大豆贮藏蛋白β亚基含量主效QTL（qBSC-1）的图位克隆

β subunit is one of the major components of 7S conglycinin of soybean seed storage protein. Reducing of β subunit content improve protein nutritional quality, but for the processing property, lower β subunit content has its pros and cons. Therefore to clarify the genetic and molecular mechanism of β subunit content is of great significance to different purpose-orientated soybean protein quality improvement and breeding. Previously we found the β subunit content is controlled by a novel single locus, named qBSC-1, which explained 72.75% of phenotypic variance, located on the chromosome 20 of soybean genome. qBSC-1 spans a region of 1.5cM, which equals to a physical distance of 266kb, including 23 predicted gene models. In this project, we plan to first develop mapping markers based on genome resequencing data, and fine map qBSC-1 using F6 residual heterozygous lines derived from a cross between a land race with low β subunit content and a cultivar with normal β subunit content as enlarged mapping population. The preliminary molecular mechanism ofβsubunit content regulation would be addressed by functional complementary analysis and spatio-temporal expression analysis. At the meanwhile association study and clustering analysis would be utilized to develop markers tightly associated to β subunit content, and analyze qBSC-1 allele geographic distribution and the selection effect during the evolution of qBSC-1. This study would provide profound reference information for theβsubunit related germplasm evaluation and new cultivar breeding.

β亚基是大豆籽粒贮藏蛋白7S伴球蛋白的主要成分，降低β亚基含量有利于提高大豆蛋白品质，但对加工品质则有利有弊，阐明β亚基含量调控的遗传和分子机理对大豆蛋白品质定向改良及满足不同育种需求具有重要意义。前期研究发现，β亚基含量由一个主效QTL（qBSC-1）控制，解释72.75%的表型变异，定位在第20号染色体上遗传距离为1.5cM的区域，物理距离约为266kb，包括23个基因，是一个新的基因位点。本研究拟扩大定位群体，利用β亚基低含量地方品种与正常含量栽培品种杂交得到的F6代残余杂合系，采用已有重测序数据开发定位标记，快速精细定位qBSC-1，通过功能互补验证和表达分析，图位克隆qBSC-1，初步阐明β亚基含量调控的分子机理。同时通过关联分析和聚类分析，开发标记并分析qBSC-1等位基因地理分布规律和qBSC-1在进化过程中的选择效应，为β亚基含量相关种质资源评价和新品种培育提供参考。

β亚基是大豆籽粒贮藏蛋白7S伴球蛋白的主要成分，降低β亚基含量有利于增加含硫氨基酸含量，提高大豆蛋白品质，但对加工品质则有利有弊，但β亚基含量调控的遗传和分子机理仍不清楚。申请人前期研究结果显示，大豆β亚基含量受一个主效QTL（qBSC-1）控制，能解释72.75%的表型变异，定位在第20号染色体上遗传距离为1.5cM的区域，物理距离约为266kb，包括23个基因，是一个新的基因位点。本研究在前期基础上，扩大定位群体，但由于β亚基含量受环境影响较大，限制了有效群体的大小。本研究通过BSA测序、转录组分析、qRT-PCR分析，标记开发与基因型分析等方法，结合氨基酸含量分析，将定位区间缩小至93.5kb范围内，包含11个编码基因，其中2个基因表达水平发生变化，目前正在进行遗传互补验证。此研究为进一步阐明大豆β亚基调控肌理，为进一步提高大豆品质提供了理论依据。