水稻孕穗期耐冷基因qCTB7的克隆及功能分析

The low temperature is one of the main limiting factor of rice production in our country and in the world. It has significance to explain the cold tolerance in rice and guide the practice of cold-resistant breeding by rice cold tolerance gene excavations and cold tolerance molecular mechanisms study. Booting stage of rice is the most sensitive period to low temperature. Cold injury in this period would cause the most serious loss of rice yield. However, there is no report on rice cold tolerance gene by map-based cloning at booting stage. Cold-tolerant NILs were developed by backcrossing KMXBG, reported to be the most cold-tolerant rice variety at booting stage, as donor, with a cold-sensitive variety, Towada. Cold tolerance of a BC6F2 and other segregating populations was evaluated at several locations over two years. A stable expression cold tolerance QTL, qCTB7, was detected on chromosome 7. The QTL explained 21% of the phenotypic variances (spikelet fertility) and was fine mapped to a 92kb interval. Recombinant plants were used to expand the mapping population and the target gene was fine mapped to a 30kb interval. The candidate genes were forecasted and cloned. By transgenic complementation test, the functionality of the candidate genes will be verified and Cold tolerance mechanism will be analysed，which will provide gene resource and breeding materials for cold tolerance breeding.

低温是我国和世界水稻生产中的主要限制因子之一, 发掘水稻耐冷基因,研究耐冷分子机制，对解释水稻耐冷性，指导耐冷育种实践具有重要意义。水稻孕穗期是对低温反应最敏感的时期，这一时期的冷害造成的水稻产量损失最为严重。但是，目前还没有水稻孕穗期耐冷基因图位克隆的报道。本研究以目前世界上鉴定出来的孕穗期最耐冷品种昆明小白谷为供体亲本、以冷敏感品种十和田为受体培育的耐冷近等基因系为材料，通过对BC6F2等分离群体进行多年多点的耐冷鉴定,在7号染色体上检测到一个稳定表达的耐冷QTL，qCTB7，对表型（结实率）的贡献率为21%，并精细定位到92kb的物理区间内。进一步利用重组单株扩大定位群体，将目标基因精细定位于30kb的区间内，预测并克隆候选基因，为水稻耐冷育种提供基因资源。

孕穗期低温是影响水稻高产、稳产的重要环境因素，挖掘和克隆控制水稻孕穗期耐冷性的相关基因对于开展水稻耐低温的分子育种具有重要意义。本研究利用云南强耐冷品种昆明小白谷和日本冷敏感品种十和田组配的高世代回交群体，对课题组之前已定位的孕穗期耐冷位点qCTB7进行了进一步的精细定位，最终将qCTB7定位到7号染色体长臂InDel7-43至RM21862的28K的区间范围内。通过测序比对，确定了两个可能的候选基因，Os07g0577700和Os07g0577900，它们分别编码琥珀酰辅酶A连接酶和SNARE螺旋卷曲结构域蛋白，为进一步的基因功能研究奠定了基础。