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

将吸血节肢动物的唾液注射到脊椎动物宿主体内，含有许多用于防止血液凝固的化合物，这些化合物在逃避宿主检测方面很重要。 虽然植物和动物对寄生虫产生不同的防御，与吸血节肢动物形成鲜明对比，但对毛虫的唾液如何干扰宿主植物防御反应知之甚少。该项目将通过观察毛虫唾液是否：1）减弱毛虫摄取的宿主植物的酶防御，以及2）破坏参与防御诱导的植物信号通路，来确定毛虫唾液是否有助于逃避植物防御。本实验旨在测试玉米穗虫唾液和唾液中的主要酶葡萄糖氧化酶对植物防御信号肽系统素的转运和活性以及茉莉酸生物合成的影响。 已知系统素和茉莉酸都介导氧化酶的产生增加和昆虫抗性。 还将测试唾液葡萄糖氧化酶诱导水杨酸产生的能力，这是表达针对植物病原体的系统获得性抗性、抑制茉莉酸合成和随后的昆虫抗性所需的。 几个毛虫植物组合将被用来测试这些机制的重要性。 这些目标的完成将提供一个概念框架的适应性比较植物饲养节肢动物对他们的主机的血液喂养节肢动物。 这些实验可能提供了第一个证据，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。

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.