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ABSTRACT The shoot apical meristem (SAM) gives rise to the aboveground organs of plants. The size of the SAM is relatively constant due to the balance between stem cell replenishment and cell recruitment into new organs. In angiosperms, the transcription factor WUSCHEL (WUS) promotes stem cell proliferation in the central zone of the SAM. WUS forms a negative feedback loop with a signaling pathway activated by CLAVATA3 (CLV3). In the periphery of the SAM, the ERECTA family receptors (ERfs) constrain WUS and CLV3 expression. Here, we show that four ligands of ERfs redundantly inhibit the expression of these two genes. Transcriptome analysis confirmed that WUS and CLV3 are the main targets of ERf signaling and uncovered new ones. Analysis of promoter reporters indicated that the WUS expression domain mostly overlaps with the CLV3 domain and does not shift along the apical-basal axis in clv3 mutants. Our three-dimensional mathematical model captured gene expression distributions at the single-cell level under various perturbed conditions. Based on our findings, CLV3 regulates cellular levels of WUS mostly through autocrine signaling, and ERfs regulate the spatial expression of WUS, preventing its encroachment into the peripheral zone.
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HAIRY MERISTEM proteins regulate the WUSCHEL protein levels in mediating CLAVATA3 expression
Abstract The precise regulation of stem cells in the shoot apical meristems (SAMs) involves the function of the homeodomain transcription factor (TF)‐WUSCHEL (WUS). WUS has been shown to move from the site of production‐the rib‐meristem (RM), into overlaying cells of the central zone (CZ), where it specifies stem cells and also regulates the transcription ofCLAVATA3 (CLV3). The secreted signalling peptide CLV3 activates a receptor kinase signalling that restrictsWUStranscription and also regulates the nuclear gradient of WUS by offsetting nuclear export. WUS has been shown to regulate bothCLV3levels and spatial activation, restricting its expression to a few cells in the CZ. The HAIRY MERISTEM (HAM), a GRASS‐domain class of TFs expressed in the RM, has been shown to physically interact with WUS and regulateCLV3expression. However, the mechanisms by which this interaction regulatesCLV3expression non‐cell autonomously remain unclear. Here, we show that HAM function is required for regulating the WUS protein stability, and theCLV3expression responds to altered WUS protein levels inhammutants. Thus, HAM proteins non‐cell autonomously regulatesCLV3expression.
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- Award ID(s):
- 2055690
- PAR ID:
- 10539124
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Physiologia Plantarum
- Volume:
- 176
- Issue:
- 5
- ISSN:
- 0031-9317
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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