水稻抽穗期新基因LHD4的图位克隆和功能鉴定

Heading date, one of the most important agronomic traits, is one of the leading objectives in rice breeding, which directly determines the adaptation of rice in different cultivation areas and crop seasons and is a key factor to attain the desired yield level. Recently, we have constructed a rice library of 1529 chromosome segment substitution lines (CSSLs), by using HJX74, an elite indica variety from South China, as recipient and 26 accessions including 14 indica and 12 japonica collected worldwide as donors. By using the CSSL library, 58 genes （QTLs） controlling rice heading date trait were identified, and one of them (named as LHD4) was further mapped on the substituted segment on chromosome 4 of the CSSL W05-11-5-16-2-5 by whole genome resequencing technique. In the proposed project, I propose to clone LHD4 by the methods of fine mapping and high-resolution linkage analysis using F2 population materials derived from the backcross between W05-11-5-16-2-5 and HJX74, to functionally analyse it by rice transformation and complementation experiments, to dissect its genetic position in regulating heading date trait in rice through quantitative expression analysis of LHD4 and other cloned heading date genes, and to explore its molecular evolution through allelic variation analysis. Information and knowledge generated from cloning and molecular charactierizaiton of this no-previously identified heading date gene LHD4 will help illuminate the underlying complexities of the heading process as well as aid in understanding the mechanism underlying the evolutionary diversification of heading date. More importantly, this new heading date gene can become an interesting target for selection, and facilitate the breeding of improved rice varieties adapting to the different growth conditions in variable latitudes, altitudes, and seasons or different cropping locations.

抽穗期是决定水稻品种地区与季节适应性的重要农艺性状，抽穗期基因的鉴定对于改良水稻的生产性能具有重要意义。本项目组构建了以"华粳籼74"为受体，以世界各地的26个品种为供体的染色体片段代换系（CSSL）文库，鉴定出控制水稻抽穗期的基因（QTL）共58个，并利用基因组重测序的方法将其中的一个新的水稻迟熟基因（命名为LHD4）定位到了第4染色体上。本研究拟利用CSSL扩大作图群体精细定位并克隆该基因，并在此基础上，采用水稻转基因沉默和过量表达的方法对该基因进行功能验证；利用实时定量PCR方法分析LHD4和其它生育期基因的表达情况，推测LHD4在整个水稻抽穗期基因调控网络中的位置；对不同来源水稻的LHD4座位进行序列测定，探索LHD4的分子进化。水稻抽穗期新基因LHD4的克隆和鉴定将有助于阐明水稻抽穗期的分子生物学机制，对培育具有特定抽穗期，适应相关稻作生产区域的新品种具有重要的应用价值。

抽穗期是决定水稻品种地区与季节适应性的重要农艺性状，抽穗期基因的鉴定和克隆对改良水稻的生产性能具有重要意义。本项目组前期获得了1123个以籼稻品种“华粳籼74”为受体的染色体片段代换系（CSSL）并对这些染色体片段代换系进行了抽穗期表型鉴定，发现CSSL5在早晚季均表现出迟熟表型。在此基础上，本项目通过遗传分析发现CSSL5的迟熟表型由两个具有上位性互作的水稻抽穗期QTL LHD4（重新命名为LH8）和EH3控制，EH3的功能发挥依赖于LH8的不同基因型。利用CSSL扩大作图群体精细定位并克隆LH8，发现LH8编码一个能与Hd1互作的CCAAT-box结合转录因子。本研究的研究成果将有助于阐明水稻基因互作控制抽穗期的分子机制，对于培育具有特定抽穗期、适应相关稻作生产区域的新品种和实现水稻早熟高产具有重要意义。