高浓度CO2条件下高应答水稻响应机制的研究

Climate change will bring both opportunities and challenges for food security in future.Global crop-FACE are focusing the responses of different varieties to elevated CO2, to find the genetic resources of high yield. The over 10 years study of rice-FACE indicated that under elevated CO2，the increase of yield was very limited due to the common photosynthetic down-regulation. However, we found some rice varieties have the very high increase of yield in recent years. From the some previous results, we realize that the different responses may be the result that whether rice variety can increase N uptake to keep the coordinated C and N metabolism after heading stage. So, we propose the hypothesis that under elevated [CO2],the varity of high response after heading stage can increase the root C sink, promote root growth, enhance N uptake, N assimilation and transport, coordinate C and N metabolism, avoid photosynthetic down-regualtion, and then show high response, and 14-3-3 should be the manipulated factor for regulating the root C sink. For testing the hypothesis, we will combine the field and hydroponics experiments under the FACE platform, to study the mechanism for different responses of high and low rice varieties by HPLC, 13C and 15N tracer, real-time quantitative PCR, gene overexpression and gene knock-out techniques. This research will help to understand of the genetic characteristics for rice varieties with high response to elevated CO2, and also provide a reliable basis for breeding new varieties to deal with climate chang in future.

气候变化对未来粮食安全带来了挑战和机遇，全球作物FACE都在关注作物品种对高浓度CO2响应的差异，以挖掘高产种质资源。国内外水稻FACE过去十多年的研究发现由于普遍存在的光合下调,水稻在高浓度CO2条件下增产幅度有限，而近些年我们发现某些品种具有很高的增产。比较已有结果发现高、低应答品种响应的差异，表现在穗后能否增加N吸收从而保证碳氮代谢协调。由此推测，高浓度CO2下高应答品种在穗后能增强根C库，促进根生长，增加N吸收、同化及转运，协调碳氮代谢，逃脱光合下调，从而表现出高应答，而14-3-3蛋白可能在根C库调控过程中扮演重要的角色。为验证假设，利用FACE试验平台进行大田和水培实验，通过HPLC、13C和15N示踪、荧光定量PCR、基因超量表达和基因沉默等技术，阐明高、低应答品种响应差异的机制。本研究将明确高应答水稻的种质特征，为应对气候变化的新品种选育提供技术方向和依据。

候变化为未来粮食安全带来了机遇和挑战。本研究首先选取高应答品种扬稻6号、低应答品种武运粳23为参试品种，确定高应答和低应答水稻品种每穗颖花数响应方向的差异是导致二者产量增幅不同的主要原因，并从细胞分裂素代谢及其对氮代谢的调控解释二者颖花分化数对FACE响应的差异。.通过对低应答水稻品种喷施细胞分裂素CTK（6-BA）发现，喷施6-BA后，武运粳23和NG9108在FACE条件比对照条件分别增产15%和14%，比未喷施的对照条件下分别增产19%和18%； FACE条件下武运粳23每穗二次枝梗颖花现存数要比未喷施情况下显著增加，退化率降低，每穗颖花现存数显著增加；NG9108的每穗颖花数虽无显著变化，但是显著提高FACE条件下的结实率。大田试验表明，喷施CTK后可提高低应答水稻对CO2浓度升高的响应，使其每穗颖花数增加，光合速率提高，最终提高增产幅度。.通过在低应答水稻中花11号体内过表达AP2/乙烯响应因子ERF3，结果表明，突变体材料在FACE条件下的增产幅度显著高于野生型，但是其产量较相同条件下的野生型显著减少，究其原因，主要是因高表达基因引发的“大根系”消耗过多碳水化合物，从而抑制了地上部的生长，突变体与野生型相比地上生物量减少。因此通过增大根系规模来增加是得不偿失的。.用FACE量化[CO2]升高引起的稻米全面养分变化，并以此为基础评估了全球依赖稻米为主食的前10名国家国民的营养摄入变化。结果表明：高[CO2]条件下，总体营养赤字（蛋白质、矿物质和维生素）与最低的总体人均国内生产总值的人群直接相关，初步估算大概波及全球约6亿人口。这些定性的结果表明： [CO2]升高条件下，稻米养分下降所引发的潜在的健康危机是非常巨大的，尤其是那些对依靠大米作为主要食物来源贫困人群。