Transcription activator. Regulates positively abscisic acid (ABA) response. Confers drought tolerance and sensitivity to ABA. Homodimer. In seedlings, mainly expressed in root tips, cotyledons, hypocotyls, and leaves, as well as its guard cells. In adult plant, detectable in stems, flowers, and siliques. Transiently by ABA and polyethylene glycol (PEG).