In plants, apical meristems allow continuous growth along the body axis. Within the root apical meristem (RAM), a group of slowly dividing quiescent center (QC) cells is thought to limit stem cell activity to directly neighboring cells (Cowels, 1956; van den Berg et al., 1997), thus endowing them with unique properties, distinct from displaced daughters. This binary identity of the stem cells stands in apparent contradiction with the more gradual changes in cell division potential (Bennett and Scheres, 2010) and differentiation (Yamaguchi et al., 2008; 2010; Furuta et al, 2014; Geldner, 2013; Masucci et al., 1996; Dolan and Costa, 2001) that occur as cells move further away from the QC. To address this paradox and to infer molecular organization of the root meristem, we used a whole-genome approach to determine dominant transcriptional patterns along root ontogeny zones. We found that the prevalent patterns are expressed in two opposing gradients. One is characterized by genes associated with development, the other enriched in differentiation genes. We confirmed these transcript gradients, and demonstrate that these translate to gradients in protein accumulation and gradual changes in cellular properties. We also show that gradients are genetically controlled through multiple pathways. Based on these findings, we propose that cells in the Arabidopsis root meristem gradually transition from 'stemness' towards differentiation. Overall design: This study contains high-resolution datasets from cell populations from the enitre root meristem and xylem-specific cell populations. Using fluorescence activated cell sorting, three cell populations were isolated based on their GFP expression intensity. Two-Three replicates were used per sample
Framework for gradual progression of cell ontogeny in the <i>Arabidopsis</i> root meristem.
Specimen part, Cell line, Subject
View SamplesEffect of geminivirus Cabbage leaf curl virus on Arabidopsis Col-0 at 12 days post-inoculation during short day conditions.
Global analysis of Arabidopsis gene expression uncovers a complex array of changes impacting pathogen response and cell cycle during geminivirus infection.
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View SamplesWe used microarrays to detail the global program of gene expression underlying the effect of p17 on human plasmacytoid dendritic cells and was compared to CpG profile.
HIV-1 matrix protein p17 induces human plasmacytoid dendritic cells to acquire a migratory immature cell phenotype.
Specimen part, Treatment
View SamplesWe sorted for GFP+ cells using the enhancer trap J0571 with the UAS promoter driving the expression of different BIRD genes. Different genetic backgrounds are use and listed below.
Transcriptional control of tissue formation throughout root development.
Specimen part
View SamplesAsymmetric division of cortex/endodermal initials (CEI) in the Arabidopsis root generates two layers of ground tissue and is controlled by a finely orchestrated interplay between the transcription factors, SHORT ROOT (SHR) and SCARECROW (SCR). To understand the dynamics of the SHR/SCR regulatory network we performed microarray time course experiments using inducible versions of SHR and SCR and examined their transcriptional effects specifically in the ground tissue.
Spatiotemporal regulation of cell-cycle genes by SHORTROOT links patterning and growth.
Treatment
View SamplesHow plants determine the final size of growing cells is an important, yet unanswered question. Root hairs provide an excellent model system to study this question since their final cell size is remarkably constant under given environmental conditions. In this study we demonstrate that a trihelix transcription factor GT-2-LIKE1 (GTL1) and its homolog DF1 repress root hair growth in Arabidopsis. Our transcriptional data, combined with genome-wide chromatin binding data, show that GTL1 and DF1 directly bind the RSL4 promoter and regulate its expression to repress root hair growth. Our data further show that GTL1 and RSL4 regulate each other as well as a set of common downstream genes, many of which have previously been implicated in root hair growth. This study therefore uncovers a core regulatory module that fine-tunes the extent of root hair growth by orchestrated actions of opposing transcription factors.
GTL1 and DF1 regulate root hair growth through transcriptional repression of <i>ROOT HAIR DEFECTIVE 6-LIKE 4</i> in <i>Arabidopsis</i>.
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View SamplesWe isolated QC and xylem cells by sorting GFP+ cells marked with pWOX5::GFP and pTMO5::GFP respectively.
Predicting gene regulatory networks by combining spatial and temporal gene expression data in <i>Arabidopsis</i> root stem cells.
Specimen part
View SamplesAs plant cells are fixed within their tissue context, a precise control of cell division orientation is crucial to generate complex three-dimensional organs. The transcription factor complex formed by TARGET OF MONOPTEROS5 (TMO5) and LONESOME HIGHWAY (LHW) triggers a change in cell division orientation leading to radial expansion, at least in part by activating local cytokinin biosynthesis. However, it remains unclear how cytokinin controls these oriented cell divisions. Here, we analyzed the transcriptional responses upon simultaneous induction of both TMO5 and LHW in detail. Using inferred network analysis, we identify AT2G28510/DOF2.1 as a cytokinin-dependent downstream target gene of the TMO5/LHW heterodimer complex. We further show that DOF2.1 is specifically required and sufficient for vascular cell proliferation without inducing other cytokinin-dependent effects such as the inhibition of vascular differentiation. In summary, we have identified DOF2.1 as a TMO5/LHW target gene, specifically responsible for controlling vascular cell proliferation leading to radial expansion.
DOF2.1 Controls Cytokinin-Dependent Vascular Cell Proliferation Downstream of TMO5/LHW.
Specimen part, Treatment
View SamplesLymphocytes represent basic components of vertebrate adaptive immune systems, suggesting the utility of non-mammalian models to define the molecular basis of their development and differentiation. Our forward genetic screens in zebrafish for recessive mutations affecting early T cell development revealed several major genetic pathways. The identification of lineage-specific transcription factors and specific components of cytokine signaling and DNA replication/repair pathways known from studies of immuno-compromised mammals provided an evolutionary cross-validation of the screen design. Unexpectedly, however, certain pre-mRNA processing factor genes, including tnpo3, encoding a regulator of alternative splicing, were also found to play a specific role in early T cell development. In both zebrafish and mouse, TNPO3 deficiency impairs intrathymic T cell differentiation, illustrating evolutionarily conserved and cell type-specific functions of certain pre-mRNA processing factor. Overall design: Taking advantage of the apparent evolutionary conservation of lymphocyte-based immunity, we conducted genetic screens in zebrafish aimed at identifying novel regulators of T lymphocyte development. Apart from mutations in genes encoding lymphoid lineage-specific transcription factors, and components of cytokine signaling and DNA replication/repair pathways, mutations in genes encoding pre-mRNA processing factors were also found. To examine the molecular consequences, transcriptome analyses were conducted for three mutants, snapc3, lsm8, tnpo3.
Forward Genetic Screens in Zebrafish Identify Pre-mRNA-Processing Pathways Regulating Early T Cell Development.
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