Population-specific transcriptomics of Pacific oyster after exposure to a highly pathogenic, globally distributed virus.

Authors: Calla, Bernarda; Thompson, Neil; BURGE, COLLEEN - Department Of Fish And Wildlife

Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pacific oysters are an important food product in the U.S. Pacific coast, constituting a million-dollar industry. This industry is threatened by the existence of a highly pathogenic virus, the Ostreid Herpesvirus which has devastated farms in countries around the world. In the U.S. this highly pathogenic virus has been identified in a small are in Southern California. Proactively identifying sources of oysters with increased tolerance to this disease, and understanding how more tolerant oysters respond to the virus is critical for the expansion resilient oysters stocks that support continued production. In this work we investigated the genetic mechanisms by which two different populations of oysters (“Midori” and “Miyagi”), widely used in the U.S. Pacific coast, respond to the disease. We identified markers that can inform breeding and management practices.

Technical Abstract: Disease outbreaks in marine invertebrates, particularly in cultivated species, have increased due to shifting conditions. The OsHV-1 virus and its microvariants have caused significant mortalities in Pacific oysters around the world, heavily impacting aquaculture production. This study investigates the response, at the molecular level, of Pacific oysters to OsHV-1 µVar infection in two oyster populations: The Miyagi Pacific oyster, introduced to the U.S. from Japan in the mid-1900s, and the Midori Pacific oyster introduced in 2004 and which seem to exhibit higher survival rates under disease and stress. Across both oyster lineages, we found a general and significant up-regulation of genes involved in antiviral defense, including RIG-I like receptors, the interferon pathway, and apoptosis. Between Midori and Miyagi we found, among others, genes coding for histones and histone-modifying proteins, indicating possible pre-transcriptional mechanisms of gene regulation influencing disease outcomes. Viral sensing protein (SAMD9 and NFX-1 zinc finger) also had higher expression in Midori than in Miyagi both at the basal level and in samples from oysters undergoing viral infection. Compared to Midori, Miyagi seemed to have higher up-regulation of ubiquitination pathways. We also compared the general response of Pacific oysters to OsHV-1 µVars from different geographical origins concluding that there is no marked difference between the oyster response to a U.S. microvariant compared to an Australian microvariant.