植物遭受昆虫噬咬或损伤时，不仅能开启局部防御反应，还能通过复杂的远程信号迅速激活非损伤部位茉莉素合成和抗性基因表达，提前抵御侵害。经过数十年研究，关于昆虫噬咬诱导调控的植物下游防御反应已十分清楚。但有关昆虫噬咬和损伤下植物早期信号事件，特别是早期钙信号的触发和远程传递机制仍知之甚少。因此，本论文第一部分工作筛选鉴定到植物损伤相关分子模式（DAMP）谷胱甘肽（GSH），解析了其在远程钙信号触发和传递中的作用机制。研究表明GSH以谷氨酸类受体（GLR）蛋白依赖的方式触发植物远程钙信号，激活系统叶茉莉素合成和防御基因表达。GSH含量降低的植株显著削弱损伤诱导的远程钙信号和防御反应，更易受昆虫取食侵害。本研究还发现Glu感受器蛋白（iGluSnFR）可作为GSH与Glu的胞外共感受器指示损伤诱导的GSH和Glu胞外释放。有趣的是，损伤除了能诱导局部iGluSnFR信号，还会以不依赖于GLR3.3 GLR3.6的方式触发远端叶片iGluSnFR信号，且信号传输模式与损伤诱导的远程钙信号传输类似。结合同位素示踪，我们发现DAMP分子的系统传递可能促进了植物钙信号长距离传输。以上研究工作为植物利用远程防御体系应对损伤和昆虫噬咬提供了新的见解。早在达尔文时期，食虫植物的捕虫特性和叶片运动的分子机制就备受科学家们关注。达尔文在他的研究中测试了大量不同物质诱导食虫植物叶片运动的能力，试图解析食虫植物叶片运动捕食昆虫的机理。然而，在上百年的历史研究中，食虫植物如何利用叶片运动捕食昆虫仍然是悬而未决的重大科学问题。因此，本论文第二部分工作首次鉴定到GSH作为诱导捕虫运动的关键分子，并揭示了其在捕虫过程中的作用机制。研究发现GSH能广谱性诱导食虫植物叶片运动，上调诱导食虫关键基因表达，提高消化液中的酶活，开启食虫信号。降低体内GSH水平能显著抑制茅膏菜捕虫效率。我们首次克隆了茅膏菜茉莉素受体蛋白基因DcCOI1，并验证了DcCOI1对茉莉素的感知功能。进一步研究发现，茉莉素以DcCOI1依赖的方式在茅膏菜体内激活了GSH的生物合成和运输，介导了叶片运动。该部分研究工作为食虫植物叶片运动机制提供了新的理解。综上所述，两项研究工作系统解析了小肽化合物GSH在植物远程防御信号和食虫进攻信号中的重要作用，这为理解植物在与昆虫的长期共进化历程中，如何生存下来提供了新的视角。
Upon herbivory or wounding, plant could not only initiate local defense response, but also rapidly activate jasmonate biosynthesis and defense gene expression in plant distal undamaged organs through complex remote signals, so as to resist insect infestation in advance. The downstream defense responses induced by herbivory have been well understood during past decades. However, little is known about the early signaling events upon herbivory or mechanical wounding, especially the mechanisms of triggering early long-distance calcium signaling. Therefore, the first part of this thesis has identified glutathione (GSH) as a key damage-associated molecular pattern (DAMP) molecule and analyzed its role in triggering long-distance calcium signaling. Research shows that GSH is a critical wound signal that triggers plant long-distance calcium-based defense signal in a glutamate-like receptor (GLR) protein dependent manner. Surprisingly, intensity-based glutamate-sensing fluorescent reporter (iGluSnFR) which is originally exploited as a Glu sensor is proved to be a co-sensor for both Glu and GSH, suggesting wounding might induce both Glu and GSH release in apoplast regions. Notably, apart from local increase of wound signal, wounding triggers elevation of iGluSnFR signal in distal undamaged leaf organs in a GLR3.3 GLR3.6 independent manner. Moreover, the pattern of wounding induced iGluSnFR signal transmission greatly mirrors that of [Ca2+]cyt transmission. Based on the results of isotope tracing in Arabidopsis, we find that DAMP molecules systemic propagation might have contributed to long-distance [Ca2+]cyt transmission in plant. Our findings offer new insights into highly sophisticated leaf-to-leaf defense systems evolved by plants to defend against herbivory.Since Darwin's time, the research on the characteristics of carnivorous plants and the movement of their leaves when they capture insects has attracted the attention of scientists. Charles Darwin was fascinated by these plants and in his studies, he tested large number of different substances for their capacity to induce leaf movement in carnivorous plants. However, the mechanism of how carnivorous plants use leaf movement for preying is still a key question that needs to be addressed. The second part of this thesis uncovered GSH as a new and critical chemical molecule to trigger trap closure and outer stomach formation and upregulate carnivory related gene expression in diverse carnivorous plants. Moreover, we first cloned the jasmonate receptor gene DcCOI1 in sundew and verified its function to perceive JA. We further revealed that jasmonate could activate GSH biosynthesis and transport in a DcCOI1-dependent manner and mediate trap movement in sundew. Our findings provide a new understanding for mechanism of carnivorous plant leaf movement during preying.In summary, two independent studies systematically elucidate the important roles of small peptide GSH in the long-distance defense and carnivory offense signals in plants, providing new insights into how plants survive in nature during long-term of co-evolution with insects.
