Comparative proteomic analysis of fragments from non-bleached and bleached colonies of the hydrocoral Mille-pora complanata after the 2015–2016 ENSO event in the Mexican Caribbean

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.

近年来，全球范围内的珊瑚白化事件引发了大规模珊瑚死亡，导致礁体结构快速退化，进而造成了严重的生态环境后果。扁叶千孔珊瑚（Millepora complanata，俗称火珊瑚）在礁体构建中发挥关键作用，且与虫黄藻科（Symbiodiniaceae）存在共生关系。气候变化带来的环境胁迫因子（如紫外线辐射与高温）会破坏这种共生关系，引发珊瑚白化并威胁珊瑚礁的存续。尽管该刺胞动物（cnidarian）在造礁过程中具有重要意义，但人们对其应对热胁迫的分子响应机制仍知之甚少。基于此，本研究旨在探究2015-2016年厄尔尼诺（El Niño）事件期间扁叶千孔珊瑚白化过程中的蛋白质组响应。研究人员从墨西哥加勒比海的一处珊瑚礁采集了扁叶千孔珊瑚未白化与白化群体的组织片段，并采用纳升液相色谱-串联质谱（nano-LC-MS/MS）对蛋白质组提取物进行分析。通过单变量及多变量分析，鉴定出蛋白丰度存在显著差异的蛋白。最终共鉴定到52个差异丰度蛋白，其中白化片段中24个蛋白表达上调，28个蛋白表达下调。差异丰度蛋白涉及氨基酸生物合成、碳水化合物代谢、细胞骨架组织、DNA修复、细胞外基质组成、氧化还原稳态以及蛋白质修饰等过程。本研究结果表明，热胁迫会触发一系列分子响应，包括蛋白质重折叠、囊泡运输增强、细胞骨架重排以及氧化还原活性调控，从而为深入理解造礁水螅珊瑚白化的分子机制提供了新的认知。