A spatial map of antennal-expressed ionotropic receptors in the malaria mosquito

The mosquito's antenna represents its main olfactory appendage for detecting volatile chemical cues from the environment. Whole-mount fluorescence in situ hybridization of ionotropic receptors (IRs) expressed in the antennae reveals that the antenna might be divisible into proximal and distal functional domains. The number of IR-positive cells appear stereotyped within each antennal segment (flagellomere). Highly expressed odor-tuning IRs exhibit distinct co-localization patterns with the IR coreceptors Ir8a, Ir25a, and Ir76b that might predict their functional properties. Genetic knockin and in vivo functional imaging of IR41c-expressing neurons indicate both odor-induced activation and inhibition in response to select amine compounds. Targeted mutagenesis of IR41c does not abolish behavioral responses to the amine com-pounds. Our study provides a comprehensive map of IR-expressing neurons in the main olfactory appendage of mosquitoes. These findings show organizing principles of Anopheles IR-expressing neurons, which might underlie their functional contribution to the detection of behaviorally relevant odors.

Automated summary

The mosquito's antenna is its main olfactory appendage for detecting volatile chemical cues. The antenna can be divided into proximal and distal functional domains, with a specific number of ionotropic receptors (IRs) within each segment. Highly expressed odor-tuning IRs show distinct co-localization patterns with IR coreceptors, indicating their functional properties. Knockin and functional imaging of IR41c-expressing neurons reveal both activation and inhibition to amine compounds, but targeted mutagenesis of IR41c does not abolish behavioral responses to these compounds. This study provides a comprehensive map of IR-expressing neurons in the mosquito's antenna, giving insights into their functional contribution to odor detection.