Immunotherapy: Open Access
Open Access

Abstract

Immune Transcripts of the Pacific Oyster: Crassostrea gigas Larvae that Change in Expression as a Result of Bacteria Challenge

Jing Fang, Xiaohui Cai, Fengyi Mao, Hongyu Li, Honglin Chen, Minhua Qian, Jacob R. Hambrook, Patrick C. Hanington* and Xinzhong Wu*

Background: Marine mollusks living in intertidal and estuarine areas, such as oysters, face numerous pathogen challenges during their development. Infection from bacteria such as Vibrio alginolyticus, represents a major factor affecting larval development and frequently leads to high mortality of the pacific oyster, Crassostrea gigas. The oyster immune response is known to play an important role in protecting the animal during development by mitigating the consequences of infection.

Results: In this study, we undertook a comprehensive analysis of the immune response of C. gigas larvae to V. alginolyticus challenge. We sequenced the transcriptome of the larval C. gigas at 0 hours which means the larval oyster without any treatment as control and 6, 12, 24, 48, and 72 hours post-infection. After RNA-seq, the raw reads are available through the NCBI Sequence Read Archive under accession number PRJNA623063. After filtering, a total of 58.24 Gb clean reads were produced and assembled using the reference genome of C. gigas. The distribution of quality Q30 was higher than 90.88% for each sample and the GC content ranged from 41.27% to 42.91%. When compared with sequences in the COG, GO, KEGG, Swiss-Prot, and NR databases, there were 1,267, 1,112, 2,187, 682, 1,133 differentially expressed genes annotated at 6, 12, 24, 48, 72 hours post-infection respectively. Numerous immune-related genes displayed differential expression that varied over time: toll-like receptors, tripartite motif proteins, Lectin-like factors, scavenger receptors, signaling pathway components such as Myeloid differentiation factor 88, and stress proteins such as Heat shock 70 kDa protein were all found to be higher in abundance following V. alginolyticus challenge compared to control. For analysis, these genes were divided into several categories such as pattern recognition receptors, fibrinogen-like proteins, damage-associated molecular patterns, complement factors, etc. We have also originally discovered many down-regulated immune-related genes in C. gigas larvae over the first 72 hours of infection, such as TRIM2, TRIM45, TRIM56, TRIM71, Macrophage mannose receptor 1, Apolipoprotein D, Cytochrome P450, Rho-related protein, Stress-induced protein 1, HSP68, HSP75, HSP70 B2, Heme-binding protein 1, Heme-binding protein 2, Heavy metal-binding protein HIP, Hemicentin-1, etc. These general categories allowed us to generate an immune response profile for C. gigas over the first 72 hours of infection. These results indicate that bacterial infection induces a complex pattern of immune gene expression in C. gigas larvae.

Conclusion: Our study will facilitate targeted investigation into the function of specific immune factors that may explain the diversity and evolution of invertebrate immune molecules and lead to the development of effective measures to improve the performance of oyster culture.

Published Date: 2022-11-28; Received Date: 2022-10-28