Project description:We report the discovery of a root growth program in Arabidopsis that is independent of a functional quiescent center (QC). In this regulatory program, PHABULOSA (PHB), posttranscriptionally regulated by SHR and SCR, plays a central role. In phb shr and phb scr mutants, root meristem/growth activity recovers significantly. Interestingly, this recovery does not accompany the resurgence of QC cells. PHB regulates apical root growth in stele cells of the root meristem, located proximal to the QC. Our genome-wide investigation suggests that PHB exerts its influence on root growth by regulating auxin-cytokinin homeostasis. Apical root growth was restored when cytokinin levels were genetically reduced in the shr mutant. Conversely, when miRNA-resistant PHB was expressed in the root stele cells, apical root growth and meristem functions were significantly inhibited without blocking the QC identity. Taken together, our investigation reveals two mechanisms through which SHR regulates root growth and stem cell activities: one is to specify and maintain the QC and the other is to regulate the proximal meristem activity through PHB and cytokinin. In this regulation, QC seems to be more involved in maintaining the “growth signal” and thus ensure the indeterminate root growth.
Project description:We report the discovery of a root growth program in Arabidopsis that is independent of a functional quiescent center (QC). In this regulatory program, PHABULOSA (PHB), posttranscriptionally regulated by SHR and SCR, plays a central role. In phb shr and phb scr mutants, root meristem/growth activity recovers significantly. Interestingly, this recovery does not accompany the resurgence of QC cells. PHB regulates apical root growth in stele cells of the root meristem, located proximal to the QC. Our genome-wide investigation suggests that PHB exerts its influence on root growth by regulating auxin-cytokinin homeostasis. Apical root growth was restored when cytokinin levels were genetically reduced in the shr mutant. Conversely, when miRNA-resistant PHB was expressed in the root stele cells, apical root growth and meristem functions were significantly inhibited without blocking the QC identity. Taken together, our investigation reveals two mechanisms through which SHR regulates root growth and stem cell activities: one is to specify and maintain the QC and the other is to regulate the proximal meristem activity through PHB and cytokinin. In this regulation, QC seems to be more involved in maintaining the M-bM-^@M-^\growth signalM-bM-^@M-^] and thus ensure the indeterminate root growth. Total 7 samples (2 replicates of shr-2 mutant (high PHABULOSA expression) vs. 2 replicates of shr-2 phb-6 (low/absent PHABULOSA expression). 3 replicates of Wild type used as reference sample.
Project description:Asymmetric cell division (ACD) and positional signals play critical roles in the tissue patterning during multicellular organ development. In the Arabidopsis root meristem, two major phloem cell types arise via ACDs of distinct origins: one for companion cells and the other for proto- and metaphloem sieve elements. The molecular mechanisms underlying each of these processes have been reported, however, how these two are coordinated has remained elusive. Here, we report that SHORTROOT (SHR) is the key coordinator of two ACD processes for phloem development. SHR moving into the endodermis regulates ACD for companion cells by turning on microRNA165/6. ACD that generates phloem sieve elements is mediated by SHR moving into phloem precursors. To find the downstream targets of SHR in the stele, pCRE1::erGFP was introduced into wild type and shr-2 backgrounds to express GFP in the stele cells in the root meristem. We then collected GFP-expressing stele cells from the wild type, shr-2 and pCRE1::SHRΔNLELDV:nlsGFP; shr-2 through Fluorescence Activated Cell Sorter (FACS). RNAs were extracted from the sorted cells of each line and processed for generating labeled probes to be hybridized onto GeneChip Arabidopsis Tiling 1.0R Array (Affymetrix). We then examined the influence of SHR on phloem enriched genes in the tiling array data. In this analysis, we found 224 genes that are down-regulated in shr-2 in comparison to the wild type and then restore expression in pCRE1::SHRΔNLELDV:nlsGFP; shr-2.
Project description:Genome-wide direct targets of Arabidopsis NPR1 and HAC1 were identified by chromain immunoprecipitation followed by sequencing (ChIP-seq). For the study, we used Arabidopsis expressing NPR1:GFP or HAC1:mCherry under native NPR1 or HAC1 promoter, respectively. To identify direct targets both under salicylic acid-treated and untreated conditions, we performed ChIP-seq by using 2,6-dichloroisonicotinc acid (INA; synthetic SA analog)-treated and untreated NPR1:GFP or HAC1:mCherry transgenic Arabidopsis plants.
Project description:We found that histone acetylation relays positional information and that a mutant altered in the histone deacetylase (HDAC) gene family member HDA18 exhibits altered H and N epidermal cell patterning. We then performed genome-wide location (ChIP-chip) analyses by using antibody against HDA18 in transgenic HDA18 overexpression Arabidopsis plants. These analyses identified statistically significant enriched DNA associated with HDA18. A total of 286 DNA fragments were enriched as putative HDA18 protein-binding sites. Root tips of P35S:HDA18 Arabidopsis plants (Col-0) ChIPed with HDA18 antibody vs. pre-immune mouse serum.
Project description:The Arabidopsis basic leucine zipper transcription factor bZIP29 of the bZIP group I TF family, expressed mainly in proliferative tissues, is functionally characterized in this study. In roots, bZIP29 is highly expressed in the quiescent centre and the columella cells of the root apical meristem. Mutant analyses demonstrate that bZIP29 regulates root meristem cell number and root gravitropic responses. RNA-seq transcriptome profiling of the root meristem shows that bZIP29 target genes are linked to cell wall organization, and that gene regulatory networks controlling proper root meristem organization are intensively rewired upon its perturbation.
Project description:The goal of this study is to map genome-wide ribosome occupancy on mRNAs in Arabidopsis root and shoot to characterize translatome.
Project description:Genome-wide transcriptome analysis was carried out in root tissue of Arabidopsis seedlings treated with gold (Au) as Chloroauric acid (HAuCl4). This study demonstrated remarkable changes in root transcriptome within the 12 h exposure. Most of the genes differentially expressed were related to glutathione binding, methylations, secondary metabolism, sugar metabolism, ABA, ethylene, auxin related signalling, transport and signal-transduction pathways.