Molecular elucidation of elicitors and suppressors in rice blast disease by using as the marker the Sekiguchi lesion formation in lesion mimic mutants

• Project/Area Number: 12660046
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 植物保護
• Research Institution: Shimane University
• Principal Investigator: ARASE Sakae Shimene University, Life and Environmental Science, Professor, 生物資源科学部, 教授 (40127478)
• Project Period (FY): 2000 – 2002
• Project Status: Completed (Fiscal Year 2002)
• Budget Amount: ¥3,700,000 (Direct Cost: ¥3,700,000); Fiscal Year 2002: ¥500,000 (Direct Cost: ¥500,000); Fiscal Year 2001: ¥500,000 (Direct Cost: ¥500,000); Fiscal Year 2000: ¥2,700,000 (Direct Cost: ¥2,700,000)
• Keywords: tryptophan decarboxylase / monoamine oxidase / Sekiguchi lesion / rice blast / rice Sekiguchi lesion mutant / reactive oxygen / catalase / 突然変異イネ / トリプタミン / エリシター / モノアミン酸化酵素 / 遺伝子対遺伝子説 / 拒否性 / 受容性

Research Abstract

An antifungal compound with an infection-inhibiting activity was isolated from a rice Sekiguchi lesion (sl) mutant and identified as the indole alkaloid tryptamine. Tryptamine inhibited not only spore germination and appressorium formation of M.grisea at high concentrations (>600 μg/ml) but also the infection hypha formation in onion cells at low concentrations (150-300 μg/ml). Tryptamine is a normal compound of the rice sl mutant but accumulates further in rice with a mutant-type response (Sekiguchi lesion formation) to inoculation with M.grisea spores. A mutant type of response is involved in light-enhanced resistance. The accumulation of tryptamine was not induced, however, in rice with a wild-type response (blast lesion formation). This study strongly suggests that tryptamine plays an important role as a possible factor in light-enhanced resistance in the rice sl-mutants. Increased activities of tryptophan decarboxylase (TDC) and monoamine oxidase (MAO) were light-dependent and obs erved in sl-mutant of rice infected with M.grisea. TDC and MAO activites were already observed before penetration of M.grisea to rice cells and kept at high level even after Sekiguchi lesion formation. Spore germination fluid of M.grisea also induced the Sekiguchi lesion formation with increased activites of both enzymes activities and tryptamine accumulation. Sekiguchi lesion was also induced by the treatments with tryptamine and β-phenylethylamine, which are substrates for MAO, under the light, but not induced by non-substrates such as indole-3-propionic acid, (^^+___)-phenylethylamine and tryptophan even under the light. Light-dependent induction of Sekiguchi lesion by tryptamine was significantly inhibited in the presence of MAO inhibitors, metalaxyl and semicarbazide, and H_2O_2-scavengers, ascorbic acid and catalase. H_2O_2 in leaves with Sekiguchi lesion was demonstrated directly in situ by strong DAB staining. On the other hand, H_2O_2 induced Sekiguchi lesion on leaves of cv. Sekiguchi-asahi under the light, but not under the dark. This difference was associated with decrease of the catalase activity in infected leaves under the light and no decrease under the dark. We hypothesize that H_2O_2-induced breakdown of cellular organelles such as chloroplast and mitochondria in mesophtll cells may bring about high activities of TDC and MAO and development of Sekiguchi lesion, and that the Sl gene products in wild type rice may function as a suppressor of organelle breakdown cased by chemical or environmental stress.

Research Products

• [Publications] 上野 誠, 田島尚子, 磯田 淳, 本田雄一, 荒瀬 栄: "島根県に発生した突然変異イネ群に存在する抗菌物質"島根大学生物資源科学部研究報告. 7. 9-14 (2002)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Arase, S., Ueno, M., Toko, M., Itoh, K., Honda, Y., Ozoe, Y.: "Light-dependent accumulation of tryptamine in the rice Sekiguchi lesion mutant infected with Magnaporthe grisea"Journal of Phytopathology. 149. 409-413 (2001)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Arase, S., Ueno, M., Honda, Y.: "Advances in Microbial Toxin Research and its Biotechnological Exploitation"Kluwer Academic/Plenum Press, New York, USA. 1-288 (2002)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Arase,S., Ueno,M., Toko,M., Itoh,K., Honda,Y., Ozoe,Y.: "Light-dependent accumulation of tryptamine in the rice Sekiguchi lesion mutant infected with Magnaporthe grisea"J. Phytopathol.. 149. 409-413 (2001)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Ueno,S., Tajima,N., Isota,J., Honda,Y., Arase,S.: "Anti-fungal compounds from lesion mimic mutants of rice found in Shimane Prefecture"Bull. Fac. Life Env. Sci. Shimane Univ.. 7. 9-14 (2002)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Arase,S., Ueno,M., Honda,Y., Ed. R. K. Upadhyay: "Advances in Microbial Toxin Research and its Biotechnological Exploitation"Kluwer Academic/ Plenum Press. 1-288 (2002)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] 上野: "島根県で見出された変異イネ群に含まれる抗菌物質"島根大学生物資源科学部研究報告. 149. 409-413 (2001)
• [Publications] Arase, S. et al.: "Light-dependent accumulation of tryptamine in the rice Sekiguchi lesion mutant infected with Magnaporthe grisea"Journal of Phytopathology. 149. 409-413 (2001)
• [Publications] Arase, S., Ueno, M., Honda, Y.: "Advances in Microbial Toxin Research and its Biotechnological Exploitation"Kluwer Academic/Plenum Press, New York, USA(印刷中). (2002)
• [Publications] Arase,S. et al.: "Light-dependent accumulation of tryptamine in the rice Sekiguchi lesion mutant infected with Magnaporthe grisea"Journal of Phytopathology. (accepted).