qFL-c10-1增加棉花纤维长度的机理研究

Cotton is an important natural fiber crop, which provides natural materials for textile industry. However, the improvement of fiber quality is very difficult, and it is especially difficult to keep or improvement yield synchronously. Previously, a lot of QTLs have been mapped by linkage and association analysis, however, few of them have been applied in cotton breeding because different parents are used and few stable favorite QTLs are found. On the other hand, reverse genetics have identified many genes related to fiber quality, but they have not been applied in cotton breeding. Therefore, exploring fiber quality related genes and their genetic mechanism through forward genetics will be helpful to the genetic improvement of cotton fiber quality..In our lab, more than 10 years ago, a F2 population was developed by crossing the fiber quality superior varity ‘DH962’ and high-yield cultivar ‘Jimian5’, a linkage map was constructed and used to QTL mapping fiber quality traits. Later, a recombinant inbred line (RIL) population was constructed by the single seed decent method; the fiber quality traits were phenotyped through 6 years at 2 sites and phenotypic data from 8 environments were obtained, and QTLs for fiber quality traits were mapped; At the same time, the RILs were crossed respectively with two parents to generate two immortalized backcross populations, which were phenotyped through 2 years at 2 sites to obtain phenotypic data from 4 environments. QTL mapping was also conducted on fiber quality traits. Among all these populations, a stable QTL, qFL-c10-1, was detected in the previous F2 population, a RIL population in 3 environments and the two BCF1 populations, explaining 5.79-37.09% of the phenotypic variations. The genetic interval of this QTL is 8.2cM, corresponding to 470kb of physical distance, containing twelve genes. Based on re-sequencing data of 282 upland cotton accessions, SNPs and Indels within the 470kb were used to conduct association mapping, and a significant locus was found to be located at the stop codon of Gh_A10G1922, which is consisted with the mutation in this gene. Tissue expression pattern indicated that Gh_A10G1922 is preferentially expressed during fiber elongation. Gh_A10G1922 is annotated to be a Kunitz type soybean trypsin inhibitor, which has not been reported in cotton. This study intends to study the function of Gh_A10G1922 in order to elucidate the genetic mechanism of this gene on fiber elongation, and to evaluate the effect of this gene on the improvement of fiber length by molecular marker assisted selection.

棉花是重要的天然纤维作物，但纤维品质的改良困难很大，通过QTL定位和反向遗传学发现了许多纤维品质QTL和基因，但尚未应用到育种中。本课题组10余年前以纤维品质优良品系DH962和高产品种冀棉5号构建了F2群体并用于QTL定位。之后，将其发展为RIL群体，同时该RIL群体与2个亲本回交，构建了2个永久回交群体。利用这些群体定位到一个多环境稳定的增加纤维长度的QTL，qFLc10-1。该QTL的遗传距离为8.2cM，对应470kb，有12个基因。结合重测序数据进行关联分析，关联到的显著性位点位于Gh_A10G1922的终止密码子处。该基因在纤维伸长时期优势表达，注释为Kunitz型大豆胰蛋白酶抑制因子，在棉花中尚未见报道。本研究拟对Gh_A10G1922进行功能研究以期阐明其对纤维伸长的作用机理，通过分子标记辅助选择评价其对纤维长度改良的效应。

棉花是世界上重要的经济作物之一，陆地棉占据每年棉花产量的95%。在很长一段时间里，育种者专注于提高棉花的产量。近年来，随着纺织工艺的不断创新，对棉花品质的要求越来越高，提高棉纤维品质变得极其重要。一般来说，棉纤维品质由五个性状组成，即长度、强度、马克隆值、伸长率和整齐度。其中，纤维长度是衡量纤维品质的主要因素。因此，精细定位并克隆陆地棉纤维长度相关的QTL位点，对了解纤维发育的遗传基础和促进棉花品质改良至关重要。.在前期研究中，本实验室以冀棉5号和DH962为亲本，构建了F2、重组自交系（RIL）和永久回交群体，并进行了产量和纤维品质相关QTL定位。在A10染色体上定位到了一个在多环境中稳定遗传的纤维长度QTL qFL-c10-1。基于前期的研究结果，利用重组系DJ61与冀棉5号构建了1081个单株的F2分离群体。通过连锁分析和后代重组实验，将qFL-c10-1定位到一个96.5 kb的基因组区域，该区域仅包含一个未有功能注释的基因Ghir_A10G022020（命名为GhFL10）。序列分析发现GhFL10在冀棉5号和DJ61的启动子区域和编码区存在多个变异，其中DJ61的启动子区有一个214 bp的缺失。组织表达模式分析表明，GhFL10基因在纤维伸长时期差异表达。亚细胞定位结果显示GhFL10在细胞核和细胞质内均有表达。因此，GhFL10是一种功能未知的蛋白质。利用RNA_seq技术寻找差异表达基因，同时使用酵母双杂交筛选与GhFL10相互作用的蛋白，我们找到了两个与GhFL10互作的差异表达NF-YA类转录因子。.本研究通过图位克隆找到了一个调控纤维长度的未知基因GhFL10，并通过蛋白互作找到了GhFL10的互作蛋白。该研究为棉花纤维伸长调控网络的构建提供了有利的基因资源，并且为后续的纤维伸长研究奠定基础。