Functional analysis of upstream factors regulating the AREB1-mediated drought stress signaling in Arabidopsis thaliana.

Abstract

Under abiotic stress conditions such as drought and high salinity, ABA levels increase in plants, and ABA regulates the expression of many genes that function in the stress tolerance. In the promoters of such ABA-regulated genes, a conserved cis-element designated ABRE (ABA-responsive element), which controls expression of ABA-responsive genes, has been identified. An Arabidopsis cDNA encoding a bZIP-type transcription factor referred as ABRE-binding (AREB) 1 protein, was isolated using the yeast one-hybrid screening. We demonstrated that AREB1 is a transcriptional activator of novel ABRE-dependent ABA signaling involved in enhancing drought stress tolerance. Moreover, the ABA-dependent multisite phosphorylation of AREB1 by SnRK2 protein kinases has been shown to regulate its own activation. In this study, mainly based on the molecular characterization of SnRK2 protein kinases using SnRK2 mutants, we will discuss the roles of the SnRK2 protein kinases via the activation of AREB1 in ABA and drought stress signaling.