Uncovering conserved transcriptional differences between biting and non-biting mosquitoes

Most female mosquitoes are reviled because they bite vertebrates and, in the process, can transmit deadly pathogens. However, blood feeding is a metabolically costly endeavor for female mosquitoes, requiring energy to find a host, as well as to produce enzymes and other metabolites to digest the bloodmeal while protecting the mosquito. Not surprisingly, several mosquito species and populations have evolved the capacity to produce eggs without blood feeding. Leveraging earlier work in biting and non-biting populations of the pitcher plant mosquito, Wyeomia smithii, we investigated whether similar genes and metabolic pathways were also differentially expressed in the Northern house mosquito, Culex pipiens. This species is a major vector of West Nile virus in North America and exists as two sub-species: Cx. pipiens pipiens (Pipiens) that require blood to produce eggs, and Cx. pipiens molestus (Molestus) that produce their first clutch of eggs without a bloodmeal. We used RNAseq to measure differences in mRNA and miRNA abundance in the heads of biting Pipiens and non-biting Molestus. We found that, like Wy. smithii, biting Pipiens upregulate transcripts in the ribosomal protein pathway. However, unlike Wy. smithii, biting Pipiens also upregulate energy production pathways (oxidative phosphorylation and the TCA cycle), and amino acid metabolism. Relative to biting pipiens, non-biting Molestus upregulated transcripts associated with sugar metabolism and reproduction (e.g. vitellogenin and cathepsin). Our results provide insights into the evolution of non-biting life histories in mosquitoes and are laying the foundation for future control strategies to prevent mosquitoes from biting and transmitting deadly diseases.