We report the complete genome sequence of Photobacterium damselae subsp. damselae strain HNDF01, isolated from diseased Plectropomus leopardus in Hainan, China. The genome consists of two circular chromosomes (4,174,829 bp) and one plasmid (160,669 bp), encoding 3,753 protein-coding genes, 217 tRNAs, 47 rRNAs, and 10 sRNAs.

Vibrio tubiashii infection has led to several Babylonia areolata pandemics on the southeast coast of China, yet the immune response of the ivory shell against V. tubiashii and the specific pathogen–host interaction remain unclear. This dynamic study aimed to characterize the response of B. areolata to V. tubiashii infection with the use of pathology, transcriptomics, an enzymatic assay, and inflammatory cytokines. Hepatopancreatic cells showed marked vacuolar degeneration with intact cell membrane and extensive cytoplasmic vacuolization after infection. The dynamic transcriptome of the hepatopancreatic tissue was analyzed by RNA-seq after V. tubiashii infection, and a total of 2733 (3 h), 5610 (24 h), 3323 (48 h), and 418 (72 h) differentially expressed genes (DEGs) were identified during infection. The GO and KEGG analyses showed that the DEGs were enriched in metabolic regulation, lysosome, and multiple immune-related pathways such as the MAPK signaling pathway. The immune response of B. areolata was distinct, where the early stage of immune response (3 h) showed binding, focal adhesion, and apoptosis, as well as an activated antioxidant system. Here, expression of TNF-α, IL-1, and IL-8 was significantly increased in the hepatopancreas, whereas expression of IL-6 and IL-17 increased afterward. During the middle stage (24 h and 48 h), a large number of DEGs were suppressed, especially those associated with metabolism and lysosomes, although their expression returned to normal during prolonged infection (72 h). The PPI network showed that ppp2, atp6, and sos1 were the top immune-related DEGs during infection. Key infection-related and time-course-related genes were analyzed by WGCNA. This study illustrates that oxidative stress, inflammation, and apoptosis are strategies of the hepatopancreatic immune response in B. areolata against V. tubiashii infection and enlightens conservation and production by furthering our understanding of gastropod immunity.