蝗虫微孢子干扰飞蝗群集的神经和信息化学机制

Paranosema locustae is an entomophagous microsporidia and has been researched and applied for controlling grasshopper and locusts over the world, but the neurophysiological and molecular mechanism that Paranosema locustae affects locust's aggregation behavior hasn't been reported so far. In the light of parasitic relationship between Paranosema locustae and Locusta migratoria, we have proved the morphological and behavioral phase transformation of Locusta migratoria could be disrupted by Paranosema locustae. In the project, these methods,technologies and equipments, such as scribing, separating, purifying and 16sRNA analysis, head space collection and adsorption equipment, gas chromatography and high performance liquid chromatography, real time quantitative PCR and comparison of the threshold method, will be applied for the studies on abnormal neurochemical and physiological mechanism of Locusta migratoria resulted from the infection of Paranosema locustae, research contents include the differences of intestine bacteria of Locusta migratoria infected and uninfected with Paranosema locustae, the effects of Paranosema locustae on the main active ingredients of aggregation pheromone of Locusta migratoria, substantial changes in central nervous system neurotransmitters and relevant gene expression levels in the Locusta migratoria infected and uninfected with Paranosema locustae. Through the study of the project, it will be disclosed the neurochemical and information chemical mechanism Paranosema locustae results in the abnormal behavior of Locusta migratoria by disrupting the emitting of the main active ingredients of aggregation pheromone and the synthesis of neurotransmitters of Locusta migratoria. These results will provide theoretical basis for controlling locusts with microsporidia.

蝗虫微孢子是当前世界上研究和应用较广的蝗虫病原物，但有关昆虫病原物影响飞蝗群集行为的神经化学和分子机制尚未见报道。本项目基于蝗虫微孢子对飞蝗的高致病性，在明确了微孢子侵染可显著干扰飞蝗形态和行为型变的基础上，采用细菌分离纯化和16SrRNA分析、顶空收集吸附和气相色谱、高效液相色谱和实时定量PCR及阈值比较等方法和技术，研究微孢子侵染导致飞蝗群集异常的信息和神经化学及其分子机制，重点研究微孢子侵染对飞蝗肠道细菌群落的影响及其与飞蝗聚集信息素主要活性成分释放量变化之间的关系、感病和健康飞蝗中枢神经系统中行为相关的神经递质的含量差异以及微孢子侵染对飞蝗体内参与合成重要神经递质的基因表达水平的影响，以期明确微孢子对飞蝗释放聚集信息素主要活性成分的干扰作用和微孢子侵染对蝗虫本身及群体内其它蝗虫神经递质的影响, 最终导致蝗虫群集行为异常的神经化学及分子机制，为利用微孢子杀虫剂来防治蝗虫提供理论依据。

蝗虫是世界上最重要的害虫，而蝗虫微孢子是当前世界上研究和应用较广的环境友好的蝗虫病原物。有关蝗虫病原物抑制飞蝗群集行为的神经化学和分子机制尚未有系统报道。研究发现，蝗虫微孢子可以抑制飞蝗后肠相关细菌的生长发育，被蝗虫微孢子侵染2周后，飞蝗后肠相关细菌的数量减少了21.3%，其后肠细菌群落多样性也明显低于健康蝗虫。进一步研究发现，蝗虫微孢子病可以改变飞蝗群集化学信息指纹谱，干扰了飞蝗聚集信息素的释放，接种后9和10天，飞蝗聚集信息素的主要成分之一壬醛的释放量分别下降了40.3%和53.2%。研究结果证明了蝗虫微孢子通过抑制飞蝗肠道内与聚集信息素合成相关的细菌的生长发育来干扰飞蝗聚集信息素的合成，从而阻止了飞蝗的聚集行为和型变。飞蝗群集程度的减弱又抑制了飞蝗的聚集行为并减少了中枢神经系统相关神经递质的产生。被微孢子侵染2周后，飞蝗的一种主要的神经递质血清素的释放量比健康蝗虫下降了40.2%。健康飞蝗，从5龄生长到成虫，血清素升高了1.7倍，而同期的病蝗没有变化。而且与感病飞蝗紧邻的健康飞蝗的中枢神经系统中的血清素的含量也比与健康蝗虫相邻的飞蝗下降了36.8%。血清素可以传递群集信息并诱导聚集行为，导致微孢子病原抑制了散居型飞蝗向群居型的转变。同时，蝗虫微孢子病也引起相关的其他神经递质的变化，如抑制了牛磺酸的释放，促进了酪胺、瓜氨酸和精氨酸等的释放。进一步深入研究发现，蝗虫微孢子可导致与主要神经递质合成相关的靶基因表达水平的变化，接种蝗虫微孢子病原的飞蝗的与神经递质多巴胺和血清素相关的靶基因pale和vat1的表达水平比健康蝗虫相比显著下降37.4倍。本项目的研究结果, 揭示了昆虫肠道寄生物通过改变寄主昆虫肠道细菌群落及其相关的行为化学物质和神经递质来调控寄主的行为，最终明确了蝗虫微孢子病导致蝗虫群集行为异常的神经化学及分子机制，为高效利用微孢子杀虫剂来防治蝗虫提供了新的理论依据和防治思路。