Identification, diversity, and evolution analysis of thioester-containing protein family in Pacific oyster (Crassostrea gigas) and immune response to biotic and abiotic stresses

Thioester-containing proteins (TEPs) play a vital role in the innate immune response to biotic and abiotic stresses. In this study, the TEPs in C. gigas were identified, and their gene structure, phylogenetic relationships, collinearity relationships, expression profiles, sequence diversity, and alternative splicing were analyzed. Eight Tep genes were identified in C. gigas genome. Functional analysis and evolutionary relationships indicated a high level of homology to other mollusks TEPs. The transcriptome quantitative analysis results showed that the Tep genes in C. gigas respond to heat stress and Vibrio stress. Alternative splicing analysis revealed four Tep genes (designated A2M_1, CD109_3, CD109_5, complement C3) encode multiple alternative splice variants. Analysis of gene structure and multiple alignments revealed that seven CD109_5 variants are produced through the alternative splicing of the 19th exon, which encodes the highly variable central region. Sequence diversity analysis revealed thirteen missense variants within the 19th exon region of these seven CD109_5 alternative splice variants. Furthermore, the differential alternative splicing analysis showed significant induction of CD109_5, A2M_1 and A2M_2 variants after infection with V. parahaemolyticus. This study explores the Tep genes of C. gigas, providing insights into the molecular mechanisms underlying the involvement of C. gigas TEPs in innate immunity.