基于全基因组关联的玉米叶片衰老的遗传解析

The most directly phenomenon of leaf senescence is chlorophyll breakdown. Chlorophyll, an important factor being yield, can capture the light energy and transform light to involve in the photosynthesis to provide basic energy for the life. The analysis of chlorophyll metabolism in maize leaves has important theoretical and practical significance for improving photosynthetic efficiency, improving maize yield and delaying senescence speed. Based on the data of 500 inbred lines and the corresponding 550k SNP markers provided by the National Maize Improvement Center, genome-wide association analysis would be conducted for the chlorophyll compounds content and degradation rate of the spike-leaf tissue in different days after pollination during the maturing stage. According to gene annotation, 3-5 genes would be selected for in-depth analysis. Also, F2 population T-test and expression analysis from different variants would be used to evaluate the genetic effects and expression patterns. Finally, identify the optimal alleles associated with the chlorophyll content and degradation rate, and preliminary dissect the genetic mechanism of leaf senescence in maize.

叶片衰老最直接的表现为叶绿素降解。叶绿素是产量形成的重要影响因子,通过捕获光能和转化光能完成光合作用为生命体提供基本能源物质。玉米叶片叶绿素代谢机理的解析对改良玉米叶片光合效率，提高玉米产量和缓解叶片早衰具有重要的理论和实践意义。本研究在国家玉米改良中心提供的500份自交系的自然群体和对应的550k SNP的标记信息的基础上，以授粉后不同天数穗位叶组织中动态变化的叶绿素组分含量和降解速率为性状，采用全基因组关联分析方法、挖掘控制授粉后期叶绿素组分含量和降解速率的候选基因，根据基因注释选择3-5个基因挖掘功能位点；并在此基础上利用不同遗传背景的F2群体T-test、不同变异位点材料表达分析进行遗传效应和表达模式的评估，最终确定与叶绿素组分含量和降解速率相关的优良等位基因，初步解析玉米叶片衰老的遗传机理。

玉米叶片叶绿素代谢机理的解析对改良玉米叶片光合效率，提高玉米产量和缓解叶片早衰具有重要的理论和实践意义。本研究通过对玉米吐丝期叶绿素指数（SPAD值）开展全基因组关联分析，检测到 37 个显著性关联 SNP 标记，进一步开展功能富集注释和分析，锚定了参与色素合成和光合系统作用Zm00001d015331、Zm00001d004962、Zm00001d041824和Zm00001d015988等若干个候选基因。同时开展了代谢途径驱动的候选基因关联分析，以玉米脱镁叶绿酸氧化酶基因ZmPAO和红色叶绿素代谢产物还原酶ZmRCCR为目的基因开展了玉米成熟期后不同时期的候选基因关联分析，鉴定到这两个基因与叶绿素组分含量和降解相关的位点若干。最后，通过对黑暗诱导叶片衰老的转录组测序分析，构建了一个基因共表达网络，确定了与光合作用密切相关的10个模块和多个基因，并发现节点基因与调节网络，复制事件，驯化和改良相关，同时捕获了在不同光照环境中叶绿体光合装置和光合碳同化所涉及的基因集的动态表达图谱。本研究的结果可以进一步开展叶绿素代谢和光合机理研究提供一定的参考。