MHC class I evolution; from Northern pike to salmonids

Abstract Background Salmonids are of major importance both as farmed and wild animals. With the changing environment comes changes in pathogenic pressures so understanding immune system all salmonid species is essence. Major histocompatibility complex (MHC) genes key players adaptive signalling infection to responding T-cells populations. Classical MHC class I (MHCI) genes, defined by high polymorphism, broad expression patterns peptide binding ability, have a role inducing immunity. In salmonids, fourth whole genome duplication that occurred 94 million years ago has provided salmonids with duplicate MHCI regions, while Northern Pike, basal sister clade represent which not experienced this duplication. Results Comparing gene organization evolution sequences pike versus displays picture how many these evolved. Regional Ia Ib Z lineage duplicates orthologs sequences. Instead, unique duplications regions well Salmo Oncorhynchus branch. Species-specific even more pronounced for some L genes. Conclusions Although expanded their U separately salmonids. However, similarity between suggest transposable machinery was present common ancestor. The MHCIa MHCIb were formed during MYA since split from before branch separated. As seen tetrapods, non-classical diversified classical counterpart. One lineage, massive species-specific after approximately 25 MYA. Based on what we currently know about large variation number also signals functional diversity