Postdoc The university of Tennessee Knoxville, Tennessee
Body of Abstract: Stem cells in the shoot apical meristem (SAM) give rise to above-ground organs like stems, leaves, and flowers. The size of the SAM remains constant over time due to the precise balance of stem cell replenishment versus cell recruitment into forming organs. The WUSCHEL (WUS)/ CLAVATA3 (CLV3) negative feedback loop is central to SAM size regulation. WUS promotes the maintenance of stem cells in the central zone of the SAM. A signaling pathway activated by the extracellular ligand CLV3 inhibits WUS expression, while WUS promotes CLV3 expression. Another signaling pathway consisting of ERECTA family (ERf) receptors and EPIDERMAL PATTERNING FACTOR-LIKE (EPFL) ligands is important for the regulation of cell differentiation in the periphery of the SAM. Using confocal microscopy and taking the benefits of 3D imaging, we investigated the expression of CLV3 and WUS in different mutant backgrounds in Arabidopsis. Our experiments indicate that the WUS expression domain mostly overlaps with the CLV3 expression domain and does not shift vertically in the clv3 mutant suggesting that CLV3 regulates WUS expression via autocrine signaling. We also show that CLV3 promotes the stability of WUS expression. We also show that four EPFLs synergistically inhibit the expression of CLV3 and WUS, and the significance of ERF/EPFL signaling for WUS expression is clearly visible in the absence of CLV3. Finally, the RNAseq experiment confirmed that ERfs inhibit WUS and CLV3 expression and uncovered new potential targets of this signaling pathway. These findings provide a better understanding of molecular mechanisms regulating the stability of the SAM.