Divergent expression of hypoxia response systems under deoxygenation in reef-forming corals aligns with bleaching susceptibility
Divergent expression of hypoxia response systems under deoxygenation in reef-forming corals aligns with bleaching susceptibility
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DOI：
10.1111/gcb.15436
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发表时间：
2020-11-16
影响因子：
11.6
通讯作者：
Voolstra, Christian R.
中科院分区：
文献类型：
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作者：
Alderdice, Rachel;Suggett, David J.;Voolstra, Christian R.
由于气候变化和局部污染，海洋生物暴露在低氧环境中的速度正在全球范围内加快。在珊瑚礁经历了长期低氧事件的地方，最近发生了大规模珊瑚漂白和死亡。然而，对氧水平的耐受性的机制基础不足以维持正常功能（即缺氧），以及它是否有助于漂白易感性，仍然是未知的。因此，我们通过实验将具有环境适应力的Acropora tenuis（大堡礁常见的造礁珊瑚）群落暴露于与其自然夜间光照周期相一致的脱氧-再氧压力下。具体而言，治疗涉及去除“夜间O-2缓冲液”以挑战固有的缺氧阈值。RNA-Seq分析显示珊瑚具有与其他后生动物同源的完整和活跃的低氧诱导因子（HIF）介导的低氧反应系统（HRS）。正如预期的那样，A。tenuis表现出抗漂白性，并表现出对缺氧诱导因子靶基因的强烈诱导。我们将同样的方法平行应用于已知易受白化影响的鹿角珊瑚的菌落，其相反地表现出漂白表型反应。这种A. selago伴随着对比的基因表达谱，表明其HIF-HRS的不同有效性。基于我们的RNA-Seq分析，我们提出（a）HIF-HRS是珊瑚管理脱氧应激的核心，（B）该系统的关键基因（和更广泛的基因网络）可能有助于珊瑚漂白敏感性的变化。我们的分析表明，热休克蛋白（HSP）70和90是重要的低氧胁迫耐受性，并进一步强调如何热休克蛋白90的表达也可能影响诱导珊瑚HIF-HRS在克服代谢危机下脱氧应力。我们认为，珊瑚HIF-HRS的差异可能是调节对其他气候变化压力（特别是热应力）的敏感性的核心，这些压力通常会驱动漂白。
Exposure of marine life to low oxygen is accelerating worldwide via climate change and localized pollution. Mass coral bleaching and mortality have recently occurred where reefs have experienced chronic low oxygen events. However, the mechanistic basis of tolerance to oxygen levels inadequate to sustain normal functioning (i.e. hypoxia) and whether it contributes to bleaching susceptibility, remain unknown. We therefore experimentally exposed colonies of the environmentally resilient Acropora tenuis, a common reef-building coral from the Great Barrier Reef, to deoxygenation-reoxygenation stress that was aligned to their natural night-day light cycle. Specifically, the treatment involved removing the 'night-time O-2 buffer' to challenge the inherent hypoxia thresholds. RNA-Seq analysis revealed that coral possess a complete and active hypoxia-inducible factor (HIF)-mediated hypoxia response system (HRS) homologous to other metazoans. As expected, A. tenuis exhibited bleaching resistance and showed a strong inducibility of HIF target genes in response to deoxygenation stress. We applied this same approach in parallel to a colony of Acropora selago, known to be environmnetally susceptible, which conversely exhibited a bleaching phenotype response. This phenotypic divergence of A. selago was accompanied by contrasting gene expression profiles indicative of varied effectiveness of their HIF-HRS. Based on our RNA-Seq analysis, we propose (a) that the HIF-HRS is central for corals to manage deoxygenation stress and (b) that key genes of this system (and the wider gene network) may contribute to variation in coral bleaching susceptibility. Our analysis suggests that heat shock protein (hsp) 70 and 90 are important for low oxygen stress tolerance and further highlights how hsp90 expression might also affect the inducibility of coral HIF-HRS in overcoming a metabolic crisis under deoxygenation stress. We propose that differences in coral HIF-HRS could be central in regulating sensitivity to other climate change stressors-notably thermal stress-that commonly drive bleaching.