| Co-Investigator(Kenkyū-buntansha) |
KODAMA Motoichiro Tottori University, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (00183343)
NAKAJIMA Hiromitsu Tottori University, Faculty of Agriculture, Professor, 農学部, 教授 (40144646)
MORI Nobuhiro United Graduate School of Agricultural Sciences, Professor, 連合農学研究科, 教授 (30127469)
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| Research Abstract |
1.Detection of Pathogens Producing Host-Specific Toxins (HSTs) and Structure Determination of HSTs
Alternaria brassicicola, the cause of black leaf spot of Brassica plants, produced a protein HST named AB-toxin only on host leaves. We found that an oligosaccharide for inducing AB-toxin production is released from host leaves after spore germination. Production of HST by germinating spores of pathogen mediated with host-derived factor is the first report. A.brassicae, the cause gray leaf spot of Brassica plants, is known to produce destruxin B as a HST, In this study, however, we found that toxicity of destruxin B is non-specific, and the pathogen produces new protein HST(s) different from destruxin B.
2.Molecular Analysis of Pathogenicity in Patnogens
A.alternata tomato pathotype, the cause Alternaria stem canker of tomato, produces HST named AAL-toxin. We isolated a HST biosynthesis gene, ALT1, whose product catalyzes the production of AAL-toxin in the pathogen. The ALT1 gene formed gene
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cluster involved in AAL-toxin biosynthesis of the pathogen. ALT1 was only present on the conditionally dispensable (CD) chromosomes in the pathogen suggesting acquisition by horizontal gene transfer.
3.Molecular Analysis of Accessibility of Pathogens in Plants
A.alternata apple pathotype, the cause of Alternaria blotch of apple, produces a HST named AM-toxin. Because a single dominant gene controls susceptibility to the pathogen and AM-toxin in apple cultivars, we attempted to detect the susceptibility-related molecules. The results indicated that susceptibility of apple cultivars closely associates with SA60, a homolog of α-subunit (60α) of chloroplast chaperonin, and SA60 appears through a point mutation of chloroplast chaperonin 60α genes in resistant cultivars of apple. AM-toxin has a primary action site in chloroplasts of susceptible apple cultivars. Therefore, SA60 proteins may be a receptor for AM-toxin. On the other hand, tomato pathogens, A.alternata tomato pathotype and Corynespora cassiicola, the cause of Corynespora target spot of tomato, produce HSTs named AL-toxin and CCT toxin, respectively. Both pathogens were investigated for the sensitivity to α-tomatine, an antifungal substance in tomato. The results indicated that tomato pathogens detoxify α-tomatine in the infection process and that the detoxification is essential for colonization of the pathogens into tissues mediated by HSTs. Less
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