CAS Engineering Laboratory for Vegetation Ecosystem Restoration on Islands and Coastal Zones, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China; Southern Marine Science and Engineering, Guangdong Laboratory (Guangzhou), Guangzhou 511458, China.
CAS Engineering Laboratory for Vegetation Ecosystem Restoration on Islands and Coastal Zones, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Total Environ. 2020 Jul 1;724:138183. doi: 10.1016/j.scitotenv.2020.138183. Epub 2020 Mar 25.
To assess the effects of nitrogen deposition on forest plants, researchers have conducted many nitrogen-addition experiments. Most of these experiments, however, failed to fully simulate atmospheric nitrogen deposition because they failed to assess interception of nitrogen deposition by the forest canopy. Here, we used transcriptomics, proteomics, and metabolomics to compare the effects of understory nitrogen addition (UAN), canopy nitrogen addition (CAN), and a control (no nitrogen addition) on carbon and nitrogen metabolism in leaves of Psychotria rubra, a dominant subtropical understory plant species in evergreen broad-leaved forests in South China. We first established a reference P. rubra transcriptome via RNA-seq and obtained a total of 93,986 unigenes from de novo assembly. Next, we quantitatively investigated the proteome and metabolome in leaves, and identified 4021 proteins and 562 metabolites. Under the CAN treatment and relative to the control, 36 genes were up-regulated and 23 were down-regulated, and we identified 46 up-regulated proteins and 49 down-regulated proteins. Under the UAN treatment and relative to the control, 1525 genes were up-regulated and 224 genes down-regulated, and we identified 35 up-regulated proteins and 71 down-regulated proteins. These differentially expressed genes and proteins were related to photosynthesis, amino acid metabolism, and flavonoid biosynthesis. Accordingly, 15 differentially accumulated metabolites in response to CAN and 20 in response to UAN were found; these differentially accumulated metabolites included 4 amino acids and 3 flavonoids. Taken together, our results show that the UAN treatment had a greater effect on photosynthesis, amino acid metabolism, and flavonoid biosynthesis than the CAN treatment. Most importantly, the results indicate that understory application of nitrogen in experiments may incorrectly estimate the effects of nitrogen deposition on nitrogen and carbon utilization by P. rubra and perhaps by other understory woody plants in the evergreen broad-leaved forests in South China as well.
为了评估氮沉降对森林植物的影响，研究人员进行了许多氮添加实验。然而，这些实验大多未能充分模拟大气氮沉降，因为它们未能评估森林冠层对氮沉降的截留。在这里，我们使用转录组学、蛋白质组学和代谢组学来比较林下氮添加（UAN）、冠层氮添加（CAN）和对照（不添加氮）对中国南方常绿阔叶林优势亚层植物红树Psychotria rubra叶片中碳氮代谢的影响。我们首先通过 RNA-seq 建立了一个参考的 P. rubra 转录组，并通过从头组装获得了总共 93986 个基因。接下来，我们定量研究了叶片的蛋白质组和代谢组，鉴定出 4021 种蛋白质和 562 种代谢物。在 CAN 处理下，与对照相比，有 36 个基因上调，23 个基因下调，我们鉴定出 46 个上调蛋白和 49 个下调蛋白。在 UAN 处理下，与对照相比，有 1525 个基因上调，224 个基因下调，我们鉴定出 35 个上调蛋白和 71 个下调蛋白。这些差异表达的基因和蛋白与光合作用、氨基酸代谢和类黄酮生物合成有关。相应地，发现了 15 种对 CAN 有差异积累的代谢物和 20 种对 UAN 有差异积累的代谢物；这些差异积累的代谢物包括 4 种氨基酸和 3 种类黄酮。总之，我们的研究结果表明，与 CAN 处理相比，UAN 处理对光合作用、氨基酸代谢和类黄酮生物合成的影响更大。最重要的是，结果表明，实验中林下施氮可能会错误地估计氮沉降对 P. rubra 以及中国南方常绿阔叶林其他亚层木本植物氮碳利用的影响。
