Fernández-González Cristina, Pérez-Lorenzo María, Pratt Nicola, Moore C Mark, Bibby Thomas S, Marañón Emilio
Department of Ecology and Animal Biology, Universidade de Vigo, 36310, Vigo, Spain.
Ocean and Earth Science, University of Southampton, SO14 3ZH, Southampton, UK.
J Phycol. 2020 Jun;56(3):818-829. doi: 10.1111/jpy.12983. Epub 2020 Mar 26.
Temperature and nutrient supply are key factors that control phytoplankton ecophysiology, but their role is commonly investigated in isolation. Their combined effect on resource allocation, photosynthetic strategy, and metabolism remains poorly understood. To characterize the photosynthetic strategy and resource allocation under different conditions, we analyzed the responses of a marine cyanobacterium (Synechococcus PCC 7002) to multiple combinations of temperature and nutrient supply. We measured the abundance of proteins involved in the dark (RuBisCO, rbcL) and light (Photosystem II, psbA) photosynthetic reactions, the content of chlorophyll a, carbon and nitrogen, and the rates of photosynthesis, respiration, and growth. We found that rbcL and psbA abundance increased with nutrient supply, whereas a temperature-induced increase in psbA occurred only in nutrient-replete treatments. Low temperature and abundant nutrients caused increased RuBisCO abundance, a pattern we observed also in natural phytoplankton assemblages across a wide latitudinal range. Photosynthesis and respiration increased with temperature only under nutrient-sufficient conditions. These results suggest that nutrient supply exerts a stronger effect than temperature upon both photosynthetic protein abundance and metabolic rates in Synechococcus sp. and that the temperature effect on photosynthetic physiology and metabolism is nutrient dependent. The preferential resource allocation into the light instead of the dark reactions of photosynthesis as temperature rises is likely related to the different temperature dependence of dark-reaction enzymatic rates versus photochemistry. These findings contribute to our understanding of the strategies for photosynthetic energy allocation in phytoplankton inhabiting contrasting environments.
温度和养分供应是控制浮游植物生态生理学的关键因素，但它们的作用通常是单独研究的。它们对资源分配、光合策略和新陈代谢的综合影响仍知之甚少。为了表征不同条件下的光合策略和资源分配，我们分析了一种海洋蓝细菌（聚球藻PCC 7002）对温度和养分供应多种组合的响应。我们测量了参与暗反应（核酮糖-1,5-二磷酸羧化酶/加氧酶，rbcL）和光反应（光系统II，psbA）的蛋白质丰度、叶绿素a、碳和氮的含量以及光合作用、呼吸作用和生长速率。我们发现，rbcL和psbA的丰度随着养分供应的增加而增加，而psbA因温度升高而增加仅发生在养分充足的处理中。低温和丰富的养分导致核酮糖-1,5-二磷酸羧化酶/加氧酶丰度增加，我们在广泛纬度范围内的天然浮游植物群落中也观察到了这种模式。只有在养分充足的条件下，光合作用和呼吸作用才会随温度升高而增加。这些结果表明，养分供应对聚球藻属的光合蛋白质丰度和代谢速率的影响比温度更强，并且温度对光合生理和代谢的影响取决于养分。随着温度升高，光合资源优先分配到光反应而非暗反应中，这可能与暗反应酶促速率与光化学对温度的不同依赖性有关。这些发现有助于我们理解生活在不同环境中的浮游植物光合能量分配策略。
