Jennifer Hudson1, Nandan Deshpande2, Catherine Leblanc3 and Suhelen Egan1
1 Centre for Marine Science and Innovation, School of Biological, Earth and Environmental Sciences, The University of New South Wales, Sydney, Australia
2Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney NSW 2052, Australia
3CNRS, Sorbonne Université, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, 29680 Roscoff, France
Host-microbe interactions are essential for the health of marine organisms but can be highly sensitive to changing environmental conditions. As such, increasing global seawater temperatures can promote host stress and lead to the emergence of opportunistic pathogens, leading to an increase in the occurrence of diseases in marine organisms. Disease outbreaks affecting macroalgae are of particular concern due to their critical role as habitat forming organisms. However, there is a limited understanding of the cellular response strategies used by macroalgae to respond to opportunistic pathogens while subjected to thermal stress. In this study, we used mRNA-Seq analysis to investigate the response of the model macroalga Delisea pulchra (Rhodophyta), after exposure to a known opportunistic pathogen (Aquimarina sp. AD1) relative to a closely related benign strain (Aquimarina sp. AD10). Using de novo assembly methods, 27,586 unique transcripts belonging to D. pulchra were identified that were mostly affiliated with stress response and signal transduction processes. However, following pathogen exposure a clear downregulation of genes encoding for protein metabolism, stress response, energy generation and photosynthesis functions was observed, relative to the benign strain. This transcriptional repression of genes encoding for core cellular processes is predicted to ultimately interfere with the macroalgal pathogen response, leading to infection, tissue damage and bleaching symptoms. Overall, this study highlights the potential pathogen response mechanisms of macroalgae and contributes to an improved understanding of host-pathogen interactions in a changing marine environment.