Abstract
We have previously reported that a cytochrome P450 gene that encodes steviol synthase was identified in Arabidopsis. Transgenic Arabidopsis plants overexpressing this steviol synthase gene showed semi-dwarfism like mild gibberellin (GA)-deficient mutants. GA analysis indicated that the levels of non 13-hydroxy GAs including GA4 were decreased, whereas those of 13-hydroxy GAs including GA1 (which is less active in Arabidopsis) were increased in the transgenic plants. To identify rice ortholog of this gene from the same gene family (CYP714), we made transgenic Arabidopsis plants that overexpress each rice CYP714 gene whose function is unknown. We found that two of these overexpressor plants show semi-dwarfism. GA analysis indicated that the endogenous GA profiles of these plants were similar to those of the overexpressor of the Arabidopsis steviol synthase gene. These results suggest that rice has at least two cytochrome P450 genes that are involved in GA 13 hydroxylation.
