82.トリプトファンデカルボキシラーゼ阻害がイネの抵抗反応に及ぼす影響(口頭発表)

概要

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Rice leaves accumulate tryptophan derived secondary metabolites including serotonin and its hydroxycinnamic acid amides in response to pathogen attack. These compounds have been implicated in the physical defense system against pathogen invasion by deposition in the cell walls. Serotonin is biosynthesized from tryptophan via tryptamine, and tryptophan decarboxylase (TDC) catalyzes the first committed reaction. (S)-α-(Fluoromethyl) tryptophan (S-αFMT) was utilized to investigate the effects of inhibition of TDC on the defense responses of rice leaves. S-αFMT was enatiospecifically synthesized from L-tryptophan. S-αFMT effectively inhibited TDC activity extracted from rice leaves infected by Bipolaris oryzae. The treatment of rice seedlings with S-αFMT suppressed the accumulation of serotonin in a dose-dependent manner in the B. oryzae-inoculated leaves. The lesions formed on the leaves treated with S-αFMT lacked deposition of brown materials, and those leaves were severely damaged in comparison with the leaves that were not treated with S-αFMT. The feeding of tryptamine to S-αFMT-treated seedlings restored the accumulation of tryptophan derived metabolites as well as deposition of brown materials. In addition, the tryptamine feeding reduced the damage caused by fungal infection. Accordingly, the accumulation of tryptophan derived metabolites was suggested to be a part of effective defense responses of rice.
2009-10-06