Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, MI, 48824, USA.
Department of Plant Biology, Michigan State University, East Lansing, MI, 48824, USA.
New Phytol. 2017 Sep;215(4):1533-1547. doi: 10.1111/nph.14638. Epub 2017 Jun 26.
The plant hormone jasmonate (JA) promotes the degradation of JASMONATE ZIM-DOMAIN (JAZ) proteins to relieve repression on diverse transcription factors (TFs) that execute JA responses. However, little is known about how combinatorial complexity among JAZ-TF interactions maintains control over myriad aspects of growth, development, reproduction, and immunity. We used loss-of-function mutations to define epistatic interactions within the core JA signaling pathway and to investigate the contribution of MYC TFs to JA responses in Arabidopsis thaliana. Constitutive JA signaling in a jaz quintuple mutant (jazQ) was largely eliminated by mutations that block JA synthesis or perception. Comparison of jazQ and a jazQ myc2 myc3 myc4 octuple mutant validated known functions of MYC2/3/4 in root growth, chlorophyll degradation, and susceptibility to the pathogen Pseudomonas syringae. We found that MYC TFs also control both the enhanced resistance of jazQ leaves to insect herbivory and restricted leaf growth of jazQ. Epistatic transcriptional profiles mirrored these phenotypes and further showed that triterpenoid biosynthetic and glucosinolate catabolic genes are up-regulated in jazQ independently of MYC TFs. Our study highlights the utility of genetic epistasis to unravel the complexities of JAZ-TF interactions and demonstrates that MYC TFs exert master control over a JAZ-repressible transcriptional hierarchy that governs growth-defense balance.
植物激素茉莉酸（JA）促进 JASMONATE ZIM-DOMAIN（JAZ）蛋白的降解，从而解除对执行 JA 反应的多种转录因子（TF）的抑制。然而，关于 JAZ-TF 相互作用的组合复杂性如何维持对生长、发育、繁殖和免疫等诸多方面的控制，人们知之甚少。我们使用功能丧失突变来定义核心 JA 信号通路中的上位性相互作用，并研究 MYC TF 在拟南芥中对 JA 反应的贡献。在 jaz 五重突变体（jazQ）中，组成型 JA 信号主要被阻止 JA 合成或感知的突变所消除。jazQ 和 jazQ myc2 myc3 myc4 八重突变体的比较验证了 MYC2/3/4 在根生长、叶绿素降解和对病原菌丁香假单胞菌易感性中的已知功能。我们发现 MYC TF 还控制 jazQ 叶片对昆虫取食的增强抗性和 jazQ 叶片生长受限。上位转录谱反映了这些表型，进一步表明三萜类生物合成和硫代葡萄糖苷分解代谢基因在 jazQ 中独立于 MYC TF 上调。我们的研究强调了遗传上位性在揭示 JAZ-TF 相互作用复杂性方面的效用，并表明 MYC TF 对控制生长-防御平衡的 JAZ 抑制性转录层次结构具有主控作用。
