artemisinin precursor artemisinic aldehyde, albeit with unnatural stereochemistry. The substrate specificity, product stereochemistry, and expression pattern of A. annua Dbr1 point to its involvement in planta in the detoxification of 2-alkenals, which may be generated under oxidative stress conditions.
We present evidence that the capitate glandular trichomes of Blanzyopteris praedentata, a lianescent seed fern from the Upper Carboniferous of France, possessed a specialized, touch-sensitive mechanism that triggered the opening of the secretory cell by contact. The trichomes are interpreted as functionally similar to those of some modern flowering plants, which release a sticky exudate when touched and ruptured that functions to disable plant-feeding arthropods.
The fronds and compound tendrils of the Stephanian (Late Carboniferous) seed fern Blanzyopteris praedentata pos-sess several types of trichomes, two of which may, based on their morphology, have functioned as deterrents against herbivores. Bands of upwardly curved trichomes, occurring on the adaxial surfaces of tendrils, frond-and pinna rachides, are also known from extant plants, where they create mechanical obstacles. Other trichomes that are glan-dular occur on most parts of the foliage and tendrils and represent a different form of defence mechanism. These tri-chomes apparently possessed a touch-sensitive mechanism that opened the secretory cell when touched. They are interpreted as functionally similar to the so-called 'explosive' trichomes of certain extant Cucurbitaceae and Solan-aceae. Studies of living Oleander aphids (Aphis nerii) on Sicana odorifera (Cucurbitaceae) demonstrate the effec-tiveness of the physical component of this defence. When touched and ruptured by an aphid, the trichomes of S. odorifera rapidly release a sticky exudate, which adheres to the animal's legs; the accumulation of exudate on the legs eventually impedes the aphid. Based on these studies, hypotheses are presented on the types of animals that might have been deterred by the glandular trichomes of B. praedentata in the Late Carboniferous.
The terpenoids, or isoprenoids, are a large family of natural products that are best known as constituents of the essential
oils in plants. Because of their pleasant flavor and aromatic properties, essential oils have an economic importance in perfumery,
cosmetic, pharmaceutical and various other industries. However, expression profiles of regulatory genes in essential oil production
have not been dissected entirely, which may be an interesting topic of future research. In this report, we review recent studies
on isoprenoids biosynthesis in plants. We also discuss the progress of our recent research activities on isoprenoid studies.
Artemisinin is effective against both chloroquine-resistant and -sensitive strains of Plasmodium species. However, the low yield of artemisinin from cultivated and wild plants is a serious limitation to the commercialization
of this drug. Optimization of artemisinin yield either in vivo or in vitro is therefore highly desirable. To this end, we
have overexpressed the 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGR) gene (hmgr) from Catharanthus
roseus L. in Artemisia annua L. and analyzed its influence on artemisinin content. PCR and Southern blot analyses revealed that the transgenic plants
showed stable integration of the foreign hmgr gene. The reverse transcriptase-PCR results suggested that the hmgr was expressed at the transcriptional level in transgenic lines of Artemisia annua L., while the high-performance liquid chromatography analysis showed that artemisinin content was significantly increased
in a number of the transgenic lines. Artemisinin content in one of the A. annua transgenic lines was 38.9% higher than that in non-transgenic plants, and HMGR enzyme activity in transgenic A. annua L. was also higher than that in the non-transgenic lines.
Keywords
Artemisia
annua L.–Genetic transformation–RT-PCR–HPLC–Artemisinin
Segregation analysis between Lysopersicon esculentum (cultivated tomato) and L. hirsutum (wild form) in conjunction with positional verification by using near-isogenic lines demonstrated that biosynthesis of two structurally different classes of sesquiterpenes in these species is controlled by loci on two different chromosomes. A locus on chromosome 6, Sesquiterpene synthase1 (Sst1), was identified for which the L. esculentum allele is associated with the biosynthesis of β-caryophyllene and α-humulene. At this same locus, the L. hirsutum allele is associated with biosynthesis of germacrene B, germacrene D, and an unidentified sesquiterpene. Genomic mapping, cDNA isolation, and heterologous expression of putative sesquiterpene synthases from both L. esculentum and L. hirsutum revealed that Sst1 is composed of two gene clusters 24 centimorgans apart, Sst1-A and Sst1-B, and that only the genes in the Sst1-A cluster are responsible for accumulation of chromosome 6–associated sesquiterpenes. At a second locus, Sst2, on chromosome 8, the L. hirsutum allele specified accumulation of α-santalene, α-bergamotene, and β-bergamotene. Surprisingly, the L. esculentum allele for Sst2 is not associated with the expression of any sesquiterpenes, which suggests that cultivated tomato may have a nonfunctional allele. Sesquiterpene synthase cDNA clones on chromosome 6 do not cross-hybridize on genomic DNA gel blots with putative sesquiterpene synthases on chromosome 8, an indication that the genes in Sst1 and Sst2 are highly diverged, each being responsible for the biosynthesis of structurally different sets of sesquiterpenes.
Plants that contain high concentrations of the defense compounds of the phenylpropene class (eugenol, chavicol, and their derivatives) have been recognized since antiquity as important spices for human consumption (e.g. cloves) and have high economic value. Our understanding of the biosynthetic pathway that produces these compounds in the plant, however, has remained incomplete. Several lines of basil (Ocimum basilicum) produce volatile oils that contain essentially only one or two specific phenylpropene compounds. Like other members of the Lamiaceae, basil leaves possess on their surface two types of glandular trichomes, termed peltate and capitate glands. We demonstrate here that the volatile oil constituents eugenol and methylchavicol accumulate, respectively, in the peltate glands of basil lines SW (which produces essentially only eugenol) and EMX-1 (which produces essentially only methylchavicol). Assays for putative enzymes in the biosynthetic pathway leading to these phenylpropenes localized many of the corresponding enzyme activities almost exclusively to the peltate glands in leaves actively producing volatile oil. An analysis of an expressed sequence tag database from leaf peltate glands revealed that known genes for the phenylpropanoid pathway are expressed at very high levels in these structures, accounting for 13% of the total expressed sequence tags. An additional 14% of cDNAs encoded enzymes for the biosynthesis of S-adenosyl-methionine, an important substrate in the synthesis of many phenylpropenes. Thus, the peltate glands of basil appear to be highly specialized structures for the synthesis and storage of phenylpropenes, and serve as an excellent model system to study phenylpropene biosynthesis.
Cryofixation and conventional chemical fixation methods were employed to examine the ultrastructure of developing peltate glandular trichomes of peppermint (Mentha piperita). Our results are discussed in relation to monoterpene production and the mechanism of essential oil secretion. Peltate glands arise as epidermal protuberances (initials) that divide asymmetrically to produce a vacuolate basal cell, a stalk cell, and a cytoplasmically dense apical cell. Further divisions of the apical cell produce a peltate trichome with one basal cell, one stalk cell, and eight glandular (secretory) disc cells. Presecretory gland cells resemble meristematic cells because they contain proplastids, small vacuoles, and large nuclei. The secretory phase coincides with the separation and filling of the sub-cuticular oil storage space, the maturation of glandular disc cell leucoplasts in which monoterpene biosynthesis is known to be initiated, and the formation of extensive smooth endoplasmic reticulum at which hydroxylation steps of the monoterpene biosynthetic pathway occur. The smooth endoplasmic reticulum of the secretory cells appears to form associations with both the leucoplasts and the plasma membrane bordering the sub-cuticular oil storage cavity, often contains densely staining material, and may be involved with the transport of the monoterpene-rich secretion product. Associated changes in the ultrastructure of the secretory stage stalk cell are also described, as is the ultrastructure of the fragile post-secretory gland for which cryofixation methods are particularly well suited for the preservation of organizational integrity.
Circumstantial evidence based on ultrastructural correlation, specific labeling, and subcellular fractionation studies indicates that at least the early steps of monoterpene biosynthesis occur in plas-tids. (4S)-Limonene synthase, which is responsible for the first dedicated step of monoterpene biosynthesis in mint species, appears to be translated as a preprotein bearing a long plastidial transit peptide. Immunogold labeling using polyclonal antibodies raised to the native enzyme demonstrated the specific localization of limonene synthase to the leucoplasts of peppermint (Mentha piperita) oil gland secretory cells during the period of essential oil production. Labeling was shown to be absent from all other plastid types examined, including the basal and stalk cell plastids of the secretory phase glandular trichomes. Furthermore, in vitro translation of the preprotein and import experiments with isolated pea chloroplasts were consistent in demonstrating import of the nascent protein to the plastid stroma and proteolytic processing to the mature enzyme at this site. These experiments confirm that the leucoplastidome of the oil gland secretory cells is the exclusive location of limonene synthase, and almost certainly the preceding steps of monoterpene biosynthesis, in peppermint leaves. However, succeeding steps of monoterpene metabolism in mint appear to occur outside the leucoplasts of oil gland cells.
Engineered minichromosomes provide the ability to target transgenes to a defined insertion position for predictable expression on an independent chromosome. This technology promises to provide a means to add many genes to a synthetic chromosome in sequential manner. An additional advantage is that the multiple transgenes will not be inserted into the normal chromosomes and thus will not exhibit linkage drag when converging the transgenes to different germplasm nor will they be mutagenic. Telomere truncation coupled with the introduction of site-specific recombination cassettes has proven to be an easy method to produce minichromosomes. Telomere truncation results from the transformation of plasmids carrying a block of telomere repeats at one end. Minichromosomes consisting of little more than a centromere have been produced for B chromosomes of maize. Such small chromosomes have been studied for their meiotic behavior, which differs from normal sized chromosomes in that homologue pairing is rare or nonexistent and sister chromatid cohesion fails at meiosis I. Potential modifications of the minichromosomes that can address these issues are discussed. Minichromosomes can be recovered from transformed plants that are polyploid or that carry an additional chromosome as the preferred target for truncation. Site-specific recombination has been demonstrated to operate on these terminally located sites. By introducing normal B chromosomes into lines with engineered mini-B chromosomes, the latter can be increased in copy number, which provides the potential to augment the expression of the introduced genes. Because the vast majority of plant species have the same telomere sequence, the truncating transgenes should be effective in most plants to generate engineered minichromosomes. Such chromosomes establish the means to add or subtract multiple transgenes, multigene complexes, or whole biochemical pathways to plants to change their properties for agronomic applications or to use plants as factories for the production of foreign proteins or metabolites.
Isomers of (7S)-nepetalactone are the principal constituents of the essential oil accumulated by plants of the genus Nepeta (catmints), with the cis,cis-isomer predominating in the catmint N. racemosa. An enzyme which catalyses the NAD+-dependent oxidation of cis,cis-nepetalactol to cis,cis-nepetalactone has been identified in cell-free extracts of N. racemosa leaves. This enzyme has been partially purified and has been shown to be located within trichomes present on the surface of leaves of this species. Because glandular trichomes have been shown to be the site of accumulation of nepetalactones in N. racemosa and N. cataria, the presence of such activity within the trichomes suggests that nepetalactol may be an intermediate in the biosynthesis of nepetalactone.
The possibilities for the production of the antimalarial artemisinin by biological and chemical means are explored. These include native biosynthesis, genetic modification of Artemisia annua and other plants, engineering of microbes, total and partial chemical synthesis and combinations of the above
Artemisinin, a sesquiterpene lactone endoperoxide derived from the glandular secretory trichomes (GSTs) of Artemisia annua, provides the basis for the most effective treatments of malaria. The biology and biochemistry of GSTs of the Asteraceae and their biosynthesis of isoprenoids is reviewed. Recent efforts to understand the biosynthesis of artemisinin in A. annua GSTs are discussed in detail. This includes the development in the authors' laboratory of an expressed sequence tag (EST) approach to identifying the relevant biosynthetic genes using isolated GST as a source of mRNA. This has lead to the isolation of a cDNA encoding CYP71AV1, a multifunctional cytochrome P450 which catalyzes multiple oxidations of the sesquiterpene intermediate amorpha-4,11-diene to artemisinic acid. Further biochemical and molecular genetic work is required to elucidate the precise route from artemisinic alcohol to artemisinin and to engineer more efficient low cost production of artemisinin-based antimalarial drugs
The synthesis of nor‐Ambreinolide (8) from (‐)‐sclareol (1) was carried out by treatment with KMnO4‐Ac2O and further alkaline hydrolysis. 8 was directly transformed into (‐)‐ambrox (11) by reduction with metal borohydride in the presence of Lewis acids.
On the basis of the variability and location of the secretory tissues in the plant body, the following are suggested: (1) In relation to their surrounding environment, the secretory tissues fulfill two very important ecological functions - protection against herbivores and pathogens and attraction of pollinators. (2) The protective function preceded the function of attraction. (3) The protective secretory tissues are suggested to have expanded during the course of evolution from the leaf mesophyll outside, to the epidermis and its trichomes, and inside the plant body, to the primary and secondary phloem, and, in a few cases, also to the secondary xylem.
In jungen Drüsenschuppen ist das Cytoplasma in allen Zellen zunächst noch organisiert wie in den benachbarten Epidermiszellen. Nur das Endoplasma–Reticulum ist vermehrt und seine Zisternen erweitert. Die Vakuolen sind meistens mit einer stark osmiophilen Substanz gefüllt. Bei der Ausbildung eines gewöhnlich stark kontrastierten Subcuticularraumes gehen in den Schuppen – beginnend mit den Drüsenzellen – eine Reihe von Veränderungen vor sich, welche schließlich mit dem Absterben der Zellen enden. Es werden verschiedene Stadien dieser Veränderungen beschrieben. Der Subcuticularraum bildet sich durch Abheben der Cuticula und der verdickten Cuticularschicht von der Zelluloseschicht. An der Basis der Drüsenschuppen erweitert sich die Cuticularschicht in der Zellwand der Basalzelle allmählich, ergreift die gesamte Außenwand der Stielzelle und setzt sich auch noch bis in die peripheren Teile der Querwände zwischen den Schuppenzellen fort. Die Bedeutung dieser Cutinisierung wird diskutiert.
Summary
In young labiatous glandular trichomes the cytoplasm of all cells is first of all still organized as in neighbouring epidermis cells. Merely the endoplasmatic reticulum has been increased, and its cisternae are dilated. The vacuoles are most of the time filled with a strongly osmophilic substance. As the subcuticular space being normally strongly stained gets developed, a number of changes takes place within the labiatous glandular trichomes starting with the secretion cells. The changes are terminated by the death of the cells. Various stages of these changes are described. The subcuticular space is formed through lifting of the cuticle and the thickened cuticular layer from the cellulosic layer. At the basis of the labiatous glandular trichomes the cuticular layer is gradually widened within the cell wall of the foot cell. Then the cutinization is extended over the entire outer wall of the stalk cell and progresses even to the périphérie parts of both cross walls. The function of the cutinization is discussed.