title: Diversity and evolution of the rhoph1/clag multigene family of Plasmodium falciparum.
abstract: A complex of high-molecular-mass proteins (PfRhopH) of the human malaria parasite Plasmodium falciparum induces host protective immunity and therefore is a candidate for vaccine development. Understanding the level of polymorphism and the evolutionary processes is important for advancements in both vaccine design and knowledge of the evolution of cell invasion in this parasite. In the present study, we sequenced the entire open reading frames of seven genes encoding the proteins of the PfRhopH complex (rhoph2, rhoph3, and five rhoph1/clag gene paralogs). We found that four rhoph1/clag genes (clag2, 3.1, 3.2, and 8) were highly polymorphic. Amino acid substitutions and indels are predominantly clustered around amino acid positions 1000-1200 of these four rhoph1/clag genes. An excess of nonsynonymous substitutions over synonymous substitutions was detected for clag8 and 9, indicating positive selection. The McDonald-Kreitman test with a Plasmodium reichenowi orthologous sequence also supports positive selection on clag8. Based on the ratio of interspecific genetic distance to intraspecific distance, the time to the most recent common ancestor of the clag2 and 8 polymorphisms was estimated to be 1.89 and 0.87 million years ago, respectively, assuming divergence of P. falciparum and P. reichenowi 6 million years ago. In addition to a copy number polymorphism, gene conversion events were detected for the rhoph1/clag genes on chromosome 3, which likely play a role in increasing the diversity of each locus. Our results indicate that a high diversity of the PfRhopH1/Clag multigene family is maintained by diversifying selection forces over a considerably long period.
authors.affiliation: Department of Molecular Parasitology, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime 791-0295, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Iriko
authors.forename: Osamu
authors.initials: O
authors.lastname: Kaneko
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Otsuki
authors.forename: Takafumi
authors.initials: T
authors.lastname: Tsuboi
authors.forename: Xin-Zhuan
authors.initials: XZ
authors.lastname: Su
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Tanabe
authors.forename: Motomi
authors.initials: M
authors.lastname: Torii
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D005785:Gene Conversion; D018628:Gene Dosage; D054643:INDEL Mutation; D008969:Molecular Sequence Data; D010802:Phylogeny; D010963:Plasmodium falciparum / Q000235:genetics*; D011110:Polymorphism, Genetic; D015800:Protozoan Proteins / Q000235:genetics*; D012641:Selection, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D016054:DNA, Protozoan; D015800:Protozoan Proteins; C065352:rhoptry associated protein, Plasmodium