劣变燕麦种胚细胞及线粒体AsA-GSH循环响应抗坏血酸引发的协同机制

Oat is widely cultivated as a high quality crops for grain and forage, but the higher lipid content has limited the extensive use of its seeds due to the potential for lipid-derived rancidity and the associated deterioration. Priming with physiological activator is an important way to improve the seed vigor e.g. ascorbic acid (AsA). AsA is an important physiological activator, which participates in many metabolism and redox reaction. Thus, there are very important theoretical value and practical meaning to study the mechanisms of priming with AsA for maintaining seed vigor and exerting genetic potential. Oat seeds with 10% moisture content were deteriorated in 45°C to obtain samples with specific level of vigor, and primed different time with AsA. Their embryo is separated to plantule, hypocotyle and radicle, the changes in cellular and mitochondrial ultrastructure were observed by transmission electron microscope in different parts. The expression levels of enzymes in cellular and mitochondrial AsA-GSH cycle are determined in different embryonic parts by mass spectrometry and SWATH, and functional genes associated with expression of differential proteins were identified by qRT-PCR. The collaborative mechanism of AsA-GSH cycle between embryonic cells and their mitochondria will be illuminated by this study, and to provide theoretical basis for systematically revealing the internal mechanism of improving seed vigor by AsA priming.

燕麦是广泛种植的优质粮饲兼用作物，其种子因富含脂肪而易发生劣变，从而降低其利用价值。采用抗坏血酸（AsA）等生理活性物质引发是提高种子活力的重要途径。AsA是种子内主要的生理活性物质，参与许多物质代谢和氧化还原反应。因此，探索AsA引发种子的抗氧化机制对保持种子活力和发挥其遗传潜能具有非常重要的意义。本项目以10%含水量燕麦种子为材料，经45°C控制劣变后，用AsA引发不同的时间段获得试验样品。将种胚分离为胚芽、胚轴和胚根，通过透射电镜观察其细胞及线粒体超微结构的动态变化，采用SWATH技术分析其细胞和线粒体内抗坏血酸-谷胱甘肽（AsA-GSH）循环酶的差异表达，并结合qRT-PCR技术验证AsA-GSH循环差异表达酶的基因转录。本研究可阐明AsA引发燕麦种胚细胞和线粒体AsA-GSH循环的协同抗氧化机制，为系统揭示AsA引发提高种子活力的内在机理提供理论依据。

种子活力会在贮藏过程不断下降，这是限制农牧业生产成败的关键。所以，探索如何最大限度地保持种子活力，对植物种质资源多样性的科学利用具有至关重要的意义，同时也是一个难于解决的课题。抗坏血酸（AsA）是生命体内普遍存在的生理活性物质，也是许多物质代谢和氧化还原反应的重要参与者，其含量减少是导致种子活力下降的主要原因。因此，本研究以燕麦种子为材料，通过分析AsA引发对劣变燕麦种子活力的修复水平，探索劣变燕麦种子经AsA引发后种胚细胞及线粒体超微结构变化及其AsA-GSH循环的抗氧化响应。研究发现，1 mmol L-1的AsA引发0.5 h时劣变燕麦种子的活力水平最高，其种胚线粒体AsA-GSH循环的抗氧化酶活性最强，线粒体超微结构最完整；AsA引发的修复作用主要依赖于线粒体APX和MDHAR，两者在清除H2O2过程的贡献大于其GR和DHAR，且其关键是APX蛋白的差异表达上调，这为种子贮藏及其科学利用提供了理论依据。