Genome-wide analysis of SHORTROOT targets in the Arabidopsis root stele
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ABSTRACT:
ORGANISM(S): Arabidopsis thaliana
PROVIDER: GSE130061 | GEO | 2019/08/01
REPOSITORIES: GEO
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Project description:The vascular system of plants consists of xylem, phloem and procambium in a specific pattern. The phloem consists of sieve elements, the apparatus for bulk flow of photo-assimilates, and companion cells, which mediate transport of photo-assimilates between the sieve elements and surrounding cells and support the biological activities of the sieve element cells. The regulatory mechanisms of vascular development are being uncovered. Here we show that PHLOEM EARLY DOFs (PEARs) and related genes (collectively phloem-Dofs) not only regulate the number of procambium cell files, but also positively regulate phloem differentiation. Overexpression of phloem-Dofs induced cells that expressed either sieve element or companion cell marker genes, which are mutually exclusive. Conversely, disruption of phloem-Dofs caused loss of phloem. Phloem-Dofs induce CLAVATA3/EMBRYO SURROUNDING REGION-RELATED25 (CLE25) and CLE26 peptides, which in turn inhibit expression of phloem-Dofs and phloem formation, forming a negative feedback loop. Disruption of multiple genes for either phloem-expressed CLEs, BARELY ANY MERISTEM (BAM)-class receptors, or their coreceptors, CLAVATA3 INSENSITIVE RECEPTOR KINASEs (CIKs), caused excess formation of phloem cell files. We further show that phloem-Dofs are under positive self and mutual regulation. These positive and negative feedback loops create the proper phloem pattern.
2022-05-05 | GSE166182 | GEO
Project description:ABSTRACT:The SODIUM POTASSIUM ROOT DEFECTIVE 1 (NaKR1) encodes a soluble metal binding protein that is specifically expressed in companion cells of the phloem. The nakr1-1 mutant phenotype includes high Na+, K+, Rb+ and starch accumulation in leaves, short roots, late flowering and decreased long-distance transport of sucrose. Using traditional and DNA microarray-based mapping, a 7 bp deletion was found in an exon of NaKR1 that caused a premature stop. The mutant phenotypes were complemented by the native gene and by GFP and GUS fusions driven by the native promoter. NAKR1-GFP was mobile in the phloem, it moved into sieve elements and into a novel symplasmic domain of the root meristem. Grafting experiments revealed that the high Na+ accumulation was due primarily to loss of NaKR1 function in the leaves. This supports a role for the phloem in recirculating Na+ to the roots to limit Na+ accumulation in leaves. The onset of root phenotypes coincided with NaKR1 expression after germination. Short root length was primarily due to a decrease in cell division rate in the root meristem indicating a role for NaKR1 expression in the phloem in root meristem maintenance. 3 hybridizations each of mutant NAKR1 and wildtype for deletion identification.
2010-12-23 | E-GEOD-24385 | biostudies-arrayexpress
Project description:ABSTRACT:The SODIUM POTASSIUM ROOT DEFECTIVE 1 (NaKR1) encodes a soluble metal binding protein that is specifically expressed in companion cells of the phloem. The nakr1-1 mutant phenotype includes high Na+, K+, Rb+ and starch accumulation in leaves, short roots, late flowering and decreased long-distance transport of sucrose. Using traditional and DNA microarray-based mapping, a 7 bp deletion was found in an exon of NaKR1 that caused a premature stop. The mutant phenotypes were complemented by the native gene and by GFP and GUS fusions driven by the native promoter. NAKR1-GFP was mobile in the phloem, it moved into sieve elements and into a novel symplasmic domain of the root meristem. Grafting experiments revealed that the high Na+ accumulation was due primarily to loss of NaKR1 function in the leaves. This supports a role for the phloem in recirculating Na+ to the roots to limit Na+ accumulation in leaves. The onset of root phenotypes coincided with NaKR1 expression after germination. Short root length was primarily due to a decrease in cell division rate in the root meristem indicating a role for NaKR1 expression in the phloem in root meristem maintenance.
2010-12-23 | GSE24385 | GEO
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.
2012-12-31 | E-GEOD-33015 | biostudies-arrayexpress
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.
2012-12-31 | GSE33015 | GEO
Project description:Flowering of Arabidopsis thaliana is accelerated by several environmental cues, including exposure to long days. The photoperiod-dependent promotion of flowering involves the transcriptional induction of FLOWERING LOCUS T (FT) in the phloem of the leaf. FT encodes a mobile protein that is transported from the leaves to the shoot apical meristem, where it forms part of a regulatory complex that induces flowering. Whether FT also has biological functions in leaves of wild-type plants remains unclear. In order to address this issue, we first studied the leaf transcriptomic changes associated with its over expression in the companion cells of the phloem. To this end, transgenic A. thaliana plants that misexpress FT from the pGAS1 promoter in a ft-10 tsf-1 double mutant background were employed (pGAS1:FT ft-10 tsf-1). In these transgenic plants, the use of the pGAS1 promoter ensures that the FT transgene is expressed in phloem companion cells of the minor veins, recreating the spatial pattern of expression described for the native gene. In this studuy, the transcriptome of leaves of pGAS1:FT ft-10 tsf-1 transgenic plants was compared to that of ft-10 tsf-1 and Col-0 plants using Tiling Arrays.
2020-02-05 | GSE125054 | GEO
Project description:This sudy focuses on the identification of transcripts in the shoot phloem of the model plant Arabidopsis thaliana. Transcripts expressed in the phloem tissue (parenchyma cell, companion cell, sieve element) were excised by laser microdissection pressure catapulting (LMPC). These were compared with transcripts isolated from leaf phloem exudates by EDTA-chelation technique. Optimization of sample harvest resulted in RNA of high quality from both sources. Modifications of the RNA amplification procedure obtained RNA of sufficient yield and quality for microarray experiments. Microarrays (Affymetrix, ATH1) hybridized with RNA derived from phloem tissue by LMPC or phloem sap allowed us to differentiate between phloem located and mobile transcript species. The datasets provide a search criterion for phloem-based signals and will facilitate reverse genetic studies and forward genetic screens for phloem and long distance RNA signaling mutants. Keywords: profiles of mobile and stationary Arabidopsis phloem transcripts
2008-09-01 | GSE10247 | GEO
Project description:This sudy focuses on the identification of transcripts in the shoot phloem of the model plant Arabidopsis thaliana. Transcripts expressed in the phloem tissue (parenchyma cell, companion cell, sieve element) were excised by laser microdissection pressure catapulting (LMPC). These were compared with transcripts isolated from leaf phloem exudates by EDTA-chelation technique. Optimization of sample harvest resulted in RNA of high quality from both sources. Modifications of the RNA amplification procedure obtained RNA of sufficient yield and quality for microarray experiments. Microarrays (Affymetrix, ATH1) hybridized with RNA derived from phloem tissue by LMPC or phloem sap allowed us to differentiate between phloem located and mobile transcript species. The datasets provide a search criterion for phloem-based signals and will facilitate reverse genetic studies and forward genetic screens for phloem and long distance RNA signaling mutants. Experiment Overall Design: Arabidopsis plants were cultivated under short day conditions (8 h light) until flowering. Phloem tissue was isolated by Lasermicrodissection and Pressure Catapulting (LMPC) and phloem exudate by EDTA-chelation technique. In both experiments poly-A-RNA was extracted and amplified before hybridization of microarrays (Affymetrix, ATH1). For both experiments three LMPC-derived phloem tissue (LMPC-derived phloem_1-3) and three phloem exudate samples (Phloem exudate_1-3) were analysed. Precise protocols of plant growth, sample harvest, RNA extraction and amplification are provided in Deeken et al., 2008.
2008-10-25 | E-GEOD-10247 | biostudies-arrayexpress
Project description:Symplasmicly connected cells called sieve elements form a network of tubes in the phloem of vascular plants. Sieve elements have essential functions as they provide routes for photoassimilate distribution, the exchange of developmental signals, and the coordination of defense responses. Nonetheless, they are the least understood main type of plant cells. They are extremely sensitive, possess a reduced endomembrane system without Golgi apparatus, and lack nuclei and translation machineries, so that transcriptomics and similar techniques cannot be applied. Moreover, the analysis of phloem exudates as a proxy for sieve element composition is marred by methodological problems. We developed a simple protocol for the isolation of sieve elements from leaves and stems of Nicotiana tabacum at sufficient amounts for large-scale proteome analysis. By quantifying the enrichment of individual proteins in purified sieve element relative to bulk phloem preparations, proteins of increased likelyhood to function specifically in sieve elements were identified. To evaluate the validity of this approach, YFP-constructs of genes encoding three of the candidate proteins were expressed in plants. Tagged proteins occurred exclusively in sieve elements. Two of them, a putative cytochrome b561/ferric reductase and a reticulon-like protein, appeared restricted to ER segments that were inaccessible to the luminal ER marker, HDEL-GFP, suggesting a previously unknown differentiation of the endomembrane system in sieve elements. Evidently, our list of promising candidate proteins provides a valuable exploratory tool for sieve element biology.
2022-02-17 | PXD030457 | Pride
Project description:Leaves are asymmetric, with differential functionalization of abaxial and adaxial tissues. The bundle sheath (BS) surrounding the vasculature of the C3 crop barley is dorsoventrally differentiated into three domains: adaxial structural, lateral S-type, and abaxial L-type. S-type cells seem to transfer assimilates towards the phloem. Here we used single-cell RNA sequencing to investigate BS differentiation in C4 maize. Abaxial BS (abBS) cells of rank-2 intermediate veins specifically expressed three SWEET sucrose uniporters (SWEET13a, b, and c) and UmamiT amino acid efflux transporters. SWEET13a, b, c were also identified in the phloem parenchyma (PP). Thus maize acquired a unique mechanism for phloem loading in which abBS cells provide the main pathway for apoplasmic sucrose transfer towards the phloem. This pathway predominates in veins responsible for phloem loading (rank-2 intermediate), while rank-1 intermediate and major veins export sucrose from the phloem parenchyma (PP) adjacent to the sieve element companion cell (SE/CC) complex, as in Arabidopsis. We surmise that abBS identity is subject to dorsoventral patterning and has components of PP identity. The observations provide first insights into the unique properties of abBS cells, cells previously considered to fulfill the same functions as other bundle sheath cells (BSCs), and a basis for understanding the C4 syndrome.
2021-03-02 | GSE157758 | GEO