Regulation of ARGONAUTE10 Expression Enables Temporal and Spatial Precision in Axillary Meristem Initiation in Arabidopsis.
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ABSTRACT:
SUBMITTER: Zhang C
PROVIDER: S-EPMC7774873 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The shoot apical meristem (SAM) comprises a group of undifferentiated cells that divide to maintain the plant meristem and also give rise to all shoot organs. SAM fate is specified by class III HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIP III) transcription factors, which are targets of miR166/165. In Arabidopsis, AGO10 is a critical regulator of SAM maintenance, and here we demonstrate that AGO10 specifically interacts with miR166/165. The association is determined by a distinct structure of the miR166/165 duplex. Deficient loading of miR166 into AGO10 results in a defective SAM. Notably, the miRNA-binding ability of AGO10, but not its catalytic activity, is required for SAM development, and AGO10 has a higher binding affinity for miR166 than does AGO1, a principal contributor to miRNA-mediated silencing. We propose that AGO10 functions as a decoy for miR166/165 to maintain the SAM, preventing their incorporation into AGO1 complexes and the subsequent repression of HD-ZIP III gene expression.
| S-EPMC4124879 | biostudies-literature
Project description:Plants retain the ability to produce new organs throughout their life cycles. Continuous aboveground organogenesis is achieved by meristems, which are mainly organized, established, and maintained in the shoot apex and leaf axils. This paper will focus on reviewing the recent progress in understanding the regulation of shoot apical meristem and axillary meristem development. We discuss the genetics of plant meristems, the role of plant hormones and environmental factors in meristem development, and the impact of epigenetic factors on meristem organization and function.
| S-EPMC7216077 | biostudies-literature
Project description:BACKGROUND: Stem cells located in the centre of the shoot apical meristem are required for the repetitive formation of new organs such as leaves, branches and flowers. In Arabidopsis thaliana, the ZWILLE/PINHEAD/AGO10 (ZLL) gene encodes a member of the ARGONAUTE (AGO) protein family and is required to maintain shoot meristem stem cells during embryogenesis. In the Landsberg erecta (Ler) acession, ZLL is essential for stem cell maintenance, whereas in the Columbia (Col) accession its requirement appears masked by genetic modifiers. The genetic basis for this variation has remained elusive. RESULTS: To understand the impact of natural variation on shoot stem cell maintenance, we analysed 28 wild-type Arabidopsis accessions from around the world and show that ZLL function is essential for stem cell maintenance in accessions mainly originating from Germany, but is dispensable for accessions from other regions. Quantitative Trait Loci (QTL) mapping using Ler/Col recombinant inbred lines indicated that at least five genomic regions, referred to as FLETSCHE (FHE) 1-5, modify ZLL function in stem cell maintenance. Characterisation of Col zll near isogenic lines confirmed that the major QTL, FHE2, is preferentially maintained as a Ler allele in seedlings lacking stem cells, suggesting that this region harbours an important modifier of ZLL function. Comparison of torpedo-stage embryo expression profiles to QTL map data revealed candidate FHE genes, including the Arabidopsis Cyclophilin-40 homologue SQUINT (SQN), and functional studies revealed a previously uncharacterised role for SQN in stem cell regulation. CONCLUSIONS: Multiple genetic modifiers from different Arabidopsis accessions influence the role of ZLL in embryonic stem cell maintenance. Of the five FHE loci modifying stem cell maintenance in Ler-0 and Col-0, FHE2 was the most prominent and was tightly linked to the SQN gene, which encodes a cofactor that supports AGO1 activity. SQN shows variable embryonic expression levels between accessions and altered ZLL-dependency in transgenic assays, confirming a key role in stem cell maintenance. Reduced SQN expression levels in Col-0 correlate with transposon insertions adjoining the transcriptional start site, which may contribute to stem cell maintenance in other ZLL-independent accessions.
| S-EPMC4046819 | biostudies-literature
Project description:Gene regulatory networks (GRNs) control development via cell type-specific gene expression and interactions between transcription factors (TFs) and regulatory promoter regions. Plant organ boundaries separate lateral organs from the apical meristem and harbor axillary meristems (AMs). AMs, as stem cell niches, make the shoot a ramifying system. Although AMs have important functions in plant development, our knowledge of organ boundary and AM formation remains rudimentary. Here, we generated a cellular-resolution genomewide gene expression map for low-abundance Arabidopsis thaliana organ boundary cells and constructed a genomewide protein-DNA interaction map focusing on genes affecting boundary and AM formation. The resulting GRN uncovers transcriptional signatures, predicts cellular functions, and identifies promoter hub regions that are bound by many TFs. Importantly, further experimental studies determined the regulatory effects of many TFs on their targets, identifying regulators and regulatory relationships in AM initiation. This systems biology approach thus enhances our understanding of a key developmental process.
| S-EPMC4299377 | biostudies-literature
Project description:Background: The carpel margin meristem is a vital multi-potent structure located in the medial domain of the Arabidopsis thaliana gynoecium, the female floral reproductive organ. The carpel margin meristem generates ovules that upon fertilization become seeds. The molecular mechanisms that specify this meristematic region and regulate its organogenic potential are poorly understood. Here, we present an analysis of the transcriptional profile of the medial domain of the Arabidopsis gynoecium highlighting the developmental stages that immediately proceed ovule initiation, the earliest stages of seed development. Results: Using a floral synchronization system and a SHATTERPROOF2 domain-specific reporter construct, paired with fluorescence-activated cell sorting, we assayed the transcriptome of the gynoecial medial domain with temporal and spatial precision. Our analysis reveals a set of genes that are differentially-expressed within the SHATTERPROOF2 expression domain that marks portions of the developing medial domain. Many members of this gene set have been shown previously to function during the development of medial domain-derived structures, including the ovules, thus validating our approach. Other uncharacterized members of this gene set, including a set of differentially-expressed cis-natural antisense transcripts, are potential novel regulators of medial domain development and candidates for future functional studies. Several members of the REM family of transcriptional regulators were enriched in the SHP2-expressing cell population including a previously unrecognized REM family member (At5g60142). Analysis of the abundance of specific transcriptional isoforms identified genes that may exhibit âisoform switchingâ behavior during gynoecial development. Conclusions: This data set provides genome-wide transcriptional insight into the development of the gynoecial medial domain that contains the carpel margin meristem, an important reproductive structure that gives rise to the ovules in Arabidopsis thaliana. Four samples (YFP-positive, YFP-negative, all-sorted, and non-sorted). Four biological replicates of each sample (except YFP-positive, collected in triplicated). Strand-specific libraries were sequenced (single-end) in two lanes of a HiSeq 2500 Illumina flow cell (each lane was later analyzed as a technical replicate).
2016-02-29 | E-GEOD-74458 | biostudies-arrayexpress
Project description:The cell walls of the shoot apical meristem (SAM), containing the stem cell niche that gives rise to the above-ground tissues, are crucially involved in regulating differentiation. It is currently unknown how these walls are built and refined or their role, if any, in influencing meristem developmental dynamics. We have combined polysaccharide linkage analysis, immuno-labeling, and transcriptome profiling of the SAM to provide a spatiotemporal plan of the walls of this dynamic structure. We find that meristematic cells express only a core subset of 152 genes encoding cell wall glycosyltransferases (GTs). Systemic localization of all these GT mRNAs by in situ hybridization reveals members with either enrichment in or specificity to apical subdomains such as emerging flower primordia, and a large class with high expression in dividing cells. The highly localized and coordinated expression of GTs in the SAM suggests distinct wall properties of meristematic cells and specific differences between newly forming walls and their mature descendants. Functional analysis demonstrates that a subset of CSLD genes is essential for proper meristem maintenance, confirming the key role of walls in developmental pathways.
| S-EPMC5024349 | biostudies-literature
Project description:Background: The carpel margin meristem is a vital multi-potent structure located in the medial domain of the Arabidopsis thaliana gynoecium, the female floral reproductive organ. The carpel margin meristem generates ovules that upon fertilization become seeds. The molecular mechanisms that specify this meristematic region and regulate its organogenic potential are poorly understood. Here, we present an analysis of the transcriptional profile of the medial domain of the Arabidopsis gynoecium highlighting the developmental stages that immediately proceed ovule initiation, the earliest stages of seed development. Results: Using a floral synchronization system and a SHATTERPROOF2 domain-specific reporter construct, paired with fluorescence-activated cell sorting, we assayed the transcriptome of the gynoecial medial domain with temporal and spatial precision. Our analysis reveals a set of genes that are differentially-expressed within the SHATTERPROOF2 expression domain that marks portions of the developing medial domain. Many members of this gene set have been shown previously to function during the development of medial domain-derived structures, including the ovules, thus validating our approach. Other uncharacterized members of this gene set, including a set of differentially-expressed cis-natural antisense transcripts, are potential novel regulators of medial domain development and candidates for future functional studies. Several members of the REM family of transcriptional regulators were enriched in the SHP2-expressing cell population including a previously unrecognized REM family member (At5g60142). Analysis of the abundance of specific transcriptional isoforms identified genes that may exhibit “isoform switching” behavior during gynoecial development. Conclusions: This data set provides genome-wide transcriptional insight into the development of the gynoecial medial domain that contains the carpel margin meristem, an important reproductive structure that gives rise to the ovules in Arabidopsis thaliana.
2016-02-29 | GSE74458 | GEO
Project description:In seed plants, shoot branching is initiated by the formation of new meristems in the axils of leaves, which subsequently develop into new axes of growth. This study describes the genetic control of axillary meristem formation by the LATERAL SUPPRESSOR (LAS) gene in Arabidopsis thaliana. las mutants show a novel phenotype that is characterized by the inability to form lateral shoots during vegetative development. The analysis shows that axillary meristem formation is differently regulated during different phases of development. During reproductive development, axillary meristems initiate in close proximity to the shoot apical meristem and do not require LAS function. In contrast, during the vegetative phase, axillary meristems initiate at a distance to the SAM and require LAS function. This control mechanism is conserved between the distantly related species tomato and Arabidopsis. Monitoring the patterns of LAS and SHOOT MERISTEMLESS transcript accumulation allowed us to identify early steps in the development of leaf axil identity, which seem to be a prerequisite for axillary meristem initiation. Other regulators of shoot branching, like REVOLUTA and AUXIN RESISTANT 1, act downstream of LAS. The results are discussed in the context of the "detached meristem" and the "de novo formation" concepts of axillary meristem formation.
| S-EPMC196050 | biostudies-literature
Project description:The aerial architecture of flowering plants is determined to a large extent by shoot growth and shoot branching arising from the initiation and growth of axillary meristems. We have identified an Arabidopsis mutant, supershoot (sps), which is characterized by a massive overproliferation of shoots, such that a single plant can generate 500 or more inflorescences. Analysis of the mutant plants shows that the primary defect is because of an increase in the number of meristems formed in leaf axils, together with release of bud arrest, resulting in reiterative branch formation from rosette and cauline leaves. The SPS gene is shown here to encode a cytochrome P450, and together with a 3- to 9-fold increase in levels of Z-type cytokinins in sps mutant plants, indicate a role for SPS in modulating hormone levels. The expression pattern of SPS, with strong expression at the leaf axils, correlates well with the phenotypic defects. Our results indicate that control of shoot branching in Arabidopsis may be accomplished in part by suppression of axillary meristem initiation and growth through the localized attenuation of cytokinin levels at sites of bud initiation.
| S-EPMC312715 | biostudies-literature
Project description:Plants produce new organs post-embryonically throughout their entire life cycle. This is due to stem cells present in the shoot and root apical meristems, the SAM and RAM, respectively. In the SAM, stem cells are located in the central zone where they divide slowly. Stem cell daughters are displaced laterally and enter the peripheral zone, where their mitotic activity increases and lateral organ primordia are formed. How the spatial arrangement of these different domains is initiated and controlled during SAM growth and development, and how sites of lateral organ primordia are determined in the peripheral zone is not yet completely understood. We found that the SHORTROOT (SHR) transcription factor together with its target transcription factors SCARECROW (SCR), SCARECROW-LIKE23 (SCL23) and JACKDAW (JKD), promotes formation of lateral organs and controls shoot meristem size. SHR, SCR, SCL23, and JKD are expressed in distinct, but partially overlapping patterns in the SAM. They can physically interact and activate expression of key cell cycle regulators such as CYCLIND6;1 (CYCD6;1) to promote the formation of new cell layers. In the peripheral zone, auxin accumulates at sites of lateral organ primordia initiation and activates SHR expression via the auxin response factor MONOPTEROS (MP) and auxin response elements in the SHR promoter. In the central zone, the SHR-target SCL23 physically interacts with the key stem cell regulator WUSCHEL (WUS) to promote stem cell fate. Both SCL23 and WUS expression are subject to negative feedback regulation from stem cells through the CLAVATA signaling pathway. Together, our findings illustrate how SHR-dependent transcription factor complexes act in different domains of the shoot meristem to mediate cell division and auxin dependent organ initiation in the peripheral zone, and coordinate this activity with stem cell maintenance in the central zone of the SAM.
| S-EPMC10642969 | biostudies-literature