63.イネのOsCPS4ノックダウン株の特徴付け(口頭発表)

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Phytoalexins are low-molecular-weight compounds produced after exposure to microorganism attack, elicitor and ultraviolet, and have been suggested to serve as plant antibiotics. Fourteen diterpenoid phytoalexins has been identified from rice (Oryza sativa): momilactones A & B, phytocassanes A to E, oryzalexins A to F and S. We isolated 6 cDNAs encoding diterpene cyclases responsible for their biosynthesis. OsCPS4 encodes syn-copalyl diphosphate synthase involved in the biosynthesis of momilactones and oryzalexin S. Momilactone B was also identified as an allelopathic substance exuded from rice roots. We have isolated a mutant (cps4-tos) of OsCPS4, in which Tos17 was inserted. Quantitative analysis indicated that endogenous levels of momilactones in leaf blades, roots and mature seeds of cps4-tos were quite lower than those of wild type. Consequently, the contents of momilactones exuded from roots of cps4-tos were lower than those of wild type. Disease resistance of cps4-tos leaf blade against rice blast fungus was almost the same as that of wild type. Interestingly, more weeds grew around the cps4-tos plants rather than around the wild type plants. It might be due to the lower levels of momilactone B exuded from roots of cps4-tos.
2010-10-01