Molecular breeding of rice by modulating gibberellin metabolic pathway
2003
Tanaka, H. | Itoh, H. | Sakamoto, T. | Kayano, T. | Koga-Ban, Y. | Kobayashi, M. | Matsuoka, M.
Gibberellin (GA) promotes various growth and development processes in higher plants. Some dwarf mutants in rice were identified as being GA-deficient. We have isolated cDNA clones for rice 3beta-hydroxylase and 2beta-hydroxylase based on the conserved DNA sequences among 2-oxoglutarate-dependent dioxygenase. We showed that there were at least two distinct genes for rice 3beta-hydroxylase and that one of them (OsGA3ox2) corresponded to the locus d18, the rice dwarf gene. The enzyme 3beta-hydroxylase can regulate a biosynthesis of the active form of GA. In contrast, 2beta-hydroxylase catalyzes to inactivate an active form of GA. The overexpression of the 2beta-hydrozylase gene would also decrease the content of the active form of GA. We constructed two sets of chimeric DNA: one was antisense OsGA3ox2 cDNA driven by the rice actin promoter, and the other was sense OsGA2ox1. They were introduced into rice cv. Nipponbare by the Agrobacterium-mediated transformation method and dwarfed transgenic plants were obtained.
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