LIR介导赤霉素与光强互作调控拟南芥开花的分子机制研究

Plant growth and development are coordinated controlled by endogenous hormones and environmental factors. The suitable flowering time is important for the reproduction of the plant and the continuation of the race. Both the gibberellin (GA) and light can promote the flowering time of plants, the mechanism of interaction between them is not clear. The early research of the project found that, increasing light intensity promoted flowering of Arabidopsis, and the regulation of flowering time was mediated by GA signaling pathway. The LIR (Light Intensity Response) gene was obtained by screening the expression profile of light intensity response genes, and found that overexpression of LIR transgenic plants showed the early flowering phenotype, and down-regulation of LIR plants showed the late flowering phenotype. Moreover, LIR could interact with DELLA protein which is the negative regulator of GA signaling pathway in yeast-two hybrid, and LIR could be transported long distances from the ground to the roots. Therefore, this project will further study the signaling pathway of LIR gene in the light intensity and GA regulation of Arabidopsis flowering, and demonstrate whether the LIR is the mobile signal molecule from mesophyll cells to vascular bundles which regulates the flowering, finally, establish the molecular mechanism of the interaction between GA and light signaling pathway in regulation of Arabidopsis flowering. This project will provide a potential way to improve the crop yield and quality through fine-regulation of the timing of floral transition in agricultural production.

植物的生长发育受内源激素和外界环境的协同调控。合适的开花时间对植物个体的繁殖和种族的延续都有重要意义。赤霉素（Gibberellin，GA）和光都能促进植物开花，但二者互作调控开花的具体机制并不清楚。前期研究发现，增加光强促进拟南芥开花；GA途径参与光强对拟南芥开花时间的调控。通过分析光强响应基因的表达谱获得LIR（Light Intensity Response）基因，发现过表达LIR的转基因植株早花，而下调LIR的植株则晚花；LIR能与GA信号途径的负调控因子DELLA蛋白互作；并且LIR蛋白能够从地上长距离运输至根部。在此基础上，本项目将进一步研究LIR基因介导光强和GA调控拟南芥开花时间的信号途径，阐述LIR是否是从叶肉细胞到维管束之间传递开花信号的分子，最终阐明GA与光强互作调控拟南芥开花的分子机制，为通过改变农作物的开花时间来提高其产量和品质提供理论知识和新的线索。

植物的生长发育受内源激素和外界环境的协同调控。合适的开花时间对植物个体的繁殖和种族的延续都有重要意义。赤霉素（Gibberellin，GA）和光都能促进植物开花，但二者互作调控开花的具体机制并不清楚。本项目研究发现，增加光强促进拟南芥开花，GA途径参与光强对拟南芥开花时间的调控。通过分析光强响应基因的表达谱获得LIR（Light Intensity Response）基因，发现过表达LIR的转基因植株早花，而下调LIR的植株则晚花。LIR参与光强对开花时间的调控，能够上调开花整合基因FT和SOC1的表达。遗传分析表明，LIR促进开花依赖于COP1-CO-FT途径。LIR通过与COP1蛋白互作抑制COP1对CO蛋白的降解，导致CO蛋白的积累，进而促进植物早花。进一步研究发现，GA信号途径的负调控因子DELLA蛋白与LIR蛋白能够在体内发生互作，GA促进LIR蛋白的积累，LIR的蛋白水平不仅受体内GA水平的调控，而且依赖于GID1-SLY1-DELLA信号途径。利用不同组织特异性启动子驱动LIR-GFP融合基因表达，发现叶肉细胞特异启动子pCAB3和维管束特异启动子pSUC2驱动的LIR-GFP都能促进拟南芥开花。在pCAB3::LIR-GFP植株中发现，除了在叶肉细胞检测到LIR-GFP信号外，在根的维管束细胞中也检测到LIR-GFP表达；而在pSUC2::LIR-GFP植株中，除了在维管束检测到LIR-GFP信号外，在叶肉细胞中也能够检测到LIR-GFP信号。嫁接实验证实LIR蛋白是一个可移动的信号分子，介导叶肉细胞和维管束之间开花信号的传递。通过本项目的研究，揭示了GA与光强互作通过LIR调控拟南芥开花的分子机制，这为通过改变农作物的开花时间来提高其产量和品质提供理论知识和新的线索。