一品红DFR基因短日照条件下促进花青素积累的分子机理研究

Poinsettia not only has high ornamental value but also is an important model plant because the color of its bracts can turn red from green under short-day conditions. However, there are not researches on the molecular mechanism of anthocyanin accumulation in poinsettia. Our project group performed comparative transcriptome research and qualitative and quantitative analysis of anthocyanin in preliminary work. Based on comprehensive analysis of the data from these two studies, it was observed that the substantial accumulation of anthocyanin was probably promoted by DFR gene downstream anthocyanin biosynthesis pathway under short-day conditions. In view of this, our research will make use of methods of molecular genetics, such as correlation analysis of gene expression patterns and anthocyanin content, mutant phenotype recovery and genetic transformation, to further confirm the function of DFR gene in anthocyanin accumulation under short-day conditions. This research will also use methods of gene expression regulation, such as cloning of promoter and sequence analysis, transcription factor screening, analysis of transcription factor binding activity and analysis of the composition of transcription complex, to reveal the regulation mechanism of DFR gene expression inhibited by long-day conditions and promoted by short-day conditions. This research will not only elucidate the molecular mechanism of anthocyanin accumulation in poinsettia bracts but also provide the important theoretical basis for studies on metabolic network of plant anthocyanin. Moreover, the results of this research will provide theoretical supports and gene resources applied in genetic improvement of poinsettia.

一品红苞片短日照下由绿变红，因此其不仅具有极高的观赏价值，也是研究光周期调控花青素代谢的重要模式植物。然而，目前尚无光周期调控一品红花青素积累的分子机理研究。本项目组前期进行了一品红苞片比较转录组学研究和花青素定性定量分析，综合分析二者数据，发现花青素合成通路下游DFR基因很可能在短日照条件下促进花青素大量积累。因此，本项目将通过基因表达模式与花青素含量的关联分析、突变体表型恢复以及遗传转化等分子遗传学方法，进一步明确DFR基因短日照下促进花青素积累的功能；还将通过基因启动子克隆和序列分析、转录因子筛选、转录因子结合活性分析以及转录复合体构成分析等基因表达调控研究方法，明确长日照抑制而短日照促进DFR基因表达的调控机制。以上研究不仅有望揭示光周期调控一品红苞片花青素积累的分子机理，也可为植物花青素代谢网络研究提供重要理论依据。此外，本项目研究结果将为一品红的遗传改良提供理论支持和基因资源。

一品红（Euphorbia pulcherrima）是大戟科（Euphorbiaceae）大戟属的灌木或小乔木，其叶片在短日照条件下可由绿色变为红色、紫色、粉色等彩色的颜色，是重要的观赏树种。一品红不仅具有很高的观赏价值，还是用于研究光周期调控花青素代谢机理的重要模式植物。本研究比较了一品红绿色叶片和正在变红的苞片中，花青素生物合成通路的代谢产物组成模式和比较转录组学测序结果，旨在阐明其颜色变化的机理。代谢产物分析结果表明，花青素生物合成通路的远下游基因，例如黄烷酮醇还原酶（DFR，dihydroflavonol 4-reductase）基因，在绿色苞片中可能被抑制表达。转录组测序结果共获得91917条单一转录物，其中72条被归类于黄酮类生物合成通路。基因表达谱和色素化合物含量相关性的综合分析结果表明，DFR基因很可能在短日照条件下促进了一品红苞片花青素的积累。转基因研究表明，一品红DFR过量表达显著增加了拟南芥（Arabidopsis thaliana）中花青素含量。研究结果验证了DFR在短日照条件下能够促进一品红苞片花青素的积累。此外，本研究结果为阐明植物花青素生物合成机理提供了理论参考，也为一品红的遗传改良提供了候选基因。