Lyell Centre for Earth and Marine Science and Technology, Edinburgh, EH14 4BA, UK.
School of Energy, Geoscience, Infrastructure and Society, Heriot-Watt University, Edinburgh, EH14 4AS, UK.
BMC Biol. 2022 Dec 27;20(1):291. doi: 10.1186/s12915-022-01480-3.
Despite a global prevalence of photosynthetic organisms in the ocean's mesophotic zone (30-200+ m depth), the mechanisms that enable photosynthesis to proceed in this low light environment are poorly defined. Red coralline algae are the deepest known marine benthic macroalgae - here we investigated the light harvesting mechanism and mesophotic acclimatory response of the red coralline alga Lithothamnion glaciale.
Following initial absorption by phycourobilin and phycoerythrobilin in phycoerythrin, energy was transferred from the phycobilisome to photosystems I and II within 120 ps. This enabled delivery of 94% of excitations to reaction centres. Low light intensity, and to a lesser extent a mesophotic spectrum, caused significant acclimatory change in chromophores and biliproteins, including a 10% increase in phycoerythrin light harvesting capacity and a 20% reduction in chlorophyll-a concentration and photon requirements for photosystems I and II. The rate of energy transfer remained consistent across experimental treatments, indicating an acclimatory response that maintains energy transfer.
Our results demonstrate that responsive light harvesting by phycobilisomes and photosystem functional acclimation are key to red algal success in the mesophotic zone.
尽管海洋中层（30-200+ 米深）存在大量光合作用生物，但在这种低光照环境中进行光合作用的机制仍不清楚。红色珊瑚藻是已知的海洋深海底栖大型藻类中分布最深的一种，在这里，我们研究了红色珊瑚藻 Lithothamnion glaciale 的光捕获机制和中层适应反应。
藻红蛋白和藻胆蛋白最初吸收后，能量在 120 皮秒内从藻胆体转移到光系统 I 和 II。这使得 94%的激发能传递到反应中心。低光强，在较小程度上还有中层光谱，导致色素和藻胆蛋白发生显著的适应性变化，包括藻红蛋白光捕获能力增加 10%，叶绿素 a 浓度和光系统 I 和 II 的光子需求降低 20%。能量转移率在整个实验处理中保持一致，表明适应反应能维持能量转移。
我们的研究结果表明，藻胆体的响应性光捕获和光系统功能适应是红色藻类在中层成功生存的关键。
