Survival and transcriptomic responses to differen perkinsus marinus exposure mentiods in and eastern oyster family

Authors: SULLIVAN, MARY - University Of Rhode Island; Proestou, Dina

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2021
Publication Date: 4/26/2021
Citation: Sullivan, M., Proestou, D.A. 2021. Survival and transcriptomic responses to differen perkinsus marinus exposure mentiods in and eastern oyster family. Aquaculture. https://www.sciencedirect.com/science/article/pii/S0044848621004944?via%3Dihub.

Interpretive Summary: Contrasting exposure methods that differ in effective barriers to infection assists in teasing apart behavioral, cellular and humoral aspects of host parasite interactions. Transcriptome analysis among groups subject to distinct modes of exposure can further characterize the molecular basis of observed phenotypes. Eastern oyster survival in response to Perkinsus marinus is dependent on mode of exposure. Oysters exposed through feeding utilize multiple barriers minimize initial parasite load. Results of the transcriptome analysis suggest that low parasite concentrations are kept in check via controlled cell death in the absence of inflammation, thereby allowing high survival. In contrast, oysters exposed via direct injection into the adductor muscle tissue responded to a heavier infection with lower survival that can be explained by prolonged (at least 7 d) over-expression of several transcripts involved in the innate immune response including those associated with proinflammatory cytokine pathways. The heightened immune response in the injected group may have increased parasite virulence. The higher starting point in the injected group also may have prevented parasite load from falling below the threshold where apoptosis could reduce the negative effects of infection. The variable response to mode of parasite exposure in oysters highlighted key aspects of this host-parasite interaction and underscored the importance of considering dosing method when interpreting resistance phenotypes and their suitability as selection targets for genetic improvement.

Technical Abstract: Controlled laboratory challenges enable definition and measurement of disease response phenotypes as well as characterization of gene expression patterns during the infection process. Stage of infection and dosing method likely affect response measures. Exploring variation among them can enhance our understanding of this host-parasite interaction. Here we compared response traits and global expression patterns over time in Eastern oysters exposed to P. marinus via two dosing methods. All exposed animals received a dose of 5 × 106 cultured P. marinus cells g-1 wet tissue weight but oysters in the injected group had higher initial parasite load and significantly reduced survival probability compared to the fed group. We identified differentially expressed transcripts between fed and control animals at multiple time points post exposure. Immediately after infection, transcripts associated with apoptosis and reducing cell damage from reactive oxygen species were upregulated in the fed group compared to controls. The comparison between fed and injected groups early in the infection process revealed increased innate immune activity and proinflammatory cytokine activity in the injected group. Later in the infection process, the fed group expressed transcripts associated with growth, at a higher level than the injected group. This study demonstrates that dosing method impacts initial parasite load, survival, and transcriptomic response to Dermo disease and highlights the importance of considering dosing method to understand interactions between P. marinus and Eastern oyster.