Mixed Messages in Caterpillar Saliva: Disruptive and Deceptive Signals for Plant Defenses

节肢动物将吸血后的唾液注入脊椎动物宿主体内，唾液中含有许多防止血液凝固的化合物，这些化合物对逃避宿主的检测非常重要。虽然植物和动物都对它们的寄生虫产生不同的防御，与吸血节肢动物形成鲜明对比，但关于毛毛虫的唾液如何干扰寄主植物的防御反应，我们知之甚少。本项目将通过观察毛毛虫唾液是否：1)减弱毛毛虫摄取的寄主植物的酶防御，2)破坏参与防御诱导的植物信号通路，来确定毛毛虫唾液是否有助于逃避植物防御。本实验旨在测试唾液和玉米耳虫体内的主要唾液酶葡萄糖氧化酶对植物中防御信号肽、系统素和茉莉酸生物合成的运输和活性的影响。已知系统素和茉莉酸都介导氧化酶和抗虫能力的增加。唾液葡萄糖氧化酶诱导水杨酸产生的能力也将被测试，水杨酸是表达对植物病原体的系统性获得性抗性、茉莉酸合成的抑制以及随后的昆虫抗性所必需的。几个毛毛虫和植物的组合将被用来测试这些机制的重要性。完成这些目标将为比较植食性节肢动物与血食性节肢动物对宿主的适应性提供一个概念框架。这些实验可能提供了草食动物唾液在抑制宿主酶防御和破坏植物抵抗草食动物攻击的防御信号通路中发挥作用的第一个证据。

Saliva of blood-feeding arthropods injected into their vertebrate hosts contains many chemical compounds used to prevent the clotting of blood, which are important in evading host detection. Although both plants and animals produce diverse defenses against their parasites, and in stark contrast to the blood feeding arthropods, very little is known about how the saliva of caterpillars interfere with host plant defense responses. This project will determine if caterpillar saliva assists in evasion of plant defenses by observing whether caterpillar saliva: 1) attenuates the enzymatic defenses of the host plant ingested by caterpillars, and 2) disrupts plant signaling pathways involved in defense induction. Experiments are designed to test the ability of saliva and the predominant salivary enzyme in the corn earworm, glucose oxidase, to affect transport and activity of the defense signal peptide, systemin, and biosynthesis of jasmonic acid in plants. Both systemin and jasmonic acid are known to mediate increased production of oxidative enzymes and insect resistance. The ability of salivary glucose oxidase to induce salicylic acid production, required for the expression of systemic acquired resistance against plant pathogens, inhibition of jasmonic acid synthesis, and subsequent insect resistance will also be tested. Several caterpillar-plant combinations will be used to test the importance of these mechanisms. Completion of these objectives will provide a conceptual framework for the comparison of adaptations plant-feeding arthropods use against their hosts to those of blood feeding arthropods. These experiments may furnish the first evidence that herbivore saliva plays a role in suppressing host enzymatic defenses and disrupting defense signal pathways used by plants to resist herbivore attack.