The serpin superfamily in channel catfish: Identification, phylogenetic analysis and expression profiling in mucosal tissues after bacterial infections

• A complete set of 25 serpin genes were identified in channel catfish genome.
• Lineage-specific gene expansion or gene loss among the serpins was observed.
• Expression of serpins genes were regulated in a tissue-specific and time-dependent manner after bacterial infections.

The superfamily of serine protease inhibitors (serpins) are broadly distributed in all kingdoms of life. Serpins play critical roles in an array of fundamental biological processes. In this study, we identified a complete set of 25 serpin genes from channel catfish genome by comprehensive data mining of existing genomic resources. Phylogenetic analysis verified their identities and supported the classification of serpins into six families as in mammals. Extensive comparative genomic analyses suggested that most serpins were conserved among vertebrates, while some were lineage-specific. Analysis of serpin gene expression in mucosal tissues after bacterial infections indicated that serpin genes were regulated in a tissue-specific and time-dependent manner. Distinct expression patterns between infections of the two pathogens were observed, indicating that much more rapid host responses of serpin expression were initiated after ESC infection than after columnaris infection. These studies set the foundation for future studies of host–pathogen interactions.