Plants have evolved a plethora of effective mechanisms to protect themselves from biotic stresses. Jasmonates (JAs) are employed as vital defence signals against both insect and pathogen attack. Jasmonic acid (JA) signalling plays a central role in plant defence and development. S-nitrosylation, a redox-based post-translational modification plays an important role in plant disease resistance. S-nitrosoglutathione (GSNO) is formed by the reaction of antioxidant glutathione (GSH) and nitric oxide (NO) and acts as a mobile reservoir of NO bioactivity. The Arabidopsis thaliana S-NITROSOGLUTATHIONE REDUCTASE (AtGSNOR1) controls multiple modes of disease resistance via S-nitrosylation. In this context, the Arabidopsis lossof- function mutant atgsnor1-3 exhibits higher susceptibility to Botrytis cinerea a necrotrophic pathogens and Pieris rapae insect attack. Accumulation of JA was reduced in atgsnor1-3 after mechanical wounding. JA marker genes were also downregulated in atgsnor1-3 compared to Col-0 after Methyl Jasmonate (Me-JA) treatment. The relative gene expression of Vegetative Storage Protein (VSP) was reduced in atgsnor1-3 compared to wild type. Further, protein-protein interaction experiments in yeast two hybrid assays revealed an inhibition of Coronatine-insensitive 1 (COI1) and Jasmonate ZIM domain (JAZ1) interactions upon NO donor application. Interestingly it was also shown that Nitric oxide donor may inhibited the degradation of JAZ1-β-glucoronidase (GUS) fusion protein driven by a CaMV35s:: JAZ1-GUS transgene in GUS histochemical analysis but not in flurometric assay. A biotin switch assay of recombinant JAZ1-Maltose-binding protein (MBP) has shown that JAZ1-MBP was S-nitrosylated and mass spectrometry suggested Cysteine229 (Cys229) was the site of this modification. Further, CaMV35S::JAZ1-Flag transgene expressed in either a wild-type or atgsnor1-3 genetic background, suggested that JAZ1 was S-nitrosylated in vivo. Collectively, our data imply that JA-signalling engaged in response to either insect predation or attempted B. cinerea infection is under redox control as high SNO in atgsnor1-3 has disrupted the JA signalling pathway. Furthermore, our data suggest that S-nitrosylation of Cys-229 of JAZ1 may control JA-mediated signalling by blocking the interaction of this protein with COI1, thus reducing the turnover of JAZ1 by the 26S proteasome and consequently enabling continued JAZ1-mediated repression of JA-dependent gene expression in the presence of Me-JA. Thus our findings highlight the importance of NO and associated S-nitrosylation in JA signalling during plant immune response.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19035号 / 農博第2113号 / 新制||農||1031(附属図書館) / 学位論文||H27||N4917(農学部図書室) / 31986 / 京都大学大学院農学研究科応用生命科学専攻 / (主査)教授 宮川 恒, 教授 西田 律夫, 教授 間藤 徹 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM