昆虫前肠生物学研究

Insect foregut is short and is also the first place to communicate with the living environment when taking foods. Most insects live on the plants. Plants can also produce many toxic metabolites like phenolics. In addition, bacteria that deposit on food are also pathogenic. Thus, insects must detoxify plant metabolites and clear the polluted bacteria from food on time. Insects living on the field can succeed in living on the plant metabolite and even bacteria on foods. Insect foregut is the first place to face plant phenolics and bacteria, and thus the foregut may have functions like detoxification and immunity protection. Due to it, we select the foregut and salivary gland of the silkworm as model. We will analyze the transcriptome in the foregut and salivary gland through RNAseq and the proteomics in the two tissues through mass spectral analysis. We are going to identify proteins including the potential prophenoloxidase that have close relationship with detoxification and/or immunity through molecular and biochemical studies. With this study, we hope to understand how insects adapt and guarantee the success of taking food and digestion during the progress of evolution. This study may find novel proteins as targets for pest biological control in the future.

昆虫前肠是昆虫在取食和消化时最先同外界接触并进行物质交流的地方。自然界中大部分昆虫以植物为食，通过添食研究表明植物产生的次生代谢物（如酚类物质）很多对昆虫是有毒的，而食物表面沉积的微生物一部分可能有致病性，因此昆虫需要及时消解有毒的次生代产谢物并清除食物上的病原物。自然界中的昆虫大都可以适应摄入的微量次生代谢物和污染的微生物，由于前肠首当其冲的面对来自食物的次生代谢物和细菌，因此可能具有一定解毒和免疫保护功能。为此本申请以家蚕的前肠及其附属唾液腺为研究对象，通过RNAseq解析两个组织的转录组异同、通过质谱分析研究前肠内容物和唾液腺的分泌蛋白质组，确定由前肠和唾液腺分泌的与解毒、免疫等有关的蛋白，进一步通过分子生物学、生化学等手段确认它们（包括初步发现的前肠多酚氧化酶）的解毒和免疫功能，从而认识在进化历程中，昆虫是如何适应并保证取食和消化的顺利进行，同时也为害虫的生物防治提供新的靶标蛋白。

植物酚类物质是一类重要的次生代谢产物，酚类物质对人类健康十分有益，但是在添食情况下对昆虫是有毒性的。在自然界中昆虫很少因为食物中酚类物质发生中毒现象，表明昆虫具有对酚类物质解毒功能。项目以家蚕为研究对象，对前肠及唾液腺的转录组和分泌物的蛋白质组进行解析，发现前肠存在多酚氧化酶，利用敲除多酚氧化酶基因果蝇检测验证发现多酚氧化酶对果蝇的解毒至关重要，在添食L-DOPA后幼虫发育停滞，化蛹率也非常低，进一步研究发现给家蚕幼虫添食L-DOPA溶液后，L-DOPA在前肠中被多酚氧化酶代谢成中间产物，并被运输到后肠用于粪便黑化，这个研究工作表明多酚氧化酶对昆虫酚类物质解毒很重要，如果对多酚氧化酶活性进行有效抑制，可以利用植物中的酚类物质进行害虫防治。此外在这个项目资助下对中肠和皮肤发育、免疫就行了拓展研究，相关研究对害虫的生物防治也有一定的参考意义。