Abstract
Abscisic acid (ABA) is a plant hormone involved in various stress responses such as drought and salinity. We have demonstrated that an Arabidopsis aldehyde oxidase (AAO3) catalyzes the last step of ABA biosynthesis. Expression of AAO3 is rapidly induced by dehydration in leaves, indicating that AAO3 plays an important role on ABA biosynthesis during stress response. Further expression analysis revealed that drought and osmotic stress induced the expression of AAO3 in shoots, but the treatments had a little effect on the expression of AAO3 in roots. On the other hand, salt (NaCl) treatment efficiently induced the expression of AAO3 in roots. Exogenously applied ABA induced the expression of AAO3 both in shoots and roots. These data indicate the existence of complex regulation mechanism of AAO3 expression depending on stress and plant organ. To reveal the detailed regulation mechanism of AAO3 expression, promoter analysis is now in progress.
