凝集素参与埃及伊蚊抵御Cry11A毒素过程的分子机理

Bacillus thuringiensis subsp. israelensis (Bti) has been widely and effectively used for mosquito control. However, the molecular mechanism that mosquitoes defend against Bti infections is largely unknown. Understanding of Bti-mosquito interactions will help to develop new Bt toxins for mosquitoes and mosquito-borne disease management. It has been previously shown that a mosquito lectin, galectin, may be invovled in Aedes aegypti's defense against intoxication of Cry toxin. Because lectin carbohydrate-binding domains are highly homologous to the cry receptor-binding domains, we hypothesis that lectins may be involved in defensive response to Cry toxin by interactions with Cry toxins or putative Cry toxin receptors to alter binding of Cry toxins to Cry toxin receptors. In order to investigate roles of C-type lectin and galectin families in defensive response of Ae. aegypti against Cry11A resistance, we will select lectin genes which showed significant variations in their expression levels when the host larvae were chanllenged with Bti. The selected genes and their expressions in association with resistance to Bti will be verified by real-time PCR and RNA interference (RNAi). We will then further investigate interactions among lectins, Cry toxins and the host membrane receptors. The selected lectins will also be expressed in insect cell lines, and the lectin proteins will be used to test their interation with putative Cry receptors and Cry toxins in vitro and in vivo.

Bti可有效防治重要医学媒介蚊虫，但其侵染蚊虫的机理尚不明确。对感染Bti的埃及伊蚊幼虫及对照转录组高通量测序分析，发现二者间凝集素基因表达水平有显著差异。通过抑制其中一种凝集素galectin-14的表达发现蚊虫对Bti的敏感性显著提高。由于凝集素与糖结合的功能基团结构和Bt Cry毒素与受体结合的功能区高度相似，推断凝集素可能参与抑制Bti毒素和中肠受体的结合。本项目拟对已鉴定的凝集素基因（C-型凝集素和半乳凝集素）进行验证，筛选出10~20个在Cry11Aa处理后表达量显著变化的基因并进行功能验证，找出1~2个对Cry11Aa毒力有影响的基因；通过原核和真核表达这些基因并应用多种分子生物学技术分别从体外和体内条件研究凝集素、毒素和糖基化的受体蛋白三者间的互作，从而明确凝集素在蚊虫抵御Cry毒素过程中的分子机理，深入了解蚊虫对Bt毒素的应答机制，为研发新型高效生物灭蚊剂提供科学依据。

Bti可有效防治重要医学媒介蚊虫，但其侵染蚊虫的机理尚不明确。项目通过对感染Bti的埃及伊蚊幼虫及对照转录组高通量测序分析，发现二者间凝集素基因表达水平有显著差异。通过抑制其中一种凝集素galectin14的表达发现蚊虫对Bti的敏感性显著提高。由于凝集素与糖结合的功能基团结构和Bt Cry毒素与受体结合的功能区高度相似，推断凝集素可能参与抑制Bti毒素和中肠受体的结合。因此本项目除了对已鉴定出的galectin14基因外，也找出可在中肠表达的其它4个galectin基因，通过原核表达这些基因并应用多种分子生物学技术分别从体外和体内条件研究凝集素、毒素和糖基化的受体蛋白三者间的互作，从而明确凝集素在蚊虫抵御Cry毒素过程中的分子机理，深入了解蚊虫对Bt毒素的应答机制，为研发新型高效生物灭蚊剂提供科学依据。