Proteomic Profiling for Metabolic Pathways Involved in Interactive Effects of Elevated Carbon Dioxide and Nitrogen on Leaf Growth in a Perennial Grass Species

Elevated atmospheric CO2 and nitrogen are major environmental factors affecting shoot growth. The objectives of this study are to determine the interactive effects of elevated CO2 and nitrogen on leaf growth in tall fescue (Festuca arundinacea) and to identify major proteins and associated metabolic pathways underlying CO2-regulation of leaf growth under insufficient and sufficient nitrate conditions using proteomic analysis. Plants of tall fescue treated with low nitrate level (0.25 mM, LN), moderate nitrate level (4 mM, MN) and high nitrate level (32 mM, HN) were exposed to ambient (400 μmol mol–1) and elevated (800 μmol mol–1) CO2 concentrations in environment-controlled growth chambers. Increased atmospheric CO2 concentration increased leaf length and shoot biomass, which corresponded to increased content of indo-acetic acid, gibberellic acid, cytokinins and reduced content of abscisic acid under sufficient nitrate conditions (MN and HN conditions). Low nitrate supply limited shoot growth and hormonal responses to elevated CO2. Proteomic analysis of plants exposed to elevated CO2 under LN and MN conditions demonstrated the increases in the abundance of many proteins due to elevated CO2 under MN condition involved with cell cycle and proliferation, transcription and translation, photosynthesis (ribosomal and chlorophyll a/b-binding proteins), amino acids synthesis, sucrose and starch metabolism, as well as ABA signaling pathways (ABA-induced proteins). Our results revealed major proteins and associated metabolic pathways associated with the interactive effects of elevated CO2 and nitrate regulating leaf growth in a perennial grass species.大气CO₂浓度升高与氮素是影响植物地上部生长的关键环境因子。本研究旨在明确CO₂浓度升高与氮素交互作用对高羊茅（Festuca arundinacea）叶片生长的影响，并采用蛋白组学（proteomic analysis）技术，解析硝态氮不足与充足条件下CO₂调控叶片生长的核心蛋白及相关代谢通路。将经低硝态氮水平（0.25 mM，LN）、中硝态氮水平（4 mM，MN）及高硝态氮水平（32 mM，HN）处理的高羊茅植株，置于环境可控生长箱中，分别在大气背景浓度（400 μmol mol–1）与升高浓度（800 μmol mol–1）CO₂条件下培养。在硝态氮充足条件（MN与HN处理）下，大气CO₂浓度升高可提升叶片长度与地上部生物量，该效应与吲哚乙酸（indole-acetic acid）、赤霉素（gibberellic acid）、细胞分裂素（cytokinins）含量升高，以及脱落酸（abscisic acid）含量降低密切相关。低硝态氮供给会抑制地上部生长，同时削弱植株对CO₂浓度升高的激素响应。对LN与MN处理下经CO₂浓度升高处理的植株进行蛋白组学分析后发现，MN处理下CO₂浓度升高所诱导的大量蛋白丰度上升，这些蛋白涉及细胞周期与增殖、转录与翻译、光合作用（核糖体蛋白及叶绿素a/b结合蛋白）、氨基酸合成、蔗糖与淀粉代谢，以及脱落酸信号通路（ABA诱导蛋白）。本研究结果明确了CO₂浓度升高与硝态氮的交互作用调控多年生禾本科植物叶片生长的核心蛋白及相关代谢通路。