大豆百粒重杂种优势位点qSWT_13_1遗传和分子机制研究

Soybean 100-seed weight is one of the three elements of yield components. However, the heterosis of 100-seed weight has not been reported. We have detected a major heterosis QTL for this trait (designated as qSWT_13_1) in an F2 population derived between a cultivar and wild soybean genotype. This QTL has been fine mapped on chromosome 13 using an F7:8 sub-population derived from near isogenic lines (NILS) and Barcsoyssr_13_911 and Barcsoyssr_13_918 were the two SSR markers flanking the locus. The physical distance between these two markers is about 80Kb and 6 candidate genes are contained in this chromosome segment. The 100-seed weight of those plants heterozygous at this locus was 4-5 g higher than those of the parent genotypes. We propose to investigate the genetic mechanism of heterosis by generating and analysing large segregating populations for the qSWT_13_1 locus. High-throughput genotyping will be exploited to identify individuals from the large segregating populations with various combinations of the candidate genes. The molecular basis of the heterosis would be further assessed using the yeast two-hybrid system and real time PCR. The related genes involved in qSWT_13_1 metabolism and signal transduction pathways will be analyzed by establishing the gene expression profile of the transcriptomics and defining the gene ontology function. The results of this work would be necessary for understanding the genetic mechanisms of heterosis effect of 100-seed weight.

百粒重是大豆产量构成三要素之一，百粒重杂种优势效应未见相关报道。申请人在栽培大豆和野生大豆杂交组合的F2群体中发现百粒重杂种优势位点qSWT_13_1，通过次生群体将其精细定位于13号染色体80Kb范围内，包含6个候选基因，杂合型较亲本型百粒重高4-5克。本研究拟在建立大规模分离群体基础上，通过高通量基因型筛选，创造候选基因重组型近等基因系，分析其杂种优势形成的遗传机制，明确等位基因的超显性效应或非等位基因间互补/互作效应；通过定量PCR确定候选基因表达量变化，酵母双杂交确定候选基因表达蛋白互作关系，分析杂种优势形成的分子基础；通过建立基因表达谱和差异基因功能注释，分析杂交种和亲本间qSWT_13_1下游代谢途径和信号转导途径相关基因表达量变化规律。本研究将首次在大豆中明确百粒重杂种优势效应形成的遗传机制，获得相应的分子生物学证据，并为下一步研究杂种优势代谢和信号转导途径筛选相关基因。

研究超显性效应遗传机制，是植物遗传学家和作物育种家共同努力的目标。本研究在利用大豆杂交组合“冀豆12”דZYD2738”，首次发现大豆百粒重杂种优势位点qSWT_13_1基础上，衍生形成包含7568个单株的次级分离群体，从中筛选原定位区间两侧标记Barcsoyssr_13_908和Barcsoyssr_13_936之间发生交换的关键交换单株共计152株。衍生形成152个NIL-F2次级分离群体。根据NIL-F2次级分离群体百粒重分布特征推测关键交换单株基因型。当百粒重在后代中呈现双峰分布特征，推测衍生出该次级分离群体的关键交换单株中，qSWT_13_1基因型为杂合；当百粒重在后代中呈现单峰分布特征，推测衍生出该次级分离群体的关键交换单株中，qSWT_13_1基因型为纯合。同时，在Barcsoyssr_13_908至Barcsoyssr_13_936之间，参考Williams82大豆公共基因组序列、野生大豆重测序结果，开发扩增效果好、亲本间表现多态的3个SNP/Indel/SSR标记。利用新开发的标记，检测关键交换株标记指纹图谱。结合关键交换株中qSWT_13_1基因型推断数据，通过高精度连锁分析，qSWT_13_1被进一步定位在Barcsoyssr_13_908和Barcsoyssr_13_922之间。通过生物信息学分析和亲本间序列比对，确定Glyma13g22030为候选基因，qSWT_13_1杂种优势效应是由Glyma13g22030单基因控制的超显性效应引起。针对qSWT_13_1的剩余杂合系在石家庄、兰州和杭州同时进行多环境评价，结果表明，该位点在3个环境下对百粒重、蛋白含量都具有杂种优势效应，而对油分含量无杂种优势效应。本项目执行期间，发表SCI收录研究论文2篇；申请受理专利1项（201410251971.3）；培养硕士研究生2名。