Transcriptional responses of Aedes aegypti chemosensory tissues in response to volatile DEET and citronella oil.

DEET and citronella oil are two of the most widely used mosquito repellents; however, their impact on chemosensory tissues is not fully understood. In their vapour phase, the repellency effect involves the olfactory system, with mosquitoes detecting and responding to diverse odorants through their antennae and mouthparts (maxillary palps and proboscis). In this study, we first performed repellency behavioural assays that indicated both DEET and citronella effectively impaired female Aedes aegypti host-seeking capabilities (i.e. landing on a host and taking a blood meal). We next used RNA sequencing to assess global gene expression changes in Ae. aegypti antennae, mouthparts and headless bodies in response to volatile repellent exposure. The resultant transcriptional changes were considerably greater in the mosquito mouthparts than in the other tissues. The most notable responses in olfactory-related genes to both repellents were the suppressed expression of the three subunits comprising the mosquito CO2 receptor (Gr1, 2 and 3). Genes associated with mitochondrial function and metabolism were also suppressed. Exposure to DEET was further characterized by substantial inhibition of cytochrome P450 mRNA expression, the primary detoxification enzymes in insects. Overall, our study provides novel insights into the olfactory and physiological responses of Ae. aegypti chemosensory tissues in response to DEET and citronella exposure.