The Fate of Duplicated Regions of the Atlantic Salmon (Salmo salar) Genome

Gene and genome duplications have played a major role in vertebrate evolution. Salmonids provide a useful resource for studying the consequences of these events as their common ancestor underwent a genome duplication between 25 and 120 million years ago. To understand how a genome reorganizes itself to cope with duplicated chromosomes and the importance of gene duplications for evolution and adaptation, homeologous regions of the Atlantic salmon genome were identified and studied within a large insert, genomic BAC library; these BACs contain the metallothionein loci, a gene known to have remained in duplicate since the tetraploidization event. A BAC from each region was subsequently shotgun subcloned and sequenced. Sequence analysis revealed the presence of 10 genes, retaining their collinearity between the BACs, although pseudogenization events have occurred in one of the duplicate loci in two instances. Comparative genomic analysis revealed the existence of extraordinary conservation of synteny over time.