Project description:Wounding is a primary trigger of organ regeneration but how wound stress reactivates cell proliferation and promotes cellular reprogramming remains elusive. In this study we combined the transcriptome analysis with quantitative hormonal analysis to investigate how wounding induces callus formation in Arabidopsis thaliana. Our time-course RNA-seq analysis revealed that wounding induces dynamic transcriptional changes that can be categorized into five clusters with distinct temporal patterns. Gene ontology analyses uncovered that wounding modifies the expression of hormone biosynthesis and response genes, and quantitative analysis of endogenous plant hormones revealed accumulation of cytokinin prior to callus formation. Mutants defective in cytokinin synthesis and signalling display reduced efficiency in callus formation, indicating that de novo synthesis of cytokinin has major contribution in wound-induced callus formation. We further demonstrate that type-A ARABIDOPSIS RESPONSE REGULATOR (ARR)-mediated cytokinin signalling regulates the expression of CYCLIN D3;1 (CYCD3;1) and mutations in CYCD3;1 and its homologs CYCD3;2-3 cause defects in callus formation. Our transcriptome data, in addition, showed that wounding activates multiple developmental regulators, and we found novel roles of ETHYLENE RESPONSE FACTOR 115 (ERF115) and PLETHORA3 (PLT3), PLT5, PLT7 in wound-induced callus formation. Together, this study provides novel mechanistic insights into how wounding reactivates cell proliferation during callus formation.
Project description:Plant-parasitic cyst nematodes induce the formation of hypermetabolic feeding sites, termed syncytia, as their sole source of nutrients. The formation of the syncytium is orchestrated by the nematode in part by modulation of phytohormone responses, including cytokinin. In response to infection by the nematode H. schachtii, cytokinin signaling is transiently induced at the site of infection and in the developing syncytium. Arabidopsis lines with reduced cytokinin sensitivity show reduced susceptibility to nematode infection, indicating that cytokinin signaling is required for optimal nematode development. Furthermore, lines with increased cytokinin sensitivity also exhibit reduced nematode susceptibility. To ascertain why cytokinin hypersensitivity reduces nematode parasitism, we examined the transcriptomes in wild-type and a cytokinin-hypersensitive type-A arr Arabidopsis mutant in response to H. schachtii infection. Genes involved in the response to biotic stress and defense response were elevated in the type-A arr mutant in the absence of nematodes and were hyper-induced following H. schachtii infection, which suggests that the Arabidopsis type-A arr mutants impede nematode development because they are primed to respond to pathogen infection. These results suggest that cytokinin signaling is required for optimal H. schachtii parasitism of Arabidopsis, but that elevated cytokinin signaling triggers a heightened immune response to nematode infection.
Project description:Cytokinins are plant hormones with biological functions ranging from coordination of plant growth and development to the regulation of senescence. A series of 2-chloro-N6-(halogenobenzylamino)purine ribosides was prepared and tested for cytokinin activity in selected bioassays. Several compounds showed significant activity, especially in delaying senescence in detached wheat leaves. We used microarrays to gather information about the reprogramming of gene transcription when senescent Arabidopsis leaves were treated with selected C2-substituted aromatic cytokinin ribosides that showed high activity in the senescence bioassay. Arabidopsis senescent leaves were treated with cytokinins and subsequently used for RNA extraction and hybridization on Affymetrix microarrays. 21-days old Arabidopsis leaves were treated with the appropriate cytokinin or left untreated (DMSO only).
Project description:De novo shoot organogenesis (DNSO) is a commonly used pathway for plant biotechnology, and is a hormonally regulated process, where auxin and cytokinin coordinates suites of genes encoding transcription factors, general transcription factors, and RNA metabolism machinery genes. Here we report that silencing Arabidopsis thaliana CTD phosphatase-like 4 (CPL4RNAi), which increases phosphorylation level of RNA polymerase II (pol II) CTD, altered lateral root development and DNSO efficiency of the host plants, suggesting an importance of precise control of pol II activities during DNSO. Under standard condition, roots of CPL4RNAi lines produced no or few lateral roots. When induced by high concentration of auxin, CPL4RNAi lines failed to produce focused auxin maxima at the meristem of lateral root primordia, and produced fasciated lateral roots. By contrast, root explants of CPL4RNAi lines were highly competent for DNSO. Efficient DNSO of CPL4RNAi lines were observed even under 10 times less cytokinin required for wild type explants. Transcriptome analysis showed CPL4RNAi but not wild type explants expressed high levels of shoot meristem related genes during priming by high auxin/cytokinin ratio, and subsequent shoot induction with cytokinin. These results indicate that CPL4 functions as a repressor of the early stage of DNSO, during acquisition of competency by high auxin/cytokinin ratio, perhaps via regulation of pol II activities.
Project description:Cytokinins are plant hormones with biological functions ranging from coordination of plant growth and development to the regulation of senescence. A series of 2-chloro-N6-(halogenobenzylamino)purine ribosides was prepared and tested for cytokinin activity in selected bioassays. Several compounds showed significant activity, especially in delaying senescence in detached wheat leaves. We used microarrays to gather information about the reprogramming of gene transcription when senescent Arabidopsis leaves were treated with selected C2-substituted aromatic cytokinin ribosides that showed high activity in the senescence bioassay.
Project description:To obtain detailed information about gene expression during stamen development in Arabidopsis thaliana, we compared, by microarray analysis, the gene expression profile of wild-type inflorescences to those of the floral mutants apetala3, sporocyteless/nozzle, and male sterile 1, in which different aspects of stamen formation are disrupted. These experiments led to the identification of groups of genes with predicted expression at early, intermediate and late stages of stamen development. Additional experiments aimed at characterizing gene expression specifically during microspore formation. To this end, we compared the gene expression profiles of wild-type flowers of distinct developmental stages to those of the male sterile 1 mutant. Computational analysis of the datasets derived from this experiment led to the identification of genes that are likely involved in the control of key developmental processes during microsporogenesis. Keywords: mutant comparison, developmental series
Project description:We found that Arabidopsis plants constitutively expressing OsRR6 exhibit reduced cytokinin sensitivity, adventitious root formation and enhanced anthocyanin accumulation. In addition they are hypersensitive to red, far-red and blue light in hypocotyl growth assay and also flower little early as compared to wild type.Therefore, to identify the downstream pathways affected in the OsRR6 overexpression plants, we performed transcriptome profiling of overexpression line vs wild type using Affymetrix microarray platform.