American lobster (Homarus americanus) immune gene expression during Aerococcus viridans var. homari challenge

The Canadian lobster (Homarus americanus) fishery is Canada's most economically significant fishing industry and is a critical component of many rural Atlantic Canadian communities. Aerococcus viridans var. homari is a Gram-positive bacterium that can cause mortalities in wild and live-stocked lobsters. We used an RNA sequencing (RNA-seq) approach to examine the expression of more than 29,000 hepatopancreatic genes in H. americanus during an A. viridans var. homari infection challenge to determine how lobster immune gene expression changes during infection. The infection challenge identified 1,803 differentially expressed genes, of which at least 87 are related to immune or stress responses. Of particular note are several anti-lipopolysaccharide factors (ALFs), pentraxin serum amyloid A (SAA), lectins, Toll-like proteins, cytokines, relish, cactus, myeloid differentiation factor, and genes related to antioxidant defence, coagulation, and hyperglycemic hormone regulation. Compared to a previous study using microarray technology, our RNA-seq approach uncovered a broader array of immune genes that were previously undetected in H. americanus. This study provides additional evidence that ALFs and SAA-5-like proteins are critical players in immune defence. Differential expression of ALFs and lectin genes may indicate a tailored response specific to A. viridans var. homari, highlighting the complexity of the immune system of lobster in recognizing and responding to specific pathogens.