A CLV3-WUS positive feedback loop in individual cells enhances shoot stem cell thermotolerance in Arabidopsis.

CLAVATA3 (CLV3) has long been thought to be a negative regulator of the WUSCHEL (WUS) expression domain, whereas cytokinin signaling increases WUS expression at the transcriptional level. Whether these two pathways in WUS regulation are coordinated in the stem cell niche remains unknown. Here, we show that CLV signaling has a dual-directional effect on WUS by limiting its expression domain but maintaining its expression level. CLV1 phosphorylates the transcription factor BRASSINAZOLE RESISTANT 1 (BZR1) to release the inhibitory effect of BZR1 on cytokinin biosynthesis, which relays the CLV signal to maintain WUS expression levels in individual cells. Under heat stress, decreased CLV signaling enhances the stability of BZR1 in the nucleus to repress cytokinin biosynthesis and WUS content, protecting stem cells from heat shock. Our results establish a positive feedback loop between CLV3 and WUS, which is mediated by multiple hormone interactions and required for maintaining shoot stem cell thermotolerance.