Molecular Characterization of the Major Histocompatibility Complex Class Ia Gene in the Black-Spotted Frog, Pelophylax nigromaculata

The genes of the major histocompatibility complex (MHC) are attractive candidates for investigating the link between adaptive variation and individual fitness. We improved rapid amplification of cDNA ends to obtain the whole coding sequence of the MHC class Ia gene of the black-spotted frog (Pelophylax nigromaculata), the most common amphibian in China. We also used genome walking to characterize the partial introns adjacent to exon 3 of the MHC Ia gene. Based on the sequences obtained, we designed locus-specific primers to investigate the molecular polymorphisms of this species in southeast China. The MHC class Ia gene showed a high level of genetic diversity, indicating that this species retains a relatively high potential for survival, despite a population decline among frog species in general and many other amphibians.