氮素和糖源对植物光周期调控的信号通路研究

The phenomenon of delayed flowering after the application of nitrogen fertilizer has been known for a long time in agriculture but the detailed molecular basis is largely unclear. Our previous study indicated that low-N induces ferredoxin-NADP+-oxidoreductase FNR1 expression and increases plastid NADPH/NADP+ ratio but decreases the ATP/AMP ratio, which in turn affects adenosine monophosphate-activated protein kinase (AMPK) and then modulates the nuclear blue-light receptor cryptochrome 1 (CRY1) phosphorylation and the protein abundance. CRY1 then functions as an input signal to modulate amplitudes of several key circadian oscillators. Sugar sources (carbohydrates) also influence the oscillation amplitude and the phase of the circadian clock mainly through the morning-expressed gene PSEUDORESPONSE REGULATOR 7 (PRR7). Detailed plant-growth-regulatory pathways from nitrogen levels and carbohydrate levels to photoreceptors and the photoperiod regulation will be studied. We are focusing on the phosphorylation status and subcellular distributions of cryptochromes and the transcriptional regulation to the key central oscillators (e.g. LHY, CCA1, TOC1 and PRR7) and the flowering output components (e.g. GI and CO). Our project aims to identify the relationship between blue light signals and nitrogen and carbohydrate metabolism signals, and provides new experimental data and ideas to nutritional signaling – environmental adaptation crosstalk researches and plant growth and flowering studies.

植物缺氮时开花提早，外施氮肥往往导致开花延迟，但其分子机制还鲜有研究。我们前期的研究发现低氮诱导铁氧还原蛋白-NADP+-氧化还原酶1（FNR1）增加和NADPH/NADP+比值升高，从而进一步引起AMP/ATP比值降低。蛋白激酶AMPK响应AMP/ATP的比值变化，介导对蓝光受体CRY1的磷酸化修饰，并负向调节其核内蛋白的稳态水平。而CRY1作为输入元件影响到光周期元件的振幅。糖源也影响生物钟的振幅和相位，主要通过调控核心振荡器PRR7。该课题拟深入研究这两条生长发育调控信号途径，重点关注隐花色素的磷酸化修饰和亚细胞分布，核心振荡器LHY、CCA1、TOC1和PRR7和生物钟输出元件CO和GI的转录水平调控。该课题将研究氮素和糖源影响光受体和光周期的精确调控机制，寻找蓝光信号与氮代谢、糖代谢信号之间的分子关联，为植物营养元素代谢、环境生理、植物开花发育调控提供新的研究思路。

植物缺氮时开花提早，外施氮肥往往导致开花延迟，但其分子机制还鲜有研究。我们前期的研究发现低氮诱导铁氧还原蛋白-NADP+-氧化还原酶1（FNR1）增加和NADPH/NADP+比值升高，从而进一步引起AMP/ATP比值降低。蛋白激酶AMPK响应AMP/ATP的比值变化，介导对蓝光受体CRY1的磷酸化修饰，并负向调节其核内蛋白的稳态水平。而CRY1作为输入元件影响到光周期元件的振幅。糖源也影响生物钟的振幅和相位，主要通过调控核心振荡器PRR7。该课题拟深入研究这两条生长发育调控信号途径，重点关注隐花色素的磷酸化修饰和亚细胞分布，核心振荡器LHY、CCA1、TOC1和PRR7和生物钟输出元件CO和GI的转录水平调控。我们发现高氮处理降低了生物钟相关基因转录产物的振幅，低氮处理增加了生物钟相关基因转录产物的振幅；NO增加了输入基因CRY1和编码中心振荡器的关键组分LHY、CCA1和TOC1的基因转录产物的振幅，而降低了输出基因CO和GI的昼夜节律转录产物的振幅。补充的5%的蔗糖逆转了NO诱导的输出基因CO和GI转录产物振幅的下降。细胞核内CRY1蛋白和AMPK蛋白都呈现出明显的周期性波动，表现在见光以后两种蛋白在细胞核中都增加，而黑暗下两种蛋白在细胞核中都减少。AMPK含量和激酶活性与细胞核内CRY1磷酸化水平正相关，与细胞核内CRY1蛋白稳态水平负相关。但是氮源对胞质AMPK和CRY1蛋白稳态水平影响不大。实验结果表明，蔗糖在转录水平上能抵消NO的影响。该课题取得的成果为研究氮素和糖源影响光受体和光周期的精确调控机制，寻找蓝光信号与氮代谢、糖代谢信号之间的分子关联，为植物营养元素代谢、环境生理、植物开花发育调控提供新的研究思路。