Zeaxanthin epoxidase that plays an important role in the xanthophyll cycle and abscisic acid (ABA) biosynthesis. Converts zeaxanthin into antheraxanthin and subsequently violaxanthin. Required for resistance to osmotic and drought stresses, ABA-dependent stomatal closure, seed development and dormancy, modulation of defense gene expression and disease resistance and non-photochemical quencing (NPQ). Through its role in ABA biosynthesis, regulates the expression of stress-responsive genes such as RD29A during osmotic stress and is required for normal plant growth during vegetative development. Is required for late skotomorphogenic growth through its role in the xanthophyll carotenoids neoxanthin, violaxanthin and antheraxanthin biosynthesis. Required for beta-aminobutyric acid (BABA)-induced priming in disease resistance, tolerance to salt and drought stresses and sterility. Participates in NPQ by regulating the level of zeaxanthin in photosynthetic energy conversion. NPQ is a process that maintains the balanc