Abstract
Dormancy of the bulbils of Dioscorea is induced by GA treatment (GA-induced dormancy).ABA treatment also inhibited the sprouting of the bulbils. So far we have tried to isolate the key genes of ABA metabolism, and succeeded in cloning the full lengths of the ORFs of DjNCED1 and 2, and DjABA8'ox1, 2 and 3 from the young sprouts of D. japonica. The recombinant proteins from the yeasts into which DjABA8'ox1 and 2 were transformed possessed the enzymatic activities of ABA8'-hydroxylase. Here,we analyzed the endogenous levels of ABA and its catabolites by LC-MS/MS as well as the key gene expression levels of ABA metabolism by semi-quantitative RT-PCR in the chilled nondormant bulbils of D. japonica incubated with aqueous GA3.The GA3 treatment increased the expression levels of DjNCED1 and 2, and decreased those of DjABA8'ox2 and 3 in the bulbils.The endogenous level of ABA in the bulbils was clearly increased by the GA3 treatment. The GA treatment might increase the endogenous level of ABA through the regulation of gene expression of ABA metabolism, leading the Discorea bulbils to GA-induced dormancy.We are grateful to Dr. Y. Jikumaru (RIKEN) for analyzing ABA and its catabolites.
