Plays an important role in the abiotic stresses-induced abscisic acid (ABA) signaling and biosynthesis. Acts as positive regulator of ABA-mediated seed germination inhibition. Functions downstream of ABF2/AREB1, ABF4/AREB2 and ABF3. Homodimer. Moves from plasma membrane to cytosol under abiotic stress. Highly expressed in seeds and at lower level in roots and senescing leaves. Expressed in leaves and flowers. Induced by abscisic acid (ABA), osmotic shock and drought stress. Slightly induced by salt stress. No visible phenotype under normal growth conditions, but mutant seeds show decreased sensitivity to abscisic acid (ABA) during germination.