Ye Jia Yuan, Tian Wen Hao, Zhou Miao, Zhu Qing Yang, Du Wen Xin, Jin Chong Wei
State Key Laboratory of Plant Physiology and Biochemistry, College of Natural Resources and Environmental Science, Zhejiang University, Hangzhou, China.
State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou, China.
Front Plant Sci. 2021 Feb 12;12:629857. doi: 10.3389/fpls.2021.629857. eCollection 2021.
The floral transition stage is pivotal for sustaining plant populations and is affected by several environmental factors, including photoperiod. However, the mechanisms underlying photoperiodic flowering responses are not fully understood. Herein, we have shown that exposure to an extended photoperiod effectively induced early flowering in plants, at a range of different nitrate concentrations. However, these photoperiodic flowering responses were attenuated when the nitrate levels were suboptimal for flowering. An extended photoperiod also improved the root nitrate uptake of by NITRATE TRANSPORTER 1.1 (NRT1.1) and NITRATE TRANSPORTER 2.1 (NRT2.1), whereas the loss of function of NRT1.1/NRT2.1 in the mutants suppressed the expression of the key flowering genes () and (), and reduced the sensitivity of the photoperiodic flowering responses to elevated levels of nitrate. These results suggest that the upregulation of root nitrate uptake during extended photoperiods, contributed to the observed early flowering. The results also showed that the sensitivity of photoperiodic flowering responses to elevated levels of nitrate, were also reduced by either the replacement of nitrate with its assimilation intermediate product, ammonium, or by the dysfunction of the nitrate assimilation pathway. This indicates that nitrate serves as both a nutrient source for plant growth and as a signaling molecule for floral induction during extended photoperiods.
花期转变阶段对于维持植物种群至关重要，并且受到包括光周期在内的多种环境因素影响。然而，光周期开花反应的潜在机制尚未完全明确。在此，我们发现，在一系列不同硝酸盐浓度下，延长光周期有效诱导了植物早花。然而，当硝酸盐水平对开花而言并非最适宜时，这些光周期开花反应会减弱。延长光周期还通过硝酸盐转运蛋白1.1（NRT1.1）和硝酸盐转运蛋白2.1（NRT2.1）提高了根系对硝酸盐的吸收，而NRT1.1/NRT2.1在突变体中的功能丧失抑制了关键开花基因（）和（）的表达，并降低了光周期开花反应对升高的硝酸盐水平的敏感性。这些结果表明，延长光周期期间根系对硝酸盐吸收的上调促成了观察到的早花现象。结果还表明，用其同化中间产物铵替代硝酸盐，或硝酸盐同化途径功能失调，也会降低光周期开花反应对升高的硝酸盐水平的敏感性。这表明硝酸盐在延长光周期期间既是植物生长的养分来源，也是成花诱导的信号分子。
