The Arabidopsis dehydrin ERD14 chaperones the brassinosteroid receptor kinase BRL3 to the plasma membrane to confer drought resistance

Brassinosteroid plant hormones are involved in growth, biotic and abiotic-stress signaling, but functional analysis of its multiple receptors has largely focused on the ubiquitously expressed BRASSINOSTEROID INSENSITIVE 1 (BR1). The vascular-expressed brassinosteroid receptor kinase BRI1-LIKE 3 (BRL3) has a specific and essential role in Arabidopsis adaptation to drought and elevated temperature. However, the mechanistic understanding of BRL3 function and regulation is scant. Here, we show the dehydrin ERD14 colocalizes with BRI1 and BRL3 at the plasma membrane and physically interacts with these receptors through the ERD14 ^Lys domain for proper receptor recruitment. erd14 mutants internalize BRL3–GFP and revert drought-resistant BRL3 over-expression phenotypes. BRL3 activation and downstream signaling events, including dephosphorylation of BES1 transcription factor, depend on the chaperone function of ERD14. Our study shows how proper chaperoning by ERD14 regulates BRL3 subcellular localization and activity of the vascular receptor, prompting re-examination of models of brassinosteroid-receptor functional diversification in plant adaptation to abiotic stress from specific cells of the vascular systems.