棉花是重要的经济作物，类黄酮含量丰富。但类黄酮影响棉花形态发育特别是纤维发育的研究较少，已有的研究也主要在棕色棉花中。进化分析表明棉花人工驯化过程中，类黄酮代谢在白色棉花中下调，但白色棉花表达谱数据显示类黄酮代谢相关基因在纤维发育过程中仍然非常活跃。本实验室前期研究发现抑制GhF3H的表达纤维变短变细，可能是该酶上游物质NAR（柚皮素）的积累抑制了纤维的伸长和次生壁的合成。基于这些结论本项目拟通过转基因棉花改变类黄酮代谢途径11个基因特别是CHS（查尔酮合成酶）和DFR（二氢黄烷醇4-还原酶）的表达水平，研究转基因棉花纤维品质和类黄酮含量的关系；分析不同纤维品质的棉花（遗传群体）内源类黄酮含量与纤维品质相关性；将这些基因的RNAi结构导入到棕色棉当中，探讨棕色色素沉积成分。综合这三个研究内容从代谢网络水平分析类黄酮物质和纤维品质的关系，阐明类黄酮调控纤维发育机理。

Flavonoids are a class of important and rich secondary metabolites in plant species. As an important economic crop, although the secondary metabolites content in cotton is very rich, there are few studies investigting effects of secondary metabolites on cotton morphogenesis, especially fiber development, with most of reserches just focused on brown cotton. In the process of cotton domestication, flavonoid metabolites in white cotton were down-regulated, but expression profiling data showed that flavonoid metabolism-related genes in the white cotton fiber were still very active. Our previous study found that inhibiting the expression of GhF3H resulted in shorter and thinner fibers by inefficiency of enzyme of GhF3H,which led to accumulation of upstream metabolite NAR (naringenin) that inhibited fiber elongation and secondary wall synthesis. In this study we will regulate expression levels of 11 genes involved in flavonoid pathway, specifically CHS (chalcone synthase) and DFR (dihydrogen flavanols 4 - reductase), by transgenic cotton, to investigate the relationship between transgenic cotton fiber quality and flavonoid content. We will also analyze the correlation between endogenous flavonoids and fiber quality via genetic analysis strategy. The RNAi constructs of these genes will be introduced into the brown cotton to explore the process of the brown pigmentation. By the above experiments,we expect to clarify the effects of flavonoid metabolic networks on fiber quality and the mechanism of flavonoids regulation of fiber development.