Genome-wide identification, phylogeny and expressional profile of the Sox gene family in channel catfish (Ictalurus punctatus)

The Sox gene family has been systematically characterized in some fish species but not in catfish Ictalurus punctatus. In this study, 25 Sox genes were identified in the channel catfish genome and classified into seven families based on their conserved domains as follows: eight genes in SoxB group (six in SoxB1 subgroup and two in SoxB2 subgroup); five genes in SoxC group; three genes in SoxD and SoxF groups; four genes in SoxE group; and one gene in SoxH and SoxK groups. The mammalian Sox groups SoxA, G, I, and J were not present in catfish. The number of introns in channel catfish Sox genes varied from zero to 13. Sox genes were distributed unevenly across 17 chromosomes. Five members of the ancestral vertebrate Sox genes (Sox1, Sox4, Sox9, Sox11 and Sox19) experienced teleost-specific whole genome duplication during evolution, and now have two copies on different chromosomes. Expression profiles analyses indicated that the accumulation of Sox genes was associated with different tissues, and the expression pattern also differed among each Sox gene group and duplicated gene. This study constitutes a comprehensive overview of the Sox gene family in channel catfish and provides new insights into the evolution of this gene family.