玉米叶夹角主效QTL的克隆与功能验证

Increasing plant density has become the most important technique for maize yield improvement in current maize production in China, in which modifying plant architecture is a major approach for breeding cultivars adapted to high-density planting. Leaf angle is a key trait that determines the plant architecture of maize. Therefore, examining the genetic and molecular mechanism underlying leaf angle is crucial to improve maize plant architecture for breeding cultivars adapted to high-density planting. Using a large population of introgression lines derived from a cross between a typical maize inbred line, W22 and a typical accession of Zea mays ssp. parviglumis, we performed a high-resolution quantitative trait locus (QTL) mapping for the leaf angle above the primary ear. Based on the previous progress, in this project, we will continue to fine map and clone the two big effect leaf angle QTLs located on chromosome 1 and 2, respectively. Through the study of genetic interaction between the two QTLs, genetic transformation, association mapping, and transcriptome sequencing, we aim to clone the genes for qLa1 and qLa2 and reveal the underlying molecular regulatory mechanism, and develop molecular markers for molecular marker-assisted breeding.

提高玉米种植密度已成为我国进一步提高玉米单产水平最重要的技术措施，株型改良是培育耐密高产玉米品种的主要手段，叶夹角是决定玉米株型紧凑程度的主要直观形态指标，研究玉米叶夹角的遗传与分子调控机制对玉米株型改良，培育耐密高产玉米新品种具有重要的理论和实践意义。课题组利用一套由玉米自交系W22与大刍草(Zea mays ssp. parviglumis)杂交衍生得到的渗入系群体为材料，对玉米穗上叶夹角进行了高精度的遗传解析。本项目将在前期研究基础上，对位于第1和第2染色体上较大效应的叶夹角QTLqLa1和qLa2进行进一步精细定位和克隆，通过遗传互作分析、遗传转化、关联分析、转录组测序等技术验证qLa1和qLa2候选基因功能及研究其分子调控机理，构建叶夹角分子调控网络，开发可用于分子标记辅助育种的分子标记。

提高玉米种植密度已成为我国进一步提高玉米单产水平最重要的技术措施，株型改良是培育耐密高产玉米品种的主要手段，叶夹角是决定玉米株型紧凑程度的主要直观形态指标，研究玉米叶夹角的遗传与分子调控机制对玉米株型改良，培育耐密高产玉米新品种具有重要的理论和实践意义。课题组利用一套由玉米自交系W22与大刍草(Zea mays ssp. parviglumis)杂交衍生得到的渗入系群体为材料，对玉米叶夹角进行了遗传基础解析，重点对位于玉米第2 染色体上的一个主效QTL Compact Plant Architecture 1 (CPA1)进行了精细定位，最终将CPA1限定在3kb的物理区间，该区间位于一个AP2 转录因子上游9kb的位置；时空表达分析表明，AP2基因叶环区的差异表达决定了CPA1近等基因系(NIL）间叶夹角的差异；RNAi植株与CRISPR/CAS9敲除植株叶夹角显著减小，而过表达植株叶夹角显著增加，说明AP2基因是调控玉米叶夹角大小的重要基因；遗传与互作实验表明AP2基因位于Lg1 、Lg2基因下游；携带大刍草等位基因的NIL和CRISPR/CAS9敲除株系在密植条件下（>5000株／亩）具有显著增产效应。关于CPA1基因克隆的主要研究结果文章正在撰写中，预计2018年上半年投出发表。受该项目的部分资助，课题组进行了玉米－大刍草渗入系群体转录组分析和一个重要花期QTL的克隆，相应文章分别在Molecular Plant和PNAS发表。玉米－大刍草渗入系群体转录组分析发现CPA1的候选基因AP2转录因子显著差异表达，为随后CPA1近等基因系的时空表达分析提供了重要线索。玉米花期QTL克隆中所利用的精细定位、关联分析和遗传转化等技术为CPA1的克隆提供了重要技术支撑。