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Phylogeny of Anopheles darlingi (Diptera:Culicidae) based on the antimicrobial peptide genes cecropin and defensin. Acta Trop 2022; 227:106285. [PMID: 34921765 DOI: 10.1016/j.actatropica.2021.106285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 12/13/2021] [Accepted: 12/13/2021] [Indexed: 11/22/2022]
Abstract
Cecropins and defensins are the main classes of antimicrobial peptides in the mosquito innate immune system, acting against bacteria, fungi and protozoa. There is a knowledge gap concerning these peptide genes in anopheline mosquitoes from the Brazilian Amazon. Thus, this work aimed to describe molecular techniques for detecting the genes encoding the antimicrobial peptides cecropin A (CecA) and defensin in Anopheles darlingi mosquitoes and to perform molecular phylogeny of the sequenced genes using the maximum likelihood method and Bayesian inference with other species from different geographic areas. Our results show, for the first time, a molecular biology method for detecting CecA and defensin in Anopheles darlingi that allows for the use of these molecular markers for phylogenetic analysis in anopheline species, separating the species into single and monophyletic clades.
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Salgueiro P, Lopes AS, Mendes C, Charlwood JD, Arez AP, Pinto J, Silveira H. Molecular evolution and population genetics of a Gram-negative binding protein gene in the malaria vector Anopheles gambiae (sensu lato). Parasit Vectors 2016; 9:515. [PMID: 27658383 PMCID: PMC5034674 DOI: 10.1186/s13071-016-1800-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 09/14/2016] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Clarifying the role of the innate immune system of the malaria vector Anopheles gambiae is a potential way to block the development of the Plasmodium parasites. Pathogen recognition is the first step of innate immune response, where pattern recognition proteins like GNBPs play a central role. RESULTS We analysed 70 sequences of the protein coding gene GNBPB2 from two species, Anopheles gambiae (s.s.) and An. coluzzii, collected in six African countries. We detected 135 segregating sites defining 63 distinct haplotypes and 30 proteins. Mean nucleotide diversity (π) was 0.014 for both species. We found no significant genetic differentiation between species, but a significant positive correlation between genetic differentiation and geographical distance among populations. CONCLUSIONS Species status seems to contribute less for the molecular differentiation in GNBPB2 than geographical region in the African continent (West and East). Purifying selection was found to be the most common form of selection, as in many other immunity-related genes. Diversifying selection may be also operating in the GNBPB2 gene.
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Affiliation(s)
- Patrícia Salgueiro
- Global Health and Tropical Medicine Centre (GHTM), Unidade de Parasitologia Médica, Instituto de Higiene e Medicina Tropical (IHMT), Universidade Nova de Lisboa, Lisboa, Portugal
| | - Ana Sofia Lopes
- Global Health and Tropical Medicine Centre (GHTM), Unidade de Parasitologia Médica, Instituto de Higiene e Medicina Tropical (IHMT), Universidade Nova de Lisboa, Lisboa, Portugal
| | - Cristina Mendes
- Global Health and Tropical Medicine Centre (GHTM), Unidade de Parasitologia Médica, Instituto de Higiene e Medicina Tropical (IHMT), Universidade Nova de Lisboa, Lisboa, Portugal
| | - Jacques Derek Charlwood
- Global Health and Tropical Medicine Centre (GHTM), Unidade de Parasitologia Médica, Instituto de Higiene e Medicina Tropical (IHMT), Universidade Nova de Lisboa, Lisboa, Portugal
- London School of Hygiene and Tropical Medicine, London, UK
| | - Ana Paula Arez
- Global Health and Tropical Medicine Centre (GHTM), Unidade de Parasitologia Médica, Instituto de Higiene e Medicina Tropical (IHMT), Universidade Nova de Lisboa, Lisboa, Portugal
| | - João Pinto
- Global Health and Tropical Medicine Centre (GHTM), Unidade de Parasitologia Médica, Instituto de Higiene e Medicina Tropical (IHMT), Universidade Nova de Lisboa, Lisboa, Portugal
| | - Henrique Silveira
- Global Health and Tropical Medicine Centre (GHTM), Unidade de Parasitologia Médica, Instituto de Higiene e Medicina Tropical (IHMT), Universidade Nova de Lisboa, Lisboa, Portugal
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Chapman JR, Hellgren O, Helin AS, Kraus RHS, Cromie RL, Waldenström J. The Evolution of Innate Immune Genes: Purifying and Balancing Selection on β-Defensins in Waterfowl. Mol Biol Evol 2016; 33:3075-3087. [DOI: 10.1093/molbev/msw167] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
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Unckless RL, Lazzaro BP. The potential for adaptive maintenance of diversity in insect antimicrobial peptides. Philos Trans R Soc Lond B Biol Sci 2016; 371:20150291. [PMID: 27160594 PMCID: PMC4874389 DOI: 10.1098/rstb.2015.0291] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/12/2016] [Indexed: 02/07/2023] Open
Abstract
Genes involved in immune defence are among the fastest evolving in the genomes of many species. Interestingly, however, genes encoding antimicrobial peptides (AMPs) have shown little evidence for adaptive divergence in arthropods, despite the centrality of these peptides in direct killing of microbial pathogens. This observation, coupled with a failure to detect phenotypic consequence of genetic variation in AMPs, has led to the hypothesis that individual AMPs make minor contributions to overall immune defence and that AMPs instead act as a collective cocktail. Recent data, however, have suggested an alternative explanation for the apparent lack of adaptive divergence in AMP genes. Molecular evolutionary and phenotypic data have begun to suggest that variant AMP alleles may be maintained through balancing selection in invertebrates, a pattern similar to that observed in several vertebrate AMPs. Signatures of balancing selection include high rates of non-synonymous polymorphism, trans-species amino acid polymorphisms, and convergence of amino acid states across the phylogeny. In this review, we revisit published literature on insect AMP genes and analyse newly available population genomic datasets in Drosophila, finding enrichment for patterns consistent with adaptive maintenance of polymorphism.This article is part of the themed issue 'Evolutionary ecology of arthropod antimicrobial peptides'.
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Affiliation(s)
| | - Brian P Lazzaro
- Department of Entomology, Cornell University, Ithaca, NY 14853, USA
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Korb J, Poulsen M, Hu H, Li C, Boomsma JJ, Zhang G, Liebig J. A genomic comparison of two termites with different social complexity. Front Genet 2015; 6:9. [PMID: 25788900 PMCID: PMC4348803 DOI: 10.3389/fgene.2015.00009] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 01/09/2015] [Indexed: 11/15/2022] Open
Abstract
The termites evolved eusociality and complex societies before the ants, but have been studied much less. The recent publication of the first two termite genomes provides a unique comparative opportunity, particularly because the sequenced termites represent opposite ends of the social complexity spectrum. Zootermopsis nevadensis has simple colonies with totipotent workers that can develop into all castes (dispersing reproductives, nest-inheriting replacement reproductives, and soldiers). In contrast, the fungus-growing termite Macrotermes natalensis belongs to the higher termites and has very large and complex societies with morphologically distinct castes that are life-time sterile. Here we compare key characteristics of genomic architecture, focusing on genes involved in communication, immune defenses, mating biology and symbiosis that were likely important in termite social evolution. We discuss these in relation to what is known about these genes in the ants and outline hypothesis for further testing.
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Affiliation(s)
- Judith Korb
- Department of Evolutionary Biology and Ecology, Institute of Biology I, University of FreiburgFreiburg, Germany
| | - Michael Poulsen
- Section for Ecology and Evolution, Department of Biology, Centre for Social Evolution, University of CopenhagenCopenhagen, Denmark
| | - Haofu Hu
- China National Genebank, BGI-ShenzhenShenzhen, China
| | - Cai Li
- China National Genebank, BGI-ShenzhenShenzhen, China
- Centre for GeoGenetics, Natural History Museum of Denmark, University of CopenhagenCopenhagen, Denmark
| | - Jacobus J. Boomsma
- Section for Ecology and Evolution, Department of Biology, Centre for Social Evolution, University of CopenhagenCopenhagen, Denmark
| | - Guojie Zhang
- Section for Ecology and Evolution, Department of Biology, Centre for Social Evolution, University of CopenhagenCopenhagen, Denmark
- China National Genebank, BGI-ShenzhenShenzhen, China
| | - Jürgen Liebig
- School of Life Sciences, Arizona State UniversityTempe, AZ, USA
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Arnal A, Kengne P, Brengues C, Dabire KR, Diabate A, Bassene H, Simard F. Genetic polymorphism at an odorant receptor gene (Or39) among mosquitoes of the Anopheles gambiae complex in Senegal (West Africa). BMC Res Notes 2014; 7:321. [PMID: 24886539 PMCID: PMC4048261 DOI: 10.1186/1756-0500-7-321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 05/21/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Olfaction plays a significant role in insect behavior during critical steps of their life-cycle, such as host-seeking during foraging or the search for a mate. Here, we explored genetic polymorphism within and divergence between sibling species of the African malaria mosquito, Anopheles gambiae sensu lato in the gene sequence and encoded peptides of an odorant receptor, Or39. This study included sympatric specimens of An. gambiae sensu stricto, An. coluzzii and An. arabiensis sampled together in the village of Dielmo, Senegal. RESULTS A 1,601 bp genomic sequence composed of 6 exons and 5 introns was obtained for Or39 from 6-8 mosquitoes in each of the 3 species. DNA sequence analysis revealed a high level of molecular polymorphism (π = 0.0154; Haplotype diversity = 0.867) and high overall genetic differentiation between taxa (Fst > 0.92, P < 0.01). In total, 50 parsimony informative sites were recorded. Throughout the whole dataset, there were 13 non-synonymous mutations resulting in aminoacid changes in the encoded protein. Each of the 6 different identified peptides was species-specific and none was shared across species. Most aminoacid changes were located on the intracellular domains of the protein. However, intraspecific polymorphisms in An. gambiae and An. arabiensis as well as species-specific mutations also occurred in the first extracellular domain. CONCLUSIONS Although obtained from a limited number of specimens, our results point towards genetic differences between cryptic species within the An. gambiae complex in a gene of biological relevance that might be of evolutionary significance when exposed to disruptive selective forces.
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Affiliation(s)
- Audrey Arnal
- Institut de Recherche pour le Développement (IRD), UMR IRD 224-CNRS 5290-UM1-UM2 MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Genetique, Evolution et Contrôle), team BEES (Biology, Ecology and Evolution of vector Systems), 911 Avenue Agropolis, BP 64501, Montpellier, cedex 5 34394, France
| | - Pierre Kengne
- Institut de Recherche pour le Développement (IRD), UMR IRD 224-CNRS 5290-UM1-UM2 MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Genetique, Evolution et Contrôle), team BEES (Biology, Ecology and Evolution of vector Systems), 911 Avenue Agropolis, BP 64501, Montpellier, cedex 5 34394, France
- Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Cecile Brengues
- Institut de Recherche pour le Développement (IRD), UMR IRD 224-CNRS 5290-UM1-UM2 MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Genetique, Evolution et Contrôle), team BEES (Biology, Ecology and Evolution of vector Systems), 911 Avenue Agropolis, BP 64501, Montpellier, cedex 5 34394, France
| | - Kounbobr Roch Dabire
- Institut de Recherche en Sciences de la Santé (IRSS), P.O. Box 545, Bobo-Dioulasso, Burkina Faso
| | - Abdoulaye Diabate
- Institut de Recherche en Sciences de la Santé (IRSS), P.O. Box 545, Bobo-Dioulasso, Burkina Faso
| | - Hubert Bassene
- UMR 198 URMITE, Campus International IRD/UCAD de Hann, Dakar, Senegal
| | - Frederic Simard
- Institut de Recherche pour le Développement (IRD), UMR IRD 224-CNRS 5290-UM1-UM2 MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Genetique, Evolution et Contrôle), team BEES (Biology, Ecology and Evolution of vector Systems), 911 Avenue Agropolis, BP 64501, Montpellier, cedex 5 34394, France
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Erler S, Lhomme P, Rasmont P, Lattorff HMG. Rapid evolution of antimicrobial peptide genes in an insect host–social parasite system. INFECTION GENETICS AND EVOLUTION 2014; 23:129-37. [DOI: 10.1016/j.meegid.2014.02.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 01/08/2014] [Accepted: 02/07/2014] [Indexed: 10/25/2022]
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Damal K, Murrell EG, Juliano SA, Conn JE, Loew SS. Phylogeography of Aedes aegypti (yellow fever mosquito) in South Florida: mtDNA evidence for human-aided dispersal. Am J Trop Med Hyg 2013; 89:482-8. [PMID: 23918216 DOI: 10.4269/ajtmh.13-0102] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The invasive dengue vector Aedes aegypti has persisted for > 200 years in South Florida in the United States. We tested the hypotheses that Florida's landscape creates dispersal barriers and corridors and that long-distance human-aided dispersal structures populations of Ae. aegypti. We evaluated the phylogeography of 362 individuals from Florida's East and West Coasts with a 760-bp (418- and 342-bp fragments of ND5 and ND4, respectively) mitochondrial sequence. Populations from these two coasts were not significantly differentiated, suggesting that limited urbanization in central Florida is not a strong barrier to gene flow. Evidence for long-distance dispersal between Ft. Lauderdale and the West and Ft. Myers and the East indicates the importance of human-aided dispersal. West Coast populations showed no genetic differentiation, indicating that West Coast rivers and bays did not significantly impede gene flow. Phylogeographic analysis of haplotypes showed two distinct matrilines with no geographic patterns, suggesting multiple introductions or balancing selection.
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Affiliation(s)
- Kavitha Damal
- Division of Epidemiology, University of Utah, Salt Lake City, UT 84108, USA.
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White BJ, Collins FH, Besansky NJ. Evolution of Anopheles gambiae in Relation to Humans and Malaria. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2011. [DOI: 10.1146/annurev-ecolsys-102710-145028] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The closely related and morphologically indistinguishable mosquito species in the Afrotropical Anopheles gambiae complex differ dramatically in their contribution to malaria transmission, ranging from major vectors through minor or locally important vectors and nonvectors. Radiation of the A. gambiae complex and ongoing diversification within its nominal species appears to be a product of recent and rapid adaptation to environmental heterogeneities, notably those of anthropogenic origin. Polytene chromosome and genomic analyses suggest that paracentric chromosomal inversions and possibly other low-recombination regions have played instrumental roles in this process by facilitating ecotypic differentiation both within and across semipermeable species boundaries. Forthcoming complete genome sequences from several members of the A. gambiae complex will provide powerful tools to accelerate ongoing investigation of how genetic diversification of populations and species has shaped behavioral and physiological traits, such as vector competence, that bear on vectorial importance.
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Affiliation(s)
- Bradley J. White
- Department of Entomology, University of California, Riverside, Riverside, California 92521
| | - Frank H. Collins
- Eck Institute for Global Health and Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556
| | - Nora J. Besansky
- Eck Institute for Global Health and Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556
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Mancini E, Tammaro F, Baldini F, Via A, Raimondo D, George P, Audisio P, Sharakhov IV, Tramontano A, Catteruccia F, della Torre A. Molecular evolution of a gene cluster of serine proteases expressed in the Anopheles gambiae female reproductive tract. BMC Evol Biol 2011; 11:72. [PMID: 21418586 PMCID: PMC3068966 DOI: 10.1186/1471-2148-11-72] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 03/19/2011] [Indexed: 11/30/2022] Open
Abstract
Background Genes involved in post-mating processes of multiple mating organisms are known to evolve rapidly due to coevolution driven by sexual conflict among male-female interacting proteins. In the malaria mosquito Anopheles gambiae - a monandrous species in which sexual conflict is expected to be absent or minimal - recent data strongly suggest that proteolytic enzymes specifically expressed in the female lower reproductive tissues are involved in the processing of male products transferred to females during mating. In order to better understand the role of selective forces underlying the evolution of proteins involved in post-mating responses, we analysed a cluster of genes encoding for three serine proteases that are down-regulated after mating, two of which specifically expressed in the atrium and one in the spermatheca of A. gambiae females. Results The analysis of polymorphisms and divergence of these female-expressed proteases in closely related species of the A. gambiae complex revealed a high level of replacement polymorphisms consistent with relaxed evolutionary constraints of duplicated genes, allowing to rapidly fix novel replacements to perform new or more specific functions. Adaptive evolution was detected in several codons of the 3 genes and hints of episodic selection were also found. In addition, the structural modelling of these proteases highlighted some important differences in their substrate specificity, and provided evidence that a number of sites evolving under selective pressures lie relatively close to the catalytic triad and/or on the edge of the specificity pocket, known to be involved in substrate recognition or binding. The observed patterns suggest that these proteases may interact with factors transferred by males during mating (e.g. substrates, inhibitors or pathogens) and that they may have differently evolved in independent A. gambiae lineages. Conclusions Our results - also examined in light of constraints in the application of selection-inference methods to the closely related species of the A. gambiae complex - reveal an unexpectedly intricate evolutionary scenario. Further experimental analyses are needed to investigate the biological functions of these genes in order to better interpret their molecular evolution and to assess whether they represent possible targets for limiting the fertility of Anopheles mosquitoes in malaria vector control strategies.
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Affiliation(s)
- Emiliano Mancini
- Istituto-Pasteur - Fondazione Cenci Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, 'Sapienza' Università di Roma, Italy
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Rottschaefer SM, Riehle MM, Coulibaly B, Sacko M, Niaré O, Morlais I, Traoré SF, Vernick KD, Lazzaro BP. Exceptional diversity, maintenance of polymorphism, and recent directional selection on the APL1 malaria resistance genes of Anopheles gambiae. PLoS Biol 2011; 9:e1000600. [PMID: 21408087 PMCID: PMC3050937 DOI: 10.1371/journal.pbio.1000600] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 01/27/2011] [Indexed: 01/17/2023] Open
Abstract
The three-gene APL1 locus encodes essential components of the mosquito immune defense against malaria parasites. APL1 was originally identified because it lies within a mapped QTL conferring the vector mosquito Anopheles gambiae natural resistance to the human malaria parasite, Plasmodium falciparum, and APL1 genes have subsequently been shown to be involved in defense against several species of Plasmodium. Here, we examine molecular population genetic variation at the APL1 gene cluster in spatially and temporally diverse West African collections of A. gambiae. The locus is extremely polymorphic, showing evidence of adaptive evolutionary maintenance of genetic variation. We hypothesize that this variability aids in defense against genetically diverse pathogens, including Plasmodium. Variation at APL1 is highly structured across geographic and temporal subpopulations. In particular, diversity is exceptionally high during the rainy season, when malaria transmission rates are at their peak. Much less allelic diversity is observed during the dry season when mosquito population sizes and malaria transmission rates are low. APL1 diversity is weakly stratified by the polymorphic 2La chromosomal inversion but is very strongly subdivided between the M and S “molecular forms.” We find evidence that a recent selective sweep has occurred at the APL1 locus in M form mosquitoes only. The independently reported observation of a similar M-form restricted sweep at the Tep1 locus, whose product physically interacts with APL1C, suggests that epistatic selection may act on these two loci causing them to sweep coordinately. Immune defense genes are sometimes highly variable in host populations, reflecting selective pressure to combat diverse pathogens. In other instances, where there are only a few dominant pathogens, natural selection may favor only one or a few defense alleles. Here, we show that both adaptive strategies can occur in the same genes under different circumstances. We examined diversity in the APL1 genes of the human malaria vector mosquito Anophleles gambiae, which play a role in defense against malaria parasites. We found that the APL1 genes are exceptionally polymorphic, being 10-fold more diverse than typical A. gambiae genes. The distribution of APL1 allelic diversity, however, is strongly structured depending on whether the genes are carried by the M or S “molecular forms” of the vector, which are thought to constitute newly forming species. We show that despite the evolutionary maintenance of APL1 diversity in the S form of A. gambiae, there is evidence of strong recent directional selection on APL1 genes in the M form. Independent research has shown that Tep1, a gene which encodes a protein that physically interacts with the APL1C protein, also harbors high allelic diversity in the S form and shows evidence of recent directional selection in the M form, suggesting that the evolutionary trajectories of the Tep1 and APL1 defense loci may be correlated.
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Affiliation(s)
- Susan M. Rottschaefer
- Department of Entomology, Cornell University, Ithaca, New York, United States of America
| | - Michelle M. Riehle
- Department of Microbiology, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Boubacar Coulibaly
- Malaria Research and Training Center, University of Bamako, Bamako, Mali
| | - Madjou Sacko
- Malaria Research and Training Center, University of Bamako, Bamako, Mali
| | - Oumou Niaré
- Malaria Research and Training Center, University of Bamako, Bamako, Mali
| | - Isabelle Morlais
- Laboratoire de Recherche sur le Paludisme, Institut de Recherche pour le Développement IRD-OCEAC, Yaoundé, Cameroun
| | - Sekou F. Traoré
- Malaria Research and Training Center, University of Bamako, Bamako, Mali
| | - Kenneth D. Vernick
- Unit of Insect Vector Genetics and Genomics, Institut Pasteur, Paris, France
| | - Brian P. Lazzaro
- Department of Entomology, Cornell University, Ithaca, New York, United States of America
- * E-mail:
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Harris C, Rousset F, Morlais I, Fontenille D, Cohuet A. Low linkage disequilibrium in wild Anopheles gambiae s.l. populations. BMC Genet 2010; 11:81. [PMID: 20843306 PMCID: PMC2949739 DOI: 10.1186/1471-2156-11-81] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Accepted: 09/15/2010] [Indexed: 11/10/2022] Open
Abstract
Background In the malaria vector Anopheles gambiae, understanding diversity in natural populations and genetic components of important phenotypes such as resistance to malaria infection is crucial for developing new malaria transmission blocking strategies. The design and interpretation of many studies here depends critically on Linkage disequilibrium (LD). For example in association studies, LD determines the density of Single Nucleotide Polymorphisms (SNPs) to be genotyped to represent the majority of the genomic information. Here, we aim to determine LD in wild An. gambiae s.l. populations in 4 genes potentially involved in mosquito immune responses against pathogens (Gambicin, NOS, REL2 and FBN9) using previously published and newly generated sequences. Results The level of LD between SNP pairs in cloned sequences of each gene was determined for 7 species (or incipient species) of the An. gambiae complex. In all tested genes and species, LD between SNPs was low: even at short distances (< 200 bp), most SNP pairs gave an r2 < 0.3. Mean r2 ranged from 0.073 to 0.766. In most genes and species LD decayed very rapidly with increasing inter-marker distance. Conclusions These results are of great interest for the development of large scale polymorphism studies, as LD generally falls below any useful limit. It indicates that very fine scale SNP detection will be required to give an overall view of genome-wide polymorphism. Perhaps a more feasible approach to genome wide association studies is to use targeted approaches using candidate gene selection to detect association to phenotypes of interest.
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Affiliation(s)
- Caroline Harris
- Laboratoire de Lutte Contre les Insectes Nuisibles, Unité de Recherche 016-Institut de Recherche pour le Développement, BP 64501, 34394 Montpellier Cedex 5, France.
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Dixit R, Patole MS, Shouche YS. Identification of putative innate immune related genes from a cell line of the mosquito Aedes albopictus following bacterial challenge. Innate Immun 2010; 17:106-17. [PMID: 20123933 DOI: 10.1177/1753425909350484] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We report identification of putative innate immune related genes from a cell line of the mosquito Aedes albopictus challenged with heat-killed bacteria. Using a subtractive hybridization and sequencing approach, we analyzed a total 309 expressed sequence tags (ESTs) which clustered in 40 contigs. Thirty-five percent of genes yielded homology to known immune genes corresponding to antimicrobial peptides (AMPs), pathogen-associated molecular patterns, protease and immune signaling cascades. Interestingly, most of the genes have not been previously described from this mosquito and thus represent a class of novel immune genes. Further, 25% sequences did not match to any known species in the non-redundant databases, appear to be specific to the mosquito A. albopictus and merit further study.
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Affiliation(s)
- Rajnikant Dixit
- Molecular Biology Unit, National Center for Cell Science, Ganeshkhind, Pune, India
| | - Millind S. Patole
- Molecular Biology Unit, National Center for Cell Science, Ganeshkhind, Pune, India
| | - Yogesh S. Shouche
- Molecular Biology Unit, National Center for Cell Science, Ganeshkhind, Pune, India
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Parmakelis A, Moustaka M, Poulakakis N, Louis C, Slotman MA, Marshall JC, Awono-Ambene PH, Antonio-Nkondjio C, Simard F, Caccone A, Powell JR. Anopheles immune genes and amino acid sites evolving under the effect of positive selection. PLoS One 2010; 5:e8885. [PMID: 20126662 PMCID: PMC2811201 DOI: 10.1371/journal.pone.0008885] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Accepted: 01/04/2010] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND 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. 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 FINDINGS Within 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/SIGNIFICANCE In 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.
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Affiliation(s)
- Aristeidis Parmakelis
- Department of Ecology and Taxonomy, Faculty of Biology, National and Kapodistrian University of Athens, Panepistimioupoli Zografou, Athens, Greece
- Department of Biology, University of Crete, Heraklion, Crete, Greece
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America
- * E-mail:
| | - Marina Moustaka
- Department of Ecology and Taxonomy, Faculty of Biology, National and Kapodistrian University of Athens, Panepistimioupoli Zografou, Athens, Greece
| | - Nikolaos Poulakakis
- Department of Biology, University of Crete, Heraklion, Crete, Greece
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America
| | - Christos Louis
- Department of Biology, University of Crete, Heraklion, Crete, Greece
- Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology Heraklion, Vassilika Vouton, Heraklion, Crete, Greece
| | - Michel A. Slotman
- Department of Entomology, Texas A&M University, College Station, Texas, United States of America
| | - Jonathon C. Marshall
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America
- Department of Zoology, Weber State University, Ogden, Utah, United States of America
| | - Parfait H. Awono-Ambene
- Organisation de Coordination pour la Lutte Contre les Endémies en Afrique Centrale (OCEAC), Yaoundé, Cameroon
| | - Christophe Antonio-Nkondjio
- Organisation de Coordination pour la Lutte Contre les Endémies en Afrique Centrale (OCEAC), Yaoundé, Cameroon
| | - Frederic Simard
- Organisation de Coordination pour la Lutte Contre les Endémies en Afrique Centrale (OCEAC), Yaoundé, Cameroon
- Institut de Recherche pour le Développement (IRD), Bobo Dioulasso, Burkina Faso
| | - Adalgisa Caccone
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America
| | - Jeffrey R. Powell
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America
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Mendes C, Felix R, Sousa AM, Lamego J, Charlwood D, do Rosário VE, Pinto J, Silveira H. Molecular evolution of the three short PGRPs of the malaria vectors Anopheles gambiae and Anopheles arabiensis in East Africa. BMC Evol Biol 2010; 10:9. [PMID: 20067637 PMCID: PMC2820002 DOI: 10.1186/1471-2148-10-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2009] [Accepted: 01/12/2010] [Indexed: 12/16/2022] Open
Abstract
Background Immune responses to parasites, which start with pathogen recognition, play a decisive role in the control of the infection in mosquitoes. Peptidoglycan recognition proteins (PGRPs) are an important family of pattern recognition receptors that are involved in the activation of these immune reactions. Pathogen pressure can exert adaptive changes in host genes that are crucial components of the vector's defence. The aim of this study was to determine the molecular evolution of the three short PGRPs (PGRP-S1, PGRP-S2 and PGRP-S3) in the two main African malaria vectors - Anopheles gambiae and Anopheles arabiensis. Results Genetic diversity of An. gambiae and An. arabiensis PGRP-S1, PGRP-S2 and PGRP-S3 was investigated in samples collected from Mozambique and Tanzania. PGRP-S1 diversity was lower than for PGRP-S2 and PGRP-S3. PGRP-S1 was the only gene differentiated between the two species. All the comparisons made for PGRP-S1 showed significant P-values for Fst estimates and AMOVA confirming a clear separation between species. For PGRP-S2 and PGRP-S3 genes it was not possible to group populations either by species or by geographic region. Phylogenetic networks reinforced the results obtained by the AMOVA and Fst values. The ratio of nonsynonymous substitutions (Ka)/synonymous substitutions (Ks) for the duplicate pair PGRP-S2 and PGRP-S3 was very similar and lower than 1. The 3D model of the different proteins coded by these genes showed that amino acid substitutions were concentrated at the periphery of the protein rather than at the peptidoglycan recognition site. Conclusions PGRP-S1 is less diverse and showed higher divergence between An. gambiae and An. arabiensis regardless of geographic location. This probably relates to its location in the chromosome-X, while PGRP-S2 and PGRP-S3, located in chromosome-2L, showed signs of autosomal introgression. The two short PGRP genes located in the chromosome-2L were under purifying selection, which suggests functional constraints. Different types of selection acting on PGRP-S1 and PGRP-S2 and S3 might be related to their different function and catalytic activity.
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Affiliation(s)
- Cristina Mendes
- Centro de Malária e outras Doenças Tropicais, UEI Malária, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira, 96, 1349-008 Lisbon, Portugal
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Waniek PJ, Castro HC, Sathler PC, Miceli L, Jansen AM, Araújo CAC. Two novel defensin-encoding genes of the Chagas disease vector Triatoma brasiliensis (Reduviidae, Triatominae): gene expression and peptide-structure modeling. JOURNAL OF INSECT PHYSIOLOGY 2009; 55:840-8. [PMID: 19505471 DOI: 10.1016/j.jinsphys.2009.05.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Revised: 05/25/2009] [Accepted: 05/26/2009] [Indexed: 05/24/2023]
Abstract
Defensins are cysteine-rich peptides involved in the innate immunity of insects and many other organisms. In the present study, two novel defensin-encoding cDNAs and the respective genomic DNAs (def3 and def4) of Triatoma brasiliensis were identified and their tissue-specific and temporal expression was characterized. Both of the deduced mature peptides consisted of 43 amino acid residues and were highly similar to previously identified triatomine defensins (81.4-100%). Semi-quantitative RT-PCR data showed that def3 was constitutively expressed in the fat body and was induced in salivary glands and the small intestine at 5 and 3 days after feeding (daf), respectively. The def4 mRNA level was highly up-regulated in the stomach and fat-body tissues at 5 and 3 daf, respectively. The three-dimensional structures of these defensins were predicted using a homology modeling approach with Def-AAA, the defensin from Anopheles gambiae, as template (62-74% identity). A map of the electrostatic potential of these models revealed that, despite their similar folding patterns, mature Def2 and Def4 have a more cationic structure than is the case for Def1 and Def3. Such differences may orient the antimicrobial profile of these defensins against distinct targets in different organs of the insect.
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Affiliation(s)
- Peter J Waniek
- Laboratório de Biologia de Tripanosomatídeos, Instituto Oswaldo Cruz-IOC/FIOCRUZ, Av. Brasil 4365, Zip Code: 21045-900, Rio de Janeiro, Brazil.
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Wilding CS, Weetman D, Steen K, Donnelly MJ. High, clustered, nucleotide diversity in the genome of Anopheles gambiae revealed through pooled-template sequencing: implications for high-throughput genotyping protocols. BMC Genomics 2009; 10:320. [PMID: 19607710 PMCID: PMC2723138 DOI: 10.1186/1471-2164-10-320] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Accepted: 07/16/2009] [Indexed: 02/04/2023] Open
Abstract
Background Association mapping approaches are dependent upon discovery and validation of single nucleotide polymorphisms (SNPs). To further association studies in Anopheles gambiae we conducted a major resequencing programme, primarily targeting regions within or close to candidate genes for insecticide resistance. Results Using two pools of mosquito template DNA we sequenced over 300 kbp across 660 distinct amplicons of the An. gambiae genome. Comparison of SNPs identified from pooled templates with those from individual sequences revealed a very low false positive rate. False negative rates were much higher and mostly resulted from SNPs with a low minor allele frequency. Pooled-template sequencing also provided good estimates of SNP allele frequencies. Allele frequency estimation success, along with false positive and negative call rates, improved significantly when using a qualitative measure of SNP call quality. We identified a total of 7062 polymorphic features comprising 6995 SNPs and 67 indels, with, on average, a SNP every 34 bp; a high rate of polymorphism that is comparable to other studies of mosquitoes. SNPs were significantly more frequent in members of the cytochrome p450 mono-oxygenases and carboxy/cholinesterase gene-families than in glutathione-S-transferases, other detoxification genes, and control genomic regions. Polymorphic sites showed a significantly clustered distribution, but the degree of SNP clustering (independent of SNP frequency) did not vary among gene families, suggesting that clustering of polymorphisms is a general property of the An. gambiae genome. Conclusion The high frequency and clustering of SNPs has important ramifications for the design of high-throughput genotyping assays based on allele specific primer extension or probe hybridisation. We illustrate these issues in the context of the design of Illumina GoldenGate assays.
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Affiliation(s)
- Craig S Wilding
- Vector Group, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
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Obbard DJ, Welch JJ, Little TJ. Inferring selection in the Anopheles gambiae species complex: an example from immune-related serine protease inhibitors. Malar J 2009; 8:117. [PMID: 19497100 PMCID: PMC2698913 DOI: 10.1186/1475-2875-8-117] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Accepted: 06/04/2009] [Indexed: 12/16/2022] Open
Abstract
Background Mosquitoes of the Anopheles gambiae species complex are the primary vectors of human malaria in sub-Saharan Africa. Many host genes have been shown to affect Plasmodium development in the mosquito, and so are expected to engage in an evolutionary arms race with the pathogen. However, there is little conclusive evidence that any of these mosquito genes evolve rapidly, or show other signatures of adaptive evolution. Methods Three serine protease inhibitors have previously been identified as candidate immune system genes mediating mosquito-Plasmodium interaction, and serine protease inhibitors have been identified as hot-spots of adaptive evolution in other taxa. Population-genetic tests for selection, including a recent multi-gene extension of the McDonald-Kreitman test, were applied to 16 serine protease inhibitors and 16 other genes sampled from the An. gambiae species complex in both East and West Africa. Results Serine protease inhibitors were found to show a marginally significant trend towards higher levels of amino acid diversity than other genes, and display extensive genetic structuring associated with the 2La chromosomal inversion. However, although serpins are candidate targets for strong parasite-mediated selection, no evidence was found for rapid adaptive evolution in these genes. Conclusion It is well known that phylogenetic and population history in the An. gambiae complex can present special problems for the application of standard population-genetic tests for selection, and this may explain the failure of this study to detect selection acting on serine protease inhibitors. The pitfalls of uncritically applying these tests in this species complex are highlighted, and the future prospects for detecting selection acting on the An. gambiae genome are discussed.
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Affiliation(s)
- Darren J Obbard
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK.
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Viljakainen L, Pamilo P. Selection on an antimicrobial peptide defensin in ants. J Mol Evol 2009; 67:643-52. [PMID: 18956133 DOI: 10.1007/s00239-008-9173-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Accepted: 10/06/2008] [Indexed: 11/26/2022]
Abstract
Ants live in crowded nests with interacting individuals, which makes them particularly prone to infectious diseases. The question is, how do ants cope with the increased risk of pathogen transmission due to sociality? We have studied the molecular evolution of defensin, a gene encoding an antimicrobial protein, in ants. Defensin sequences from several ant species were analyzed with maximum likelihood models of codon substitution to infer selection. Positive selection was detected in the mature region of defensin, whereas the signal and pro regions seem to be evolving neutrally. We also found a significantly higher rate of nonsynonymous substitutions in some phylogenetic lineages, as well as dN/dS >1, suggesting varying selection pressures in different lineages. Earlier studies on the molecular evolution of insect antimicrobial peptide genes have focused on termites and dipteran species, and detected positive selection only in duplicated termicin genes in termites. These findings, together with our present results, provide an indication that the immune systems of social insects (ants and termites) and dipteran insects may have responded differently to the selection pressure caused by microbial pathogens.
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Affiliation(s)
- Lumi Viljakainen
- Department of Biology and Biocenter Oulu, University of Oulu, P.O. Box 3000, Oulu 90014, Finland.
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Viljakainen L, Evans JD, Hasselmann M, Rueppell O, Tingek S, Pamilo P. Rapid Evolution of Immune Proteins in Social Insects. Mol Biol Evol 2009; 26:1791-801. [DOI: 10.1093/molbev/msp086] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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Garver LS, Dong Y, Dimopoulos G. Caspar controls resistance to Plasmodium falciparum in diverse anopheline species. PLoS Pathog 2009; 5:e1000335. [PMID: 19282971 PMCID: PMC2647737 DOI: 10.1371/journal.ppat.1000335] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Accepted: 02/12/2009] [Indexed: 02/04/2023] Open
Abstract
Immune responses mounted by the malaria vector Anopheles gambiae are largely regulated by the Toll and Imd (immune deficiency) pathways via the NF-kappaB transcription factors Rel1 and Rel2, which are controlled by the negative regulators Cactus and Caspar, respectively. Rel1- and Rel2-dependent transcription in A. gambiae has been shown to be particularly critical to the mosquito's ability to manage infection with the rodent malaria parasite Plasmodium berghei. Using RNA interference to deplete the negative regulators of these pathways, we found that Rel2 controls resistance of A. gambiae to the human malaria parasite Plasmodium falciparum, whereas Rel 1 activation reduced infection levels. The universal relevance of this defense system across Anopheles species was established by showing that caspar silencing also prevents the development of P. falciparum in the major malaria vectors of Asia and South America, A. stephensi and A. albimanus, respectively. Parallel studies suggest that while Imd pathway activation is most effective against P. falciparum, the Toll pathway is most efficient against P. berghei, highlighting a significant discrepancy between the human pathogen and its rodent model. High throughput gene expression analyses identified a plethora of genes regulated by the activation of the two Rel factors and revealed that the Toll pathway played a more diverse role in mosquito biology than the Imd pathway, which was more immunity-specific. Further analyses of key anti-Plasmodium factors suggest they may be responsible for the Imd pathway-mediated resistance phenotype. Additionally, we found that the fitness cost caused by Rel2 activation through caspar gene silencing was undetectable in sugar-fed, blood-fed, and P. falciparum-infected female A. gambiae, while activation of the Toll pathway's Rel1 had a major impact. This study describes for the first time a single gene that influences an immune mechanism that is able to abort development of P. falciparum in Anopheline species. Further, this study addresses aspects of the molecular, evolutionary, and physiological consequences of the observed phenotype. These findings have implications for malaria control since broad-spectrum immune activation in diverse anopheline species offers a viable and strategic approach to develop novel malaria control methods worldwide.
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Affiliation(s)
- Lindsey S. Garver
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Yuemei Dong
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - George Dimopoulos
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
- * E-mail:
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Lehmann T, Hume JCC, Licht M, Burns CS, Wollenberg K, Simard F, Ribeiro JMC. Molecular evolution of immune genes in the malaria mosquito Anopheles gambiae. PLoS One 2009; 4:e4549. [PMID: 19234606 PMCID: PMC2642720 DOI: 10.1371/journal.pone.0004549] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Accepted: 12/31/2008] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND 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. METHODOLOGY/FINDINGS 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. SIGNIFICANCE AND CONCLUSIONS 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.
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Affiliation(s)
- Tovi Lehmann
- Division of Parasitic Diseases, Entomology Branch, Centers for Disease Control & Prevention, Chamblee, Georgia, United States of America.
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Dixit R, Sharma A, Mourya DT, Kamaraju R, Patole MS, Shouche YS. Salivary gland transcriptome analysis during Plasmodium infection in malaria vector Anopheles stephensi. Int J Infect Dis 2009; 13:636-46. [PMID: 19128996 DOI: 10.1016/j.ijid.2008.07.027] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Revised: 06/19/2008] [Accepted: 07/12/2008] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Understanding the tissue-specific molecular cross-talk mechanism during the mosquito-parasite interaction is of prime importance in the design of new strategies for malaria control. Because mosquito salivary glands are the final destination for the parasite maturation and transmission of vector-borne diseases, identification and characterization of salivary genes and their products are equally important in order to access their effect on the infectivity of the parasite. During the last five years there have been several studies on the sialomes of Anopheles mosquitoes, however very limited information is available on the changes in the salivary gland transcriptome in the presence of Plasmodium, and this information is limited to the mosquito Anopheles gambiae. METHODS In this study we aimed to explore and identify parasite-induced transcripts from the salivary glands of Anopheles stephensi, using a subtractive hybridization protocol. RESULTS Ninety-four percent of expressed sequence tags (ESTs) showed close homology to previously known families of mosquito salivary gland secretary proteins, representing the induced expression of alternative splicing and/or additional new members of the protein family. The remaining 6% of ESTs did not yield significant homology to any known proteins in the non-redundant database and thus may represent a class of unknown/novel salivary proteins. Primary analysis of the ESTs also revealed identification of several novel immune-related transcripts, including defensin and cecropins, probably involved in counter-activation of the antagonistic defense system. A comprehensive description of each family of proteins has been discussed in relation to the tissue-specific mosquito-parasite interaction. CONCLUSION This is the first report on the identification of new putative salivary genes, presumably activated during parasite infection.
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Affiliation(s)
- Rajnikant Dixit
- Molecular Biology Unit, National Center for Cell Science, Ganeshkhind, Pune, India.
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Obbard DJ, Callister DM, Jiggins FM, Soares DC, Yan G, Little TJ. The evolution of TEP1, an exceptionally polymorphic immunity gene in Anopheles gambiae. BMC Evol Biol 2008; 8:274. [PMID: 18840262 PMCID: PMC2576239 DOI: 10.1186/1471-2148-8-274] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Accepted: 10/07/2008] [Indexed: 01/20/2023] Open
Abstract
Background Host-parasite coevolution can result in balancing selection, which maintains genetic variation in the susceptibility of hosts to parasites. It has been suggested that variation in a thioester-containing protein called TEP1 (AGAP010815) may alter the ability of Anopheles mosquitoes to transmit Plasmodium parasites, and high divergence between alleles of this gene suggests the possible action of long-term balancing selection. We studied whether TEP1 is a case of an ancient balanced polymorphism in an animal immune system. Results We found evidence that the high divergence between TEP1 alleles is the product of genetic exchange between TEP1 and other TEP loci, i.e. gene conversion. Additionally, some TEP1 alleles showed unexpectedly low variability. Conclusion The TEP1 gene appears to be a chimera produced from at least two other TEP loci, and the divergence between TEP1 alleles is probably not caused by long-term balancing selection, but is instead due to two independent gene conversion events from one of these other genes. Nevertheless, TEP1 still shows evidence of natural selection, in particular there appears to have been recent changes in the frequency of alleles that has diminished polymorphism within each allelic class. Although the selective force driving this dynamic was not identified, given that susceptibility to Plasmodium parasites is known to be associated with allelic variation in TEP1, these changes in allele frequencies could alter the vectoring capacity of populations.
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Affiliation(s)
- Darren J Obbard
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, West Mains Rd, Edinburgh EH9 3JT, UK.
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Mirabello L, Conn JE. Population analysis using the nuclear white gene detects Pliocene/Pleistocene lineage divergence within Anopheles nuneztovari in South America. MEDICAL AND VETERINARY ENTOMOLOGY 2008; 22:109-119. [PMID: 18498609 DOI: 10.1111/j.1365-2915.2008.00731.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Anopheles (Nyssorhynchus) nuneztovari Gabaldón (Diptera: Culicidae), a locally important malaria vector in some regions of South America, has been hypothesized to consist of at least two cryptic incipient species. We investigated its phylogeographic structure in several South American localities to determine the number of lineages and levels of divergence using the nuclear white gene, a marker that detected two recently diverged genotypes in the primary Neotropical malaria vector Anopheles darlingi Root. In An. nuneztovari, five distinct lineages (1-5) were elucidated: (1) populations from northeastern and central Amazonia; (2) populations from Venezuela east and west of the Andes; (3) populations from Colombia and Venezuela west of the Andes; (4) southeastern and western Amazonian Brazil populations, and (5) southeastern and western Amazonian Brazil and Bolivian populations. There was a large amount of genetic differentiation among these lineages. The deepest and earliest divergence was found between lineage 3 and lineages 1, 2 and 4, which probably accounts for the detection of lineage 3 in some earlier studies. The multiple lineages within Amazonia are partially congruent with previous mtDNA and ITS2 data, but were undetected in many earlier studies, probably because of their recent (Pleistocene) divergence and the differential mutation rates of the markers. The estimates for the five lineages, interpreted as recently evolved or incipient species, date to the Pleistocene and Pliocene. We hypothesize that the diversification in An. nuneztovari is the result of an interaction between the Miocene/Pliocene marine incursion and Pleistocene climatic changes leading to refugial isolation. The identification of cryptic lineages in An. nuneztovari could have a significant impact on local vector control measures.
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Affiliation(s)
- L Mirabello
- Department of Biomedical Sciences, School of Public Health, University at Albany, State University of New York, Albany, New York, USA
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Cohuet A, Krishnakumar S, Simard F, Morlais I, Koutsos A, Fontenille D, Mindrinos M, Kafatos FC. SNP discovery and molecular evolution in Anopheles gambiae, with special emphasis on innate immune system. BMC Genomics 2008; 9:227. [PMID: 18489733 PMCID: PMC2405807 DOI: 10.1186/1471-2164-9-227] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2007] [Accepted: 05/19/2008] [Indexed: 01/10/2023] Open
Abstract
Background Anopheles innate immunity affects Plasmodium development and is a potential target of innovative malaria control strategies. The extent and distribution of nucleotide diversity in immunity genes might provide insights into the evolutionary forces that condition pathogen-vector interactions. The discovery of polymorphisms is an essential step towards association studies of susceptibility to infection. Results We sequenced coding fragments of 72 immune related genes in natural populations of Anopheles gambiae and of 37 randomly chosen genes to provide a background measure of genetic diversity across the genome. Mean nucleotide diversity (π) was 0.0092 in the A. gambiae S form, 0.0076 in the M form and 0.0064 in A. arabiensis. Within each species, no statistically significant differences in mean nucleotide diversity were detected between immune related and non immune related genes. Strong purifying selection was detected in genes of both categories, presumably reflecting strong functional constraints. Conclusion Our results suggest similar patterns and rates of molecular evolution in immune and non-immune genes in A. gambiae. The 3,214 Single Nucleotide Polymorphisms (SNPs) that we identified are the first large set of Anopheles SNPs from fresh, field-collected material and are relevant markers for future phenotype-association studies.
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Affiliation(s)
- Anna Cohuet
- Institut de Recherche pour le Développement, UR 016, BP 64501, 911 Avenue Agropolis, 34394 Montpellier Cedex 5, France.
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Molecular and phylogenetic analysis of a novel salivary defensin cDNA from malaria vector Anopheles stephensi. Acta Trop 2008; 106:75-9. [PMID: 18275930 DOI: 10.1016/j.actatropica.2008.01.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2007] [Revised: 12/22/2007] [Accepted: 01/03/2008] [Indexed: 02/05/2023]
Abstract
Manipulating the endogenous immune responses of the mosquito such as temporal and spatial expression of antimicrobial peptides may help in the development of a refractory mosquito, unable to transmit malaria. In mosquito several small antimicrobial peptides are activated locally in the midgut and salivary glands upon Plasmodium infection. Anopheles stephensi, the major urban malaria vector in India, has been considered as an important insect model to study vector-parasite interactions; however, so far no reports are available on the antimicrobial peptides from this mosquito species. In the present study, we report identification and molecular characterization of a novel cDNA encoding defensin like peptide, isolated from the salivary gland subtractive hybridization cDNA library of mosquito A. stephensi. Defensin cDNA is 396 base pair long, bearing an open reading frame of 96 amino acids. Deduced amino acid sequence of A. stephensi defensin (Astp_def) contains a signal peptide sequence of 24 amino acids followed by 32-amino acids long putative propeptide domain and a 40-amino acid mature peptide domain carrying 23-amino acid long consensuses sequence signature of insect defensin. Mature peptide of Astp_def carries six conserved cysteine residues, with a predicted molecular weight of 4.20kDa, and isoelectric point of 8.30, characteristic features of cationic defensins. Amino acid sequence similarity and phylogenetic analysis indicated a higher variation in the pre-propeptide region, as compared to the mature defensin peptide, assuring the presence of finely tuned immune responses to counter pathogens.
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Parmakelis A, Slotman MA, Marshall JC, Awono-Ambene PH, Antonio-Nkondjio C, Simard F, Caccone A, Powell JR. The molecular evolution of four anti-malarial immune genes in the Anopheles gambiae species complex. BMC Evol Biol 2008; 8:79. [PMID: 18325105 PMCID: PMC2288592 DOI: 10.1186/1471-2148-8-79] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Accepted: 03/06/2008] [Indexed: 12/14/2022] Open
Abstract
Background If the insect innate immune system is to be used as a potential blocking step in transmission of malaria, then it will require targeting one or a few genes with highest relevance and ease of manipulation. The problem is to identify and manipulate those of most importance to malaria infection without the risk of decreasing the mosquito's ability to stave off infections by microbes in general. Molecular evolution methodologies and concepts can help identify such genes. Within the setting of a comparative molecular population genetic and phylogenetic framework, involving six species of the Anopheles gambiae complex, we investigated whether a set of four pre-selected immunity genes (gambicin, NOS, Rel2 and FBN9) might have evolved under selection pressure imposed by the malaria parasite. Results We document varying levels of polymorphism within and divergence between the species, in all four genes. Introgression and the sharing of ancestral polymorphisms, two processes that have been documented in the past, were verified in this study in all four studied genes. These processes appear to affect each gene in different ways and to different degrees. However, there is no evidence of positive selection acting on these genes. Conclusion Considering the results presented here in concert with previous studies, genes that interact directly with the Plasmodium parasite, and play little or no role in defense against other microbes, are probably the most likely candidates for a specific adaptive response against P. falciparum. Furthermore, since it is hard to establish direct evidence linking the adaptation of any candidate gene to P. falciparum infection, a comparative framework allowing at least an indirect link should be provided. Such a framework could be achieved, if a similar approach like the one involved here, was applied to all other anopheline complexes that transmit P. falciparum malaria.
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Affiliation(s)
- Aristeidis Parmakelis
- Department of Ecology and Evolutionary Biology, Yale University, 21 Sachem Street, 06511, New Haven, CT, USA.
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Slotman MA, Parmakelis A, Marshall JC, Awono-Ambene PH, Antonio-Nkondjo C, Simard F, Caccone A, Powell JR. Patterns of selection in anti-malarial immune genes in malaria vectors: evidence for adaptive evolution in LRIM1 in Anopheles arabiensis. PLoS One 2007; 2:e793. [PMID: 17726523 PMCID: PMC1945087 DOI: 10.1371/journal.pone.0000793] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2007] [Accepted: 07/18/2007] [Indexed: 01/28/2023] Open
Abstract
Background Co-evolution between Plasmodium species and its vectors may result in adaptive changes in genes that are crucial components of the vector's defense against the pathogen. By analyzing which genes show evidence of positive selection in malaria vectors, but not in closely related non-vectors, we can identify genes that are crucial for the mosquito's resistance against Plasmodium. Methodology/Principle Findings We investigated genetic variation of three anti-malarial genes; CEC1, GNBP-B1 and LRIM1, in both vector and non-vector species of the Anopheles gambiae complex. Whereas little protein differentiation was observed between species in CEC1 and GNBP-B1, McDonald-Kreitman and maximum likelihood tests of positive selection show that LRIM1 underwent adaptive evolution in a primary malaria vector; An. arabiensis. In particular, two adjacent codons show clear signs of adaptation by having accumulated three out of four replacement substitutions. Furthermore, our data indicate that this LRIM1 allele has introgressed from An. arabiensis into the other main malaria vector An. gambiae. Conclusions/Significance Although no evidence exists to link the adaptation of LRIM1 to P. falciparum infection, an adaptive response of a known anti-malarial gene in a primary malaria vector is intriguing, and may suggest that this gene could play a role in Plasmodium resistance in An. arabiensis. If so, our data also predicts that LRIM1 alleles in An. gambiae vary in their level of resistance against P. falciparum.
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Affiliation(s)
- Michel A Slotman
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America.
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Slotman MA, Reimer LJ, Thiemann T, Dolo G, Fondjo E, Lanzaro GC. Reduced recombination rate and genetic differentiation between the M and S forms of Anopheles gambiae s.s. Genetics 2006; 174:2081-93. [PMID: 17057242 PMCID: PMC1698612 DOI: 10.1534/genetics.106.059949] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Accepted: 10/01/2006] [Indexed: 11/18/2022] Open
Abstract
Genetic differentiation between the largely sympatric molecular forms M and S of Anopheles gambiae appears mostly limited to division 6 and part of division 5 of the X chromosome. This region is adjacent to the centromere and includes the rDNA that was used to define these forms. This localized differentiation between populations that experience gene flow strongly suggests that this region contains genes responsible for reproductive isolation. Regions adjacent to centromeres are known to experience less recombination in several species and it has recently been suggested that low recombination rates can facilitate the accumulation and maintenance of isolation genes in partially isolated populations. Therefore, we measured the recombination rate in division 5D/6 directly and estimate that it is at least 16-fold reduced across this region compared to the remainder of the X chromosome. Additionally, sequence data from four loci from field-collected mosquitoes from several West African countries show very strong differentiation between the molecular forms in division 5D/6, whereas none was observed in two loci elsewhere on the X chromosome. Furthermore, genetic variation was substantially lower in division 5D/6 compared to the two reference loci, and the inferred genealogies of the division 5D/6 genes show patterns consistent with selective sweeps. This suggests that the reduced recombination rate has increased the effect of selection on this region and that our data are consistent with the hypothesis that reduced recombination rates can play a role in the accumulation of isolation genes in the face of gene flow.
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Affiliation(s)
- Michel A Slotman
- Department of Entomology, University of California, Davis 95616, USA.
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