Abstract
Scleractinian corals face unprecedented threats from global climate change, particularly ocean acidification and elevated sea surface temperatures. While transcriptomic studies have provided valuable insights into stress responses, proteomic alterations reflect the ultimate functional metabolic state of the organism. In this study, we conducted a quantitative proteomic analysis on the key reef-building coral Acropora muricata exposed to ocean acidification (pH lowered by 0.3 units below ambient) and thermal stress (+3°C above local ambient maximum) in a factorial 14-day mesocosm experiment. Using isobaric Tandem Mass Tag (TMT) labeling coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS), we identified and quantified 2,418 host proteins. Combined thermal and acidification stress induced a synergistic molecular response, characterized by the significant upregulation of molecular chaperones (HSP70, HSP90) and antioxidant enzymes (superoxide dismutase, catalase) to mitigate protein denaturation and oxidative damage. Conversely, key calcification-related proteins, including carbonic anhydrases and coral acid-rich proteins (CARPs), exhibited severe downregulation under low pH and elevated temperature. Furthermore, pathways involved in mitochondrial ATP synthesis and lipid metabolism were altered, highlighting an energetic trade-off favoring cellular maintenance over skeletal growth. These findings reveal the complex proteomic networks mediating coral resilience and vulnerability under multi-stressor conditions.
