Génétique et Physiologie des Microalgues, InBioS/Phytosystems, Institut de Botanique, Université de Liège, B22, Liège, 4000, Belgium.
Unit of Cell Biology, GIGA-Neurosciences, CHU Sart-Tilman, University of Liège, Liège, B36, 4000, Belgium.
New Phytol. 2020 Nov;228(3):855-868. doi: 10.1111/nph.16738. Epub 2020 Jul 21.
Disentangling the metabolic functioning of corals' endosymbionts (Symbiodiniaceae) is relevant to understanding the response of coral reefs to warming oceans. In this work, we first question whether there is an energetic coupling between photosynthesis and respiration in Symbiodiniaceae (Symbiodinium, Durusdinium and Effrenium), and second, how different levels of energetic coupling will affect their adaptive responses to global warming. Coupling between photosynthesis and respiration was established by determining the variation of metabolic rates during thermal response curves, and how inhibition of respiration affects photosynthesis. Adaptive (irreversible) responses were studied by exposing two Symbiodinium species with different levels of photosynthesis-respiration interaction to high temperature conditions (32°C) for 1 yr. We found that some Symbiodiniaceae have a high level of energetic coupling; that is, photosynthesis and respiration have the same temperature dependency, and photosynthesis is negatively affected when respiration is inhibited. Conversely, photosynthesis and respiration are not coupled in other species. In any case, prolonged exposure to high temperature caused adjustments in both photosynthesis and respiration, but these changes were fully reversible. We conclude that energetic coupling between photosynthesis and respiration exhibits wide variation amongst Symbiodiniaceae and does not determine the occurrence of adaptive responses in Symbiodiniaceae to temperature increase.
解析珊瑚共生藻（虫黄藻）的代谢功能对于理解珊瑚礁对海洋升温的响应至关重要。在这项工作中，我们首先探讨了共生藻（包括共生藻属、厚柱藻属和依弗伦藻属）的光合作用和呼吸作用之间是否存在能量偶联，其次，不同水平的能量偶联将如何影响它们对全球变暖的适应反应。通过测定热响应曲线过程中代谢率的变化以及呼吸作用抑制对光合作用的影响来确定光合作用和呼吸作用之间的偶联。通过将具有不同光合作用-呼吸作用相互作用水平的两种共生藻属在高温条件（32°C）下暴露 1 年，研究了适应性（不可逆）反应。我们发现，一些共生藻属具有高水平的能量偶联；也就是说，光合作用和呼吸作用具有相同的温度依赖性，当呼吸作用受到抑制时，光合作用会受到负面影响。相反，在其他物种中，光合作用和呼吸作用没有偶联。无论如何，长时间暴露在高温下会导致光合作用和呼吸作用都发生调整，但这些变化是完全可逆的。我们的结论是，共生藻属之间的光合作用和呼吸作用之间的能量偶联存在广泛的变化，并且不会决定共生藻属对温度升高的适应性反应的发生。
