Induction of vitellogenesis-related genes in Cx. quinquefasciatus by non-steroidal ecdysone agonists

Non-steroidal ecdysone agonists have been developed for the control of Lepidopteran and Coleopteran pests, leading to the potential of these chemicals for the effective control of disease-vectoring insects, including mosquitoes. In our study, we investigated the expression of ecdysone-dependent vitellogenesis-related genes in Culex quinquefasciatus in order to identify an effective molecular tool for detecting the biological activity of ecdysone agonists. The expression levels of 36 genes that were identified as linked to blood feeding were investigated for newly eclosed females over a 72h period before and after the blood meal. We found that the expression of the vitellogenin A gene (vitA) was highly up-regulated (>10,000-fold) following a blood meal compared to the vitA gene expression in females that were not given a blood meal. Similar up-regulation patterns of vitA expression occurred in non-blood-fed females when these mosquitoes were treated with the ecdysone agonists, tebufenozide and methoxyfenozide. The dose required for induction of vitA expression was much lower for methoxyfenozide compared with tebufenozide, suggesting a more specific effect of methoxyfenozide in Cx. quinquefasciatus. Our finding of vitA expression in Cx. quinquefasciatus in response to ecdysone agonists provides an approach to evaluate the biological activities of novel ecdysone agonists targeted against mosquitoes.