玉米穗长主效基因qEL10的克隆与功能分析

Ear length is strongly associated with maize kernel yield, and is thus the important target of maize breeding. However, the genetic mechanism underlying formation of ear length remains largely unknown. Previously, we constructed single segment substitute lines with two elite inbred line Xu178 and Zong3, and identified a line, 15SS1283, the ear length of which was significantly longer than that of Xu178. Subsequently, using the BC5F1 population of 15SS1283 and Xu178, the QTLqEL10 was mapped to a 11.3Mb region between molecular markers M169 and M116. In this present project, we will apply BC7F2 population, fine mapping, the sequencing of candidate genes and transgenic technology to clone the qEL10. For dissecting the molecular mechanism of formation of ear length, the morphological difference of female inflorescence meristem of 15SS1283 and Xu178 will be analyzed by scanning electron microscope. The expression difference of qEL10 gene in 15SS1283 and Xu178 will be determined by qRT-PCR and mRNA in situ hybridization. Additionally, favorable haplotype of qEL10 will be exploited via association analysis. This study will provide a new gene resource and theoretical basis for the breeding of new maize varieties with high yield.

玉米穗长与籽粒产量密切相关，是高产育种中重要选择目标。然而穗长形成的遗传调控机制并不清楚。课题组前期利用许178背景的综3单片段代换系为材料，发现代换系15SS1283穗长显著长于受体许178。通过许178与15SS1283构建的BC5F1群体将控制穗长的主效QTLqEL10定位于标记M169和M116之间，物理距离为11.3Mb。本项目拟利用最小单片段代换系与许178组配的 BC7F2群体，通过精细定位、候选基因测序和转基因技术，克隆穗长主效QTLqEL10。通过扫描电镜分析单片段代换系和受体许178雌穗分生组织的形态差异，通过qRT-PCR、原位杂交技术明确qEL10基因在单片段代换系和受体许178中的表达差异，从而初步解析qEL10调控穗长形成的作用机理；应用候选基因关联分析挖掘qEL10优良单倍型。本研究将为高产玉米新品种的选育提供基因资源和理论依据。

产量是玉米生产过程中的首要目标，穗长是影响玉米产量的重要因素之一。本项目通过对许178（短穗）背景的单片段代换系（长穗）进行精细定位、候选基因测序和表达分析，鉴定到一个调控玉米穗长的主效基因ZmDCL4。在基因启动子区，许178存在一个转座子插入，单片段代换系无转座子插入；单片段代换系幼嫩雌花序ZmDCL4基因表达量显著高于许178。通过候选基因关联分析，在ZmDCL4基因区挖掘到一个与穗长表型显著关联的SNP位点。转录组测序和激素含量分析表明ZmDCL4可能通过激素途径调控玉米穗长的发育。研究结果为高产玉米新品种的培育提供了基因资源。