A Synergistic Transcriptional Regulation of Olfactory Genes Drives Blood-Feeding Associated Complex Behavioral Responses in the Mosquito Anopheles culicifacies

Abstract

Decoding the molecular basis of host seeking and blood feeding behavioral evolution/adaptation in the adult female mosquitoes may provide an opportunity to design new molecular strategy to disrupt human-mosquito interactions. Although there is a great progress in the field of mosquito olfaction and chemo-detection, little is known about the sex-specific evolution of the specialized olfactory system of adult female mosquitoes that enables them to drive and manage the complex blood-feeding associated behavioral responses. A comprehensive RNA-Seq analysis of prior and post blood meal olfactory system of An. culicifacies mosquito revealed a minor but unique change in the nature and regulation of key olfactory genes that may play a pivotal role in managing diverse behavioral responses. Based on age-dependent transcriptional profiling, we further demonstrated that adult female mosquito's chemosensory system gradually learned and matured to drive the host-seeking and blood feeding behavior at the age of 5–6 days. A time scale expression analysis of Odorant Binding Proteins (OBPs) unravels unique association with a late evening to midnight peak biting time. Blood meal-induced switching of unique sets of OBP genes and Odorant Receptors (Ors) expression coincides with the change in the innate physiological status of the mosquitoes. Blood meal follows up experiments further provide enough evidence that how a synergistic and concurrent action of OBPs-Ors may drive “prior and post blood meal” associated complex behavioral events. A dominant expression of two sensory appendages proteins (SAP-1 & SAP2) in the legs of An. culicifacies suggests that this mosquito species may draw an extra advantage of having more sensitive appendages than An. stephensi, an urban malarial vector in the Indian subcontinents. Finally, our molecular modeling analysis predicts crucial amino acid residues for future functional characterization of the sensory appendages proteins which may play a central role in regulating multiple behaviors of An. culicifacies mosquito.SIGNIFICANCE Evolution and adaptation of blood feeding behavior not only favored the reproductive success of adult female mosquitoes but also make them important disease-transmitting vectors. An environmental exposure after emergence may favor the broadly tuned olfactory system of mosquitoes to drive complex behavioral responses. But, how these olfactory derived genetic factors manage female specific “pre and post” blood meal associated complex behavioral responses are not well known. Our findings suggest that a synergistic action of olfactory factors may govern an innate to prime learning strategy to facilitate rapid blood meal acquisition and downstream behavioral activities. A species-specific transcriptional profiling and an in-silico analysis predict that “sensory appendages protein” may be a unique target to design disorientation strategy against the mosquito Anopheles culicifacies.

Hemocyte‐specific FREP13 abrogates the exogenous bacterial population in the hemolymph and promotes midgut endosymbionts in Anopheles stephensi

“…After 3-4 days of dsRNA injection, hemocyte tissue was collected from 20 or 30 mosquitoes and checked for the efficiency of silencing by quantitative real-time PCR. 50 For the control group, age-matched mosquitoes were injected with dsRNA prepared from the bacterial LacZ gene. To test the effect of AsFREP13 silencing on gut microbiome proliferation, we provided rabbit blood-meals to both control and knockdown mosquito groups (3-4 days after dsRNA injection), and then collected the hemocytes and midgut samples.…”

SalivaryAsHPX12influence pre-blood meal associated behavioral properties in the mosquitoAnopheles stephensi

“…The navigation trajectory during active host-seeking is achieved by coordinated neuro-olfactory actions to find and locate a suitable vertebrate host (12), and once located the desired host, the salivary actions facilitate rapid blood meal acquisition process. Several studies suggest that during blood feeding the salivary cocktail composition is rapidly depleted (24), but how the host-odor activated salivary glands manages 'prior and post' blood-meal associated changing physiologies is largely unknown (26).…”

“…If taken infectious blood meal, it may also affect their ability to transmit several infectious diseases (5)(6)(7)(8)(9)(10). The harmonious actions of the neuro-olfactory system drive mosquito's successful navigation towards a vertebrate host (11), but it is the salivary gland that facilitates rapid blood meal uptake from the respective host (12). The mosquito's salivary cocktail contains crucial bioactive molecules having antihomeostatic (13)(14)(15), anti-inflammatory, and immunomodulatory properties (16)(17)(18)(19), which counteract the host defense for rapid blood meal acquisition, usually in less than two minutes.…”

Membrane Proteins Mediating Reception and Transduction in Chemosensory Neurons in Mosquitoes

“…Changes in transcript levels of receptor genes in A. gambiae are correlated with moderate chemosensory neuron sensitivity shifts following a blood meal ( Rinker et al, 2013a ). In addition to expression shifts due to feeding state changes, there may be natural fluctuations in chemosensory protein abundance based on time of day ( Rund et al, 2013 ; De Das et al, 2018 ). Mosquito feeding often peaks at dawn or dusk ( Clements, 1992 ); thus, there may exist a relationship between functional demands for chemosensory proteins and temporal regulation of gene expression in peripheral neurons.…”