野生二粒小麦4AL染色体臂上光周期敏感基因的精细定位与候选基因克隆

Photoperiod (Ppd) is a critical environmental factor affecting wheat heading date. So far, several Ppd genes were discovered on homoeologous group 2 chromosomes and 7BS of wheat. Phenotype analysis of a set of the chromosome arm substitution lines (CASLs) which were created by introducing wild emmer (Triticum turgidum subsp. Dicoccoides, TTD) into the background of common wheat variety Chinese Spring (CS) and kept only in my laboratory, revealed the significant differences in the heading date. One of the CASLs, CASL4AL showed the opposite heading date under short day and long day treatments compared to the CS, being 80 days later and 20 days earlier respectively. A dominant QTL was mapped on middle region of chromosome arm 4AL by using F2 populations derived from (CASL4AL x CS)F1, which is very sensitive to long day and named as QPpd-A3. These results indicated that there is a new Ppd gene on TTD chromosome arm 4AL. In this proposal, both CASL4AL and CS will be used to compared the difference of floral and inflorescence development under diverse photoperiod treatments. The recombinant inbred lines were developed in F6 generation progenies of the cross between CASL4AL and CS and will be used as the population to construct the fine map for cloning of QPpd-A3. Transcriptome analysis of the CASL4AL and CS will be carried out to select the candidate gene in the QPpd-A3 mapping regions. By using the bioinformatics procedure, the key genes related to photoperiod and their signal transduction pathways will be revealed by analysis of the transcriptome data. Combining all above analysis, this study will build a theoretical basis for studying the flowering mechanism in wheat, and also helps to provide the useful Ppd genes in the future wheat breeding.

光周期是影响小麦抽穗期的关键环境因子，迄今已在小麦第二染色体同源群和7BS上发现了光周期基因（Ppd-1和Ppd-B2）。在对中国春（CS）-野生二粒小麦（TTD）染色体臂置换系（CASL）的表型研究中，本课题组发现CASL4AL在短日/长日照下有截然不同的抽穗期，分别比CS迟抽穗约80天和早抽穗20天，并在TTD 4AL染色体臂远端定位到一个主效QTL，表明在TTD 4AL存在一个新的光周期敏感基因位点，命名为QPpd-A3。本项目以CASL4AL和CS为材料，通过不同光周期下幼穗发育进程观察以揭示光周期与CASL4AL幼穗发育的关系；利用构建的重组自交系进行QPpd-A3精细定位，结合转录组测序结果进行候选基因的筛选和克隆；利用生物信息学分析方法寻找小麦光周期相关信号转导通路；亲本间候选基因DNA序列比较和表达谱分析验证候选基因的功能。本研究将为丰富小麦光周期调控开花的理论奠定基础。

抽穗期是小麦生产非常重要的农艺性状，直接或间接影响产量、品质、抗病和抗逆等。目前基本明确控制小麦抽穗期的相关基因有三大类，即春化、光周期和早熟基因。光周期是影响小麦抽穗期的关键环境因子，迄今已在小麦第2染色体同源群和7BS上发现了光周期基因（Ppd-1和Ppd-B2），本项目组从以色列Weizmann科学院引进了一套以普通小麦品种中国春（CS）为背景的野生二粒小麦染色体臂置换系(Chromosome arm substitution lines, CASLs)，初步试验发现CASL 4AL 短日/长日照下有截然不同的抽穗期，分别比中国春（CS）迟抽穗约80天和早抽穗20天，在CASL 4AL染色体臂远端定位到一个主效QTL，表明在CASL 4AL存在一个新的光周期敏感基因位点，命名为QPpd-A3。本项目以CASL4AL和CS为材料，通过不同光周期下幼穗发育进程观察明确了不同光周期下CASL4AL和CS幼穗发育的差异以及其与光周期的关系；利用转录组测序分析揭示了CASL4AL染色体组成的复杂性，其中除了置换臂4A上存在大量的变异外，在其他染色体上也存在TTD片段的渗入。利用构建F2和F2:3进行精细定位将QPpd-A3锚定在M576与wmc468之间（616.23 Mb-617.00 Mb），并对其候选基因进行了分析。本研究将为丰富小麦光周期调控开花的理论奠定基础。