| Budget Amount *help |
¥15,200,000 (Direct Cost: ¥15,200,000)
Fiscal Year 2001: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2000: ¥5,400,000 (Direct Cost: ¥5,400,000)
Fiscal Year 1999: ¥7,600,000 (Direct Cost: ¥7,600,000)
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| Research Abstract |
1) A toxin that produced by Pseudomonas syringae pv. Actinidiae, which causes canker disease of kiwifruit plants, was identified as a phaseolotoxin, and the gene (arg K) for toxin-insensitive OCTase (ROCTase) tolerant to phaseolotoxin was cloned from the bacterium itself. In plants, OCTase is located in chloroplasts. Thus, the argK gene was fused with a transit peptide (TP) gene of Rubisco small subunit (SS) from tobacco plant to transfer the gene into chloroplasts. The fused gene was introduced to kiwifruit plants by Agrobacterium-mediated transformation. Transgenic plants were selected by kanamycin-resistance and by phaseolotoxin tolerance, When the selected transgenic plants were spray-inoculated by P. syringae pv, actinidiae, the transgenics exhibited few symptoms although control plants developed a lot of symptoms, and the bacterial multiplication was suppressed in the transgenic plants. Thus, these transgenic plants were not only tolerant to phaseolotoxin but also resistant to ca
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nker disease by P. syringae pv. Actinidiae.
2) Dollar spot disease of bentgrass is caused by Sclerotinia homoeocarpa that produces some toxic substances in the culture medium. The culture filtrate inhibited the seed germination and root development of bentgrass and other plants, suggesting that this phytotoxin is host non-specific. Thus, the phytotoxic substances from the culture filtrate of S. homoeocarpa were purified by solvent extraction, column chromatography, and liquid chromatography. The chemical structures of the toxins were determined as diterpenes by Mass and NMR spectrometry.
3) Mutants of Burkholderia glumae, the causal agent of rice seedling rot and grain rot diseases, were isolated by transposon (Tn) mutagenesis with Tn 4431 harboring tetracycline (Tc) resistance gene, which was carried on the suicide vector pUCD623. The resulting Tc-resistant colonies were screened for the loss of toxin production, and also for the lack of pathogenicity to rice seedlings. >From analysis of the mutants with a single copy of Tn insertion on the genomic DNA, it was shown that the genomic region neighboring the insertion of Tn has the genes highly homologous to repA gene and par A and B genes, which are related to replication or distribution of chromosome or plasmids. Also, analysis of the natural mutants with lack of pathogencity showed loss of par A and B, but with rep A. Thus, it was suggested that a part of the genomic DNA of B. glumae was lost or transferred during the successive incubation in a medium, and the DNA deletion has to do with the loss of pathogenicity in B. glumae. Less
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