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Abstract In diapausing mosquitoes, cold tolerance and prolonged lifespan are important features that are crucial for overwintering success. In the mosquito Culex pipiens, we suggest that PDZ domain-containing protein (PDZ) (post synaptic density protein [PSD95], drosophila disc large tumor suppressor [Dlg1], and zonula occludens-1 protein [zo-1]) domain-containing protein is involved with these diapause features for overwintering survival in Culex mosquitoes. The expression level of pdz was significantly higher in diapausing adult females in the early stage in comparison to their nondiapausing counterparts. Suppression of the gene that encodes PDZ by RNA interference significantly decreased actin accumulation in the midgut of early-stage adult diapausing females. Inhibition of pdz also significantly reduced the survivability of diapausing females which indicates that this protein could play a key role in preserving the midgut tissues during early diapause. 

Abstract Culex pipiens, the northern house mosquito, is a major vector of West Nile virus. To survive the severe winter, adult mosquitoes enter a diapause programme. Extended lifespan and an increase in lipid storage are key indicators of diapause. Post‐translational modifications to histone proteins impact the expression of genes and have been linked to the lifespan and energy utilisation of numerous insects. Here, we investigated the potential contribution of epigenetic alterations in initiating diapause in this mosquito species. Multiple sequence alignment of H3 sequences from other insect species demonstrates a high conservation of the H3 histone inCx. pipiensthroughout evolution. We then compared the levels of histone methylation in the ovaries and fat body tissues of diapausing and non‐diapausingCx. pipiensusing western blots. Our data indicate that histone methylation levels in the ovaries ofCx. pipiensdo not change during diapause. In contrast, H3K27me2 levels decrease more than twofold in the fat body of diapausing mosquitoes relative to non‐diapausing counterparts. H3K27 methylation plays a crucial role in chromosome activation and inactivation during development in many insect species. This is predominantly governed by polycomb repressor complex 2. Intriguingly, a previous ChIP‐seq study demonstrated that the transcription factor FOXO (Forkhead box O) targets the genes that comprise this complex. In addition, H3K27me2 exhibits dynamic abundance throughout the diapause programme inCx. pipiens, suggesting its potential role in the initial activation of the diapause programme. This study expands our understanding of the relationship between alterations in epigenetic regulation and diapause. 

Abstract Understanding the development process of male and female mosquitoes provides important basic information for sterile insect release programmes and is important for improving other vector control strategies. However, little is known about the molecular mechanisms that distinguish male from female‐specific developmental processes in this species. We used IlluminaRNA‐seq to identify sex‐specific genes during pupal and adult stages. One hundred and forty‐seven genes were expressed only in pupal males, 56 genes were expressed in adult males and another 82 genes were commonly expressed in both male samples. In addition, 26 genes were expressed only in the pupal females, 163 genes were found in the adult females and only one gene was expressed in both female samples. A further quantitative real‐time PCR validation of selected genes from the RNA sequencing (RNA‐seq) analysis confirmed upregulation of those genes in a sex‐specific manner, including: fibrinogen and fibronectin, a zinc finger protein, phospholipase A(2) and a serine protein for female pupae; venom allergen 3, a perlecan, testis‐specific serine/threonine‐protein kinase 1, testis‐specific serine/threonine‐protein kinase 6 and cytochrome c‐2 for male pupae; a salivary protein, D7 protein precursor, trypsin 7 precursor, D7 protein and nanos for female adults; and tetraspanin F139, cytosol aminopeptidase, testis‐specific serine/threonine‐protein kinase 1, a testis‐specific serine/threonine‐protein kinase 6 and a C‐type lectin for male adults. These findings provide insight into the development and physiology ofCulexmosquitoes, which will help in the development of more effective control methods for these disease vectors.