Biotechnology Research Center, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Department of Biosciences, Teikyo University, Utsunomiya, Tochigi, Japan.
Sci Rep. 2017 Jan 9;7:40175. doi: 10.1038/srep40175.
Biosynthesis of sakuranetin, a flavonoid anti-fungal phytoalexin that occurs in rice, is highly dependent on jasmonic acid (JA) signalling and induced by a variety of environmental stimuli. We previously identified OsNOMT, which encodes naringenin 7-O-methyltransferase (NOMT); NOMT is a key enzyme for sakuranetin production. Although OsNOMT expression is induced by JA treatment, the regulation mechanism that activates the biosynthetic pathway of sakuranetin has not yet been elucidated. In this study, we show that JA-inducible basic helix-loop-helix transcriptional factor OsMYC2 drastically enhances the activity of the OsNOMT promoter and is essential for JA-inducible sakuranetin production. In addition, we identified 2 collaborators of OsMYC2, OsMYC2-like protein 1 and 2 (OsMYL1 and OsMYL2) that further activated the OsNOMT promoter in synergy with OsMYC2. Physical interaction of OsMYC2 with OsMYL1 and OsMYL2 further supported the idea that these interactions lead to the enhancement of the transactivation activity of OsMYC2. Our results indicate that JA signalling via OsMYC2 is reinforced by OsMYL1 and OsMYL2, resulting in the inductive production of sakuranetin during defence responses in rice.
樱花素是一种在水稻中产生的黄酮类抗真菌植物抗毒素，其生物合成高度依赖茉莉酸（JA）信号，并受多种环境刺激诱导。我们之前鉴定了编码柚皮素 7-O-甲基转移酶（NOMT）的 OsNOMT；NOMT 是樱花素产生的关键酶。尽管 OsNOMT 的表达受 JA 处理诱导，但激活樱花素生物合成途径的调控机制尚未阐明。在这项研究中，我们表明 JA 诱导的基本螺旋-环-螺旋转录因子 OsMYC2 极大地增强了 OsNOMT 启动子的活性，是 JA 诱导樱花素产生所必需的。此外，我们鉴定了 2 个 OsMYC2 的协作因子，即 OsMYC2 样蛋白 1 和 2（OsMYL1 和 OsMYL2），它们与 OsMYC2 协同进一步激活 OsNOMT 启动子。OsMYC2 与 OsMYL1 和 OsMYL2 的物理相互作用进一步支持了这些相互作用导致 OsMYC2 的转录激活活性增强的观点。我们的结果表明，通过 OsMYC2 的 JA 信号通过 OsMYL1 和 OsMYL2 得到加强，导致水稻防御反应中樱花素的诱导产生。
