Project description:In recent years, extensive mortality caused by global-scale bleaching events has led to the rapid degradation of reef structures, resulting in severe environmental consequences. The hydrocoral Millepora complanata (fire coral) plays a critical role in reef structure and relies on a symbiotic relationship with Symbiodiniaceae. Environmental stressors derived from climate change, such as UV radiation and elevated temperatures disrupt this symbiosis, leading to bleaching and threatening reef survival. Despite its importance in reef building, the molecular response of this cnidarian to thermal stress have been poorly explored. For this reason, the objective of this study is to investigate the proteomic response of M. complanata to bleaching during the 2015–2016 El Niño event. Fragments from non-bleached and bleached colonies of the hydrocoral M. complanata were collected from a coral reef in the Mexican Caribbean, and proteomic extracts were analyzed using nano-liquid chromatography–tandem mass spectrometry (nano-LC-MS/MS). Uni- and multivariate analyses were applied to identify significant differences in protein abundance. A total of 52 proteins showed differential abundance, including 24 that showed increased expression and 28 whose expression decreased in bleached fragments. Differentially abundant proteins were associated with amino acid biosynthesis, carbohydrate metabolism, cytoskeleton organization, DNA repair, extracellular matrix composition, redox homeostasis, and protein modification. These findings indicate that heat stress triggers molecular responses involving protein refolding, enhanced vesicle transport, cytoskeletal reorganization, and adjustments in redox activity, thereby contributing to a better understanding of the molecular mechanisms underlying bleaching in reef-building hydrocorals.
