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The molecular receptive range of a lactone receptor in Anopheles gambiae.

ABSTRACT: In an environment filled with a complex spectrum of chemical stimuli, insects rely on the specificity of odorant receptors (ORs) to discern odorants of ecological importance. In nature, cyclic esters, or lactones, represent a common class of semiochemicals that exhibit a range of diversity through ring size and substituents, as well as stereochemistry. We have used heterologous expression to explore the lactone sensitivity of AgOr48, an odorant-sensitive OR from the principal malaria vector mosquito, Anopheles gambiae. Voltage clamp and calcium-imaging experiments revealed that AgOr48 is particularly sensitive to changes in the size of the lactone ring and in the length of the carbon chain substituent. In addition, the two enantiomers of a strong agonist, ?-decalactone, elicited significantly different potency values, implicating AgOr48 as an enantioselective odorant receptor. Investigation of the molecular receptive range of this lactone receptor may contribute to a greater understanding of ligand-OR interactions and provide insight into the chemical ecology of An. gambiae.

SUBMITTER: Pask GM

PROVIDER: S-EPMC3522515 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature

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The molecular receptive range of a lactone receptor in Anopheles gambiae.

Pask Gregory M GM Romaine Ian M IM Zwiebel Laurence J LJ

Chemical senses 20120902 1

In an environment filled with a complex spectrum of chemical stimuli, insects rely on the specificity of odorant receptors (ORs) to discern odorants of ecological importance. In nature, cyclic esters, or lactones, represent a common class of semiochemicals that exhibit a range of diversity through ring size and substituents, as well as stereochemistry. We have used heterologous expression to explore the lactone sensitivity of AgOr48, an odorant-sensitive OR from the principal malaria vector mosq ...[more]

PMID: 22944613

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Project description:As pathogens that circumvent the host immune response are favoured by selection, so are host alleles that reduce parasite load. Such evolutionary processes leave their signature on the genes involved. Deciphering modes of selection operating on immune genes might reveal the nature of host-pathogen interactions and factors that govern susceptibility in host populations. Such understanding would have important public health implications.We analyzed polymorphisms in four mosquito immune genes (SP14D1, GNBP, defensin, and gambicin) to decipher selection effects, presumably mediated by pathogens. Using samples of Anopheles arabiensis, An. quadriannulatus and four An. gambiae populations, as well as published sequences from other Culicidae, we contrasted patterns of polymorphisms between different functional units of the same gene within and between populations. Our results revealed selection signatures operating on different time scales. At the most recent time scale, within-population diversity revealed purifying selection. Between populations and between species variation revealed reduced differentiation (GNBP and gambicin) at coding vs. noncoding- regions, consistent with balancing selection. McDonald-Kreitman tests between An. quadriannulatus and both sibling species revealed higher fixation rate of synonymous than nonsynonymous substitutions (GNBP) in accordance with frequency dependent balancing selection. At the longest time scale (>100 my), PAML analysis using distant Culicid taxa revealed positive selection at one codon in gambicin. Patterns of genetic variation were independent of exposure to human pathogens.Purifying selection is the most common form of selection operating on immune genes as it was detected on a contemporary time scale on all genes. Selection for "hypervariability" was not detected, but negative balancing selection, detected at a recent evolutionary time scale between sibling species may be rather common. Detection of positive selection at the deepest evolutionary time scale suggests that it occurs infrequently, possibly in association with speciation events. Our results provided no evidence to support the hypothesis that selection was mediated by pathogens that are transmitted to humans.

Project description:BackgroundAnopheles gambiae mosquitoes exhibit an endophilic, nocturnal blood feeding behavior. Despite the importance of light as a regulator of malaria transmission, our knowledge on the molecular interactions between environmental cues, the circadian oscillators and the host seeking and feeding systems of the Anopheles mosquitoes is limited.ResultsIn the present study, we show that the blood feeding behavior of mosquitoes is under circadian control and can be modulated by light pulses, both in a clock dependent and in an independent manner. Short light pulses (approximately 2-5 min) in the dark phase can inhibit the blood-feeding propensity of mosquitoes momentarily in a clock independent manner, while longer durations of light stimulation (approximately 1-2 h) can induce a phase advance in blood-feeding propensity in a clock dependent manner. The temporary feeding inhibition after short light pulses may reflect a masking effect of light, an unknown mechanism which is known to superimpose on the true circadian regulation. Nonetheless, the shorter light pulses resulted in the differential regulation of a variety of genes including those implicated in the circadian control, suggesting that light induced masking effects also involve clock components. Light pulses (both short and long) also regulated genes implicated in feeding as well as different physiological processes like metabolism, transport, immunity and protease digestions. RNAi-mediated gene silencing assays of the light pulse regulated circadian factors timeless, cryptochrome and three takeout homologues significantly up-regulated the mosquito's blood-feeding propensity. In contrast, gene silencing of light pulse regulated olfactory factors down-regulated the mosquito's propensity to feed on blood.ConclusionOur study show that the mosquito's feeding behavior is under circadian control. Long and short light pulses can induce inhibition of blood-feeding through circadian and unknown mechanisms, respectively, that involve the chemosensory system.

Dataset Information

The molecular receptive range of a lactone receptor in Anopheles gambiae.

Publications

The molecular receptive range of a lactone receptor in Anopheles gambiae.

Similar Datasets

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