Tea Research Institute, Chinese Academy of Agricultural Sciences, No. 9 South Meiling Road, Hangzhou, 310008, Zhejiang, China.
Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, No. 9 South Meiling Road, Hangzhou, 310008, Zhejiang, China.
J Chem Ecol. 2020 Mar;46(3):308-316. doi: 10.1007/s10886-020-01158-6. Epub 2020 Feb 4.
Polyphenol oxidases (PPOs) as inducible defense proteins, contribute to tea (Camellia sinensis) resistance against tea geometrid larvae (Ectropis grisescens), and this resistance has been associated with the jasmonic acid (JA) signaling by testing geometrid performance in our previous work. However, the regulation of PPO-based defense by JA and other hormone signaling underlying these defense responses is poorly understood. Here, we investigated the role of phytohormones in regulating the PPO response to tea geometrids. We profiled levels of defense hormones, PPO activity and CsPPO genes in leaves infested with tea geometrids. Then, hormone levels were manipulated by exogenous application of methyl jasmonate (MeJA), gibberellin acid (GA), abscisic acid (ABA), JA biosynthesis inhibitors (sodium diethyldithiocarbamate trihydrate, DIECA and salicylhydroxamic acid, SHAM) and GA inhibitor (uniconazole, UNI). Upon geometrid attack, JA levels significantly increased, whereas GA levels notably decreased and ABA level was slightly decreased. And the PPO activity significantly increased in line with the transcript levels of CsPPO2 and CsPPO4 but not CsPPO1. There were an obvious antagonistic cross-talk between JA and GA signals and an association among JA signals, PPO response and herbivore resistance in tea plants. Pretreatment with MeJA increased PPO activity by activating the transcripts of CsPPO2 and CsPPO4, whereas application of JA inhibitor DIECA suppressed PPO activity. GA strongly enhanced PPO activity, but ABA did not alter PPO activity. These findings strongly suggest that JA is a central player in PPO-mediated tea resistance against tea geometrids in a manner that prioritizes defense over growth.
多酚氧化酶（PPO）作为诱导防御蛋白，有助于茶树（Camellia sinensis）抵抗茶尺蠖幼虫（Ectropis grisescens），并且这种抗性与茉莉酸（JA）信号有关，这是我们之前的工作中通过测试尺蠖性能得出的。然而，JA 和其他激素信号对基于 PPO 的防御的调节以及这些防御反应的基础，知之甚少。在这里，我们研究了植物激素在调节茶树对茶尺蠖的 PPO 反应中的作用。我们分析了受茶尺蠖侵害的叶片中防御激素、PPO 活性和 CsPPO 基因的水平。然后，通过外源施用茉莉酸甲酯（MeJA）、赤霉素酸（GA）、脱落酸（ABA）、JA 生物合成抑制剂（二乙基二硫代氨基甲酸钠三水合物、DIECA 和水杨羟肟酸、SHAM）和 GA 抑制剂（烯效唑、UNI）来操纵激素水平。在尺蠖攻击后，JA 水平显著增加，而 GA 水平显著降低，ABA 水平略有降低。PPO 活性与 CsPPO2 和 CsPPO4 的转录水平显著增加，但与 CsPPO1 无关。在茶树中，JA 和 GA 信号之间存在明显的拮抗交叉对话，以及 JA 信号、PPO 反应和植食性抵抗之间存在关联。用 MeJA 预处理可通过激活 CsPPO2 和 CsPPO4 的转录来增加 PPO 活性，而用 JA 抑制剂 DIECA 处理则抑制 PPO 活性。GA 强烈增强 PPO 活性，但 ABA 不改变 PPO 活性。这些发现强烈表明，JA 是 PPO 介导的茶树抵抗茶尺蠖的核心参与者，以防御优先于生长的方式。
