茶树儿茶素组分含量主效QTL精细定位及候选基因挖掘

Catechins are one of the main components which determine processing suitability of fresh tea leaves and sensory quality of made tea. Catechins content of fresh leaves directly affect tea fermentation and the taste of made tea. Therefore, illustrating molecular mechanisms controlling catechins content will be useful for quality breeding of tea plant. In the previous investigations, we have detected two stable and major QTLs for tea catechins content by linkage mapping based on an F1 segregating population. In this program, we will use NGS-based reduced-representation sequencing technology to increase marker density in the positions, close to where the QTLs located in the linkage map. Fine mapping of two major QTLs will be performed by association mapping using a natural population consisting of 371 tea plant accessions, and then candidate gene mining will be carried out by chromosome walking and bioinformatics analysis. Furthermore, gene expression pattern will be analyzed by qRT-PCR, and elite alleles associated with catechins content will be measured in the representative cultivars of tea plant. The results of this program will surely enrich our understanding of genetic mechanisms of tea catechins, and can serve as the theoretical basis and provide material resources for future genetic improvement of tea plant.

儿茶素是决定茶叶适制性和加工品质的主要组分之一，其含量的高低影响着茶叶的发酵能力及其茶汤的滋味。因此，研究控制儿茶素组分含量的分子机制，可以为茶树品质育种提供理论依据。课题组前期通过构建F1分离群体，联合多个环境表型，首次鉴定出2个稳定表达的儿茶素组分含量主效QTL。在此研究基础上，本项目拟采用简化基因组测序技术对目标QTL区域进行标记加密，利用371份茶树种质群体进行标记和表型性状的关联分析，实现对目标QTL进行精细定位，然后通过染色体步移和生物信息学分析，挖掘目标QTL所在区域的候选基因，并进一步利用荧光定量RT-PCR检测基因表达水平的差异，探讨其调控机理和作用模式，同时发掘优异等位变异及其载体品种。本项目的成功实施将丰富儿茶素性状的遗传理论，为今后茶树遗传改良提供必要的理论和材料基础，具有重要的理论意义和应用价值。

儿茶素是茶叶的重要品质成分，阐明控制儿茶素含量的分子机制是开展茶树品质育种的基础。本项目采用简化基因组测序技术构建高密度遗传图谱，对前期定位的目标QTL进行标记加密，并利用生物信息学分析、基因表达分析和关联分析等手段，进行目标QTL的精细定位和候选基因挖掘。主要研究结果如下：（1）采用SLAF-Seq技术对作图群体亲本以及F1子代进行简化基因组测序，开发了6042个SNP标记对SSR遗传图谱进行加密，将平均图距缩小至1.0 cM；（2）综合5年表型数据，将目标QTL定位在连锁群LG11的12.3-15.5 cM，遗传效应分析表明，目标QTL主要控制二、三羟基儿茶素比例；（3）利用极端表型样本进行转录组分析，发现F3’5’H表达量与二羟基儿茶素含量呈负相关，基因定位结果显示，F3’5’H位于目标QTL区间；（4）克隆F3’5’H基因组序列，发掘了132个SNP，并利用自然群体和F1群体进行关联分析，发现10个功能性SNP位点。