玉米开花期QTL的克隆与功能验证

Flowering time is an important adaptive trait that can directly or indirectly affect crop yield and resistance to biotic and abiotic stresses. Dissecting the genetic architecture of maize flowering time and further elucidating the underlying molecular regulatory and evolutionary mechanism are not only crucial to understand the process of maize domestication and adaptation but also have important implications for maize breeding. Using a large population of introgression lines derived from a cross between a typical maize inbred line, W22 and a typical accession of teosinte (Zea mays ssp. parviglumis) , we conducted a high-resolution quantitative trait locus (QTL) mapping for maize flowering time. Based on the previous progress, in this project, we will continue to fine map and clone the big-effect flowering time QTL located on chromosome 3 (qDTA3-2). Through expression profiling, association mapping and genetic transformation, we aim to clone the gene for qDTA3-2 and reveal the underlying molecular regulatory mechanism, which will provide new information for constructing the molecular regulatory network of maize flowering time. By analyzing the natural genetic variation at the causal gene of qDTA3-2, molecular markers that tag the elite allelic variant will be developed and used for molecular marker-assisted breeding.

开花期是一个重要的适应性性状，直接或间接影响产量、抗病、抗逆等许多农艺性状，解析玉米开花期的遗传结构，研究其分子调控和分子进化机制，对于理解玉米驯化适应过程和指导育种实践具有重要意义。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866份渗入系群体为材料，对玉米开花期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3染色体上较大效应的开花期QTLqDTA3-2进行进一步精细定位和克隆。通过表达分析、关联分析和遗传转化等手段克隆qDTA3-2功能基因，研究其分子调控机制，构建玉米开花期分子调控网络，在自然群体中挖掘优良等位变异，开发可用于分子标记辅助育种的分子标记。

开花期是一个重要的适应性性状，直接或间接影响产量、抗病、抗逆等许多农艺性状，解析玉米开花期的遗传结构，研究其分子调控和分子进化机制，对于理解玉米驯化适应过程和指导育种实践具有重要意义。实验室前期利用一套由玉米自交系W22与大刍草杂交衍生得到的BC2S3群体对玉米开花期进行了遗传定位分析，本项目对位于玉米第3染色体上的开花期QTLqDTA3-2进行了精细定位和克隆。通过精细定位，最终将qDTA3-2限定于29kb的物理区间，确定其功能基因为ZmMADS69。利用突变体和过表达材料证实ZmMADS69是一个开花期促进因子，同时调控株型和产量性状。经过分子实验和遗传分析阐释了ZmMADS69调控玉米开花的分子通路，即ZmMADS69抑制ZmRap2.7的表达减轻ZmRap2.7对ZCN8的抑制，从而增加顶端分生组织中成花素复合体的含量，最终激活成花决定基因ZmMADS4和ZmMADS67表达，最终促进开花。此外，群体遗传学分析显示ZmMADS69在玉米的驯化适应过程中受到了强烈选择，ZmMADS69早花等位基因的选择促进了玉米从热带地区向温带地区的传播。这些研究结果增强了我们对玉米开花期分子遗传基础的理解，也为玉米的分子遗传改良提供了重要靶基因。相关研究结果已发表于New Phytologist杂志上，本项目为第一标注。