Adaptive Evolution Of Temperature Receptor Genes In Vertebrates

Temperature sensation is of great significance to animal survival,and the temperature receptor genes play an important role in this process.In the process of adaptation to different habitats and core body temperatures,the temperature receptor genes of animals may have undergone adaptive evolution.In this study,we analyzed the adaptive evolution of temperature receptor genes in different vertebrate groups.The coding region sequences of temperature receptor genes of four bird species(Cyanopica cyanus,Parus major,Struthio camelus and Dromaius novaehollandiae)were obtained by skin transcriptome sequencing,and the gene sequences from other 256 species were combined for our analyses.The branch model and branch-site model of PAML software were used to analyze the selection pressure of 11 temperature receptor genes in different groups.In addition,the amino acid sequences of10 temperature receptor genes in birds and mammals were analyzed for phylogenetic reconstruction and convergent evolution.The results of selection pressure analysis showed that in the ancestral mammal and the ancestral bird of endothermic animals,six and one temperature receptor genes were detected to have positive selection signals,respectively;two positive selection genes were detected in latimeria,amphibian,tesudines and squamata of living ectothermic animals,respectively;positive selection genes were detected in the remaining five common ancestors of taxa studied except the ancestral archosaur,among which the most positive selection genes were detected in the ancestral amniote animals and the common ancestor of reptiles and birds,both of them with six positive selection genes.This showed that the temperature receptor genes have occurred extensive adaptive evolution in various vertebrate groups.In both endothermic and ectothermic animals,the positively selected temperature receptor genes were found,suggesting environmental temperature and core body temperature may play a certain role in the evolution of temperature receptor genes.Phylogenetic analysis showed that TRPV4 genes of endothermic animals,birds and mammals,are clustered in the same branch;in addition,through the reconstruction of ancestral sequence,four amino acid sites of TRPV4 gene was found to have parallel substitutions in the bird ancestor and the mammal ancestor.This indicates that the temperature receptor gene TRPV4 of birds and mammals have undergone convergent evolution.The results of this study may be helpful to understand the adaptation of vertebrates to environmental diversity from the perspective of temperature adaptation.