BES1/BZR1 Homolog 3 cooperates with E3 ligase AtRZF1 to regulate osmotic stress and brassinosteroid responses in Arabidopsis

Abstract

Proline (Pro) metabolism plays important roles in protein synthesis, redox balance, and abiotic stress response. However, whether they share a cross-talk with brassinosteroid (BR) signaling regulation remains unclear. Here, we introduced an Arabidopsis intergenic enhancer double mutant namely proline content alterative 41 (pca41) which T-DNA tagged in atrzf1 mutant background. The pca41 showed that T-DNA inserted at the site of gene encoded for BEH3. The pca41 possessed an insensitive phenotype that was stronger than atrzf1 observed under osmotic stress including high Pro accumulation and decreased reactive oxygen species levels. Analysis of physiological, genetic, and molecular networks revealed that negative regulation of BEH3 in abiotic stress was linked to BR-signaling pathway. Obtained data also suggested that AtRZF1, an E3 ubiquitin ligase, might control dehydration, abscisic acid, and BR responses in a BEH3-dependent manner. Under darkness, the pca41 displays the long hypocotyl phenotype, which is similar to atrzf1 and beh3, suggesting that BEH3 acts in the same pathway as AtRZF1. Furthermore, overexpression of BEH3 resulted in dehydration-induced sensitive phenotype, and this sensitive phenotype is reversed by exogenous BR application. Taken together, our results suggest that AtRZF1 and BEH3 might play an important role in osmotic stress response via ubiquitination and BR-signaling cross-talk.