Abstract
We have revealed that AAO3, one of the four Arabidopsis aldehyde oxidase (AAO) genes, is involved the last step of ABA biosynthesis. Although aao3 mutant showed wilty phenotype, seed dormancy of aao3 was not significantly reduced. However, endogenous ABA level in aao3 seed was reduced compared to that in wild type, and aao3 seed can germinate in the presence of uniconazole, a gibberellin biosynthesis inhibitor. Furthermore, the expression of NCEDs in aao3 siliques was significantly increased. In contrast, AAO4 is the major AAO expressed in siliques, but a mutant defective in this gene did not show any ABA related phenotypes in seed. In addition, it has been shown that AAO1 and AAO2 do not efficiently oxidize abscisic aldehyde. These results suggest that AAO3 plays a major role on ABA biosynthesis also in seeds. To further determine the extent of redundancy among four AAOs, now we are conducting double mutant analysis.
