玉米果穗不同部位种子活力差异的机理及功能标记开发

Seed vigor is an important indicator of evaluating seed quality. To sow seeds with high vigor is a simple and efficient method for increasing crop yield. In previous publications on mechanisms of seed vigor, seeds with different vigor, caused by ageing and priming and affected mainly by external environmental factors, were their materials. In the present study, however, our materials are the maize seeds located in different position on the ear which have different vigor generated during grain filling stage and mainly affected by intrinsic factors. The mechanism may differ with the former. In the present study, through comparative analysis of soluble sugar, phytohormone and activity of key enzyme of seeds located in different position on the ear, we will find functional markers closely related to seed vigor of them. By comparative analysis of digital gene expression profile of seeds with different grain position, we will find differentially expressed genes (DEG) of them firstly. And then we will do research about inducible expression patterns of upstream genes of DEG enriched metabolic pathways. After that, overexpress them in Arabidopsis, and then get seeds of transgenic plants for seed vigor detection. Finally, we will identify upstream genes closely related to seed vigor of seeds located in different position on the ear. Researches on these upstream genes will be of importance to understand mechanisms undelying different vigor of seeds with different grain position. The present project has not only theoretical importance but also practice guidance to seed producing and processing.

种子活力是衡量种子播种质量的重要指标，选用高活力种子是提高产量最简单有效的方法。前人对种子活力机理方面的研究，以通过老化或引发处理得到的活力有差异的种子为材料，其活力差异主要受外部因素影响，本研究以玉米果穗不同部位发育过程中自然形成的、存在活力差异的种子为材料，活力差异主要受内部因素影响，其机理很可能与前者不同。本课题通过对不同粒位种子可溶性糖、植物激素和关键酶活性的比较分析，发现与不同粒位种子活力密切相关的功能标记；通过数字基因表达谱比较分析，发现不同粒位种子差异表达基因，选择差异表达基因显著富集通路中的上游基因，对其诱导表达模式进行研究，将其在拟南芥中过量表达，收获种子后检测活力水平，发现与不同粒位玉米种子活力差异密切相关的上游基因，这类基因的研究对于理解不同粒位种子活力差异的机理具有重要意义。本项目对于指导种子生产、加工具有重要的理论意义和潜在的应用价值。

种子活力是衡量种子播种质量的重要指标，选用高活力种子是实现一播全苗、苗强苗壮的重要保障。前期研究发现玉米果穗中、下部种子活力显著高于果穗上部种子，中、下部种子活力高不是表现在出苗更快，而是表现在幼苗更壮，苗强苗壮对于农业生产非常重要。.本项目首先研究了玉米果穗不同部位种子抗寒性、细胞膜完整性及吸胀过程中细胞膜修复能力、激素水平和关键酶活性等生理生化水平的差异；然后分别从转录组、蛋白组和DNA甲基化组水平研究了果穗不同部位种子在吸胀不同时间的差异。研究发现，中部种子抗寒性较强，干种子细胞膜完整性及吸胀过程中细胞膜修复能力较强，α-淀粉酶和乙醇脱氢酶活性较高，控制萌发的关键激素ABA/GA4比值较低；组学研究发现，果穗不同部位种子活力的差异受表观遗传机制调控，中部种子的DNA甲基化和H3K9me3水平低于上部种子；中部种子吸胀后在转录水平能更迅速地做出反应；中部种子吸胀24h时的蛋白质合成能力、能量代谢水平和细胞分裂速度均较高。综合本项目研究结果，认为α-淀粉酶和乙醇脱氢酶活性、胚中的ABA/GA4相对值以及ADP, ATP载体蛋白GRMZM2G105571_P01、磷酸盐载体蛋白GRMZM2G015401_P01和水通道蛋白GRMZM2G103983_P01的相对表达量，可作为筛选能萌发出壮苗的种子的功能标记。.前人对种子活力机理方面的研究，以通过老化或引发处理得到的活力有差异的种子为材料，其活力差异主要受外部因素影响，本研究以玉米果穗不同部位发育过程中自然形成的、存在活力差异的种子为材料，活力差异主要受内部因素影响，类似研究未见报道。本项目取得结果对于理解不同粒位种子活力差异的机理具有重要理论价值，对于指导高活力种子生产和种子精选分级具有潜在的应用价值。