大麦阶段性白化基因的精细定位及候选基因分析

Variations of leaf color are very special in the kingdom of plant, and different kinds of them have been reported. As a visualized marker, this type of variation has been used successfully in illustrating the pathway of photosynthesis and cultivation of male sterile line in rice, so the importance of it in therotical study and heterosis utilization is re-recognized, and scientists are paying more and more attention on it..Though dozens of mutants with changed leaf color have been identified, few genes controlled them have been isolated using map-based cloning. The natural mutant "whs18" was found from "Edamai No.6" in the field, which showed stable and inheritable character of stage green-revertible albino. Compared with the original parent, the flag leaf of "whs18" was shorter, heading date and the mature stage were later, while the other agronomic traits showed no significant change, such as plant height, number of spikes, setting percentage, thousand kernel weight. Further anlaysis showed that this interesting phenomemon was controlled by a single recessive nucler gene, and was named SGRA (Stage Green-Revertible Albino). Based on the F2 population derived from "Edamai9706" and "whs18", this study will mainly focus on mapping and fine mapping of this gene. Potential candidate gene(s) will be screened and analyzed with the help of the colinearity between barley and rice、wheat、brachypodium genomes. Cause of the formation of this trait will also be discussed.The current study will provide valube information for cloning of SGRA gene using forward genetic methods and fully understanding the molecular mechanisms of the formation of albino in barley, as well as utilizing the gene and the mutant in agriculture in future.

叶色突变是植物界中的一种特殊现象，存在多种变异形式。作为直观的形态标记，叶色变异在解析光合作用途径和作物杂交育种中已得到成功应用。尽管已经报道了近百个叶色突变体，通过图位克隆所获得的叶色调控基因却很有限。whs18是本课题组在鄂大麦6号中发现的自然白化突变株，叶片由下至上表现为稳定且可遗传的绿叶-条状白化叶-绿叶的立体表现特征。与原始亲本相比，突变体旗叶显著变短，抽穗期和成熟期略晚，但株高、穗数、结实率、千粒重等农艺性状无明显差异。前期结果表明该阶段性白化性状受一对隐性核基因控制，命名为SGRA。本项目拟首先利用衍生于鄂大麦9706和whs18的F2分离群体对该基因进行初步定位，在此基础上通过比较基因组学等方法进行该基因的精细定位和候选基因筛选，并对该性状的形成原因进行初步探讨，为克隆该基因并研究其与大麦阶段性白化的关系奠定基础，为最终在分子育种和农业生产上应用该基因和突变体提供理论依据。

叶色突变是特异存在于植物界的一种普遍现象，存在多种变异形式。随着越来越多的叶色突变体被深入挖掘，这类突变体已成为解析植物光合作用、光形态建成以及抗病机制等代谢过程的理想实验材料。另外，作为极易辨别的形态标记，叶色标记已被我国科学家成功应用于培育水稻不育系，并用于提高杂交种子的纯度。叶色突变在理论研究及育种中的应用价值也因此得到重新认识，并越来越受到科学家的关注。大麦阶段性白化突变体“whs18”是本课题组在鄂大麦6号中发现的天然突变株，初步探讨该性状形成原因并对其调控基因进行定位，将为我们进行该基因的克隆并研究其与大麦阶段性白化性状的关系奠定基础，并为我们最终在农业生产上应用该性状及其调控基因提供理论依据。经过连续多年的田间观察，我们发现在正常田间生长条件下，该突变体前期叶片表现正常绿色，5-6叶期开始，新生叶逐步经历黄化、白化、条纹白、转绿的阶段性变化过程，整个过程约持续3个月。与野生型相比，whs18旗叶显著变短，抽穗期和成熟期略晚。阶段性白化对大麦的株高、穗数、结实率、千粒重等重要农艺性状和产量性状也产生了不同程度的负向影响。该阶段性白化性状受温度诱导，而且该性状的产生与相应叶片内叶绿素含量的降低及叶绿体超微结构受损有关。该性状是由一个隐性核基因控制的质量性状，暂将其命名为HvSGRA（Stage green-revertible albino）。利用衍生于鄂大麦9706和whs18的F2分离群体，通过基于SSR和SLAF-seq的BSA法，最终将该基因定位在大麦基因组上两个相邻的FP contig之间，其中包含6个功能基因。对这6个基因进行克隆和测序比较发现，与野生型相比，whs18中fructokinase 1-like 基因的第三个外显子发生了一个C-A突变，从而产生了一个终止密码子，可能导致该基因翻译的提前终止，并导致阶段性白化现象的发生。进一步进行该基因的图位克隆并验证其与性状的关系也将为我们进一步深入探讨该性状形成的机理及基因的作用机理奠定基础，为该突变体及其调控基因在农业生产和作物育种中得到成功应用提供理论依据。