增施氮肥提高水稻每穗颖花数的成花素途径解析

The number of spikelets per panicle of rice is an important factor that determines the yield. Nitrogen fertilizer application before panicle initiation is well known to increasing spikelet number per panicle and then get more spikelets per area unit. However, excessive application also delayed the growth period and affected the stable rice production. At the same time, it also led to the increase of production cost and environmental pollution. My previous studies indicated that nitrogen fertilizer promotes the expressions of flowering repressive genes, thus decrease the florigen transcription. At the same time, application of nitrogen fertilizer can also reduce the expression of florigen binding protein in young panicle, and then inhibit signal transduction of florigen. Thus, the transition of vegetative growth to reproductive growth was delayed. Our recent results show that the rice RCN1, a florigen homolog, responds to nitrogen treatment. After it lost its function, the effect of nitrogen fertilizer on spikelet differentiation is significantly reduced. Thus, the project will study the regulation of nitrogen fertilizer in rice panicle differentiation process. To clarifying the role of the florigen signal pathway in increasing the number of spikelet per panicle in rice with increasing nitrogen fertilizer, and revealing the function of important regulatory genes such as RCN1. The regulation pathway of promoting the differentiation of rice branch and spikelet by nitrogen will be built. The project will provide a new theoretical basis for the cultivation measures to control rice yield formation. It also helps to innovate cultivation measures, and provide new ideas for high yield and high efficiency cultivation.

水稻每穗颖花数是决定单产的重要因子，生产上通过增施氮素穗肥能够显著地促进颖花分化，达到提高单位面积颖花数的目的。但过量施用氮肥不仅会使生育期延迟，影响水稻稳产，还会导致生产成本上升，并造成环境污染。我们前期研究发现，氮肥能够促进叶片中开花抑制基因的表达，从而抑制成花素编码基因转录。同时增施氮肥还能通过降低幼穗中成花素结合蛋白的表达量来抑制成花素信号的转导，延迟营养生长向生殖生长的转换。我们近期的研究结果显示，水稻成花素同家族基因RCN1能够响应氮素处理，而且其功能的丧失显著降低了氮肥促进颖花分化的效果。鉴于此，本项目将以氮肥调控水稻幼穗分化过程为研究对象，明确成花素途径在增施氮肥提高水稻每穗颖花数中的作用，揭示RCN1等重要调控基因的功能，构建一条氮肥促进水稻枝梗与颖花分化的调控途径。本项目的实施将为栽培措施调控水稻产量形成提供新的理论依据，并为革新栽培技术，实现高产高效栽培提供新的思路。

PEBP基因家族在进化中高度保守，是植物发育过程中最为重要的基因家族之一。在水稻中，PEBP基因家族中的FT-like亚家族参与调控成花转变和穗发育。但是，TFL1-like和MFT-like亚家族在水稻发育中的作用仍不明确。本研究通过创制相关遗传材料，结合不同的环境因子，尤其是氮肥，探究它们对产量的影响以及对环境的响应情况，揭示了PEBP家族成员在水稻响应氮肥等外界环境抽穗、产量形成以及种子休眠萌发中的多样性功能。RCN突变后水稻抽穗时间提前，其中RCN1、RCN3对抽穗期影响最大。rcn1 rcn3双突材料对短日处理较野生型更为敏感，表现为较短天数的短日处理就能诱导抽穗，且抽穗历期较野生型明显缩短。rcn1 rcn3也参与氮对水稻抽穗的调控，表现为在高氮条件下，rcn1 rcn3抽穗延迟效应较野生型变缓。本研究揭示了RCN1~RCN4在水稻株高、抽穗期和产量形成中具有重要作用，明确了rcn突变体在高、低氮素下的表现型变化。阐明了成花素介导氮素调控水稻枝梗和颖花分化的分子机制。