State Key Laboratory of Genetic Engineering, Zhongshan Hospital and School of Life Sciences, Human Phenome Institute, Metabonomics and Systems Biology Laboratory at Shanghai International Centre for Molecular Phenomics, Fudan University, Shanghai 200438, P. R. China.
CAS Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Innovation Academy for Precision Measurement Science and Technology, CAS, Wuhan 430071, P. R. China.
J Proteome Res. 2020 Jun 5;19(6):2457-2470. doi: 10.1021/acs.jproteome.0c00181. Epub 2020 May 27.
Seed germination is essential for plant survival, germplasm resource preservation, and worldwide food supplies, although the germination-associated seed biochemical variations are not fully understood. With the NMR-based metabonomics, we quantitatively analyzed the comprehensive metabolite composition (metabonome) of mung-bean () seeds at eight time points of germination covering all three phases. We found that mung-bean seed metabonomes were dominated by 63 metabolites including lipids, amino acids, oligo-/monosaccharides, cyclitols, cholines, organic acids, nucleotides/-sides, nicotinates, and the shikimate pathway-mediated secondary metabolites. During germination, metabolic changes included mainly the degradation of proteins and raffinose family oligosaccharides, glycolysis, tricarboxylic acid (TCA) cycle, anaerobic respiration, biosynthesis of osmolytes and antioxidants together with the metabolisms of nucleotides/-sides, nicotinates, and amino acids. Oligosaccharide degradation was the primary energy source for germination, which coupled with the mobilization of starch and protein storages to produce sugars and amino acids for biomaterial and energy generations. Osmotic and redox regulations were prerequisites for seed germination together with mitochondrial reparations and generations to enable TCA cycle. During the postgermination growth stage (phase-3), the use of small molecules including amino acids and saccharides was switched to meet the growth demands of radicle cells. Small metabolites passed freely through seed testa leaking into the culture media during early germination but were reabsorbed by seed cells around the postgermination growth stage. Extra after-ripening accelerated these metabolic processes of seeds in phase-1, especially the biosynthesis of cyclitols, choline, and nicotinates, increasing the germination uniformity in terms of speed and percentage. Germination-resistant seeds were incapable of activating the germination-associated metabolic processes.
种子萌发对于植物的生存、种质资源的保存和全球粮食供应至关重要，但人们对与萌发相关的种子生化变化还不完全了解。本研究采用基于 NMR 的代谢组学方法，定量分析了绿豆（）种子在萌发的三个阶段的 8 个时间点的综合代谢产物组成（代谢组）。结果发现，绿豆种子代谢组主要由 63 种代谢物组成，包括脂质、氨基酸、寡糖/单糖、环己醇、胆碱、有机酸、核苷酸/核苷、烟酸和莽草酸途径介导的次生代谢物。在萌发过程中，代谢变化主要包括蛋白质和棉子糖家族寡糖的降解、糖酵解、三羧酸（TCA）循环、无氧呼吸、渗透剂和抗氧化剂的生物合成以及核苷酸/核苷、烟酸和氨基酸的代谢。寡糖降解是萌发的主要能量来源，它与淀粉和蛋白质储存的动员相结合，为生物材料和能量的产生提供糖和氨基酸。渗透调节和氧化还原调节是种子萌发的前提条件，同时伴随着线粒体的修复和产生，以维持 TCA 循环。在萌发后的生长阶段（阶段 3），小分子量化合物（包括氨基酸和糖）的利用被切换以满足胚根细胞的生长需求。在早期萌发过程中，小分子可以自由通过种皮渗漏到培养基中，但在萌发后的生长阶段周围的种子细胞会重新吸收这些小分子。后熟加速了种子在阶段 1 中的这些代谢过程，特别是环己醇、胆碱和烟酸的生物合成，提高了种子萌发的速度和百分率的均匀性。萌发抗性种子无法激活与萌发相关的代谢过程。
