Comparative transcriptome reveal the potential adaptive evolutionary genes in Andrias davidianus

To search the evidence of molecular evolution mechanism for aquatic and cave habitat in Andrias davidianus, the evolution analysis was carried out among several species transcriptome data. The transcriptome data of Notophthalmus viridescens, Xenopus tropicalis, Cynops pyrrhogaster, Hynobius chinensis and A. davidianus were obtained from the Genbank and reassembled except Xenopus tropicalis. The BLAST search of transcriptome data obtained 1244 single-copy orthologous genes among five species. A phylogenetic tree showed A. davidianus to have the closest relationship to H. chinensis. Fourteen positively selected genes were detected in A. davidianus and N. vridescens group and fifteen in A. davidianus and H. chinensis group. Five genes were shared in the both groups which involved in the immune system, suggesting that A. davidianus adaptation to an aquatic and cave environment required rapid evolution of the immune system compared to N. viridescens and H. chinensis.