Development of abscisic acid biosynthesis inhibitor and its effect on plants

Abstract

To facilitate elucidation of the functions of ABA and to find new mutants involved in ABA signaling, we developed a new inhibitor of ABA biosynthesis and named it abamine. Abamine was a potent competitive inhibitor of the double-bond cleavage enzyme of 9-cis-epoxycarotenoid dioxygenase, with a Ki of 38.8 microM. In 0.4 M mannitol solution, which mimics the effects of osmotic stress. abamine both inhibited stomatal closure in spinach leaves, which was restored by co-application of ABA, and increase in luminescence intensity in RD29B::LUC transgenic Arabidopsis. The ABA content of plants in 0.4 M mannitol was increased approximately 16-fold compared with controls, whereas 50 to 100 microM of abamine inhibited about 50% of this ABA accumulation in both spinach leaves and Arabidopsis. These results demonstrate that abamine is a novel ABA biosynthesis inhibitor targeting the oxidative cleavage of 9-cis-epoxycarotenoids, and it affects plant responses regulated by ABA.