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Proc Natl Acad Sci U S A. 2011 Jan 4;108(1):244-9. doi: 10.1073/pnas.1013648108. Epub 2010 Dec 20.

Adaptive divergence between incipient species of Anopheles gambiae increases resistance to Plasmodium.

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1
Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.

Abstract

The African malaria mosquito Anopheles gambiae is diversifying into ecotypes known as M and S forms. This process is thought to be promoted by adaptation to different larval habitats, but its genetic underpinnings remain elusive. To identify candidate targets of divergent natural selection in M and S, we performed genomewide scanning in paired population samples from Mali, followed by resequencing and genotyping from five locations in West, Central, and East Africa. Genome scans revealed a significant peak of M-S divergence on chromosome 3L, overlapping five known or suspected immune response genes. Resequencing implicated a selective target at or near the TEP1 gene, whose complement C3-like product has antiparasitic and antibacterial activity. Sequencing and allele-specific genotyping showed that an allelic variant of TEP1 has been swept to fixation in M samples from Mali and Burkina Faso and is spreading into neighboring Ghana, but is absent from M sampled in Cameroon, and from all sampled S populations. Sequence comparison demonstrates that this allele is related to, but distinct from, TEP1 alleles of known resistance phenotype. Experimental parasite infections of advanced mosquito intercrosses demonstrated a strong association between this TEP1 variant and resistance to both rodent malaria and the native human malaria parasite Plasmodium falciparum. Although malaria parasites may not be direct agents of pathogen-mediated selection at TEP1 in nature--where larvae may be the more vulnerable life stage--the process of adaptive divergence between M and S has potential consequences for malaria transmission.

PMID:
21173248
PMCID:
PMC3017163
DOI:
10.1073/pnas.1013648108
[Indexed for MEDLINE]
Free PMC Article

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