高浓度CO2下根系性状驱动的碳氮协同对水稻规避光合下调及增加产量的影响

Taking advantage of future elevated CO2 and increasing rice photosynthetic rate and yield is crucial for maintaining food security of China and the world. Due to the well-known photosynthetic down-regulation, the yield increase at elevated CO2 is much lower than the theoretic expectations, which cannot be fully explained by the previous ‘reproductive sink limitation’ theory. From the standpoint of ‘coordination of above- and below-ground’, we hypothesized that the growth of below-ground root systems cannot meet the nutrients needs for the above-ground growth is one of the essential reasons for the unbalance between carbon and nitrogen metabolism. To prove this hypothesis, we will compare above- and below- ground growth and physiological characters of three rice genotypes (high- and low- yield response, large-root mutant) using 13C and 15N tracer, RNA-seq, and minirhizotron techniques on a FACE platform. The objective of this project is to (1) figure out the relationship between root growth, architecture, and physiology and the carbon and nitrogen metabolisms; (2) justify the role of increasing root growth and nitrogen uptake, transport and assimilation in maintaining the coordination between carbon and nitrogen metabolisms, escaping photosynthetic down-regulation and increasing yield; (3) uncover the molecular adaptive strategy of different rice cultivars to elevated CO2 and provide significant breeding guides and technical support in adapting future climate change.

利用未来高浓度CO2提高水稻光合作用进而提高产量，对维护我国乃至世界粮食安全都具有重要的意义。由于普遍存在的光合下调现象，高浓度CO2下水稻增产率远低于理论预测值。以往“穗库限制”理论并没有完全解释水稻光合下调的原因，本研究从“上下协同”角度出发，推测高浓度CO2下，根系生长不能匹配地上部增长对于养分的需求，是水稻碳氮代谢失衡的主要原因之一。为验证假设，利用FACE平台，通过13C和15N示踪、转录组测序、微根窗等技术，比较高浓度CO2条件下低应答（野生型）、高应答和根突变水稻品种的根系生长、构型、生理状况以及与碳氮代谢、光合作用之间的关系，进而验证扩大根系，增强根对N的吸收、同化及转运能力对协助水稻保持碳氮代谢协同、规避光合下调、实现高增产的作用。本研究将初探不同水稻品种响应CO2浓度升高的与根系性状及光合下调相关的基因调控机理，为应对气候变化的新品种选育提供技术方向和支持。

为探索高CO2浓度下，水稻光合下调的机理，本研究在以往“穗库限制”理论的基础上，从“上下协同”角度出发，验证高浓度CO2下，根系生长不能匹配地上部增长对于养分的需求，是水稻碳氮代谢失衡的主要原因之一。本研究发现高CO2浓度会使水稻出现光合适应现象，根系体积与干重不断增大是为了弥补碳氮代谢失调带来的叶库和穗库的损失，根库为规避光合适应提高产量做出了重要贡献。本研究初步探索了不同水稻品种响应CO2浓度升高的与根系性状及光合下调相关的基因调控机理，为应对气候变化的新品种选育提供技术方向和支持。