Bollati Elena, Rosenberg Yaeli, Simon-Blecher Noa, Tamir Raz, Levy Oren, Huang Danwei
Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
Department of Biology, Marine Biology Section, University of Copenhagen, Helsingør, Denmark.
Mol Ecol. 2022 Feb;31(3):884-901. doi: 10.1111/mec.16263. Epub 2021 Nov 22.
Urbanized coral reefs are often chronically affected by sedimentation and reduced light levels, yet many species of corals appear to be able to thrive under these highly disturbed conditions. Recently, these marginal ecosystems have gained attention as potential climate change refugia due to the shading effect of suspended sediment, as well as potential reservoirs for stress-tolerant species. However, little research exists on the impact of sedimentation on coral physiology, particularly at the molecular level. Here, we investigated the transcriptomic response to sediment stress in corals of the family Merulinidae from a chronically turbid reef (one genet each of Goniastrea pectinata and Mycedium elephantotus from Singapore) and a clear-water reef (multiple genets of G. pectinata from the Gulf of Aqaba/Eilat). In two ex-situ experiments, we exposed corals to either natural sediment or artificial sediment enriched with organic matter and used whole-transcriptome sequencing (RNA sequencing) to quantify gene expression. Analysis revealed a shared basis for the coral transcriptomic response to sediment stress, which involves the expression of genes broadly related to energy metabolism and immune response. In particular, sediment exposure induced upregulation of anaerobic glycolysis and glyoxylate bypass enzymes, as well as genes involved in hydrogen sulphide metabolism and in pathogen pattern recognition. Our results point towards hypoxia as a probable driver of this transcriptomic response, providing a molecular basis to previous work that identified hypoxia as a primary cause of tissue necrosis in sediment-stressed corals. Potential metabolic and immunity trade-offs of corals living under chronic sedimentation should be considered in future studies on the ecology and conservation of turbid reefs.
城市化的珊瑚礁常常长期受到沉积物和光照水平降低的影响，但许多珊瑚物种似乎能够在这些高度受干扰的条件下茁壮成长。最近，这些边缘生态系统因其悬浮沉积物的遮光效应以及作为耐胁迫物种的潜在储存库，而作为潜在的气候变化避难所受到关注。然而，关于沉积物对珊瑚生理的影响，尤其是在分子水平上的研究很少。在这里，我们研究了来自长期浑浊珊瑚礁（来自新加坡的梳状角孔珊瑚和象鼻菌珊瑚各一个基因型）和清澈水珊瑚礁（来自亚喀巴湾/埃拉特的多个梳状角孔珊瑚基因型）的梅氏珊瑚科珊瑚对沉积物胁迫的转录组反应。在两个异地实验中，我们将珊瑚暴露于天然沉积物或富含有机物的人工沉积物中，并使用全转录组测序（RNA测序）来量化基因表达。分析揭示了珊瑚对沉积物胁迫的转录组反应的共同基础，这涉及与能量代谢和免疫反应广泛相关的基因表达。特别是，沉积物暴露诱导了无氧糖酵解和乙醛酸旁路酶以及参与硫化氢代谢和病原体模式识别的基因的上调。我们的结果表明缺氧可能是这种转录组反应的驱动因素，为之前将缺氧确定为受沉积物胁迫的珊瑚组织坏死的主要原因的工作提供了分子基础。在未来关于浑浊珊瑚礁生态和保护的研究中，应考虑生活在长期沉积物环境下的珊瑚潜在的代谢和免疫权衡。
