Transcriptome profiling reveals sex-specific gene expressions in pupal and adult stages of the mosquito Culex pipiens

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 of Culex mosquitoes, which will help in the development of more effective control methods for these disease vectors.