章鱼胺介导粘虫幼虫密度依赖的抗病免疫机制

许多型变昆虫存在密度依赖的抗病性：与低密度种群相比，高密度种群对病原菌的抵抗力明显提高。然而有关密度依赖的抗病性变化机制所知甚少。我们研究发现，章鱼胺对粘虫幼虫密度依赖的抗病性具有正调节作用。作为神经激素，章鱼胺可调节昆虫的压力反应和免疫反应。我们推测：章鱼胺在昆虫重塑免疫系统适应密度变化中可能起重要作用。本项目首先通过研究高、中、低密度饲养的粘虫幼虫章鱼胺含量、酪氨酸脱羧酶和酪胺β羟化酶活性及其基因表达量、蛋白表达的差异，弄清粘虫不同密度幼虫章鱼胺含量变化的原因；分析不同密度饲养和注射章鱼胺的幼虫转录组数据，筛选出幼虫密度依赖的抗病关键基因。最后，通过RNA干扰幼虫章鱼胺合成相关基因、抗病关键基因，测定幼虫抗病性的变化。通过以上研究阐明章鱼胺介导粘虫幼虫密度依赖的抗病免疫机制，为揭示昆虫感知种群密度信号机理、害虫爆发机制提供新的视角，还可为微生物农药的科学使用提供依据。

There is growing evidence that insects in high-density population invest relatively more in pathogen resistance than those in low-density population. This density-dependent disease resistance has been reported in some phase polyphenism insects. However, the mechanism of density-dependent disease resistance has been largely ignored. Our previous results showed that octopamine had positive adjustment on the larval density-dependent resistance to pathogen. As a neurohormone, octopamine modulates larval stress and immune response. We suppose that octopamine may be play an important role in insect reconfiguring immune system for adapting high density. In this study, the content of octopamine, the activity of tyrosine decarboxylase (Tdc) and tyramine beta-hydroxylase (Tbh) enzyme, and the expression profile of Tdc and Tβh gene and protein will be compared in the larvae form high, medium, low densities. This will clarify the variation reason for the content of octopamine from different densities larvae. The key gene of larval density dependent disease resistance will be screened through transcriptome analysis of larvae from different densities and larvae injected octopamine. The larval resistance to disease will be determined by RNA interference expression of octopamine synthase gene and screened key gene. These studies will illuminate the regulation mechanism of octopamine on the larval density dependent resistance to disease. It will provide new insights for unveiling the mechanism of insect density sensing system and pest outbreak, and applying microbial pesticides.