Genome-wide analysis and expression profile of the thioester-containing proteins (TEP) in Micropterus salmoides

Thioester-containing proteins (TEPs) play vital roles in the innate immune responses to biotic and abiotic stresses. However, comprehensive genome-wide identification and expression analyses of the TEP gene family in Micropterus salmoides (M. salmoides) are lacking. In this study, 21 TEP genes were identified in the genome of M. salmoides, including 7 copies in A2M, two in CD109, five in C3, four in C4, and single copies of C5, A2ML1, and CPAMD8. Functional analyses and evolutionary relationships indicated a high level of homology with other teleost TEPs. Transcript sequence variants analysis identified numerous non-synonymous single nucleotide variants (nsSNVs) in TEP gene transcripts, with MsA2ML1, MsC3, and MsC4 being among the most affected. These variants, while potentially reflecting genomic diversity, require further validation to distinguish true polymorphisms from transcriptional or technical artifacts. Alternative splicing (AS) analysis has revealed multiple splicing sites and events in the TEPs of M. salmoides. Differential alternative splicing (DAS) analysis showed a significant induction of MsA2ML1 variants after infection with Aeromonas. Analysis of the gene structure and multiple sequence alignments revealed that these variants were produced through AS of the 18th exon. Both transcriptome quantification and qRT-PCR validation confirmed TEP gene responsiveness to Aeromonas infection in M. salmoides. Our study provides the first comprehensive characterization of the TEPs repertoire in largemouth bass, and reveals infection-induced AS as a novel layer of regulatory complexity in teleost innate immunity.