| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2000: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1999: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
Pseudomonas avenae (Acidovorax avenae) is a Gram-negative bacterium that causes a seedling disease characterized by the formation of brown stripes on the sheaths of infected plants. The host range of P.avenae is wide among monocotyledonous plants however, individual strains of the pathogen infect only one or a few host species. We shown that a rice-incompatible strain, N1141, caused a resistance response in cultured rice cells such as induction of the hypersensitive cell death and accumulation of EL2 or chitinase mRNAs which thought to be the defense-related gene, whereas a rice compatible strain, H8301, did not. Based on these results, we postulated that such induced resistance in rice cells is mediated by the recognition of a specific elicitor molecule produced by the incompatible strain of P.avenae. To identify the specific elicitor, a strain-specific antibody which was raised against N1141 and then absorbed with H8301 cells was prepared. When a cell extracts of strain N1141 was separated by SDS-PAGE and immunostained with the N1141 strain-specific antibody, only a flagellin protein was detected. Purified N1141 flagellin induced the hypersensitive cell death in cultured rice cells whereas the H8301 flagellin did not. A flagellin-deficient N1141 mutant constructed by marker exchange method completely lost the induction ability of hypersensitive cell death and the expression ability of the EL2 gene, whereas a flagellin-deficient compatible strain did not induce such resistance response in same manner as the compatible wild type. These results demonstrated that the resistance response in cultured rice cells is induced by the flagellin existing in the incompatible strain of P.avenae but not in the flagellin of the compatible strain. On the other hand, Cht-1 and PAL genes were not reduced in the N1141 flagellin-deficient mutant-inoculated cultured rice cells, suggesting that the induction of Cht-1 gene is regulated by another signal pathway.
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