温湿度变化引起蚜虫跌落行为的分子机制

Aphids are able to sense the elevated temperature and humidity of the breath of an approaching herbivore and thus salvage most of the colony by simultaneously dropping off the plant in large numbers immediately before the plant is eaten. At present, little is known about molecular mechanisms of aphid dropping behaviors arisen from variation of temperature and humidity. It is necessary to resolve this issue and search for new ideas on aphid control. Previous tests showed that the gene family members of TRP channel in aphids were supposed to be involved in sensing variation of temperature and humidity after treatment by channel blockers combined with behavioral analysis. In this proposal, starting with behavioral tests, aphid receptor genes sensing variation of temperature and humidity will be identified and functionally characterized through methods of bioinformatics, molecular biology, electrophysiology and functional genomics. Based on this, we need to reconstruct sensory pathway of temperature and humidity in heterologous expression system and fruit fly mutant to elucidate physiological function of receptors, and also record physiological responses of neurons activated by heat and humidity. The results will elucidate the cellular and molecular basis of aphids dropping behavior arisen from heat and humidity and provide a new idea and molecular targets for developing aphid repellents.

蚜虫能够感受到食草动物呼吸产生的湿热气流，并立即从植株上掉落，避免了随着植物一起被取食。目前，对于温湿度变化引起蚜虫跌落行为的分子机制尚不清楚。前期通过注射TRP通道阻断剂结合行为学测定研究，明确了TRP基因家族成员参与了蚜虫对温湿度变化的感受。本项目采用生物信息学、分子生物学、电生理学和功能基因组学等方法，鉴定和克隆蚜虫温湿度受体基因；通过体外表达重建蚜虫感受温湿度变化的通道系统，明确蚜虫温湿度受体的生理功能以及蚜虫触角上感受温湿度的主要感觉神经元，从神经和分子水平上阐明温湿度变化引起蚜虫跌落行为的分子机制，为发展蚜虫驱避剂提供新的思路和靶标。

蚜虫能够感受到哺乳动物呼出的湿热气流从植株上立即掉落，是遇到危险后做出的一种逃避行为。研究蚜虫感受温湿度变化的分子机制对蚜虫绿色防控具有十分重要的意义。本研究以模式昆虫豌豆蚜为研究对象，从解析蚜虫产生跌落行为的关键影响因子入手，利用人工模拟装置明确了温度在豌豆蚜感受湿热气流而产生跌落行为的过程中占主导作用，进一步研究发现切除触角的蚜虫跌落率显著降低，表明触角是关键的热识别组织。由于昆虫TRP家族蛋白对于昆虫温度感受至关重要，随后利用TRP通道阻断剂处理法，明确了该基因家族参与了豌豆蚜对温湿度变化的感受。本研究进一步分析了豌豆蚜TRPA亚家族的相关基因，推测TRPA1基因可能在豌豆蚜感受温度变化中起到关键作用。我们从豌豆蚜触角中克隆了该基因，利用荧光定量PCR技术明确豌豆蚜ApisTRPA1基因的时空表达模式，利用免疫荧光技术明确ApisTRPA1基因定位在蚜虫触角原生感觉圈。随后，利用爪蟾卵母细胞表达结合双电极电压钳技术记录了ApisTRPA1的体外功能，明确温度从20℃升高到40℃能够显著地激活该受体，进一步通过RNAi技术明确了ApisTRPA1基因在豌豆蚜感受温度升高从而引起跌落的过程中起到了重要的作用。利用单感器记录技术明确了触角原生感觉圈中的第5节和第6节大板形感器神经元能够被逐渐升高的热刺激强烈激活，并且证实ApisTRPA1基因的沉默影响了神经元对热刺激的敏感性，初步阐明了ApisTRPA1介导了豌豆蚜触角外周神经系统温敏神经元对温度的感受。此外，利用电生理和行为学研究技术，从外周神经水平上明确了豌豆蚜TRPA1受体调控的化学感受功能，证实了肉桂醛和香茅醛能够激活TRPA1受体表达的神经元并引起豌豆蚜的驱避行为。本项研究结果为发展蚜虫行为调控技术提供新的靶标和理论基础。