Absicsic acid (ABA), an apocarotenoid synthesized by oxidative cleavage of epoxy-carotenoids, is involved in developmental progresses such as seed maturation and dormancy and the response to various environmental stresses in higher plants. The use of carotenoid biosynthesis inhibitors, such as norflurazon and fluridone, has been shown to be useful major tools in studies on the determination of physiological fimctions of endogenous ABA and regulation of the pathway in plants. They give the serious damage to plants due to their ability to reduce the amount of carotenoid in plants. Therefor, the regulation of biosynthetic pathway downstream of zeaxanthin by inhibitors has been reported to be important for the regulation of ABA levels without any side effect on plants. For this reason, we have investigated the discovery of specific ABA biosynthesis inhibitors for the purpose of regulation of endogenous ABA biosynthesis.
