[Show abstract][Hide abstract] ABSTRACT: Soil management affects chemical and microbiological properties of soils in ways that impact plant growth. We examined effects of amendment treatments and contrasting management treatments on chemical and microbiological soil properties and on expression of selected defense genes in laboratory-grown tomatoes (Solanum lycopersicum). Treatments imposed on a conventionally managed Maury silt loam included: compost, manure, vetch (Vicia villosa), inorganic N, and non-treated control. Non-amended, organically managed Maury soil, collected from the same location was also studied. Compost, manure, and vetch increased total organic C (TOC) and permanganate oxidizable C (POXC) in soil. Organically managed soil also had greater TOC and POXC than the control treatment. Soil N was increased by compost, manure, vetch and inorganic N treatment. Microbial communities from compost, vetch and manure treatments differed from each other and from communities in the other treatments. Defense genes: ChiB (chitinase), Osm (osmotin), and GluA (β-1,3-glucanase) were generally expressed less in plants from manure treated soil and organically managed soil. The PR1b (pathogenesis-related protein PR1b) gene was expressed more in plants from compost, inorganic N, and vetch treatments. Defense gene expression was negatively related to Gram-negative bacterial biomarkers, which were greatest in manure treated soil and organically managed soil. These results suggest that increased relative abundance of Gram-negative members of soil microbial communities in manure treated or organically managed soils may indirectly reduce the steady state expression of defense genes in plants, allowing plants to shift resources from defense to other beneficial functions such as fruit or biomass production.
[Show abstract][Hide abstract] ABSTRACT: Plant biomass from different species is heterogeneous, and this diversity in composition can be mined to identify materials of value to fuel and chemical industries. Agave produces high yields of energy-rich biomass, and the sugar-rich stem tissue has traditionally been used to make alcoholic beverages. Here, the compositions of Agave americana and Agave tequilana leaves are determined, particularly in the context of bioethanol production. Agave leaf cell wall polysaccharide content was characterized by linkage analysis, non-cellulosic polysaccharides such as pectins were observed by immuno-microscopy, and leaf juice composition was determined by liquid chromatography. Agave leaves are fruit-like-rich in moisture, soluble sugars and pectin. The dry leaf fiber was composed of crystalline cellulose (47-50% w/w) and non-cellulosic polysaccharides (16-22% w/w), and whole leaves were low in lignin (9-13% w/w). Of the dry mass of whole Agave leaves, 85-95% consisted of soluble sugars, cellulose, non-cellulosic polysaccharides, lignin, acetate, protein and minerals. Juice pressed from the Agave leaves accounted for 69% of the fresh weight and was rich in glucose and fructose. Hydrolysis of the fructan oligosaccharides doubled the amount of fermentable fructose in A. tequilana leaf juice samples and the concentration of fermentable hexose sugars was 41-48 g/L. In agricultural production systems such as the tequila making, Agave leaves are discarded as waste. Theoretically, up to 4000 L/ha/yr of bioethanol could be produced from juice extracted from waste Agave leaves. Using standard Saccharomyces cerevisiae strains to ferment Agave juice, we observed ethanol yields that were 66% of the theoretical yields. These data indicate that Agave could rival currently used bioethanol feedstocks, particularly if the fermentation organisms and conditions were adapted to suit Agave leaf composition.
PLoS ONE 08/2015; 10(8):e0135382. DOI:10.1371/journal.pone.0135382 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Lignin is an aromatic biopolymer involved in providing structural support to plant cell walls. Compared to the other cell wall polymers, i.e., cellulose and hemicelluloses, lignin has been considered a hindrance in cellulosic bioethanol production due to the complexity involved in its separation from other polymers of various biomass feedstocks. Nevertheless, lignin is a potential source of valuable aromatic chemical compounds and upgradable building blocks. Though the biosynthetic pathway of lignin has been elucidated in great detail, the random nature of the polymerization (free radical coupling) process poses challenges for its depolymerization into valuable bioproducts. The absence of specific methodologies for lignin degradation represents an important opportunity for research and development. This review highlights research development in lignin biosynthesis, lignin genetic engineering and different biological and chemical means of depolymerization used to convert lignin into biofuels and bioproducts.
[Show abstract][Hide abstract] ABSTRACT: Plants have a diverse internal microbial biota that has been shown to have an important influence on a range of plant health attributes. Although these endophytes have been found to be widely occurring, few studies have correlated agricultural production practices with endophyte community structure and function. One agricultural system that focuses on preserving and enhancing soil microbial abundance and biodiversity is organic farming, and numerous studies have shown that organically managed system have increased microbial community characteristics. Herein, the diversity and specificity of culturable bacterial endophytes were evaluated in four vegetable crops: corn, tomato, melon, and pepper grown under organic or conventional practices. Endophytic bacteria were isolated from surface-sterilized shoot, root, and seed tissues and sequence identified. A total of 336 bacterial isolates were identified, and grouped into 32 species and five phyla. Among these, 239 isolates were from organically grown plants and 97 from those grown conventionally. Although a diverse range of bacteria were documented, 186 were from the Phylum Firmicutes, representing 55% of all isolates. Using the Shannon diversity index, we observed a gradation of diversity in tissues, with shoots and roots having a similar value, and seeds having the least diversity. Importantly, endophytic microbial species abundance and diversity was significantly higher in the organically grown plants compared to those grown using conventional practices, potentially indicating that organic management practices may increase endophyte presence and diversity. The impact that these endophytes could have on plant growth and yield was evaluated by reintroducing them into tomato plants in a greenhouse environment. Of the bacterial isolates tested, 61% were found to promote tomato plant growth and 50-64% were shown to enhance biomass accumulation, illustrating their potential agroecosystem application.
[Show abstract][Hide abstract] ABSTRACT: Methiozolin is a recently introduced herbicide for selective control of Poa annua in golf greens. The objective of this study is to characterize the herbicide symptomologies exhibited by Arabidopsis thaliana treated with a range of methiozolin rates (5nM to 50uM) and to provide further insight into its potential mode of action. Treated seedlings exhibited a range of unique visual characteristics. Root growth was inhibited by methiozolin at 5 nM but this rate had little effect on chlorophyll content at 7 or 14 days after treatment (DAT). Chlorophyll content was significantly different between 7 and 14 DAT and was significantly reduced at rates greater than 5 nM at 14 DAT. Analysis of cell expansion in methiozolin treated Arabidopsis seedlings were inconsistent with the radial cell swelling symptomology indicative of cellulose biosynthesis inhibitors. Methiozolin has also been proposed to be a pigment inhibitor by inhibiting the conversion of tyrosine to 4-hydroxyphenylpyruvate by the enzyme tyrosine aminotransferase (TAT). Arabidopsis has six predicted TATs enzyme and we test five out of the six gene knockouts to screen for their increased susceptibility to methiozolin.
Weed Scince Society of America, Lexington Kentucky; 02/2015
[Show abstract][Hide abstract] ABSTRACT: In a screen for root hair morphogenesis mutants in Arabidopsis thaliana L. we identified a T-DNA insertion within a type III J-protein AtDjC17 caused altered root hair development and reduced hair length. Root hairs were observed to develop from trichoblast and atrichoblast cell files in both Atdjc17 and 35S::AtDJC17. Localization of gene expression in the root using transgenic plants expressing proAtDjC17::GUS revealed constitutive expression in stele cells. No AtDJC17 expression was observed in epidermal, endodermal, or cortical layers. To explore the contrast between gene expression in the stele and epidermal phenotype, hand cut transverse sections of Atdjc17 roots were examined showing that the endodermal and cortical cell layers displayed increased anticlinal cell divisions. Aberrant cortical cell division in Atdjc17 is proposed as causal in ectopic root hair formation via the positional cue requirement that exists between cortical and epidermal cell in hair cell fate determination. Results indicate a requirement for AtDJC17 in position-dependent cell fate determination and illustrate an intriguing requirement for molecular co-chaperone activity during root development.
[Show abstract][Hide abstract] ABSTRACT: Plant cell walls provide physical strength, regulate the passage of bio-molecules, and act as the first barrier of defense against biotic and abiotic stress. In addition to providing structural integrity, plant cell walls serve an important function in connecting cells to their extracellular environment by sensing and transducing signals to activate cellular responses, such as those that occur during pathogen infection. This mini review will summarize current experimental approaches used to study cell wall functions during plant-pathogen interactions. Focus will be paid to cell imaging, spectroscopic analyses, and metabolic profiling techniques
[Show abstract][Hide abstract] ABSTRACT: Cellulose biosynthesis is a common feature of land plants. Therefore, cellulose biosynthesis inhibitors (CBIs) have a potentially broad acting herbicidal mode of action and are also useful tools in decoding fundamental aspects of cellulose biosynthesis. Here, we characterize the herbicide indaziflam as a CBI and provide insight into its inhibitory mechanism. Indaziflam treated seedlings exhibited the CBI-like symptomologies of radial swelling and ectopic lignification. Furthermore, indaziflam inhibited the production of cellulose within < 1 hour of treatment and in a dose dependent manner. Unlike the CBI isoxaben, indaziflam had strong CBI activity in both a monocotylonous (Poa annua L.) and a dicotyledonous plant (Arabidopsis thaliana L.). Arabidopsis mutants resistant to known CBIs, isoxaben or quinoxyphen, were not cross-resistant to indaziflam suggesting a different molecular target for indaziflam. To explore this further, we monitored the distribution and mobility of fluorescently labeled CELLULOSE SYNTHASE A (CESA) proteins in living cells of Arabidopsis during indaziflam exposure. Indaziflam caused a reduction in the velocity of YFP:CESA6 particles at the plasma membrane (PM) focal plane when compared to controls. Microtubule (MT) morphology and motility were not altered after indaziflam treatment. In the hypocotyl expansion zone, indaziflam caused an atypical increase in the density of PM localized CESA particles. Interestingly, this was accompanied by a cellulose synthase interacting 1 (CSI1) independent reduction in the normal coincidence rate between MT and CESA. As a CBI, for which there is little evidence of evolved weed resistance, indaziflam represents an important addition to the action mechanisms available for weed management.
[Show abstract][Hide abstract] ABSTRACT: In plants, cellulose biosynthesis is an essential process for anisotropic growth and therefore is an ideal target for inhibition. Based on the documented utility of small-molecule inhibitors to dissect complex cellular processes we identified a cellulose biosynthesis inhibitor (CBI), named acetobixan, by bio-prospecting among compounds secreted by endophytic microorganisms. Acetobixan was identified using a drug-gene interaction screen to sift through hundreds of endophytic microbial secretions for one that caused synergistic reduction in root expansion of the leaky AtcesA6prc1-1 mutant. We then mined this microbial secretion for compounds that were differentially abundant compared with Bacilli that failed to mimic CBI action to isolate a lead pharmacophore. Analogs of this lead compound were screened for CBI activity, and the most potent analog was named acetobixan. In living Arabidopsis cells visualized by confocal microscopy, acetobixan treatment caused CESA particles localized at the plasma membrane (PM) to rapidly re-localize to cytoplasmic vesicles. Acetobixan inhibited 14C-Glc uptake into crystalline cellulose. Moreover, cortical microtubule dynamics were not disrupted by acetobixan, suggesting specific activity towards cellulose synthesis. Previous CBI resistant mutants such as ixr1-2, ixr2-1 or aegeus were not cross resistant to acetobixan indicating that acetobixan targets a different aspect of cellulose biosynthesis.
PLoS ONE 04/2014; 9(4):e95245. DOI:10.1371/journal.pone.0095245 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Morlin (7-ethoxy-4-methyl chromen-2-one) is coumarin and acts as a cellulose biosynthesis inhibitor (CBI). Plants treated with morlin display radially swollen organs and at a cellular level morlin slows down the velocity of the CESA complex and changes the rate at which microtubules grow and shrink. Despite its potential as a herbicide, the mode of action of this chemical remains poorly understood. To attempt to elucidate further details on how morlin impacts cell biology, a whole genome microarray was performed on wild type Arabidopsis treated with morlin. Transcript abundance data was screened for genes that could be influenced by the presence of the compound. Genes that were differentially expressed after morlin treatment were selected as candidate interactors. To study these further, homozygous T-DNA knockout alleles were isolated and each allele was examined for resistance or sensitivity to morlin. Employing a series of dual drug experiments combining morlin with several other CBIs was conducted to establish similarity of mechanism. These data confirm the uniqueness of morlin action mechanism.
National Conference on Undergraduate Research; 04/2014
[Show abstract][Hide abstract] ABSTRACT: Pyrolysis-GC/mass spectrometry (Py-GC/MS) and thermogravimetric analysis (TGA) was used to analyze the thermal decomposition of several endocarp sources, namely, coconut shells, walnut shells, peach pits, and olive pits, as well as their respective lignin fractions. To determine whether extraction procedures influenced pyrolysate composition and thermal decomposition processes, lignin was extracted from these feedstocks using two different procedures based on the use of formic acid and sulfuric acid (National Renewable Energy Laboratory (NREL) laboratory analytical procedure), after which the lignin-derived pyrolysates and TGA profiles were compared. Qualitative analysis of the distribution of pyrolysates provided predictive information about the structure and composition of the lignin in each sample. Results suggest that the lignin extract pyrolysates contained a different distribution of linkages and monomers in comparison to the non-extracted biomass, suggesting that lignin processing can influence bio-oil composition. Moreover, we identify the types of products obtainable by pyrolysis of these feedstocks and their lignin extracts. Heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy (HSQC NMR) and Fourier transform infrared spectroscopy (FTIR) were also used to elucidate the structures of the extracted lignin samples.
BioEnergy Research 03/2014; 8(1):1-19. DOI:10.1007/s12155-014-9526-5 · 3.54 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Natural food colorants with functional properties are of increasing interest. Prior reports indicate the chemical suitability of sorghum leaf 3-deoxyanthocyanidins as natural food colorants. Via mutagenesis assisted breeding, we isolated and characterized a sorghum variety that greatly over-accumulates 3-deoxyanthocyanidins of leaf tissue, named REDforGREEN (RG). Interestingly, RG not only caused increased 3-deoxyanthocyanidins, but also caused increased tannins, chlorogenic acid and total phenolics in the leaf tissue. Chemical composition of pigments was established through high performance liquid chromatography (HPLC) that identified luteolinidin (LUT) and apigeninidin (APG) as the main 3-deoxyanthocianidin species. Specifically, 3-deoxyanthocianidin levels were 1768 μg.g-1 LUT and 421 μg.g-1 APG in RG leaves compared with trace amounts in wild type representing 1000-fold greater in the mutant leaves. Thus RG represents a useful sorghum mutagenesis variant to develop as a functionalized food colorant.
Journal of Agricultural and Food Chemistry 01/2014; 62(6). DOI:10.1021/jf405324j · 2.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Plant cell walls are composed of highly glycosylated proteins and polysaccharides, including pectin, hemicelluloses, and cellulose, which form a complex and dynamic extracellular matrix that modulates cell expansion. The primary cell wall polysaccharide is cellulose, and it stands as the most abundant biopolymer in the world. Although genetic screens have identified a handful of genes that participate in cellulose biosynthesis, the complexity of events contributing to activation of the CesA at the plasma membrane, its motility and interaction with other polymers and proteins suggest that the list of players is far from complete. This chapter examines the use of chemical genetics to dissect and extend our understanding of cellulose biosynthesis in plants.
Plant Chemical Biology, 1st edited by Dominique Audenaert, Paul Overvoorde, 01/2014: chapter 5.1: pages 205-217; John Wiley & Sons, Inc.., ISBN: 9780470946695
[Show abstract][Hide abstract] ABSTRACT: Herein we report the fast pyrolysis of dried, ground Scenedesmus sp. at two different reactor scales. Pyrolysis was performed at 480 degrees C and 1 bar in both an isothermal spouted bed reactor and a dynamic pyrolysis-GC/MS unit, each with 2 s vapor residence times. Bio-oil products were characterized on the basis of GC-MS, simulated distillation GC, elemental analysis, calorific content and total acid number. The ratio of crude oil: char obtained from the spouted bed reactor was 3.76 by weight, the average calorific content of the oil being 18.4 MJ/kg. The average total acid number (68 mg KOH/g) was lower than typical bio-oil produced via wood pyrolysis. Simulated distillation results indicated that a significant proportion of the oil corresponded to the boiling range typical for heavy gas oil (343 degrees C-524 degrees C). Elemental analysis showed the oil contained an average of 27.6 wt.% oxygen and 8.6 wt.% nitrogen, the relatively high nitrogen content being a consequence of the high protein content of the algae. According to GC-MS data, the oil consisted of various hydrocarbons as well as oxygenated and nitrogenous species, including indoles, fatty acids and amides. Pyrolysis-GC-MS was also performed on Scenedesmus sp. in order to provide insights into the nature of the primary pyrolysis products.
Renewable Energy 12/2013; 60:625-632. DOI:10.1016/j.renene.2013.06.016 · 3.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Calmodulin N-methyltransferase (CaM KMT) is an evolutionarily conserved enzyme in eukaryotes that transfers three methyl groups to a highly conserved lysyl residue at position 115 in calmodulin (CaM). We sought to elucidate whether the methylation status of CaM plays a role in CaM-mediated signaling pathways by gene expression analyses of CaM KMT and phenotypic characterization of Arabidopsis thaliana lines wherein CaM KMT was overexpressed (OX), partially silenced, or knocked out. CaM KMT was expressed in discreet spatial and tissue-specific patterns, most notably in root tips, floral buds, stamens, apical meristems, and germinating seeds. Analysis of transgenic plants with genetic dysfunction in CaM KMT revealed a link between the methylation status of CaM and root length. Plants with suppressed CaM methylation had longer roots and CaM KMT OX lines had shorter roots than wild type (Columbia-0). CaM KMT was also found to influence the root radial developmental program. Protein microarray analyses revealed a number of proteins with specificity for methylated forms of CaM, providing candidate functional intermediates between the observed phenotypes and the target pathways. This work demonstrates that the functionality of the large CaM family in plants is fine-tuned by an overarching methylation mechanism.
The Plant Cell 11/2013; 25(11). DOI:10.1105/tpc.113.119115 · 9.34 Impact Factor