Genome-wide identification and immune response analysis to vibrio for heme peroxidase in the blood clam Anadara...

Heme peroxidases (HPs), an essential class of oxidoreductases that may have an important role in molluscan immune defense, remain inadequately studied in mollusks. In this study, HPs in Anadara granosa (AgHPs) were comprehensively analyzed on a genome-wide scale and their immune responses under stress from three species of Vibrio were investigated. A total of 18 AgHPs were identified in the genome of A. granosa, unequally distributed in four subfamilies, peroxinectin (Pxt), prostaglandin G/H synthase (PGHS), dual oxidases (DuOx) and peroxidasin (Pxd). AgHPs were mainly expressed in gills and mantle, with AgHP6 being the only member expressed in hemocytes. The immune response of A. granosa to Vibrio stress demonstrated dynamic alterations in gene expression, characterized by prominent upregulation of AgHP3 and AgHP4 in both gills and mantle, alongside significant downregulation of several other genes; these expression changes likely underpin antimicrobial immunity in A. granosa and suggest distinct regulatory mechanisms and functional roles. Further analyses suggest that AgHP11 (Pxt) may enhance cell adhesion when invaded by exogenous bacteria, and AgHP3 (PGHS) and AgHP4 (PGHS) contribute to the immunity by synthesizing various prostaglandins. AgHP6 (DuOx) and AgHP7 (DuOx) may activate epithelial immunity by reducing expression levels. Additionally, during the anti-Vibrio process, hemoglobin may substitute for ROS-producing HPs to provide antimicrobial defense in A. granosa. This study represents the first genome-wide identification and immune response analysis of HPs in A. granosa, laying a foundation for future research into the immune functions of HPs in mollusks.