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 in control of WUSCHEL (WUS) expression domain, whereas cytokinin signaling increases WUS expression at the transcriptional level. Whether these two important pathways on WUS regulation are coordinated in stem cell niche is 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. Upon heat stress, decreased CLV signaling enhances the stability of BZR1 in the nucleus to repress cytokinin biosynthesis and WUS content to protect stem cells from heat shock. Our results revealed a positive feedback loop between CLV3 and WUS that is mediated by multiple hormone interactions, which are critical for plants to adapt to harsh environments.