Sequence variation in the melanocortin-1 receptor gene (Mc1r) does not explain variation in the degree of melanism in a widespread amphibian

摘要

Variation in nucleotide sequence of the melanocortin-1 receptor gene (Meir) is associated with melanism in several mammalian, avian and reptilian species, but no attempts have been made to understand the genetic underpinnings of melanism in amphibians. We isolated the complete coding sequence (945 bps) of McIr from the common frog ( Rana temporaria) and compared the predicted amino acid sequence with that of fish, reptiles, birds and mammals. We investigated associations between nucleotide substitutions and the level of dorsal melanism among 28 individuals from two populations with pronounced differences in melanism. According to our results, the transmembrane regions of Mclr are conserved across vertebrates. In the population comparison, we only found five nucleotide sites with synonymous substitutions; none is being associated with the level of melanism. Our results suggest that either other genes or regulatory regions outside the coding sequence of Mclr are responsible for expression of melanism in R. temporaria.