Ostreid herpesvirus 1 (OsHV-1) is a viral pathogen that causes disease and mortality in Pacific oysters. Incidences of this disease have been reported in Australia, France, New Zealand, and the USA, prompting efforts to mitigate its adverse effects. In this context, genetic tools often hold the key to comprehending how diseases impact aquatic animal species. Host genetics play a fundamental role in shaping the course of infectious diseases, and this knowledge has immense potential to revolutionize selective breeding for disease tolerance.
These advancements promise a healthier and more resilient population of Pacific oysters (Crassostrea gigas), a species vital to the aquaculture industry. To achieve this, researchers from Oregon State University and Vancouver Island University conducted a study to identify candidate genes on chromosome 8, where a quantitative trait locus (QTL) seems to be the key to unlocking the oysters’ potential to combat ostreid herpesvirus 1 (OsHV-1).
Pursuing Disease Tolerance
When it comes to developing disease tolerance in aquatic animal species, identifying the genes that influence the process is a turning point. In the case of Pacific oysters, this knowledge can transform the industry by enabling selective breeding for improved disease tolerance. It’s akin to having a diverse toolbox of genes from different signaling pathways to fortify the oysters against infections.
The Discovery on Chromosome 8
In this groundbreaking study, researchers identified four families of Pacific oysters that exhibited a QTL on chromosome 8. This QTL had previously been associated with basal antiviral gene expression and survival during OsHV-1 mortality events in Tomales Bay, California. This discovery served as the first crucial clue in enhancing the oysters’ resistance to viral infections.
Phenotyping and Genotyping: Unleashing Genetic Power
To understand the genetic factors behind this QTL, individuals from these four oyster families underwent phenotyping and genotyping. This involved close examination of both physical and genetic traits. The goal was to find candidate genes linked to the QTL on chromosome 8, a key factor in disease tolerance.
Uncovering the Significant Genes
The results were nothing short of fascinating. Genome-wide allele frequencies of oysters from each family before their introduction to Tomales Bay were compared with those that survived an OsHV-1 mortality event.
The genetic investigators discovered not one but six significant, unique QTL, all of which were located on chromosome 8.
Candidate Genes with Promising Roles
Even more intriguing is that three of these QTL were assigned to candidate genes, namely, ABCA1, PIK3R1, and WBP2. These genes have previously been associated with antiviral innate immunity in vertebrates. This revelation opens up a world of possibilities, suggesting that these genes could hold the key to enhancing oysters’ ability to fend off viral infections.
Bridging the Gap Between Two Worlds
The identification of vertebrate antiviral innate immunity genes as candidate genes in Pacific oysters highlights an intriguing parallel. It underscores the similarities between the innate immune systems of these two seemingly disparate groups. The implications are profound, as they may pave the way for a better understanding of the modes of action of these genes in combating viral threats.
The Path Forward
As we delve deeper into the genetic code of Pacific oysters, the next crucial step is identifying causal variants in these candidate genes. This discovery will open the doors to extensive functional studies of these genes. Understanding their antiviral modes of action is not just an academic pursuit; it’s a practical endeavor that could lead to healthier oyster populations and a more sustainable aquaculture industry.
In conclusion, the quest to unlock disease tolerance in Pacific oysters has taken an exciting turn, with genetics leading the way. The identification of candidate genes associated with antiviral innate immunity is a promising step towards fortifying oysters against infectious threats. As we unravel the genetic mysteries of these remarkable creatures, we are not just learning about oysters; we are gaining insights into the broader world of genetics and immunity, with implications that extend far beyond the ocean’s edge.
Contact
Konstantin Divilov
Department of Fisheries, Wildlife, and Conservation Sciences
Coastal Oregon Marine Experiment Station
Oregon State University
Hatfield Marine Science Center, Newport, OR, 97365, USA
Email: divilovk@oregonstate.edu
Reference (open access)
Divilov, K., Merz, N., Schoolfield, B. et al. Genome-wide allele frequency studies in Pacific oyster families identify candidate genes for tolerance to ostreid herpesvirus 1 (OsHV-1). BMC Genomics 24, 631 (2023). https://doi.org/10.1186/s12864-023-09744-0
