| Budget Amount *help |
¥4,000,000 (Direct Cost: ¥4,000,000)
Fiscal Year 1990: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1989: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
The reception of 27KD proteoglucomannan, a blast fungus elicitor, by the putative receptors on plasma membrane of rice blade cell, enhanced the metabolic turnover of inositolphospholiped, and myoinositol 1, 4, 5-tris- phosphate was formed. The Ca^<2+> level in the host cell was elevated, and ca^<2+>-CaM complex was formed. This accompanied the phosphorylation of an unidentified protein. The O^*_ forming enzyme system and phospholipase A_2 were activated as the effector reactions. The O^*_ formed resulted in the hypersensitive reaction, and alpha-linolenate released resulted in the formation of hydroperoxides and unsaturated hydroxy C_<18> fatty acids ( UHFA ), acting as antimicrobial agents. The endogenous ethylene was formed depending on the O^*_ generation. Ethylene, alpha -linolenate and UHFAs were suggested to participate in the intercellular signaling. The groups of enzymes ( PAL, LOX, POX etc.) participated in the expression of resistance reactions ( lignification, UHFA and phytoalexin biosynthesis ) at the mid to later stage after the infection, were induced time-sequentially by the activation of defense genes. The details of the gene activation mechanism by proteinic transacting factors remain for further molecular biological exploration. Although the dynamic behaviors of polyamine discriminated the compatible and incompatible interaction as in the other resistant reactions, the implication of these earlier phenomena related to resistant reactions are still elusive and remain for future studies. A conceptual framework on the causality of induced defense mechanism in rice blade is thus outlined by timesequential analyses on the activations and inductions of enzymes concerned and by the discrimination of reaction cascades by the biochemical implications considering the transmembrane, intra- and interellular signaling.
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