AREB1, an ABA-induced transcription factor, plays a key role in drought stress response in Arabidopsis thaliana.

Abstract

AREB1 is a bZIP transcription factor that binds ABRE in the promoter region of ABA-inducible genes. Here we showed that ABA-induced posttranscriptional modification as well as expression of the AREB1 gene is required for AREB1 to activate expression of its downstream genes. Plants overexpressing an active form of AREB1 showed ABA hypersensitivity and enhanced drought tolerance, and 9 up-regulated genes in the plants were divided into two groups: LEA class genes and ABA- and drought-stress inducible regulatory genes. Moreover, in the promoter region of each gene, more than two ABRE motifs were found. By contrast, areb1 null mutant and a dominant loss-of-function mutant of AREB1 (AREB1:RD) with a repressor domain exhibited ABA insensitivity. Further, AREB1:RD plants displayed less tolerance to drought and 4 of the 9 up-regulated genes were down-regulated in the plants. These data suggest that AREB1 regulates novel ABRE-dependent ABA-signaling that enhances drought tolerance in vegetative tissues.