Circadian dependent transcriptional oscillation in the olfactory and brain tissues of Aedes and Anopheles mosquitoes regulate perireceptor events and olfactory sensitivity
Mosquitoes are the vectors of a variety of infectious diseases. Olfaction and circadian rhythm gate different behavioral events in mosquitoes. However, the mechanisms of odor detection and processing of chemical signals, which are essential for olfactory perception, is poorly understood, including how perception changes in response to zeitgeber time in different mosquito species. To this end, we performed a circadian-dependent RNA-Sequencing study of the brain and peripheral olfactory-tissues of female Anopheles and Aedes mosquitoes. Data analysis revealed a significant upregulation of genes encoding: (a) chemosensory proteins (CSPs), required for transportation of odorant molecules towards the olfactory receptors, and; (b) xenobiotic-metabolizing enzymes (XMEs) during the dusk-transition phase. While XMEs primarily function in the elimination of toxic xenobiotics, concurrent elevation of XMEs and CSPs are hypothesized to act cumulatively for the regulation of perireceptor events and odorant sensitivity. During navigation towards their vertebrate-host/floral-host/mate-partners, female mosquitoes are exposed to diverse environmental chemicals of varied release rates that require continuous degradation/biotransformation by XMEs to avoid receptor saturation in such a noisy environment. Finally, our electroantennographic (EAG) analysis with both Anopheles and Aedes mosquitoes against diverse active volatile odorants, combined with XMEs inhibitors and RNAi studies, establish the proof-of-concept that XMEs function in peri-receptor events during odorant perception and influence the odorant sensitivity in mosquitoes. Additionally, our RNA-Seq and RNAi data also revealed that daily temporal modulation of neuronal serine proteases may facilitate the reorganization of synaptic connections influencing synaptic plasticity and olfactory perception in mosquitoes. In summary, this study highlights the crucial function of XMEs in odorant reception, therefore, improved understanding of species-specific rhythmic expression may provide an important information for successful implementation of mosquito control methods. Overall design: To understand the circadian dependent molecular rhythm in the olfactory and brain tissues of the diurnal Aedes and nocturnal Anopheles mosquitoes, that drive their different behavioral activities (day time biting behavior of Aedes mosquito and night-time biting behavior of Anopheles mosquito), we performed RNA-Seq study of both olfactory and brain tissues at 4 different circadian time, 6am, 12pm, 6am and 12am. In this study total 488 samples were processed that includes two different tissues (olafctory and brain) from two different mosquito species (Aedes aegypti and Anopheles culicifacies) at four different time points (6am, 12pm, 6pm, 12am) with three biological replicates