Polymorphism, selection and tandem duplication of transferrin genes in Atlantic cod (Gadus morhua) - Conserved synteny between fish monolobal and tetrapod bilobal transferrin loci

BMC Genetics

Research Article

Petra E Petersen¹  Ave Tooming-Klunderud²  Carl André³  Davide Pirolli⁴  Maria Cristina De Rosa⁴  Øivind Andersen⁵ 

[1] Aquaculture Research Station of the Faroes, FO-430, Hvalvík, Faroe Islands;Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, Blindern, P.O. Box 1066N-0316, Oslo, Norway;Department of Marine Ecology-Tjärnö, Gothenburg University, S-45296, Strömstad, Sweden;Institute of Chemistry of Molecular Recognition - CNR and Institute of Biochemistry and Clinical Biochemistry, Catholic University of Rome, 00168, Rome, Italy;Nofima Marin, P. O. Box 5010, N-1430, Ås, Norway;Norwegian University of Life Sciences, P. O. Box 5003, N-1430, Ås, Norway;

关键词: Monolobal transferrin;    Atlantic cod;    tandem duplication;    adaptation;    positive selection;    molecular modeling;   

DOI  :  10.1186/1471-2156-12-51

 received in 2011-01-21, accepted in 2011-05-25,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundThe two homologous iron-binding lobes of transferrins are thought to have evolved by gene duplication of an ancestral monolobal form, but any conserved synteny between bilobal and monolobal transferrin loci remains unexplored. The important role played by transferrin in the resistance to invading pathogens makes this polymorphic gene a highly valuable candidate for studying adaptive divergence among local populations.ResultsThe Atlantic cod genome was shown to harbour two tandem duplicated serum transferrin genes (Tf1, Tf2), a melanotransferrin gene (MTf), and a monolobal transferrin gene (Omp). Whereas Tf1 and Tf2 were differentially expressed in liver and brain, the Omp transcript was restricted to the otoliths. Fish, chicken and mammals showed highly conserved syntenic regions in which monolobal and bilobal transferrins reside, but contrasting with tetrapods, the fish transferrin genes are positioned on three different linkage groups. Sequence alignment of cod Tf1 cDNAs from Northeast (NE) and Northwest (NW) Atlantic populations revealed 22 single nucleotide polymorphisms (SNP) causing the replacement of 16 amino acids, including eight surface residues revealed by the modelled 3D-structures, that might influence the binding of pathogens for removal of iron. SNP analysis of a total of 375 individuals from 14 trans-Atlantic populations showed that the Tf1-NE variant was almost fixed in the Baltic cod and predominated in the other NE Atlantic populations, whereas the NW Atlantic populations were more heterozygous and showed high frequencies of the Tf- NW SNP alleles.ConclusionsThe highly conserved synteny between fish and tetrapod transferrin loci infers that the fusion of tandem duplicated Omp-like genes gave rise to the modern transferrins. The multiple nonsynonymous substitutions in cod Tf1 with putative structural effects, together with highly divergent allele frequencies among different cod populations, strongly suggest evidence for positive selection and local adaptation in trans-Atlantic cod populations.

【 授权许可】

CC BY   
© Andersen et al; licensee BioMed Central Ltd. 2011