Transcriptomic analysis reveals the immune changes associated with reproduction in the clam Meretrix petechialis

Substantial mortality and economic losses in marine mollusk culture has drawn considerable attention in recent years. The changes in immune status and environmental stress are thought to be the main causes of shellfish summer mortality. The reproduction and immune defense are both physiologically demanding processes, therefore, the immune status of mollusk is likely to be affected by reproduction during breeding. In present study, we performed transcriptome and gene expression analyses in the clam Meretrix petechialis pre-/post-spawning. DEGs enrichment analysis revealed important immune signaling pathways and key genes changed after spawning. Further analysis showed females up-regulated genes involved in apoptosis, TLR signal pathway and heat shock, whereas males down-regulated complement-related genes after spawning. Additionally, both genders of clams up-regulated its immune response level to against Vibrio infection after spawning revealed by the changes of four immune-related DEGs. The up-regulation of two marker genes at the transcription and protein levels further confirmed that pathogen reinforced the expression differences of immune-related genes between the two groups. Our study provides a new insight into the understanding of molecular mechanisms underlying reproduction influenced immune differences in M. petechialis.