Abstract
Abscisic acid (ABA) is a plant hormone involved in the regulation of seed dormancy and germination. We have shown that AtNCED6 and AtNCED9 play a key role in ABA biosynthesis in seeds. Promoter-reporter analysis, in combination with in situ hybridization and RT-PCR, indicated that AtNCED6 was expressed in endosperm during early to mid seed development, whereas AtNCED9 expression was observed in the seed coat in the middle of seed development and in the embryo during late stages of seed development. These data indicate that ABA biosynthesis is regulated in tissue specific manners depending on developmental stages. However, factors controlling tissue-specific ABA biosynthesis as well as physiological roles of ABA synthesized in different tissues are not well understood. We are conducting promoter analysis of AtNCED6 and AtNCED9. In addition, identification of the genes whose expression is regulated by ABA in tissue specific manners is under progress.
