Inbios/PhytoSystems, Université de Liège, 4000, Liège, Belgium.
Sci Rep. 2020 Oct 15;10(1):17514. doi: 10.1038/s41598-020-74557-0.
The mutualistic relationship existing between scleractinian corals and their photosynthetic endosymbionts involves a complex integration of the metabolic pathways within the holobiont. Respiration and photosynthesis are the most important of these processes and although they have been extensively studied, our understanding of their interactions and regulatory mechanisms is still limited. In this work we performed chlorophyll-a fluorescence, oxygen exchange and time-resolved absorption spectroscopy measurements on small and thin fragments (0.3 cm) of the coral Stylophora pistillata. We showed that the capacity of mitochondrial alternative oxidase accounted for ca. 25% of total coral respiration, and that the high-light dependent oxygen uptake, commonly present in isolated Symbiodiniaceae, was negligible. The ratio between photosystem I (PSI) and photosystem II (PSII) active centers as well as their respective electron transport rates, indicated that PSI cyclic electron flow occurred in high light in S. pistillata and in some branching and lamellar coral species freshly collected in the field. Altogether, these results show the potential of applying advanced biophysical and spectroscopic methods on small coral fragments to understand the complex mechanisms of coral photosynthesis and respiration and their responses to environmental changes.
共生关系存在于珊瑚和它们的光合共生体之间，涉及到内共生体代谢途径的复杂整合。呼吸作用和光合作用是这些过程中最重要的两种，尽管它们已经被广泛研究，但我们对它们的相互作用和调节机制的理解仍然有限。在这项工作中，我们对小而薄的石珊瑚（Stylophora pistillata）碎片（0.3 厘米）进行了叶绿素-a 荧光、氧气交换和时间分辨吸收光谱测量。我们表明，线粒体交替氧化酶的能力约占珊瑚总呼吸的 25%，而在分离的共生藻中常见的高光依赖性氧气吸收可以忽略不计。光系统 I（PSI）和光系统 II（PSII）活性中心之间的比例以及它们各自的电子传递速率表明，在高光下，石珊瑚和一些在野外新采集的分枝珊瑚和板状珊瑚中发生了 PSI 循环电子流。总的来说，这些结果表明，在小珊瑚碎片上应用先进的生物物理和光谱方法来理解珊瑚光合作用和呼吸作用的复杂机制及其对环境变化的响应是有潜力的。
