Chini A, Fonseca S, Fernández G, Adie B, Chico J M, Lorenzo O, García-Casado G, López-Vidriero I, Lozano F M, Ponce M R, Micol J L, Solano R
Departamento de Genética Molecular de Plantas, Centro Nacional de Biotecnología-CSIC, Campus Universidad Autónoma, 28049 Madrid, Spain.
Nature. 2007 Aug 9;448(7154):666-71. doi: 10.1038/nature06006. Epub 2007 Jul 18.
Jasmonates are essential phytohormones for plant development and survival. However, the molecular details of their signalling pathway remain largely unknown. The identification more than a decade ago of COI1 as an F-box protein suggested the existence of a repressor of jasmonate responses that is targeted by the SCF(COI1) complex for proteasome degradation in response to jasmonate. Here we report the identification of JASMONATE-INSENSITIVE 3 (JAI3) and a family of related proteins named JAZ (jasmonate ZIM-domain), in Arabidopsis thaliana. Our results demonstrate that JAI3 and other JAZs are direct targets of the SCF(COI1) E3 ubiquitin ligase and jasmonate treatment induces their proteasome degradation. Moreover, JAI3 negatively regulates the key transcriptional activator of jasmonate responses, MYC2. The JAZ family therefore represents the molecular link between the two previously known steps in the jasmonate pathway. Furthermore, we demonstrate the existence of a regulatory feed-back loop involving MYC2 and JAZ proteins, which provides a mechanistic explanation for the pulsed response to jasmonate and the subsequent desensitization of the cell.
茉莉酸是植物发育和生存所必需的植物激素。然而，其信号通路的分子细节在很大程度上仍不清楚。十多年前，COI1被鉴定为一种F-box蛋白，这表明存在一种茉莉酸反应的抑制因子，它在茉莉酸的作用下被SCF(COI1)复合体靶向进行蛋白酶体降解。在这里，我们报告了在拟南芥中鉴定出茉莉酸不敏感3（JAI3）和一个名为JAZ（茉莉酸ZIM结构域）的相关蛋白家族。我们的结果表明，JAI3和其他JAZ蛋白是SCF(COI1) E3泛素连接酶的直接靶标，茉莉酸处理会诱导它们的蛋白酶体降解。此外，JAI3负调控茉莉酸反应的关键转录激活因子MYC2。因此，JAZ家族代表了茉莉酸途径中两个先前已知步骤之间的分子联系。此外，我们证明了存在一个涉及MYC2和JAZ蛋白的调节反馈环，这为对茉莉酸的脉冲反应和随后细胞的脱敏提供了一个机制解释。
