Metabolic Adaptation of a Globally Important Diatom following 700 Generations of Selection under a Warmer Temperature

Diatoms, accounting for 40% of the marine primary production and 20% of global carbon dioxide fixation, are threatened by the ongoing ocean warming (OW). However, whether and how these ecologically important phytoplankton adapt to OW remains poorly unknown. Here, we experimentally examined the metabolic adaptation of a globally important diatom species Skeletonema dohrnii (S. dohrnii) to OW at two elevated temperatures (24 and 28 degrees C compared with 20 degrees C) under short-term (similar to 300 generations) and long-term (similar to 700 generations selection. Both warming levels significantly increased the cell growth rate but decreased the chlorophyll a content. The contents of particulate organic carbon (POC) and particulate organic nitrogen (PON) decreased significantly initially (i.e., until 300 generations) at two temperature treatments but completely recovered after 700 generations of selection, suggesting that S. dohrnii ultimately developed thermal adaptation. Proteomic analysis demonstrated that elevated temperatures upregulated energy metabolism via glycolysis, tricarboxylic acid cycle, and fatty acid oxidation as well as nitrogen acquisition and utilization, which in turn reduced substance storage because of trade-off in the 300th generation, thus decreasing POC and PON. Interestingly, populations at both elevated temperatures exhibited significant proteome plasticity in the 700th generation, as primarily demonstrated by the increased lipid catabolism and glucose accumulation, accounting for the recovery of POC and PON. Changes occurring in cells at the 300th and 700th generations demonstrate that S. dohrnii can adapt to the projected OW, and readjusting the energy metabolism is an important adaptive strategy.

硅藻占海洋初级生产力的40%以及全球二氧化碳固定量的20%，受到持续的海洋变暖（OW）的威胁。然而，这些在生态上具有重要意义的浮游植物是否以及如何适应海洋变暖仍然鲜为人知。在此，我们通过实验研究了一种在全球具有重要意义的硅藻物种——多尼骨条藻（S. dohrnii）在短期（约300代）和长期（约700代）选择下，在两个升高的温度（与20℃相比，24℃和28℃）下对海洋变暖的代谢适应性。两种升温水平都显著提高了细胞生长速率，但降低了叶绿素a含量。在两种温度处理下，颗粒有机碳（POC）和颗粒有机氮（PON）的含量最初（即直到300代）显著下降，但在经过700代的选择后完全恢复，这表明多尼骨条藻最终形成了热适应。蛋白质组学分析表明，升高的温度通过糖酵解、三羧酸循环和脂肪酸氧化以及氮的获取和利用上调了能量代谢，这反过来由于在第300代的权衡而减少了物质储存，从而降低了POC和PON。有趣的是，在两个升高的温度下的种群在第700代都表现出显著的蛋白质组可塑性，主要表现为脂质分解代谢增加和葡萄糖积累，这解释了POC和PON的恢复。在第300代和第700代细胞中发生的变化表明，多尼骨条藻能够适应预测的海洋变暖，并且重新调整能量代谢是一种重要的适应策略。