Transcriptome analysis and pattern recognition receptors (PRRs) identification in different tissues of adult Pacific oysters infected with Vibrio parahaemolyticus

Abstract

Contamination of V. parahaemolyticus in raw product and culture areas of Crassostrea gigas has been a concern in food hygiene and infectious diseases in the shellfish aquaculture industry for decades. Although numerous researchers have presently objective of decreasing pathogen microorganism contaminated load in raw oysters or genetics improvement for prevention, the in-depth information at the molecular level of host-pathogen interaction in terms of immune-related genes, primarily pattern recognition receptors (PRRs) still has poor understanding. Hence, this study was focused on the biological process and differential expression of immune-related genes in PRRs against V. parahaemolyticus infection via transcriptomic analysis in the digestive gland and mantle tissues. As a result, differential gene expressions (DEGs) of transcriptomic profiling indicated that the digestive gland and mantle tissues had expressed differently in response to immune mechanisms and immune gene-related against post-infection. GO and KEGG enrichment analysis revealed up-regulated genes expressed in digestive gland tissues that demonstrated the reaction of the immune mechanism in Gram-negative bacterial adhesion against epithelium host cells and phagocytosis. In contrast, mantle tissue showed significantly oxidative stress and peroxidase reaction response against infection. Underline with up-regulated gene expression data sets in bacterial infection pathway from KEGG enrichment analysis. The result indicated that seven genes related to PRRs consisted of CgPGRP-SC2X2 (peptidoglycan recognition proteins), CgC-type-lectin, Cgperlucin-like, CgMCR1 (macrophage mannose receptor 1), CgGal-9 (galectin-9), CgLBP (lipopolysaccharide-binding protein), and CgGBP (β-1,3-glucan-binding protein) have induced at 12–24 h post-infection. In contrast, down-regulated genes expressed datasets have similarly provided gene-related expression with cell-based movement on the cytoskeleton in both digestive gland and mantle tissues. The protein binding function was studied on four successful recombinant protein expressions via an immunofluorescent assay to better understand. The result revealed that rCgGal-9 and rCgMCR1 contained carbohydrate-binding domains (CBDs), demonstrated strongly in binding functions with the outer layer of V. parahaemolyticus, clinical separation, and ATCC 17800 strains, more than rCgβGBP and rCgPGRP-SC2X2. In summary, all these results suggest, at 12–24 h post-infection, immune genes related to PRRs function were induced by V. parahaemolyticus, and the most highly up-regulated gene expression and strongly binding in bacterial infection pathways indicated to C-type lectins family and carbohydrate-binding protein domains, which play a critical role in defense mechanism. Moreover, the information from this study points out a list of interesting genes and biological mechanisms in C. gigas against V. parahaemolyticus infection and produces lists of novel relevant candidate genes for further studies.