[Show abstract][Hide abstract] ABSTRACT: While Marchantia polymorpha has been utilized as a model system to investigate fundamental biological questions for over almost two centuries, there
is renewed interest in M. polymorpha as a model genetic organism in the genomics era. Here we outline community guidelines for M. polymorpha gene and transgene nomenclature, and we anticipate that these guidelines will promote consistency and reduce both redundancy
and confusion in the scientific literature.
Full-text · Article · Dec 2015 · Plant and Cell Physiology
[Show abstract][Hide abstract] ABSTRACT: A major source of diversity in flowering plant form is the extensive variability of leaf shape and size. Leaf formation is initiated by recruitment of a handful of cells flanking the shoot apical meristem (SAM) to develop into a complex three-dimensional structure. Leaf organogenesis depends on activities of several distinct meristems that are established and spatiotemporally differentiated after the initiation of leaf primordia. Here, we review recent findings in the gene regulatory networks that orchestrate leaf meristem activities in a model plant Arabidopsis thaliana. We then discuss recent key studies investigating the natural variation in leaf morphology to understand how the gene regulatory networks modulate leaf meristems to yield a substantial diversity of leaf forms during the course of evolution.
Preview · Article · Dec 2015 · Frontiers in Plant Science
[Show abstract][Hide abstract] ABSTRACT: Visualization of nuclei in S-phase cells in tissues is important for not only cell cycle research but also developmental research because morphogenesis is usually achieved by a combination of cell proliferation and cell expansion. Recently, DNA labeling with 5-ethynyl-2′-deoxyuridine (EdU), which is an analog of thymidine, has been used to visualize nuclei in S-phase cells to assess the activity of cell proliferation during development of plants. EdU is efficiently incorporated into newly synthesized DNA, and detection of EdU is based on the covalent reaction between EdU and Alexa Fluor ® dye, which is one of useful fluorescent dyes; this allows us to use mild conditions for the assay without any DNA denaturation. This method could be easily applicable, and, indeed, has been used for various model and non-model plant species. Here, we have described a protocol developed for the detection of nuclei in S-phase cells in leaves.
[Show abstract][Hide abstract] ABSTRACT: It has been said that naturally occurring autopolyploid strains are more tolerant of biotic and/or abiotic stresses, due at least in part to the higher accumulation of secondary metabolites. Data supporting this hypothesis come from comparisons between naturally established autopolyploids and diploids; thus the high accumulation of metabolites in polyploid strains may be a secondarily acquired feature and not a direct effect of the autopolyploidy. But no detailed studies on this issue have been carried out.
Preview · Article · Aug 2015 · New Negatives in Plant Science
[Show abstract][Hide abstract] ABSTRACT: Complex morphology is an evolutionary outcome of phenotypic diversification. In some carnivorous plants, the ancestral planar leaf has been modified to form a pitcher shape. However, how leaf development was altered during evolution remains unknown. Here we show that the pitcher leaves of Sarracenia purpurea develop through cell division patterns of adaxial tissues that are distinct from those in bifacial and peltate leaves, subsequent to standard expression of adaxial and abaxial marker genes. Differences in the orientation of cell divisions in the adaxial domain cause bifacial growth in the distal region and adaxial ridge protrusion in the middle region. These different growth patterns establish pitcher morphology. A computer simulation suggests that the cell division plane is critical for the pitcher morphogenesis. Our results imply that tissue-specific changes in the orientation of cell division underlie the development of a morphologically complex leaf.
Full-text · Article · Mar 2015 · Nature Communications
[Show abstract][Hide abstract] ABSTRACT: Plant peptides play important roles in various aspects of plant growth and development. The RTFL/DVL family includes small peptides that are widely conserved among land plants. Overexpression of six RTFL genes in Arabidopsis was suggestive of their functions as negative regulators of cell proliferation and as positional cues along the longitudinal axis of the plant body
. At this time, few reports are available on RTFL paralogs in other species and the evolutionary relationship of RTFL members among land plants remains unclear. In this study, we compared and analyzed whole amino acid sequences of 188 RTFL members from 22 species among land plants and identified 73 motifs. All RTFL members could be grouped into four clades, and each clade exhibited specific motif patterns, indicative of unique evolutionary traits in the RTFL family. In agreement with this hypothesis, we analyzed two RTFL members from Oryza sativa and Arabidopsis by overexpressing them in Arabidopsis, revealing similar phenotypes suggestive of a conserved function of the RTFL family between eudicots and monocots, as well as different phenotypes and unique functions.
Full-text · Article · Feb 2015 · Journal of Plant Research
[Show abstract][Hide abstract] ABSTRACT: Morphological and molecular variation between Arundina graminifolia var. graminifolia and the dwarf variety, A. graminifolia var. revoluta, was examined to assess the validity of their taxonomic characteristics and genetic background for identification. Morphological analysis in combination with field observations indicated that A. graminifolia var. revoluta is a rheophyte form of A. graminifolia characterized by narrow leaves, whereas the other morphological characteristics described for A. graminifolia var. revoluta, such as smaller flowers and short stems, were not always accompanied by the narrower leaf phenotype. Molecular analysis based on matK sequences indicated that only partial differentiation has occurred between A. graminifolia var. graminifolia and A. graminifolia var. revoluta. Therefore, we should consider the rheophyte form an ecotype rather than a variety. Anatomical observations of the leaves revealed that the rheophyte form of A. graminifolia possessed characteristics of the rheophytes of both ferns and angiosperms, such as narrower palisade tissue cells and thinner spongy tissue cells, as well as fewer cells in the leaf-width direction and fewer mesophyll cell layers.
No preview · Article · Dec 2014 · Journal of Plant Research
[Show abstract][Hide abstract] ABSTRACT: The postembryonic development of aboveground plant organs relies on a continuous supply of cells from the shoot apical meristem. Previous studies of developmental regulation in leaves and flowers have revealed the crucial role of coordinated cell proliferation and differentiation during organogenesis. However, the importance of this coordination has not been examined in flowering stems. Very recently, we attempted to identify regulatory factors that maintain flowering stem integrity. We found that the increased cell number in clavata (clv) mutants and the decreased cell size in de-etiolated (det)3-1 resulted in flowering stems that were thicker and thinner, respectively, than in wild-type (WT) plants. Interestingly, in the cell proliferation- and cell expansion-defective double mutant clv det3-1, the flowering stems often exhibited severe cracking, resulting in exposure of their inner tissues. In this study, further quantification of the cellular phenotypes in the cotyledons and leaves revealed no differences between det3-1 and clv3 det3-1. Together, the above findings suggest that the clv3 mutation in a det3-1 background primarily affects flowering stems, while its effect on other organs is likely negligible. We propose that the coordination between cell proliferation and differentiation is not only important during leaf development, but also plays a role in the growth control of Arabidopsis flowering stems.
[Show abstract][Hide abstract] ABSTRACT: The Cayratia japonica-Cayratia tenuifolia species complex (Vitaceae) is distributed from temperate to tropical East Asia, Southeast Asia, India, and Australia. The spatiotemporal diversification history of this complex was assessed through phylogenetic and biogeographic analyses. Maximum parsimony, neighbor-joining, and maximum likelihood methods were used to analyze sequences of one nuclear (AS1) and two plastid regions (trnL-F and trnC-petN). Bayesian dating analysis was conducted to estimate the divergence times of clades. The likelihood method LAGRANGE was used to infer ancestral areas. The Asian C. japonica and C. tenuifolia should be treated as an unresolved complex, and Australian C. japonica is distinct from the Asian C. japonica-C. tenuifolia species complex and should be treated as separate taxa. The Asian C. japonica-C. tenuifolia species complex was estimated to have diverged from its closest relatives during the Late Eocene (35.1 million years ago [Ma], 95% highest posterior densities [HPD] = 23.3-47.3 Ma) and most likely first diverged in mid-continental Asia. This complex was first divided into a northern clade and a southern clade during the middle Oligocene (27.3 Ma; 95% HPD = 17.4-38.1 Ma), which is consistent with a large southeastward extrusion of the Indochina region relative to South China along the Red River. Each of the northern and southern clades then further diverged into multiple subclades through a series of dispersal and divergence events following significant geological and climatic changes in East and Southeast Asia during the Miocene. Multiple inter-lineage hybridizations among four lineages were inferred to have occurred following this diversification process, which caused some Asian lineages to be morphologically cryptic.
Full-text · Article · Jun 2014 · Molecular Phylogenetics and Evolution
[Show abstract][Hide abstract] ABSTRACT: In compound leaves, leaflet primordia are initiated directionally along the lateral sides. Our understanding of the molecular basis of leaflet initiation has improved, but the regulatory mechanisms underlying spatio-temporal patterns remain unclear. In this study, we investigated the mechanisms of acropetal (from the base to the tip) progression of leaflet initiation in Eschscholzia californica. We established an ultraviolet-laser ablation system to manipulate compound-leaf development. Local ablation at the leaflet incipient site generated leaves with asymmetric morphology. In the majority of cases, leaflets that were initiated on the ablated sides shifted apically. Finite time-course observation revealed that the timing of leaflet initiation was delayed, but the distance from the leaf tip did not decrease. These results were suggestive of the local spacing mechanism in leaflet initiation, whereby the distance from the leaf tip and adjacent pre-existing leaflet determines the position of leaflet initiation. To understand how such a local patterning mechanism generates a global pattern of successive leaflet initiation, we assessed the growth rate gradient along the apical-basal axis. Our time-course analysis revealed differential growth rates along the apical-basal axis of the leaf, which can explain the acropetal progression of leaflet initiation. We propose that a leaflet is initiated at a site where the distances from pre-existing leaflets and the leaf tip are sufficient. Furthermore, the differential growth rate may be a developmental factor underlying the directionality of leaflet initiation.
[Show abstract][Hide abstract] ABSTRACT: Mycohetetrotrophic plants lack chlorophyll and depend on mycorrhizal fungi for nutrients (Hynson et al. 2013) and are most abundant in tropical forests. Didymoplexiella Garay (Orchi-daceae, subfamily Epidendroideae, tribe Gastro-dieae, subtribe Gastrodiinae) and Didymoplexis Griff. (subtribe Gastrodiinae) are mycoheterotro-phic and closely related, differing only in the presence (Didymoplexiella) or absence (Didymo-plexis) of stelidia (Garay 1954). Didymoplexiella Garay is composed of nine species, five of which occur in Borneo (Wood & Cribb, 1994). The other species include D. denticulata Aver., described from Vietnam (Averyanov 2010), D. hainanensis X.H. Jin & S.C. Chen, described from Hainan, China (Jin et al. 2004), and D. siamensis (Rolfe ex Downie) Seidenf., which is known from Thai-land, Hainan and Taiwan, China, and Yakushi-ma, Japan (Chen et al. 2009). Didymoplexiella trichechus (J.J. Sm.) Garay was reported from Banca (Bangka) Island, Sumatra (Smith 1920) and on Mt. Talamau, Sumatra (Comber 2001), but not from outside Sumatra. Didymoplexis Griff. (subtribe Gastrodiinae) contains approximately 20 species, 3 of which: D. latilabris Schltr., D. pallens Griff, and D. striata J.J. Sm., occur on Borneo (Wood & Cribb, 1994). Recently, we (H.T. and H.O.) reported the occurrence of D. cornuta var. betung-kerihunensis Tsukaya & H.Okada in West Kalimantan, Bor-neo. Didymoplexis cornuta var. cornuta was known only from near Bogor, West Java (Smith 1925). The disjunct distribution in Java and West Kalimantan suggests that D. cornuta may also be found in other areas. During floristic studies in Central and West Kalimantan we named a new genus, several new species, and a new mycoheterotroph (Tsukaya & Short CommuniCation
[Show abstract][Hide abstract] ABSTRACT: The genus Thismia Griff. (Thismiaceae) comprises more than 45 mycoheterotrophic species (Jonker 1948; Merckx 2008; Merckx et al. 2013), including several species described within the past decade, such as T. mullarensis from Central Kalimantan (Tsukaya & Okada 2005), T. betung-kerihunensis from West Kalimantan (Tsukaya & Okada 2012a), and T. hexagona from Brunei (Dančák et al. 2013). The majority of these species appear to have been collected only once or a few times. Since mycoheterotrophs are highly dependent on the activities of both the fungi and the trees that sustain them, the richness of the myco-heterotroph flora is a good indicator of the floris-tic richness of the forests in which they occur (Merckx et al. 2013). In other words, mycohetero-trophs are easily affected by ecosystem destruction. To conserve the biodiversity of tropical forests , we need additional information on the distribution of such vulnerable mycoheterotrophs. In our floristic studies in the Kalimantan area of Borneo we found one new genus, several new species, and a new variety of mycoheterotrophs (Tsukaya & Okada 2005, 2012a, 2012b, 2013a, 2013b, Tsukaya et al. 2011). Because Kalimantan has a rich diversity of mycoheterotrophs, we compared the mycoheterotroph floras of Kali-mantan and Sabah, Borneo, starting with a botanical expedition in Maliau Basin Conservation Area, Sabah, with permission from the Maliau Basin Management Committee (YS/MBMC/ 2013/50) and Sabah Biodiversity Council [access license JKM/MBS.1000-2/2(152)]. We chose this area because Dr. Tim Utteridge, of the Royal Bo-tanic Gardens, Kew, kindly showed one of us (HT) photographs of Thismia that he took in the conservation area. We suspected the photos to represent a new species of Thismia, based on oth-A New Variety of Thismia hexagona Dančák, Hroneš, Koblová et
[Show abstract][Hide abstract] ABSTRACT: Recent accumulation of our knowledge on basic leaf development mechanisms in model angiosperm species has allowed us to pursue evolutionary development (evo/devo) studies of various kinds of leaf development. As a result, unexpected findings and clues have been unearthed aiding our understanding of the mechanisms involved in the diversity of leaf morphology, although the covered remain limited. In this review, we highlight recent findings of diversified leaf development in angiosperms.
Preview · Article · Feb 2014 · Current opinion in plant biology
[Show abstract][Hide abstract] ABSTRACT: Plant development has been evaluated at various developmental stages, from the early steps of embryogenesis to flowering. In most reports, transcription factors have been thought to play a master regulatory role in the complex networks orchestrating organogenesis. Although these efforts have increased our understanding of several major developmental pathways, our understanding of the relationships between metabolism and development remains limited. Recently, we identified a straightforward relationship linking carbohydrate metabolism and organogenesis. We found that plant development, particularly the reactivation of cell cycling after germination and the transition from heterotrophic to autotrophic growth, are highly dependent on sucrose availability. In the case of Arabidopsis thaliana, an oilseed species, we characterized the importance of cytosolic inorganic pyrophosphate hydrolysis for the success of the above transition and appropriate execution of postembryonic developmental programs. While this unprecedented and unique discovery has addressed fundamental issues concerning the biological role of the proton-pyrophosphatase (H+-PPase), it has also raised questions regarding the link between metabolism and development. Here, we summarize our present knowledge of key steps in the mobilization of storage lipids and their impact together with H+-PPase during the heterotrophic-autotrophic growth transition.
[Show abstract][Hide abstract] ABSTRACT: To gain more insight into the physiological function of nitrogen dioxide (NO2 ), we investigated the effects of exogenous NO2 on growth in Arabidopsis thaliana. Plants were grown in air without NO2 for 1 wk after sowing and then grown for 1-4 wk in air with (designated treated plants) or without (control plants) NO2 . Plants were irrigated semiweekly with a nutrient solution containing 19.7 mM nitrate and 10.3 mM ammonium. Five-week-old plants treated with 50 ppb NO2 showed a ≤ 2.8-fold increase in biomass relative to controls. Treated plants also showed early flowering. The magnitude of the effects of NO2 on leaf expansion, cell proliferation and enlargement was greater in developing than in maturing leaves. Leaf areas were 1.3-8.4 times larger on treated plants than corresponding leaves on control plants. The NO2 -induced increase in leaf size was largely attributable to cell proliferation in developing leaves, but was attributable to both cell proliferation and enlargement in maturing leaves. The expression of different sets of genes for cell proliferation and/or enlargement was induced by NO2 , but depended on the leaf developmental stage. Collectively, these results indicated that NO2 regulates organ growth by controlling cell proliferation and enlargement.
[Show abstract][Hide abstract] ABSTRACT: Ploidy level affects cell size in many organisms, and ploidy-dependent cell enlargement has been used to breed many useful organisms. However, how polyploidy affects cell size remains unknown. Previous studies have explored changes in transcriptome data caused by polyploidy, but have not been successful. The most naïve theory explaining ploidy-dependent cell enlargement is that increases in gene copy number increase the amount of protein, which in turn increases the cell volume. This hypothesis can be evaluated by examining whether any strains, mutants, or transgenics show the same cell size before and after a tetraploidization event. I performed this experiment by tetraploidizing various mutants and transgenics of Arabidopsis thaliana, which show a wide range in cell size, and found that the ploidy-dependent increase in cell volume is genetically regulated. This result is not in agreement with the theory described above.