Positive regulator of abscisic acid (ABA)-mediated signaling pathways involved in abiotic stress responses (e.g. osmotic stress) and leading to various plant adaptation (e.g. stomata closure). Interacts with COP1 coiled-coil region. Associated to the cytoskeleton in hypocotyl and cotyledon cells, but not in root cells, where observed as disconnected cytoplasmic speckles (PubMed:7753789). Localized to the plasma membrane in the epidermal cells of cotyledons and roots, including root hairs (PubMed:27372427). Mainly expressed in photosynthetic and vascular tissues. Accumulates in both dark-grown and light-grown seedlings roots and shoots, leaves and flowers (at protein level). In seedlings, accumulates in cotyledons and the hypocotyl, especially in the vein. In adult plants, mainly detected in mature leaves, particularly in vascular tissues. Also present in the vein of sepals and petals of flowers. Induced by osmotic stress (e.g. mannitol) and abscisic acid (ABA). Short hypocotyls. Increased sensitivity to osmotic stress (e.g. mannitol), but reduced sensitivity to abscisic acid (ABA) associated with lower levels of abiotic stress-related gene expression but higher ABA biosynthesis genes levels. Truncated N-terminus.