The Function Of Differential Expression Of Odorant Receptors In Culex Pipiens Quinquefasciatus And Culex Pipiens Molestus

Culex pipiens quinquefasciatus (Cx. quinquefasciatus) as a major species intropical and subtropical regions of world and south China is an important vector of thearboviral pathogens associated with filariasis, various types of encephalitis andtherefore a potentially serious threat to public health. Cx. quinquefasciatus blood feedon humans, birds and mammalian and serve as bridge vectors of pathogens fromanimals to humans. Therefor, it has been listed as the main species for control inChina. Current strategies for Cx. quinquefasciatus control mainly rely on theinsecticides spray. Unfortunately, extensive use of insecticides for mosquito controlhas led to a widespread increasing resistance. Given the resistance of Culexpopulations to modern insecticides, it is essential to searching for the effective, safety,environmental friendly methods and techniques for control of adult mosquitoes.Olfactory signals play a critical role in mediating a variety of important mosquitobehaviors including blood feeding, sugar feeding and oviposition thereby directlyaffecting the overall ability of mosquitoes to transmit pathogens. Many kinds ofolfactory proteins involved in the reception of odorants in mosquito, odorant receptors(ORs) is one kind of the main olfactory proteins. ORs as the molecular basis ofolfactory signals transduction involve in the identification the odor molecules andactivate the olfactory receptor neuron (ORNs). Understanding how they perceive theworld through small, signal-carrying molecules may lead us to discover novel controlstrategies for reducing bites and disease transmission.The species-specific ORs reflect the apparent evolution of the mosquitoes formeet the distinct ecological requirements. And, the expression pattern and level ofORs is related to the different responses. As the completion of the genome projects,many ORs have been identified in the southern house mosquito, Cx. quinquefasciatus. The function of most of ORs is still unknow. Because studying every individual ORgene would be an impossibly large workload, the usual approach is to first screensome “special” ORs and intensively investigate these in the hope that this may lead toa serendipitous result.Culex pipiens molestus (Cx. molestus) and Cx. quinquefasciatus are the membersof Culex pipiens Complex. Cx. molestus is a morphologically identical ecologicalbiotype of Cx. quinquefasciatus that can be distinguished by a host of contrastingbehavioral and physiological characteristics. For example, Cx. molestus has the abilityto produce eggs without a vertebrate blood-meal (autogeny). So we assume that theexpressions of ORs are different between the two subspecies. The ORs which higherexpression in the Cx. quinquefasciatus and lower expression in the Cx. molestus maybe involve in the blood feeding behavior.The objective of research is found out the ORs which are involved in the bloodfeeding behavior of Cx. quinquefasciatus. First, we employed RT-PCR and real-timePCR to detect expression of these ORs in different body parts and quantify their levelof expression in the heads of adult Cx. quinquefasciatus and Cx. molestus. Then, wetry to identify whether the ORs play a key role in the blood feeding behavior byRNAi.Results of this study as follows:(1) According to the132ORs sequence,192pairs of primers were designed forPCR.125OR genes were successfully amplify and sequence and7OR genes werenot.(2) We performed RT-PCR using female head, female chest, female abdomen,female legs and adult male from Cx. molestus and Cx. quinquefasciatus. The dataindicated that101OR genes were detected in every tissues of the two subspecies;24OR genes were vary in both different tissues and subspecies;13of the24OR geneswere different expression between the female head of the two subspecies.(3) This study followed the completion of high-throughput gene sequencing ofCx. quinquefasciatus and Cx. molestus which identified33OR genes with relativelymarked differential expression in adult females of these subspecies. (4) We carried out semi-quantitative RT-PCR experiments to more accuratelydetermine the43OR genes expression ratios in the heads of females of Cx. molestus(QH) and Cx. quinquefasciatus (MH). We found that transcripts of4OR genes（CquiOR25，CquiOR38，CquiOR41and CquiOR68）were equivalently expressedin both subspecies; CquiOR5, CquiOR104, CquiOR117were much more abundant inQH compared to MH (QH/MH>500) whereas transcripts of the remaining23ORgenes were either slightly more abundant in QH. And13OR genes were moreabundant in MH.(5) We carried RNAi technology to identify whether the CquiOR5, CquiOR104and CquiOR117play a key role in the blood feeding behavior. The result indicatedthat CquiOR5was involved in the blood feeding behavior and CquiOR117was not.CquiOR104was not been successful silence.