大气CO2浓度升高对大豆脂肪代谢的影响及其调控机制

Since the industrial revolution, the atmospheric CO2 concentration has been increasing rapidly. This will likely affect the growth, yield and quality of crops including soybean. CO2 is a major substrate for photosynthesis, so elevated atmospheric [CO2] would have significant impact on the photosynthesis and carbon metabolism in soybean. The lipid metabolism in soybean and subsequently the soybean grain oil content would be altered. Our previous studies found that elevated [CO2] increased the oil content of soybean grain, but the underlying mechanism on how elevated [CO2] affects the lipid metabolism in soybean remains uncertain. In this study, soybean cultivars of different oil content will be grown under either ambient or elevated [CO2] using a open-top chamber (OTC) experimental facility. We will measure photosynthesis, respiration, and the key metabolic enzymes involved in the carbon metabolism of the soybean cultivars. The oil content and the key enzymes of lipid metabolism will also be measured. We will analyze the effect of elevated [CO2] on the gene expression of acetyl CoA carboxylase (ACCase) and Acyl CoA:Diacylglycerol Acyltransferase (DGAT) of anabolic lipid metabolism in soybean grain. We will systematically investigate the interactions between carbon metabolism and lipid metabolism for different soybean cultivars under elevated [CO2] to reveal the regulatory mechanism of soybean to future, higher CO2 environments. This will provide a scientific basis for breeding soybean and improving the quality of soybean in China under a changing climate.

工业革命以来，全球大气CO2浓度持续升高，这将影响作物的生长发育及产量品质。CO2是植物光合作用的底物，大气CO2浓度升高会影响大豆光合作用，使大豆碳代谢发生变化，碳代谢的变化会影响大豆脂肪代谢，进而对大豆籽粒脂肪含量产生影响。我们前期研究发现CO2浓度升高使大豆籽粒脂肪含量升高,但目前还没有大气CO2浓度对大豆脂肪代谢方面的系统研究，其机理有待深入探究。本项目拟在开顶式气室（OTC）中开展不同CO2浓度对不同油脂含量大豆脂肪代谢影响的研究，测定与大豆籽粒脂肪含量相关的碳代谢（光合作用、呼吸作用及相关代谢关键酶）、脂肪代谢（油脂含量及脂代谢关键酶），并分析大豆籽粒脂肪合成代谢关键酶乙酰CoA羧化酶和二脂酰甘油转酰酶基因表达差异。系统研究CO2浓度升高条件下不同大豆品种的碳代谢和脂质代谢的互作关系，揭示大豆对气候变化的响应机制，为未来气候变化下我国大豆品种选育及品质提升提供理论依据。

工业革命以来全球大气CO2浓度持续升高，CO2浓度增高会对作物生长发育、产量形成及品质等产生影响。大豆是我国及世界主要的油料作物之一。本项目开展大气CO2浓度升高对大豆油脂代谢影响机制的研究，对CO2浓度升高条件下大豆叶片和籽粒碳氮代谢物、油脂代谢相关酶及相关基因表达、油脂代谢组、油脂含量等的变化进行分析。主要研究结果如下：（1）大气CO2浓度升高对大豆籽粒中基因表达的影响大于叶片，且籽粒中差异表达基因绝大多数为上调表达。叶片和籽粒中的差异表达基因均富集在淀粉、蔗糖等多种碳水化合物代谢以及MAPK信号转导途径，表明CO2浓度升高对大豆籽粒和叶片中糖类转化有较大影响。籽粒中差异代谢基因富集在多种不同类型脂质的代谢过程，CO2浓度升高促进籽粒糖代谢，糖类向脂质的合成转化被加强，有利于籽粒中脂质含量提高。（2）大气CO2浓度升高对大豆叶片代谢物的影响大于籽粒。两个部位中的差异代谢物类别差别不大，但是籽粒中类固醇及类固醇衍生物、脂肪酰基、异戊烯醇脂等脂质相关代谢物的比重显著增大，表明籽粒中脂质相关化合物显著提高，这与转录组学中差异基因的通路富集结果一致。 转录组和代谢组关联分析发现CO2浓度升高使籽粒中α-亚麻酸代谢途径显著加强。（3）早黄2号（高蛋白大豆）和中黄35（高油大豆）脂肪代谢相关物质、酶、基因表达结果表明：大气CO2浓度升高对大豆叶片糖代谢的影响更显著，对脂肪代谢有一定影响但小于糖代谢，这与转录组和代谢组结果一致。大气CO2浓度升高通过影响大豆糖代谢影响大豆脂肪代谢，进而对大豆籽粒油脂含量产生影响。本研究可为未来CO2浓度升高背景下的大豆品质提升及品种选育提供理论依据。