小麦顶小穗分化机制及其与穗粒数的关系

The terminal spikelet of wheat is located at the top of the young spike, and it is differentiated from several bract and spikelet primordia at the top of the growth cone. As a signal switch, the terminal spikelet regulates the grain number per spike. When it differentiates late, the grain number per spike is much, whereas the grain number per spike is little. So, the differentiation of terminal spikelet will directly affect the yield of wheat. In the previous work, we have preliminarily studied the differentiation of terminal spikelet, but the specific morphological and structural characteristics, physiological and biochemical changes, the type of regulated genes, and the relationship between the differentiation of terminal spikelet and grain number per spike are still unclear. .The winter and spring wheat varieties with different time on the differentiation of terminal spikelet will be treated with interval sowing and nitrogen application, which can alter the differentiation time of terminal spikelet. By using the anatomical, physiological, biochemical and molecular biological experimental techniques, this project will mainly focus on the following contents: (1) the morphological and structural characteristics of the differentiation of terminal spikelet of wheat; (2) the dynamics of the physiological and biochemical changes during the differentiation of terminal spikelet of wheat; (3) the type and function of the key genes regulating the differentiation of the terminal spikelet of wheat; and (4) the relationship between the differentiation of terminal spikelet of wheat and grain number per spike. This project is reliable in the basis of research foundation and is innovative in the content and method. The results will not only deepen the developmental mechanism of wheat spike, but also have important application value in exploring the potential of yield increasing of wheat.

小麦顶小穗位于幼穗顶端，由生长锥顶部几个苞原基和小穗原基分化而来。顶小穗作为信号“开关”调控着穗粒数，它分化得晚，穗粒数就多，反之，穗粒数就少。因此，顶小穗的分化状况会直接关系到小麦产量。在前期工作中我们已经对顶小穗分化进行了初步研究，但有关顶小穗分化过程中具体的形态结构特征、生理生化变化、调控基因种类以及顶小穗分化与穗粒数的关系目前还不清楚。.本项目拟以顶小穗分化时间不同的冬性和春性小麦品种为实验材料，采用分期播种和施氮处理改变顶小穗分化时间，运用形态解剖、生理生化和分子生物学等实验技术，重点研究：（1）小麦顶小穗分化的形态结构特征；（2）小麦顶小穗分化过程中的生理生化动态变化；（3）调控小麦顶小穗分化的关键基因种类和功能；（4）小麦顶小穗分化与穗粒数的关系。该项目有研究基础，研究内容和方法有创新性，研究结果不仅能深化小麦穗发育机理的研究，而且对于挖掘小麦的增产潜力具有重要的应用价值。

小麦的产量由亩穗数、穗粒数和千粒重共同决定，在亩穗数确定的情况下提高穗粒数和千粒重便成为小麦增产的关键突破口。穗粒数为小穗数和小穗粒数的乘积，小穗数多，一般穗粒数便高。小麦的小穗由侧小穗和顶小穗构成，其中顶小穗位于穗轴的顶端，作为终止“信号”调控着侧小穗的数量。.本项目按原计划进行。种植了不同的小麦品种，在顶小穗分化前进行低温和施氮处理，剥离幼穗后利用形态观察、树脂切片、显微和亚显微结构观察、生理指标测定、转录组测序等技术分析了小麦顶小穗的分化特征及调控基因的种类，探明了：（1）小麦顶小穗分化的显微和亚显微结构特征。（2）小麦顶小穗分化前后幼穗的部分生理特征。（3）调控小麦顶小穗分化的基因种类和功能。（4）顶小穗分化的早、晚与穗粒数的关系。.研究结果表明：（1）小麦顶小穗是在最后两个“停育”的侧小穗上方形成的，出现时间在雌雄蕊分化期之后，其构成结构与侧小穗类似。顶小穗的产生与侧小穗有严格的连续性，两者始终保持互生状态，最终的着生方向与侧小穗垂直。（2）顶小穗中的脱氢酶活性较中部小穗低，最终结实率低。顶小穗分化后不同时期生长素、赤霉素和玉米素核苷含量先下降再上升，而脱落酸含量先上升再下降。（3）顶小穗分化前后幼穗中差异表达基因数目有3215个，功能注释显示9个下调基因编码的侧生器官边界蛋白和G1-like5蛋白可能参与了穗部器官的形态建成。GO功能富集筛选到了10个与穗发育有关的条目。（4）施氮会使顶小穗的分化时间延后，最终提高了穗粒数，而春季低温可使顶小穗的分化时间提前，最终减少了穗粒数。顶小穗分化的越早，穗粒数越少，反之，穗粒数越多。.本项目自立项至今发表学术论文9篇（第一标注7篇），申请发明专利4项，参加学术会议1次，申请软件著作权2项，培养研究生3人。研究成果对深化小麦穗器官发育机理的研究、挖掘小麦的增产潜力及提高小麦产量具有重要的理论意义和实际应用价值。

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