title: Patterns of selection in anti-malarial immune genes in malaria vectors: evidence for adaptive evolution in LRIM1 in Anopheles arabiensis.
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.
  
  
  RESULTS
  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
  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.
authors.affiliation: Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America. michel.slotman@yale.edu
authors.forename: Michel A
authors.initials: MA
authors.lastname: Slotman
authors.forename: Aristeidis
authors.initials: A
authors.lastname: Parmakelis
authors.forename: Jonathon C
authors.initials: JC
authors.lastname: Marshall
authors.forename: Parfait H
authors.initials: PH
authors.lastname: Awono-Ambene
authors.forename: Christophe
authors.initials: C
authors.lastname: Antonio-Nkondjo
authors.forename: Frederic
authors.initials: F
authors.lastname: Simard
authors.forename: Adalgisa
authors.initials: A
authors.lastname: Caccone
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Powell
mesh_terms: D000818:Animals; D000852:Anopheles / Q000235:genetics*; D019143:Evolution, Molecular; D005260:Female; D014644:Genetic Variation; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism; D007303:Insect Vectors / Q000235:genetics*; D010963:Plasmodium falciparum / Q000502:physiology; D012641:Selection, Genetic
chemical_list: D019476:Insect Proteins