28.新規イネジベレリン2-酸化酵素OsGA2ox7の遺伝子発現部位とその基質特異性の解析(口頭発表)

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Concentrations of bioactive gibberellins (GAs) are controlled by the balance between their synthesis and deactivation. Therefore, it is very important to know precise expression patter ns and substrate specificity of individual GA-synthesizing and -deactivating enzymes to understand the mechanisms regulating GA levels. Out of over 12,000 rice FOX (F__-ull-length cDNA O__-ver-eX__-presser) lines, we have found the ectopic over-expression of AK101758 gene conferred super-dwarf phenotype to rice plants. The AK101758 protein was homologous to six previously known rice GA 2-oxidases (GA2oxs). A phylogenetic analysis showed AK101758 was grouped into GA2oxs that hydroxylate C19-gibberellins. Accordingly, we designated the AK101758 gene as OsGA2ox7. In situ hybridization analyses showed that OsGA2ox7 was expressed at the base of shoot apical meristems just like OsGA2ox1. Furthermore, OsGA2ox7 transcripts were observed in glumous flower primordia, indicating that the deactivation of GAs is important for the differentiation of glumous flowers. The levels of endogenous bioactive GAs, GA_1 and GA_4, and that of an immediate precursor of GA_1, GA_<20>, were reduced in the super-dwarf OsGA2ox7-FOX rice. Interestingly, the level of GA_<19> was also decreased in the super-dwarf rice, indicating that OsGA2ox7 hydroxylates upstream intermediates of GA synthesis including C20-gibberellins. OsGA2ox7 protein produced in E. coli showed GA2ox activity. The substrate specificity is currently under examination.
2008-10-06

28.新規イネジベレリン2-酸化酵素OsGA2ox7の遺伝子発現部位とその基質特異性の解析(口頭発表)

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