| Co-Investigator(Kenkyū-buntansha) |
KODAMA Motoichiro Tottori University, Faculty of Agriculture, Lecturer, 農学部, 講師 (00183343)
KOHMOTO Keisuke Tottori University, Faculty of Agriculture, Professor, 農学部, 教授 (80032093)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1995: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1994: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
Black leaf spot of Cruciferae caused by Alternaria brassicicola is a major disease in cultivated Brassica plants. Recently, we found that the pathogen produces host-specific toxin (HST), named AB-toxin. The toxin was released from the germinating spores only when spores were inoculated on host leaves, indicating that the production of AB-toxin by the pathogen is induced by substances in host leaves. Interestingly, the activity of AB-toxin was retained by membranes with a molecular weight cutoff of 5,000. In addition, the activity was heat unstable, and was lost by treatment with proteinase. Thus, unlike other HSTs, AB-toxin has a high molecular weight and is probably a protein (s). As a protein, AB-toxin may offer the advantage of being a direct gene product.
Arabidopsis thariana which is known as a model plant for molecular biology, belongs to Cruciferae. Therefore, responses to the pathogen and AB-toxin of A.thariana were investigated. When the spores of the pathogen were inoculated on leaves of 7 ecotypes of A.thariana, black spot lesions appeared on 6 ecotypes except an ecotype RLD.AB-toxin was examined for biological activity on A.thariana. The toxin was toxic to 6 ecotypes, but was harmless to RLD.These results indicate that there are ecotypes susceptible and resistant to the pathogen and AB-toxin. To investigate hereditary background of the responses of A.thariana, susceptible and resistant ecotypes were crossed. The responses of the crossed plants indicated that the resistance is determined by a single dominant gene. On the other hand, AB-toxin induced electrolyte leakage from susceptible ecotype leaves within 1 hr after treatment, indicating that AB-toxin has a primary effect on the plasma membranes of host cells.
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