Biomarkers of Winter Mortality resistance in selectively bred Sydney rock oysters (Saccostrea glomerata)

Sydney rock oysters (Saccostrea glomerata) are an important part of Australian cuisine and are considered to be a gourmet delicacy for their distinctive flavor. The species is native to Australian estuaries where it faces challenges from environmental stressors and human impacts. In addition, the Sydney rock oyster aquaculture industry has been periodically affected by outbreaks of diseases such as Queensland Unknown (QX) disease and Winter Mortality, a protozoan borne disease greatly impacting the production of the Sydney rock oyster industry. These diseases limit the production of Sydney rock oysters but do not affect other major oyster species farmed in New South Wales. Winter Mortality is a protozoan born disease affecting the production of the Sydney rock oyster industry greatly. Over the past few decades, breeding lines of Sydney rock oysters have been selected for resistance to Winter Mortality and Queensland Unknown disease. In this study, we report a proteomic comparison between the Winter Mortality selective breeding line and hatchery control oysters. We identified 22 protein features showing differential intensities between the two proteomes. The identities of 19 of these features were established using nanoflow liquid chromatography-tandem mass spectrometry. The differential proteome identified in the current study coincides well with previous analyses of stress responses in oysters, suggesting commonalities between intracellular reactions to disease and stress. For instance, cytoskeletal effects found in the current study to be associated with Winter Mortality resistance have been previously linked to intracellular stress responses. In addition, we identified novel proteins such as proteasome subunit alpha type-6 and calcium-dependent protein kinase 31, both of which are reported for the first time in disease resistant Sydney rock oysters. Results of this study will add to our understanding of stress responses and provide the first proteomic survey of Winter Mortality resistance in Sydney rock oysters.