Endogenous stress-related signal directs shoot stem cell fate in Arabidopsis thaliana.

Stem cell populations in all multicellular organisms are situated in a niche, which is a special microenvironment that defines stem cell fate. The interplay between stem cells and their niches is crucial for stem cell maintenance. Here, we show that an endogenous stress-related signal (ESS) is overrepresented in the shoot stem cell niche under natural growth conditions, and the vast majority of known stem-cell-specific and niche-specific genes responded to stress signals. Interference with the ESS in the stem cell niche by blocking ethylene signalling impaired stem cell maintenance. Ethylene-insensitive 3 (EIN3), the key transcription factor in ethylene signalling, directly actives the expression of the stress hub transcription factor AGAMOUS-LIKE 22 (AGL22) in the stem cell niche and relays ESS signals to the WUSCHEL/CLAVATA network. Our results provide a mechanistic framework for ESS signalling control of the stem cell niche and demonstrate that plant stem cells are maintained by a native stress microenvironment in vivo.