椰扁甲啮小蜂寄生对水椰八角铁甲蛹细胞免疫抑制的分子机制

Octodont nipae is a serious invasive pest insect of palm plants in South China, and the endoparasite Tetrastichus brontispae is a natural enemy of this pest, which showed huge potential in biocontrol of O. nipae. The successful parasitism is usually attributed to the impairment of host celluar and humoral immunity. However, the molecular mechanisms of celluar immune impairment in O. nipae, parasitized by T. brontispae, are kept unknown so far. In the present study, the transcriptome sequencing and RNAi techniques were used to 1) identify the celluar immune-related genes in O. nipae puape response to the parasitism by T. brontispae, 2) investigate the mRNA expression profiles of above identified genes in different types of blood cell and tissues, and 3) analyze the functions of these genes in cellular immunity. The objective of this study is to understand the cellular immune-disabling molecular mechanisms in Octodonta nipae pupae,parasitized by Tetrastichus brontispae. The results of this study would shed light on the understanding of cellular immune-disabling molecular mechanisms in O. nipae pupae, parasitized by Tetrastichus brontispae, and may also open a new window to biological control of this pest.

水椰八角铁甲是危害我国南方棕榈科植物的重大外来入侵害虫，椰扁甲啮小蜂是其重要的寄生性天敌，可通过抑制其细胞免疫和体液免疫而成功寄生，但有关该寄生蜂寄生对水椰八角铁甲蛹细胞免疫抑制的分子机制还未见报道。本项目以水椰八角铁甲蛹-椰扁甲啮小蜂系统为对象，1）对被椰扁甲啮小蜂寄生前后的水椰八角铁甲蛹进行转录组测序，筛选水椰八角铁甲蛹中差异表达的细胞免疫相关基因；2）研究上述基因在水椰八角铁甲蛹不同血细胞及组织中的表达谱，并分析椰扁甲啮小蜂寄生对这些基因表达影响的时间动态；3）应用RNAi技术分析上述基因在水椰八角铁甲蛹细胞免疫中的功能。通过上述研究，明确椰扁甲啮小蜂寄生对水椰八角铁甲蛹细胞免疫抑制的分子机制。项目研究结果对于深入了解椰扁甲啮小蜂寄生对水椰八角铁甲蛹细胞免疫抑制的分子机制及开发以害虫免疫系统为靶标的新型害虫防控技术具有重要的理论和实践意义。

本项目以水椰八角铁甲蛹-椰扁甲啮小蜂系统为对象，明确了椰扁甲啮小蜂寄生及毒液注射均可抑制寄主血细胞的包囊反应、粘附及肌动蛋白聚合能力；采用比较转录组学分析了椰扁甲啮小蜂寄生后，水椰八角铁甲蛹中大量免疫相关基因发生了差异表达，其中与包囊反应相关的钙网蛋白calreticulin、整合蛋白integrin及Rho-Family GTPase Rac1的表达量显著下调。上述包囊反应相关基因具有组织特异性，且寄生及毒液注射对这些基因表达量的影响是动态的。RNAi功能分析发现，这些基因确实与血细胞包囊、粘附及肌动蛋白聚合能力密切相关。以上结果表明，椰扁甲啮小蜂寄生对寄主水椰八角铁甲蛹细胞免疫抑制的部分分子机制为椰扁甲啮小蜂通过抑制寄主OnCRT、 OnINT及OnRac1等基因的表达，影响寄主血细胞形态的转变，进而影响血细胞的包囊能力，从而使得其蜂卵不被寄主包囊而达到成功寄生的目的。上述研究结果有助于深入理解椰扁甲啮小蜂与水椰八角铁甲蛹之间的免疫互作，同时为开发以害虫免疫系统为靶标的新型害虫防控技术提供理论基础。