Differential Evolution of the Thirteen Atlantic Salmon Hox Clusters

• Published in: Molecular Biology and Evolution
• Main Authors: Mungpakdee, Sutada, Seo, Hee-Chan, Angotzi, Anna Rita, Dong, Xianjun, Akalin, Altuna, Chourrout, Daniel
• Format: Text
• Language: English
• Published: Oxford University Press 2008
• Subjects: Research Article; Atlantic salmon
• Online Access: http://mbe.oxfordjournals.org/cgi/content/short/msn097v1; https://doi.org/10.1093/molbev/msn097

Hox cluster organization represents a valuable marker to study the effects of recent genome duplication in salmonid fish (25-100 million years ago). Using PCR amplification of cDNAs, BAC library screening and genome walking, we reconstructed 13 Hox clusters in the Atlantic salmon containing 118 Hox genes including 8 pseudogenes. Hox paralogs resulting from the genome duplication preceding the radiation of ray-finned fish have been much better preserved in salmon than in other model teleosts. The last genome duplication in the salmon lineage has been followed by the loss of one of the four HoxA clusters. Four rounds of genome duplication after the vertebrate ancestor, salmon Hox clusters display the main organizational features of vertebrate Hox clusters, with Hox genes exclusively that are densely packed in the same orientation. Recently duplicated Hox clusters have engaged a process of divergence, with several cases of pseudogenization or asymmetrical evolution of Hox gene duplicates, and a marked erosion of identity in non-coding sequences. Strikingly, the level of divergence attained strongly depends on the Hox cluster pairs, rather than on the Hox genes within each cluster. It is particularly high between both HoxBb clusters and both HoxDa clusters, while both HoxBa clusters remained virtually identical. Positive selection on the Hox protein coding sequences could not be detected.