Abstract
BackgroundIt has long been the goal of vector biology to generate genetic knowledge that can be used to “manipulate” natural populations of vectors to eliminate or lessen disease burden. While long in coming, progress towards reaching this goal has been made. Aiming to increase our understanding regarding the interactions between Plasmodium and the Anopheles immune genes, we investigated the patterns of genetic diversity of four anti-Plasmodium genes in the Anopheles gambiae complex of species.Methodology/Principal FindingsWithin a comparative phylogenetic and population genetics framework, the evolutionary history of four innate immunity genes within the An. gambiae complex (including the two most important human malaria vectors, An. gambiae and An. arabiensis) is reconstructed. The effect of natural selection in shaping the genes' diversity is examined.Introgression and retention of ancestral polymorphisms are relatively rare at all loci. Despite the potential confounding effects of these processes, we could identify sites that exhibited dN/dS ratios greater than 1.Conclusions/SignificanceIn two of the studied genes, CLIPB14 and FBN8, several sites indicated evolution under positive selection, with CLIPB14 exhibiting the most consistent evidence. Considering only the sites that were consistently identified by all methods, two sites in CLIPB14 are adaptively driven. However, the analysis inferring the lineage -specific evolution of each gene was not in favor of any of the Anopheles lineages evolving under the constraints imposed by positive selection. Nevertheless, the loci and the specific amino acids that were identified as evolving under strong evolutionary pressure merit further investigation for their involvement in the Anopheles defense against microbes in general.
Highlights
It has long been a goal of vector biology to generate genetic knowledge that can be used to ‘‘manipulate’’ natural populations of vectors to ammeliorate the impact of diseases spread by vectors
A gene silencing assay of three immunity genes of An. gambiae infected with P. falciparum, indicated that the immune response is quite different from that manifested after infection with P. berghei [14]
These genes are MDL1, MDL2, CLIPB14 and FBN8 and all of them have been implicated to be involved in the defense of Anopheles against malaria
Summary
It has long been a goal of vector biology to generate genetic knowledge that can be used to ‘‘manipulate’’ natural populations of vectors to ammeliorate the impact of diseases spread by vectors. Some of the explored methods for generating refractoriness involve using antibodies that kill parasites within the mosquito [1] and discovering genes that govern refractoriness in natural populations [2]. That An. gambiae has undergone an adaptive response to P. falciparum infection is suggested by several lines of evidence Both An. gambiae and An. stephensi mosquitoes infected with P. berghei, for which this parasite species are not natural hosts, produce 50–80 oocysts, whereas an infection with P. falciparum results in far fewer oocysts. The results of the latter study highlight one more issue, namely the importance of following up discoveries in laboratory model systems with studies on natural parasite–mosquito interactions It has long been the goal of vector biology to generate genetic knowledge that can be used to ‘‘manipulate’’ natural populations of vectors to eliminate or lessen disease burden. Aiming to increase our understanding regarding the interactions between Plasmodium and the Anopheles immune genes, we investigated the patterns of genetic diversity of four anti-Plasmodium genes in the Anopheles gambiae complex of species
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