Metabolic phenotype of heterosis in Zea mays

玉米是一种重要的作物，也是杂种优势的模式系统。利用B73和Mo 17两个玉米自交系建立了杂种优势。本文将利用这些品系研究杂种优势对玉米籽粒淀粉合成的影响。将通过逆生物合成NMR光谱分析导致葡萄糖单元并入胚乳淀粉中的代谢物通量。在通过糖酵解、葡萄糖生成和戊糖磷酸途径掺入淀粉之前，葡萄糖的“再循环”将通过该方法定量测定。用[U-13 C6]葡萄糖和未标记葡萄糖的混合物标记发育中的玉米粒。在标记淀粉被水解并且通过定量NMR确定所得葡萄糖的同位素异构体组成之后，可以从这些数据重建葡萄糖单元的“代谢历史”。比较自交和杂交籽粒将产生关于淀粉的增加是基于代谢物通量的定性还是定量变化的信息。可溶性碳水化合物的同位素组成的测定将提供额外的信息。

Maize is an important crop and a model system for heterosis. Heterosis was established for two widely used elite maize inbred lines, B73 and Mo17. These lines will used here to study the effects of heterosis on starch biosynthesis in the maize seed. Metabolite flux leading to the incorporation of glucose units into starch of the endosperm will be analysed by retrobiosynthetic NMR spectroscopy. The 'recycling' of glucose prior to incorporation into starch via glycolysis, glucogenesis and the pentose phosphate pathway will be quantitatively determined by this method. Developing maize kernels are labelled with mixture of [U-13C6]glucose and unlabelled glucose. After labelling starch is hydrolyzed and isotopomer composition of the resulting glucose is determined by quantitative NMR the "metabolic history" of the glucose units can be reconstructed from these data. The comparison of inbred and hybrid kernels will yield information on whether the increase of starch is based on qualitative or quantitative changes in metabolite flux. The determination of the isotopomer composition of soluble carbohydrates will provide additional information.