title: Molecular characterization and evolution of a gene family encoding male-specific reproductive proteins in the African malaria vector Anopheles gambiae.
abstract: BACKGROUND
  During copulation, the major Afro-tropical malaria vector Anopheles gambiae s.s. transfers male accessory gland (MAG) proteins to females as a solid mass (i.e. the "mating plug"). These proteins are postulated to function as important modulators of female post-mating responses. To understand the role of selective forces underlying the evolution of these proteins in the A. gambiae complex, we carried out an evolutionary analysis of gene sequence and expression divergence on a pair of paralog genes called AgAcp34A-1 and AgAcp34A-2. These encode MAG-specific proteins which, based on homology with Drosophila, have been hypothesized to play a role in sperm viability and function.
  
  
  RESULTS
  Genetic analysis of 6 species of the A. gambiae complex revealed the existence of a third paralog (68-78% of identity), that we named AgAcp34A-3. FISH assays showed that this gene maps in the same division (34A) of chromosome-3R as the other two paralogs. In particular, immuno-fluorescence assays targeting the C-terminals of AgAcp34A-2 and AgAcp34A-3 revealed that these two proteins are localized in the posterior part of the MAG and concentrated at the apical portion of the mating plug. When transferred to females, this part of the plug lies in proximity to the duct connecting the spermatheca to the uterus, suggesting a potential role for these proteins in regulating sperm motility. AgAcp34A-3 is more polymorphic than the other two paralogs, possibly because of relaxation of purifying selection. Since both unequal crossing-over and gene conversion likely homogenized the members of this gene family, the interpretation of the evolutionary patterns is not straightforward. Although several haplotypes of the three paralogs are shared by most A. gambiae s.l. species, some fixed species-specific replacements (mainly placed in the N- and C-terminal portions of the secreted peptides) were also observed, suggesting some lineage-specific adaptation.
  
  
  CONCLUSIONS
  Progress in understanding the signaling cascade in the A. gambiae reproductive pathway will elucidate the interaction of this MAG-specific protein family with their female counterparts. This knowledge will allow a better evaluation of the relative importance of genes involved in the reproductive isolation and fertility of A. gambiae species and could help the interpretation of the observed evolutionary patterns.
authors: Istituto-Pasteur - Fondazione Cenci Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Sapienza Università di Roma, Rome, Italy. emiliano.mancini@uniroma1.it
authors: Emiliano
authors: E
authors: Mancini
authors: Francesco
authors: F
authors: Baldini
authors: Federica
authors: F
authors: Tammaro
authors: Maria
authors: M
authors: Calzetta
authors: Aurelio
authors: A
authors: Serrao
authors: Phillip
authors: P
authors: George
authors: Isabelle
authors: I
authors: Morlais
authors: Daniel
authors: D
authors: Masiga
authors: Igor V
authors: IV
authors: Sharakhov
authors: David W
authors: DW
authors: Rogers
authors: Flaminia
authors: F
authors: Catteruccia
authors: Alessandra
authors: A
authors: della Torre
mesh_terms: D000818:Animals; D000852:Anopheles / Q000235:genetics*; D001499:Bayes Theorem; D015153:Blotting, Western; D002874:Chromosome Mapping; D019295:Computational Biology; D029721:Drosophila Proteins / Q000235:genetics; D019143:Evolution, Molecular; D005260:Female; D006239:Haplotypes / Q000235:genetics; D017404:In Situ Hybridization, Fluorescence; D007301:Insect Hormones / Q000235:genetics* / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D005810:Multigene Family / Q000235:genetics*; D010455:Peptides / Q000235:genetics
chemical_list: D029721:Drosophila Proteins; D007301:Insect Hormones; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; C056736:SP protein, Drosophila