GhXTH8调控棉花棉纤维发育及品质形成的分子机理研究

The fiber quality traits of cotton are quantitative characters controlled by multiple genes. It is very important to study the function and mechanisms of the genes controlling fiber quality for the molecular breeding in cotton. In our previous study, one major QTL controlling multiple fiber quality traits was identified on chromosome 6 with (Yumian 1 × T586) recombinant inbred line population in upland cotton, and then the possible QTL candidate gene encoding xyloglucan endotransglucosylase/ hydrolase 8 (XTH8) was identified through fine-mapping, RNA-Seq analysis and comparative cloning. Firstly, based on constructing over-expression, RNAi and fiber-specific expression vectors, the present study will analyze the function of XTH8 through analyzing the characteristics of fiber quality and fiber development, testing the component of carbonhydrates and the activity of XTH8 enzyme. Secondly, the present will analyze the expression of different promoters and the subcellular localization of XTH8 protein. Finally, the present study will analyze the pathway which XTH8 participates in through RNA-sequncing. The project not only aims to elucidate the relationship between GHXTH8 and the QTL controlling multiple fiber quality traits, but also provides a basic work for understanding the molecular mechanism of cotton fiber quality formation and molecular breeding in cotton.

棉花纤维品质性状是多基因控制的数量性状。研究棉花纤维品质性状基因/QTL的功能和作用机理对棉花分子育种具有重要意义。项目组前期利用（渝棉1号×T586）重组近交系群体在第6染色体定位到一个控制多个纤维品质性状的主效QTL，随后通过精细定位、RNA-Seq分析和对比克隆鉴定到一个编码木葡聚糖内糖基转移酶/水解酶基因GHXTH8的可能QTL候选基因。本项目拟通过构建GHXTH8超量、RNAi干涉和纤维特异表达载体，分析转基因后代的纤维品质性状表现和纤维发育特点，碳水化合物组分和木葡聚糖内糖基转移酶活性。构建启动子表达载体分析不同启动子的达特性，并对GHXTH8蛋白进行亚细胞定位。采用表达谱测序分析GHXTH8基因可能参与的调控途径。项目的完成可以揭示GhXTH8基因与棉花纤维品质QTL间的关系，以及GhXTH8基因在纤维发育中的作用，为阐明棉花纤维品质形成的分子机理和棉花分子育种奠定基础。

棉花纤维品质性状是多基因控制的数量性状。研究棉花纤维品质性状基因/QTL的功能和作用机理对棉花分子育种具有重要意义。项目组前期利用（渝棉1号×T586）重组近交系群体在第6染色体定位到一个控制多个纤维品质性状的主效QTL，随后通过精细定位、RNA-Seq分析和对比克隆鉴定到一个编码木葡聚糖内糖基转移酶/水解酶基因GHXTH8的可能QTL候选基因。本项目构建了GHXTH8超量、RNAi干涉和纤维特异表达（纤维早期表达E6和中后期表达FblA2）载体，利用农杆菌侵染下胚轴的方法分别将不同启动子载体转入YZ-1；结合GHXTH8基因表达量和纤维品质检测结果发现，在纤维起始阶段或发育早期，超量表达GhXTH8可以促进纤维突起和伸长，下调该基因也会对纤维突起和伸长抑制作用，而在纤维发育中后期超量表达该基因不影响棉花纤维品质，说明GhXTH8基因在棉花纤维的起始和发育早期有重要作用。项目的完成获得大量GhXTH8转基因棉花，为进一步揭示GhXTH8调控纤维发育奠定了基础。