柑橘木虱靶标抗性基因的微进化动力学研究

The Evolutionary Dynamics Theory states that whenever there is a difference, there will be a choice. Pest resistance to pesticides is a micro-evolutionary phenomena. We found that the rates of resistance occurance and recession displayed in different paces in different resistant genes. Besides, the number of resistant genes involved in the resistance development is still controversial.This project targets in finding out whether different resistant genes tend to develop into a single gene, or into multiple genes during the development of micro-evolution. Diaphorina citri, the principal vector of the highly destructive citrus disease called Huanglongbing (HLB) or citrus greening, is the research object of this project. Here, we use the sodium ion channel gene which mediates pyrethroid, and the nicotinic acetylcholine receptor which mediates receptors to midacloprid as the target genes for experiments due with the following three questions: (a)Whether or not there is a mutually exclusive competition or coevolution in different alleles with the same resistance gene under one kind of selection pressure? (b) Whether or not there is a mutually exclusive competition or coevolution in different resistance genes under component selection pressure? (c) What is the main factor that causes the different recovery rates of the sensitivity of resistant strain after revoking the select pressure? Above all, the project result will be advantageous for reducing the damage caused by Diaphorina citri. Furthermore, it will contribute to the development and innovation of microevolution theory in insect resistance to some extent.

进化动力学理论提出：“有差异就会有选择”。害虫对杀虫剂的抗性是一种微进化现象。害虫抗性发生和衰退的速率快慢各异，而且当前对于是否有更多的基因座位参与抗性仍有争议。因此本项目尝试探讨：在抗性微进化的演变过程中，存在于种群内不同的靶标抗性基因是倾向发展为单个基因“一枝独秀”，还是倾向发展为多个基因“齐头并进”？项目将以毁灭性柑橘病原菌虫媒-柑橘木虱为研究对象，以介导菊酯类抗性的钠离子通道和介导吡虫啉抗性的烟碱型乙酰胆碱受体为靶标基因，开展如下3个方面的研究工作：（1）一种杀虫剂选择压力条件下，相同靶标抗性基因不同等位基因之间是否存在互斥竞争或协同扩张关系；（2）多种杀虫剂混用选择压力条件下，不同靶标抗性基因之间是否存在互斥竞争或协同扩张关系；（3）撤销选择压力条件下，抗性品系敏感性恢复速率快慢各异的影响因素。研究成果不仅有助于加强控制柑橘木虱的猖獗危害，而且对于拓展和创新昆虫抗性微进化理论也具

柑橘木虱是传播黄龙病的媒介昆虫。这种危害性严重的害虫中对杀虫剂的抗性构成对柑橘产业严重威胁。目前，柑橘木虱主要是通过喷洒包括新烟碱，拟除虫菊酯和有机磷酸酯在内的广谱杀虫剂进行控制。与其他害虫种类一样，在杀虫剂选择压力下，柑橘木虱的抗药性迅速提高。此外，先前的研究还表明柑橘木虱对有机磷酸酯和拟除虫菊酯具有很高的抗性。尽管已有研究开展柑橘木虱抗药性研究，但目前尚未对柑橘木虱的解毒酶的基因进行系统研究。本项目通过分析基因组和转录组测序数据，鉴定了柑橘木虱解毒酶基因，包括49个细胞色素P450氧化酶cytochrome P450 monooxygenases (CYPs) , 12个谷胱苷肽硫转移酶glutathione-S-transferase genes (GST)和20个羧基/胆碱酯酶carboxylesterase genes (CCE)。值得注意的是，柑橘木虱中不同类型的解毒酶基因（特别是CYPs）的总数比其他昆虫物种的总数要少，这可能反映了该昆虫的寄主范围狭窄。在柑橘木虱中，解毒酶基因也没有发生明显扩增情况。此外，通过构建不同发育时期和组织转录组，并分析了所鉴定基因在不同发育阶段和不同组织之间的表达谱。通过测定柑橘木虱对吡虫啉和β-氯氰菊酯的致死中浓度，进行胁迫处理后分析了所鉴定基因对两种常用杀虫剂的表达水平变化。这些数据为将来分析柑橘木虱的解毒机理奠定基础。