Molecular evolution of the ATP-binding cassette subfamily G member 2 gene subfamily and its paralogs in birds

• Published in: BMC ecology and evolution 2020-07, Vol.20 (1), p.1-85, Article 85
• Main Authors: Ma, Shengchao, Liu, Hehe, Sun, Wenqiang, Mustafa, Ahsan, Xi, Yang, Pu, Fajun, Li, Yanying, Han, Chunchun, Bai, Lili, Hua, He
• Format: Article
• Language: English
• Subjects: ABC transporters; ABCG2; ABCG2 gene; ABCG2-like; Amino acids; Binding; Birds; Cancer; Chromosome 4; Chromosome 6; Chromosome replication; Chromosomes; Comparative analysis; Comparative studies; Evolution; Evolutionary biology; Evolutionary genetics; Gene duplication; Gene family evolution; Gene sequencing; Genes; Genomes; Genomics; Homology; Mammals; Molecular evolution; Nucleic acids; Phylogenetics; Phylogeny; Proteins
• ISSN: 1471-2148; 1471-2148; 2730-7182
• DOI: 10.1186/s12862-020-01654-z

ATP-binding cassette (ABC) transporters are involved in the active transportation of various endogenous or exogenous substances. Two ABCG2 gene subfamily members have been identified in birds. A detailed comparative study of the ABCG2 and ABCG2-like genes aid our understanding of their evolutionary history at the molecular level and provide a theoretical reference for studying the specific functions of ABCG2 and ABCG2-like genes in birds. We first identified 77 ABCG2/ABCG2-like gene sequences in the genomes of 41 birds. Further analysis showed that both the nucleic acid and amino acid sequences of ABCG2 and ABCG2-like genes were highly conserved and exhibited high homology in birds. However, significant differences in the N-terminal structure were found between the ABCG2 and ABCG2-like amino acid sequences. A selective pressure analysis showed that the ABCG2 and ABCG2-like genes were affected by purifying selection during the process of bird evolution. We believe that multiple members of the ABCG2 gene subfamily exist on chromosome 4 in the ancestors of birds. Over the long course of evolution, only the ABCG2 gene was retained on chromosome 4 in birds. The ABCG2-like gene on chromosome 6 might have originated from chromosome replication or fusion. The structural differences between the N terminus of ABCG2 protein and those of ABCG2-like proteins might lead to functional differences between the corresponding genes.