胡萝卜光周期调控抽薹开花相关基因的发掘及功能分析

Carrot (Daucus carota L.) is an out-crossing biennial species, and one of the most economical and important vegetable crops in the world. The premature bolting resulting in a complete loss of carrot commercial value has been the key effect on hindering the development of winter-spring plastic tunnel cultivation and spring cultivation in China. Limited progress has been reported on the control of bolting and flowering in carrot due to lacking the suitable materials. Vernalization is a checkpoint which carrot must pass, where premature bolting could be induced and advanced by long days (LD) in our previous study. This control was similar with those of Arabidopsis and Beet. In addition, high-throughput transcriptomic sequencing is essential to generate a large transcriptome sequence dataset for gene discovery especially to carrot, a species lacking genomic resources. In the study, a photoperiod control of bolting and flowering would be established with the wild species 'Songzi' which is very sensitive to cold temperature and LD, 'Amsterdam' resistant to premature bolting, and their backcrossing inbreed lines (BIL) with different charactersitcs of premature bolting and flowering. The transcriptome of 'Songzi' and 'Amsterdam' dealed with different days of LD will be sequenced and assembled into unigenes. The unigenes would be function annotated and grouped into different funtional categories. The unigenes differently expressed in response to LD/SD would be screened and functionally analyzed in BILs in order to find the genes related to bolting and flowering. Identification of these genes would be a key breakthrough to understand the mechanism of carrot premature bolting, and the special markers related with bolting and flowering time would be an effective tool for screening non-bolting germplasm and breeding varieties.

胡萝卜是人类维生素A的重要来源。先期抽薹已成为我国冬春大棚和早春露地栽培可持续发展的瓶颈。由于缺乏适宜的研究材料，胡萝卜抽薹开花分子机制研究进展缓慢。项目组前期工作表明胡萝卜先期抽薹是受到短暂低温作用后，在长日照条件下诱导发生的。本项目以低温和长日照极为敏感的'松滋野生'、耐抽薹的栽培种'Amsterdam'及其构建的具有不同先期抽薹开花特性的回交重组自交系（BIL）为素材，建立胡萝卜光周期开花调控模型，采用RNA-seq技术分析不同光照长度处理后各试材转录组差异基因表达，富集分析胡萝卜抽薹开花途径的相关基因，通过在BIL系开花调控过程中的功能分析确定目标基因。本项研究为胡萝卜先期抽薹的防控、种质资源抽薹特性精准鉴定、耐抽薹品种选育提供一个崭新的理论和技术平台。

胡萝卜是重要蔬菜作物之一，我国胡萝卜种植已形成了区域化、规模化、集约化的发展格局，但缺乏耐抽薹优良品种成为生产持续发展的“瓶颈”之一。由于缺乏适宜的研究材料，胡萝卜抽薹开花分子机制研究进展缓慢。本项目主要研究不同低温、日照长度、光照强度对‘松滋野生’（Ws）和‘Amsterdam’（Af）抽薹开花的影响，分析不同Ws染色体片段对BIL系先期抽薹发生的影响，采用RNA-seq技术比较分析不同日照长度处理后的Ws和Af的转录组基因表达差异，深入分析相关基因昼夜节律及其对抽薹开花的作用。结果表明胡萝卜先期抽薹发生受到基因型及环境共同互作，其中加性效应为主要遗传效应。低温春化是胡萝卜抽薹发生的必要条件，春化时间越长，抽薹发生越早，抽薹率越高，而且长日照、强光照可促进春化后植株先期抽薹的发生。通过转录组测序获得45条unigene与30个已知开花基因具有同源性，涉及光周期、春化、赤霉素及自主途径等。通过对Ws和Af不同生长季节的先期抽薹率与相关抽薹开花基因表达相关分析表明DcCOL2可延迟抽薹开花，其表达受到长日照的抑制，而DcCOL5a可促进抽薹开花，其受到长日照的促进，DcSOC1-1对于抽薹开花起着重要作用。本研究对于胡萝卜育种和栽培具有重要实践指导意义，在选育耐抽薹胡萝卜品种时不仅要注意春化作用，还应该注意光周期作用。