Transcriptome analysis reveals tissue-specific responses of Mytilus unguiculatus to Vibrio alginolyticus infection

Mytilus unguiculatus is an important economic bivalve species with wide consumption and aquaculture value. Disease is one of the primary limiting factors in mussel aquaculture, thus understanding the response of different tissues of M. unguiculatus to pathogens is crucial for disease prevention and control. In this study, we investigated the physiological and transcriptomic responses of the gills, adductor muscle, and mantle of M. unguiculatus infected with Vibrio alginolyticus. The results showed that V. alginolyticus infection caused inflammation and tissue structure changes in the gill, adductor muscle and mantle of M. unguiculatus. Meanwhile, the activities of superoxide dismutase and catalase in the three tissues increased, while the total antioxidant capacity decreased, suggesting that M. unguiculatus have an activated defense mechanism against infection-induced oxidative stress, despite a compromised total antioxidant capacity. Transcriptomic studies reveal that infected M. unguiculatus exhibits upregulation of endocytosis, lysosome activity, cellular apoptosis, and immune-related signaling pathways, indicating that M. unguiculatus responds to pathogen invasion by upregulating efferocytosis. Compared with the gill and adductor muscle, the mantle had a higher level of mytimycin, mytilin and myticin, and the three tissues also increased the expression of mytimycin to cope with the invasion of pathogens. In addition, the analysis of genes related to taste transduction pathways and muscle contraction and relaxation found that after infection with V. alginolyticus, M. unguiculatus may reduce appetite by inhibiting taste transduction in the gill, while improving muscle contraction of the adductor muscle and keeping the shell closed, to resist further invasion of pathogens and reduce the risk of pathogen transmission in the population.