以番茄为模式解析系统素和茉莉酸介导的植物防御信号通路

在番茄中，多肽信号分子系统素和经典激素茉莉酸通过一条共同的信号通路调控植物防御。本项目将从分析系统素信号通路的抑制子spr1, spr5和spr7入手解析系统素-茉莉酸介导的植物防御。我们将克隆SPR1基因并阐明其整合系统素信号和茉莉酸信号的机理。SPR5编码转录中介体Mediator的亚基MED25。我们将揭示MED25与转录因子SAP1互作正向调控（激活）系统素-茉莉酸途径的机理；我们还将揭示Mediator的另一个亚基MED15与转录因子SAP2互作负向调控（消减）系统素-茉莉酸途径的机理。SPR7编码一个Importin-ß 蛋白，我们将阐明SPR7与转录辅助因子SIP1互作正向调控系统素-茉莉酸途径而负向调控水杨酸途径的分子机理。总之，本项目将从系统素信号与茉莉酸信号的整合、茉莉酸信号途径的“激活”与“消减”、茉莉酸与水杨酸的拮抗等方面阐明系统素-茉莉酸调控植物防御的分子机理。

In tomato, the peptide signal systemin and the plant hormone jasmonate regulate plant defense to mechanical wounding, insect attack and pathogen infection through a common signaling pathway. Therefore, the systemin/jasmonate signaling pathway of tomato provides a unique model system to investigate the mechanism by which peptide and hormone signals coordinate plant defense. In this application, we propose to build up our previous success in using a forward genetic approach to identify tomato mutants that suppress system/jasmonate-regulated plant defense. The specific aims are: 1) to clone the SPR1 gene and elucidate its proposed action mechanism in systemin perception and in integrating the systemin action into the downstream jasmonate signaling pathway; 2) to elucidate how SPR5, which encodes the MED25 subunit of the Mediator transcriptional co-activator complex, interacts with the transcription factor SAP1 to activate the systemin/jasmonate signaling pathway; 3) to elucidate how MED15, another subunit of Mediator, interacts with the transcription factor SAP2 to attenuate the systemin/jasmonate signaling pathway. 4) to elucidate how SPR7, which encodes an importin-ß (IMPß), regulates the antagonistic interaction between systemin/jasmonate-signaled plant defense and salicylic acid-signaled plant defense. Results obtained from these studies promise to provide insight into the mechanisms by which the peptide systemin integrates its action with that of jasmonate, systemin/jasmonate activates and attenuates plant defense, as well as systemin/jasmonate-regulated plant defense inhibits salicylic acid-regulated plant defense.