Evolution by gene duplication, recombination and selection in MHC class I genes of Odorrana margaretae

Abstract

Amphibians have undergone catastrophic declines worldwide and the major histocompatibility complex (MHC) is an attractive candidate for investigating the link between adaptive variation and individual fitness. Nonetheless, little research has been conducted to study the amphibians MHC genes. Thus, MHC class Ia of Odorrana margaretae, a representative species of the Odorrana, was isolated and used to analyze the adaptive mechanism. We isolated alleles and determined evolution patterns of MHC class Ia in O. margaretae. The phylogenetic tree of MHC class Ia was reconstructed to understand the evolutionary relationship of Anura. In O. margaretae of MHC class Ia: there were more non-synonymous mutations compared to synonymous mutations; there are at least two loci; the recombination alleles took place for a large proportion (55.56%) of the alleles and recombination usually took place between whole exon of Ia genes of MHC class; positive selection sites were detected and most (10 of 19) located at the α1 and α2 domains belonged to the presumed ABS. The diversity of genes of MHC class Ia was led by recombination, gene duplication and positive selection. Trans-species polymorphisms of anuran genes of MHC class Ia were evident in anurans. Therefore, the MHC class Ia present demonstrative candidates for investigating the link between adaptive variation and individual fitness. We argue that knowledge of the MHC of other anuran lineage, especially focusing a genus such as O. margaretae, should provide an overall more complete picture of the organization of MHC in anurans.