水稻qHd1.1基因调控抽穗期的分子机理研究

Rice yield is strongly associated with heading date. In our previous studies, one quantitative trait loci (QTL) with pleiotropic effects on heading date and number of spikelets per panicle was designated as qHd1.1 and defined in a 200 kb marker interval on chromosome 1 through primary mapping and fine mapping using a Zhenshan97/MiYang46 recombinant inbred line(RIL) population and advanced back-cross populations. According to the target region, we designed high-density and tightly linked markers and identified 36 recombinant plants. Photoperiodic responses of near isogenic lines (NILs) implied that qHd1.1 might control heading date through photoperiod pathway. Based on these studies, qHd1.1 will be isolated by map-based cloning and its biological function will be validated using transgenic method. Meanwhile, we will reveal the action mechanism of qHd1.1 in regulating heading date and number of spikelets per panicle, identify upstream and downstream genes of qHd1.1, and elucidate the regulatory pathway for rice heading date that qHd1.1 involved in through analyzing the photoperiodic responses and molecular biology techniques. Here, cloning and characterization of qHd1.1 plays an important role in completing the regulatory network for rice heading date, elucidating the relationship between rice yield traits and heading date, and guiding agricultural production.

水稻产量与抽穗期密切相关。我们在前期研究中，应用杂交稻骨干亲本珍汕97和密阳46，配组构建了重组自交系群体和高代回交群体，经初定位和精细定位，将控制抽穗期和每穗颖花数的QTL qHd1.1界定在水稻第1染色体上200 kb的范围内。我们在目标区间设计了高密度的紧密连锁标记，筛选到36个重组单株。近等基因系的光周期反应结果表明qHd1.1可能参与了水稻抽穗期的光周期调控途径。本项研究拟采用图位克隆方法分离qHd1.1，转基因验证其生物学功能。通过光周期反应分析和分子生物学方法研究揭示qHd1.1对抽穗期和每穗颖花数的作用机理，鉴定上下游调控基因，阐明qHd1.1参与的抽穗期调控途径。qHd1.1的克隆与功能分析对进一步完善水稻抽穗期的基因调控网络,阐明抽穗期与产量性状的相互关系和指导农业生产，具有重要意义。

抽穗期决定水稻品种的种植季节和适宜生态区域。微效抽穗期QTL的克隆与应用可精准调控抽穗期，提高稻谷产量。目前已克隆了14个水稻抽穗期QTL,分布在2、3、6、7、8、10染色体上。本项研究利用在目标区域内分离区间相互交叠的BC2F10群体及其衍生的BC2F10:11近等基因系，在第1染色体上分离了1个对水稻抽穗期和产量性状兼具微效作用的QTL　qHd1.1。在自然长短日照条件下，近等基因系抽穗期的观察表明qHd1.1对抽穗期的加性效应无显著差异（2.4-2.9天），没有表现出对光周期的敏感性。互补、过量表达和RNAi试验转基因验证了qHd1.1对抽穗期的作用。qHd1.1编码的蛋白位于细胞核中，是一个转录因子。RNA-seq和qRT-PCR的结果表明，qHd1.1的表达上调可促进Ehd1和RFT1/Hd3a基因的表达，促进水稻开花。序列分析表明两亲本qHd1.1等位基因的cDNA序列相同，且在启动子区域只存在一个单碱基的变异。但亲本ZS97等位基因相对于MY46，第1内含子上有一个约9.5 Kb的插入序列变异。甲基化测序发现该插入片段包含3个高度甲基化的CpG岛，推测甲基化效应引起qHd1.1基因的表达受到抑制，并导致下游基因Ehd1、RFT1和Hd3a的表达下调，抽穗期推迟。近等基因系的分析表明qHd1.1具有多效性，珍汕97的qHd1.1迟熟等位基因增加每穗实粒数、每穗总粒数和单株产量。本项研究qHd1.1的克隆和功能分析为水稻育种的抽穗期和产量性状的精准调控提供了支持。