Lipid metabolism changes in clam Meretrix petechialis in response to Vibrio infection and the identification of Vibrio-resistance markers

Abstract Mass summer mortality events in the clam Meretrix petechialis resulting from Vibrio infection have occurred frequently in recent years, and seriously threaten the clam aquaculture industry. Metabolic processes are known to support host defense and survival in stressful conditions by regulating the allocation of metabolic resources. However, changes in lipid metabolism of clams in response to Vibrio infection are largely undescribed. In the present research, we characterized changes in key gene expression and enzyme activities associated with triglyceride-related metabolism, fatty acid de novo synthesis and fatty acid β-oxidation in M. petechialis during Vibrio infection. By mining dynamic transcriptome data before the increase in mortality, we found Vibrio infection caused significant changes in the metabolic regulations of carbohydrates, lipids, and amino acids. Our data show that levels of triglycerides (TG) decreased and free fatty acids (FFA) increased in the infected clams. Correspondingly, the synthesis activities of TG were significantly reduced relative to TG lipolysis activities after Vibrio infection. Additionally, FFA de novo synthesis was strengthened, especially before massive mortality occurred, but key genes of the fatty acid β-oxidation pathway showed no significant changes after Vibrio infection. We detected the expression of key genes related to lipid metabolism in resistant and susceptible clams under uninfected and infected conditions and found that differences in the basal expression of seven key genes (ATGL, MDY, SREBP, FAS, CPT-1, ACS, and ECH) could be used as potential biomarkers to predict different Vibrio resistance in clams. Overall, our results provide a starting point for investigating the relationship between energy metabolism changes and the emergence of massive mortality induced by bacterial infection in clams.