Differential basal expression of immune genes confers Crassostrea gigas resistance to Pacific oyster mortality syndrome

Abstract

Background: As a major threat to the oyster industry, Pacific Oyster Mortality Syndrome (POMS) is a polymicrobial disease affecting the main oyster species farmed across the world. POMS affects oyster juveniles and became panzootic this last decade, but POMS resistance in some oyster genotypes has emerged. While we know some genetic loci associated with resistance, the underlying mechanisms remained uncharacterized. So, we developed a comparative transcriptomic approach using basal gene expression profiles between different oyster biparental families with contrasted phenotypes when confronted to POMS (resistant or susceptible). Results: We showed that POMS resistant oysters show differential expression of genes involved in stress responses, protein modifications, maintenance of DNA integrity and repair, and immune and antiviral pathways. We found similarities and clear differences among different molecular pathways in the different resistant families. These results suggest that the resistance process is polygenic and partially varies according to the oyster genotype. Conclusions: We found differences in basal expression levels of genes related to TLR-NFκB, JAK-STAT and STING-RLR pathways. These differences could explain the best antiviral response, as well as the robustness of resistant oysters when confronted to POMS. As some of these genes represent valuable candidates for selective breeding, we propose future studies should further examine their function.

High temperature induces transcriptomic changes inCrassostrea gigasthat hinders progress of Ostreid herpesvirus (OsHV-1) and promotes survival

“…For instance, the number of DEGs coding for the ubiquitylation and proteasome system increased at 29°C and 12 hpc. Similarly, previous studies showed that the number of DEGs related to the ubiquitylation process increased during the first 6–12 h post-infection and was higher in resistant than in susceptible oysters ( De Lorgeril et al, 2018 , 2020 ). Moreover, the amount of protein related to the ubiquitination process was altered in infected oysters ( Corporeau et al, 2014 ).…”

Functional Insights From the Evolutionary Diversification of Big Defensins

“…Breeding programs in C. gigas produced oyster families with different (stable) levels of resistance to POMS (80,81), triggered by the OsHV-1 µvar virus. Resistance was identified as heritable (80,82) with some candidate markers having a role in distinct antiviral pathways (79,83). Big defensins and other AMPs were not identified as associated with resistance to POMS, probably because the bacteremia comes as a secondary infection in this virus-induced immunosuppressive disease.…”

Comparative Proteomics of Ostreid Herpesvirus 1 and Pacific Oyster Interactions With Two Families Exhibiting Contrasted Susceptibility to Viral Infection

“…In the context of OsHV-1 infection of Pacific oysters, De Lorgeril et al. ( 79 ) observed different basal expressions of PRR genes in Pacific oyster families with contrasted susceptibilities to OsHV-1 infection. In our study, the contrasted modulation patterns of PRRs observed in A and P-oysters underline the crucial role of PRRs in the oyster’s resistance to OsHV-1 from the first hours of infection.…”

“…In the context of viral infection, ubiquitin-related proteins coordinate an effective antiviral immune response by regulating efficient antiviral signaling pathways such as the RIG-I-like, Toll-like or interferon-like pathways ( 80 ). Several studies showed that genes related to the ubiquitination process increased during the first hours of infection (6 and 12 hpi) with a higher expression in more resistant compared to more susceptible Pacific oysters ( 20 , 41 , 79 ). In our study ubiquitin-related proteins were highly modulated in the more resistant Pacific oysters, while few of them were modulated in the more susceptible Pacific oysters.…”