Shimizu Takafumi, Miyamoto Koji, Miyamoto Kanako, Minami Eiichi, Nishizawa Yoko, Iino Moritoshi, Nojiri Hideaki, Yamane Hisakazu, Okada Kazunori
Biotechnology Research Center, The University of Tokyo, Tokyo 113-8657, Japan.
Biosci Biotechnol Biochem. 2013;77(7):1556-64. doi: 10.1271/bbb.130272. Epub 2013 Jul 7.
Jasmonate plays key roles in plant growth and stress responses, as in defense against pathogen attack. Jasmonoyl-isoleucine (JA-Ile), a major active form of jasmonates, is thought to play a pivotal role in plant defense responses, but the involvement of JA-Ile in rice defense responses, including phytoalexin production, remains largely unknown. Here we found that OsJAR1 contributes mainly to stress-induced JA-Ile production by the use of an osjar1 Tos17 mutant. The osjar1 mutant was impaired in JA-induced expression of JA-responsive genes and phytoalexin production, and these defects were restored genetically. Endogenous JA-Ile was indispensable to the production of a flavonoid phytoalexin, sakuranetin, but not to that of diterpenoid phytoalexins in response to heavy metal stress and the rice blast fungus. The osjar1 mutant was also found to be more susceptible to the blast fungus than the parental wild type. These results suggest that JA-Ile production makes a contribution to rice defense responses with a great impact on stress-induced sakuranetin production.
茉莉酸在植物生长和应激反应中发挥关键作用，比如在抵御病原体攻击方面。茉莉酰异亮氨酸（JA-Ile）是茉莉酸的一种主要活性形式，被认为在植物防御反应中起关键作用，但JA-Ile在水稻防御反应（包括植保素产生）中的作用在很大程度上仍不清楚。在此，我们通过使用osjar1 Tos17突变体发现，OsJAR1主要促进应激诱导的JA-Ile产生。osjar1突变体在JA诱导的JA反应基因表达和植保素产生方面存在缺陷，并且这些缺陷通过遗传方式得以恢复。内源性JA-Ile对于黄酮类植保素樱花素的产生是不可或缺的，但对于重金属胁迫和稻瘟病菌诱导的二萜类植保素的产生并非如此。还发现osjar1突变体比其亲本野生型对稻瘟病菌更敏感。这些结果表明，JA-Ile的产生对水稻防御反应有贡献，对胁迫诱导的樱花素产生有重大影响。
