DIFFEOMORPHISM OF AFFINE CONNECTED SPACES WHICH PRESERVED RIEMANNIAN AND RICCI CURVATURE TENSORS

<p>Organ size regulation is dependent on the precise spatial and temporal regulation of cell proliferation and cell expansion. A number of transcription factors have been identified that play a key role in the determination of aerial lateral organ size, but their functional relationship to various chromatin modifiers has not been well understood. To understand how leaf size is regulated, we previously isolated the oligocellula1 (oli1) mutant of Arabidopsis thaliana that develops smaller first leaves than the wild type (WT) mainly due to a reduction in the cell number. In this study, we further characterized oli1 leaf phenotypes and identified the OLI1 gene as well as interaction partners of OLI1. Detailed characterizations of leaf development suggested that the cell proliferation rate in oli1 leaf primordia is lower than that in the WT. In addition, oli1 was associated with a slight delay of the progression from the juvenile to adult phases of leaf traits. A classical map-based approach demonstrated that OLI1 is identical to HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES15 (HOS15). HOS15/OLI1 encodes a homolog of human transducin β-like protein1 (TBL1). TBL1 forms a transcriptional repression complex with the histone deacetylase (HDAC) HDAC3 and either nuclear receptor co-repressor (N-CoR) or silencing mediator for retinoic acid and thyroid receptor (SMRT). We found that mutations in HISTONE DEACETYLASE9 (HDA9) and a switching-defective protein 3, adaptor 2, N-CoR, and transcription factor IIIB-domain protein gene, POWERDRESS (PWR), showed a small-leaf phenotype similar to oli1. In addition, hda9 and pwr did not further enhance the oli1 small-leaf phenotype, suggesting that these three genes act in the same pathway. Yeast two-hybrid assays suggested physical interactions, wherein PWR probably bridges HOS15/OLI1 and HDA9. Earlier studies suggested the roles of HOS15, HDA9, and PWR in transcriptional repression. Consistently, transcriptome analyses showed several genes commonly upregulated in the three mutants. From these findings, we propose a possibility that HOS15/OLI1, PWR, and HDA9 form an evolutionary conserved transcription repression complex that plays a positive role in the regulation of final leaf size.</p

The AtXTH28 Gene, a Xyloglucan Endotransglucosylase/Hydrolase, is Involved in Automatic Self-Pollination in Arabidopsis thaliana

Successful automatic self-pollination in flowering plants is dependent on the correct development of reproductive organs. In the stamen, the appropriate growth of the filament, which largely depends on the mechanical properties of the cell wall, is required to position the anther correctly close to the stigma at the pollination stage. Xyloglucan endotransglucosylase/hydrolases (XTHs) are a family of enzymes that mediate the construction and restructuring of xyloglucan cross-links, thereby controlling the extensibility or mechanical properties of the cell wall in a wide variety of plant tissues. Our reverse genetic analysis has revealed that a loss-of-function mutation of an Arabidopsis XTH family gene, AtXTH28, led to a decrease in capability for self-pollination, probably due to inhibition of stamen filament growth. Our results also suggest that the role of AtXTH28 in the development of the stamen is not functionally redundant with its closest paralog, AtXTH27. Thus, our finding indicates that AtXTH28 is specifically involved in the growth of stamen filaments, and is required for successful automatic self-pollination in certain flowers in Arabidopsis thaliana

The Evolutionary Basis of Naturally Diverse Rice Leaves Anatomy

Rice contains genetically and ecologically diverse wild and cultivated species that show a wide variation in plant and leaf architecture. A systematic characterization of leaf anatomy is essential in understanding the dynamics behind such diversity. Therefore, leaf anatomies of 24 Oryza species spanning 11 genetically diverse rice genomes were studied in both lateral and longitudinal directions and possible evolutionary trends were examined. A significant inter-species variation in mesophyll cells, bundle sheath cells, and vein structure was observed, suggesting precise genetic control over these major rice leaf anatomical traits. Cellular dimensions, measured along three growth axes, were further combined proportionately to construct three-dimensional (3D) leaf anatomy models to compare the relative size and orientation of the major cell types present in a fully expanded leaf. A reconstruction of the ancestral leaf state revealed that the following are the major characteristics of recently evolved rice species: fewer veins, larger and laterally elongated mesophyll cells, with an increase in total mesophyll area and in bundle sheath cell number. A huge diversity in leaf anatomy within wild and domesticated rice species has been portrayed in this study, on an evolutionary context, predicting a two-pronged evolutionary pathway leading to the ‘sativa leaf type’ that we see today in domesticated species

The Naming of Names: Guidelines for Gene Nomenclature in Marchantia.

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

Arabidopsis Ovate Family Proteins, a Novel Transcriptional Repressor Family, Control Multiple Aspects of Plant Growth and Development

, AtOFP4 has been shown to regulate secondary cell wall formation by interact with KNOTTED1-LIKE HOMEODOMAIN PROTEIN 7 (KNAT7), and AtOFP5 has been shown to regulate the activity of a BEL1-LIKEHOMEODOMAIN 1(BLH1)-KNAT3 complex during early embryo sac development, but little is known about the function of other AtOFPs. genes may also have diverse functions in regulating plant growth and development. Further analysis suggested that AtOFP1 regulates cotyledon development in a postembryonic manner, and global transcript profiling revealed that it suppress the expression of many other genes.Our results showed that AtOFPs function as transcriptional repressors and they regulate multiple aspects of plant growth and development. These results provided the first overview of a previously unknown transcriptional repressor family, and revealed their possible roles in plant growth and development

Phenotypic Plasticity of Leaf Shape along a Temperature Gradient in Acer rubrum

Both phenotypic plasticity and genetic determination can be important for understanding how plants respond to environmental change. However, little is known about the plastic response of leaf teeth and leaf dissection to temperature. This gap is critical because these leaf traits are commonly used to reconstruct paleoclimate from fossils, and such studies tacitly assume that traits measured from fossils reflect the environment at the time of their deposition, even during periods of rapid climate change. We measured leaf size and shape in Acer rubrum derived from four seed sources with a broad temperature range and grown for two years in two gardens with contrasting climates (Rhode Island and Florida). Leaves in the Rhode Island garden have more teeth and are more highly dissected than leaves in Florida from the same seed source. Plasticity in these variables accounts for at least 6–19 % of the total variance, while genetic differences among ecotypes probably account for at most 69–87 %. This study highlights the role of phenotypic plasticity in leaf-climate relationships. We suggest that variables related to tooth count and leaf dissection in A. rubrum can respond quickly to climate change, which increases confidence in paleoclimate methods that use these variables

BOLITA, an Arabidopsis AP2/ERF-like transcription factor that affects cell expansion and proliferation/differentiation pathways

The BOLITA (BOL) gene, an AP2/ERF transcription factor, was characterized with the help of an activation tag mutant and overexpression lines in Arabidopsis and tobacco. The leaf size of plants overexpressing BOL was smaller than wild type plants due to a reduction in both cell size and cell number. Moreover, severe overexpressors showed ectopic callus formation in roots. Accordingly, global gene expression analysis using the overexpression mutant reflected the alterations in cell proliferation, differentiation and growth through expression changes in RBR, CYCD, and TCP genes, as well as genes involved in cell expansion (i.e. expansins and the actin remodeling factor ADF5). Furthermore, the expression of hormone signaling (i.e. auxin and cytokinin), biosynthesis (i.e. ethylene and jasmonic acid) and regulatory genes was found to be perturbed in bol-D mutant leave

Recent advances in understanding the roles of whole genome duplications in evolution

Ancient whole-genome duplications (WGDs)—paleopolyploidy events—are key to solving Darwin’s ‘abominable mystery’ of how flowering plants evolved and radiated into a rich variety of species. The vertebrates also emerged from their invertebrate ancestors via two WGDs, and genomes of diverse gymnosperm trees, unicellular eukaryotes, invertebrates, fishes, amphibians and even a rodent carry evidence of lineage-specific WGDs. Modern polyploidy is common in eukaryotes, and it can be induced, enabling mechanisms and short-term cost-benefit assessments of polyploidy to be studied experimentally. However, the ancient WGDs can be reconstructed only by comparative genomics: these studies are difficult because the DNA duplicates have been through tens or hundreds of millions of years of gene losses, mutations, and chromosomal rearrangements that culminate in resolution of the polyploid genomes back into diploid ones (rediploidisation). Intriguing asymmetries in patterns of post-WGD gene loss and retention between duplicated sets of chromosomes have been discovered recently, and elaborations of signal transduction systems are lasting legacies from several WGDs. The data imply that simpler signalling pathways in the pre-WGD ancestors were converted via WGDs into multi-stranded parallelised networks. Genetic and biochemical studies in plants, yeasts and vertebrates suggest a paradigm in which different combinations of sister paralogues in the post-WGD regulatory networks are co-regulated under different conditions. In principle, such networks can respond to a wide array of environmental, sensory and hormonal stimuli and integrate them to generate phenotypic variety in cell types and behaviours. Patterns are also being discerned in how the post-WGD signalling networks are reconfigured in human cancers and neurological conditions. It is fascinating to unpick how ancient genomic events impact on complexity, variety and disease in modern life

Regulation of Plant Developmental Processes by a Novel Splicing Factor

Serine/arginine-rich (SR) proteins play important roles in constitutive and alternative splicing and other aspects of mRNA metabolism. We have previously isolated a unique plant SR protein (SR45) with atypical domain organization. However, the biological and molecular functions of this novel SR protein are not known. Here, we report biological and molecular functions of this protein. Using an in vitro splicing complementation assay, we showed that SR45 functions as an essential splicing factor. Furthermore, the alternative splicing pattern of transcripts of several other SR genes was altered in a mutant, sr45-1, suggesting that the observed phenotypic abnormalities in sr45-1 are likely due to altered levels of SR protein isoforms, which in turn modulate splicing of other pre-mRNAs. sr45-1 exhibited developmental abnormalities, including delayed flowering, narrow leaves and altered number of petals and stamens. The late flowering phenotype was observed under both long days and short days and was rescued by vernalization. FLC, a key flowering repressor, is up-regulated in sr45-1 demonstrating that SR45 influences the autonomous flowering pathway. Changes in the alternative splicing of SR genes and the phenotypic defects in the mutant were rescued by SR45 cDNA, further confirming that the observed defects in the mutant are due to the lack of SR45. These results indicate that SR45 is a novel plant-specific splicing factor that plays a crucial role in regulating developmental processes

A developmental model for branching morphogenesis of lake cress compound leaf

Lake cress, Rorippa aquatica (Brassicaceae), is a semi-aquatic plant that exhibits a variety of leaf shapes, from simple leaves to highly branched compound leaves, depending on the environment. Leaf shape can vary within a single plant, suggesting that the variation can be explained by a simple model. In order to simulate the branched structure in the compound leaves of R. aquatica, we implemented reaction-diffusion (RD) patterning onto a theoretical framework that had been developed for serration distribution in the leaves of Arabidopsis thaliana, with the modification of the one-dimensional reaction-diffusion domain being deformed with the spatial periodicity of the RD pattern while expanding. This simple method using an iterative pattern could create regular and nested branching patterns. Subsequently, we verified the plausibility of our theoretical model by comparing it with the experimentally observed branching patterns. The results suggested that our model successfully predicted both the qualitative and quantitative aspects of the timing and positioning of branching in growing R. aquatica leaves