独角金内酯参与氮素调控水稻分蘖芽生长的作用机制

Ideal plant architecture is one of the fundamental conditions for increasing crop production. Therefore, nutrient supply especially nitrogen supply influences plant architecture remarkably. When nitrogen supply is increased, the rice tiller number increases significantly, vice versa. The molecular mechanism which control tiller bud growth has not yet been revealed. Strigolactone as a new phytohormone suppressing tiller outgrowth connects the tiller bud development and nitrogen supply tightly. In this project based on the research background of applicant, the state of tiller bud will be confirmed after the observation of plants under different nitrogen conditions, combined with laser micro-dissection and RNA-sequencing techniques, the genes which changed expression within the tiller bud will be isolated. Meanwhile, considering the phenotype changes of strigolactone biosynthesis and signaling mutants after the nitrogen treatment, together with the expression level of core nitrogen related genes in strigolactone mutants, the role of strigolactone involved in the regulation of tiller bud by nitrogen will be revealed. The results will shed light on the elucidation of the mechanisms that how nitrogen regulates tiller bud growth, and also provide the scientific evidence for constructing ideal rice plant architecture.

理想的株型是作物高产的重要基础之一，而营养元素尤其是氮素的供应对株型的影响显著。氮素充足时，水稻分蘖数显著增加，反之则分蘖数明显减少。然而在分子水平对分蘖芽生长调控机制的研究还未见报导。独角金内酯作为植物激素可以抑制分蘖生长，它将分蘖芽的发育与氮素的供应紧密联系在一起。本项目拟在申请人博士生阶段对分蘖芽休眠机制所做研究的基础上，通过对不同供氮条件下分蘖芽生长情况的观察确定分蘖芽所处的生长状态，结合激光显微切割和高通量测序等先进手段，获得分蘖芽内部差异表达的基因。同时结合独角金内酯生物合成和信号转导突变体对不同供氮条件产生的表型变化，以及突变体中氮转运、同化基因对供氮水平的响应，揭示独角金内酯在氮素调控水稻分蘖芽生长中的作用。本项目的结果将阐明分蘖芽生长受氮素调控的作用机制，从而为构建理想的水稻株型提供科学依据。

本项目在研期间在国际期刊发表英文论文2篇，中文核心期刊1篇，已经投稿在审SCI一篇，准备投稿SCI论文一篇。主要结论如下：1）水稻分蘖芽的伸长而不是形成受氮素浓度的影响，并且这个影响与氮素形态无关。2）不同位置的分蘖芽对氮素的响应不同，对氮素浓度敏感的分蘖芽进行分析发现，只有加氮的分蘖芽有细胞分裂S期marker基因Histone H4探针的杂交信号，定量结果表明氮素控制分蘖的伸长可能通过调节细胞分裂途径以及独角金内酯途径。3）对处于活跃状态和休眠状态的分蘖芽植株进行取样进行转录组分析，找到差异表达基因。4）通过GR24处理和15N标记实验发现，d3和d10在不同叶片氮素的分配与野生型有着显著差异，特别是d3新叶中含量明显低于野生型。这说明独角金内酯可能参与了氮素的在水稻体内的分配。