Genome-Wide Identification, Characterization, and Transcriptional Profile of the HECT E3 Ubiquitin Ligase Gene Family in the Hard-Shelled Mussel Mytilus coruscus Gould

The homologous E6-AP carboxy-terminal structural domain (HECT) contained in E3 ubiquitin ligases (E3s) is a key factor in protein degradation and maintenance of cellular homeostasis in animals. However, the functional roles and evolutionary aspects of the HECT gene family in bivalve mussels remain unclear and warrant further investigation. In this study, we identified 22 HECT genes within the genome of <i>Mytilus coruscus</i> Gould, all containing a conserved HECT structural domain derived from dispersed repeats, distributed unevenly across 11 chromosomes. Phylogenetic analysis classified <i>M. coruscus</i> HECT genes into six major classes, with amino acid sequences within the same evolutionary clade displaying similar conserved motifs. Homology analysis with HECT genes of four bivalve species revealed that <i>M. coruscus</i> and <i>Mytilus galloprovincialis</i> possessed the largest number of homologous gene pairs, showing a significant correlation between the two in the evolution of the HECT gene family. Homology analysis with HECT genes of four bivalve species revealed that <i>M. coruscus</i> and <i>M. galloprovincialis</i> possessed the largest number of homologous gene pairs, showing a significant correlation between the two in the evolution of the HECT gene family. <i>M. coruscus</i> exhibited pronounced and specific expression in gills and blood tissues. Notably, <i>Mco_UPL3</i> gene expression was significantly upregulated after 12 h of acute heat stress (33 °C) and 24 h of <i>Vibrio</i> injection (0.4 OD). Gene ontology analysis of the HECT genes in <i>M. coruscus</i> revealed that it is primarily enriched in protein modification and degradation functions. This suggests that HECT genes may play a key role in protein degradation and immunomodulation in <i>M. coruscus</i>. These findings offer valuable insights for the breeding of stress-tolerant traits in <i>M. coruscus</i>. In summary, our data shed light on the potential functions of HECT E3 ligases in response to heat stress and <i>Vibrio</i> infection, providing practical guidance for enhancing resilience through breeding in <i>M. coruscus</i>.