Department of Biology, Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Hong Kong Baptist University, Hong Kong, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China; State Key Laboratory of Environmental and Biological Analysis, Hong Kong Baptist University, Hong Kong, China.
Department of Biology, Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Hong Kong Baptist University, Hong Kong, China.
Sci Total Environ. 2022 Feb 1;806(Pt 2):150656. doi: 10.1016/j.scitotenv.2021.150656. Epub 2021 Sep 28.
Coral bleaching has become a major threat to coral reefs worldwide, but for most coral species little is known about their resilience to environmental changes. We aimed to understand the gene expressional regulation underlying natural bleaching and recovery in Pavona decussata, a dominant species of scleractinian coral in the northern South China Sea. Analyzing samples collected in 2017 from the field revealed distinct zooxanthellae density, chlorophyll a concentration and transcriptomic signatures corresponding to changes in health conditions of the coral holobiont. In the host, normal-looking tissues of partially bleached colonies were frontloaded with stress responsive genes, as indicated by upregulation of immune defense, response to endoplasmic reticulum, and oxidative stress genes. Bleaching was characterized by upregulation of apoptosis-related genes which could cause a reduction in algal symbionts, and downregulation of genes involved in stress responses and metabolic processes. The transcription factors stat5b and irf1 played key roles in bleaching by regulating immune and apoptosis pathways. Recovery from bleaching was characterized by enrichment of pathways involved in mitosis, DNA replication, and recombination for tissue repairing, as well as restoration of energy and metabolism. In the symbionts, bleaching corresponded to imbalance in photosystems I and II activities which enhanced oxidative stress and limited energy production and nutrient assimilation. Overall, our study revealed distinct gene expressional profiles and regulation in the different phases of the bleaching and recovery process, and provided new insight into the molecular mechanisms underlying the holobiont's resilience that may determine the species' fate in response to global and regional environmental changes.
珊瑚白化已成为全球珊瑚礁的主要威胁，但对于大多数珊瑚物种，人们对其适应环境变化的能力知之甚少。我们旨在了解南海北部优势种石珊瑚盔形珊瑚（Pavona decussata）自然白化和恢复的基因表达调控机制。分析 2017 年野外采集的样本，揭示了不同的虫黄藻密度、叶绿素 a 浓度和转录组特征，这些特征与珊瑚共生体健康状况的变化相对应。在宿主中，部分白化珊瑚的正常组织中，应激反应基因被前置，这表明免疫防御、内质网反应和氧化应激基因被上调。白化的特征是与细胞凋亡相关的基因上调，这可能导致共生藻数量减少，而参与应激反应和代谢过程的基因下调。转录因子 stat5b 和 irf1 通过调节免疫和凋亡途径在白化中起关键作用。白化恢复的特征是与有丝分裂、DNA 复制和重组相关的途径富集，用于组织修复，以及能量和代谢的恢复。在共生体中，白化对应于光合作用 I 和 II 活性的失衡，这加剧了氧化应激，限制了能量产生和养分吸收。总的来说，我们的研究揭示了白化和恢复过程不同阶段的明显基因表达谱和调控，并为共生体的恢复力的分子机制提供了新的见解，这可能决定了该物种对全球和区域环境变化的反应命运。
