Molecular insights into the immune response of Ruditapes philippinarum under Vibrio anguillarum infection at high temperature

High temperatures are considered one of the major environmental factors contributing to the mass death of clams in summer, and prolonged high temperatures may increase their susceptibility to bacteria. We used the Illumina HiSeq platform to perform transcriptome sequencing on clams treated with heat stress (H), Vibrio anguillarum infection (NV), and a combination of heat stress and V. anguillarum (HV). Twelve differentially expressed genes (DEGs) related to anti-oxidation (GPx-2, GST-C, HSP70B2, HSP90), immune (Big defensin, TBK1, TRIM56, TRAF3) and apoptosis (EGR-1, BCL-3, BIRC7-a, CASP-3) were verified by real-time quantitative PCR (RT-qPCR). In addition, KEGG pathway enrichment analysis showed that, compared with the control group, the V. anguillarum infection group under high-temperature conditions exhibited significant enrichment in lysosome, autophagy, and phagosome pathway genes. The expression levels of lysosome and phagosome-related genes decreased significantly in R. philippinarum treated with high temperatures and V. anguillarum, while autophagy-related genes increased significantly. Therefore, our results suggest that long-term high temperatures inhibit the immune homeostasis regulation mechanisms mediated by the lysosomal and phagosomal pathways, while enhancing autophagy function, which may be related to the large-scale death of R. philippinarum in summer. The results of this study provide new insights into the immune response of the Manila clam under high temperature conditions when infected with V. anguillarum, offering a reference for further research into the molecular mechanisms of immune resistance in R. philippinarum.