Project description:Vascular cambium is a secondary meristem which produces xylem (wood) inwards and phloem (bark) outwards. The activity of cambium leads to expansion in the diameters in plants, that is, secondary growth, and thus contributes to biomass increase. The regulation of cambium development is at multilevel including phytohormones and peptide-receptor kinase (CLE41/44-PXY) signalling pathways. However, only limited progress has been made on the transcriptional regulation level. To construct the transcriptional network that regulates cambium development, we performed a genome wide transcript profiling in sorted procambial and cambial cells in Arabidopsis roots. More than 500 genes were identified as cambium abundant genes via comparison against transcriptomes of other Arabidopsis root cell types. We then investigated the roles of almost all the cambial transcription factors (TFs) and some of their homologous genes during secondary growth. Many of the candidate TFs were highly expressed in cambium based on the promoter GUS fusion and in situ hybridization. An unbiased transcriptional regulatory network was constructed using transcript profiling data collected from inducible overexpression lines for selected candidate TFs and a few major nodes were identified in the network including WOX4 and KNAT1. Moreover, the severity of mutant phenotypes was predicted based on the network. Next, we used the predication as a guide and generated over 70 double mutants within the same or among different TF families to explore the genetic interactions of candidate genes. Phenotype characterization on the secondary growth of the mutants and the overexpression lines identified promoters and inhibitors of cambium activity. The phenotypic data also suggested the redundancy within and among TF families because the phenotypes could be enhanced when additional TFs were mutated. We also found that combinations of certain overexpression lines and mutants led to pronounced increase of cell proliferation or xylem differentiation and in the extreme case the formation of ectopic cambium. We herein propose that cambium development is orchestrated by a wide network at the transcriptional level, where each TF has a different contribution to cell proliferation and differentiation.
Project description:In-vitro induced establishment and activity of the interfascicular cambium in Arabidopsis thaliana stems under auxin treatments. We used microarrays to detail the global programme of gene expression underlying the establishment and activity of the interfascicular cambium and identified tissue-speciffic up-regulated genes during this process.
Project description:In-vitro induced establishment and activity of the interfascicular cambium in Arabidopsis thaliana stems under auxin treatments. We used microarrays to detail the global programme of gene expression underlying the establishment and activity of the interfascicular cambium and identified tissue-speciffic up-regulated genes during this process. Different tissue types from in-vitro auxin treated stems were selected at successive stages of cambium establishment using laser capture microdissection for RNA extraction and hybridization on Affymetrix microarrays. We aimed to obtain genes exclussively upregulated in the interfascicular region responsible for cambium establishment and activity.
Project description:The root epidermis of Arabidopsis provides a simple and experimentally useful model for studying the molecular basis of cell fate and differentiation. The goal of this study was to define the larger gene regulatory network that governs the differentiation of the root hair and non-hair cell types of the Arabidopsis root epidermis. Transcript levels in the root epidermis of wild-type and mutant lines were assessed by purifying populations of root epidermal cells using fluorescence-based cell-sorting. Further, the role of the plant hormones auxin and ethylene on root epidermis development was assessed by defining transcript levels in the root epidermis of plants grown on media containing IAA or ACC. These microarray results were used to construct a comprehensive gene regulatory network that depicts the transcriptional control of root epidermal cell fate and differentiation in Arabidopsis.
Project description:In plant development, a receptor kinase may be active in disparate cell types, with each requir-ing different signalling outputs. The ERECTA (ER) receptor kinase and its homologs ERL1 and ERL2 exemplify this pleiotropy. In Arabidopsis, they influence stomatal patterning, shoot meristem function, ovule morphogenesis, xylem fiber differentiation, and cell division in the vascular cambium1–6. Such diverse expression and functionality raise the question of how ER signalling can specify such distinct cell behaviours. One explanation is that cell-type specific interactions with co-receptors, ligands, or other proteins modulate signalling. However, little is known about ER interactors in the vascular cambium, a bifacial stem cell niche that generates phloem and xylem. Combinatorial mutations between ER, ERL1 and ERL2 and receptor kinases of a sec-ond family, PXY, PXL1, and PXL2, show severe cambial defects5,7. Here we discovered that PXY and PXL proteins form heterodimers with ER and ERL2. PXY signalling can be manipulated by altering levels of its cognate ligand, TDIF. In genetic analysis, plant lines in which TDIF levels were altered had dramatic phenotypes that required the presence of ER or ERL2. Our results demonstrate that PXY signalling mediated cambium regulation depends on ER signalling and explains ER function in the cambium. Because the cambium produces xylem, which constitutes the wood in vascular plants, our findings position PXY-ER heterodimers at the centre of the ac-cumulation of this versatile biomaterial and carbon sink.
Project description:The differentiation of specialized feeding sites in Arabidopsis root cells in response to nematode infestation involves substantial cellular reprogramming of host cells that is not well characterized at the molecular level. Expression data was generated from Arabidopsis root cells undergoing giant cell formation due to nematode infestation and from non-infested control root cells. Cells were laser captured 14 and 21 days after infestation.
Project description:The root epidermis of Arabidopsis provides a simple and experimentally useful model for studying the molecular basis of cell fate and differentiation. The goal of this study was to define the transcript changes in the root epidermis of mutants associated with root epidermis cell specification, including mutants that lack a visible phenotypic alteration (try, egl3, myb23, and ttg2). Transcript levels were assessed by purifying populations of root epidermal cells using fluorescence-based cell-sorting with the WER::GFP transgene. These microarray results were used to compare the effects of single and double mutants on the gene regulatory network that controls root epidermal cell fate and differentiation in Arabidopsis.
Project description:In-vivo induced establishment and activity of the interfascicular cambium in Arabidopsis thaliana stems under NPA treatments. We used microarrays to detail the global programme of gene expression underlying the establishment and activity of the interfascicular cambium.
Project description:The largest reservoir of terrestrial biomass is the wood within plant stems. Consisting of xylem cells, wood is derived from the cambium, a stem cell population that is maintained by non-cell autonomous signalling. The central component of this system is PXY, a receptor protein present on the plasma membrane of cambium cells. Here, we show that PXY protein interacts with a second membrane-localised receptor kinase, ER, to promote cambium fate. Combinatorial mutations between ER, ERL1 and ERL2 and receptor kinases of a second family, PXY, PXL1, and PXL2, show severe cambial defects, but the mechanism underpinning these phenotypes is not known. Here we discovered that PXY and PXL proteins form protein complexes with ER family members. In genetic analyses, plant lines in which PXY signalling was constitutively active had dramatic phenotypic changes that required the presence of ER or ERL2. Our results demonstrate that PXY signalling mediated cambium regulation depends on ER signalling and explains ER function in the cambium. Because the cambium produces xylem, which constitutes the wood in vascular plants, our findings position PXY-ER complexes at the centre of the accumulation of this versatile biomaterial and essential carbon sink.