Unité de Nutrition Azotée des Plantes, Unité de Recherche 511, Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, Centre de Versailles-Grignon, Route de Saint-Cyr, F-78026 Versailles Cedex, France.
New Phytol. 2009 Oct;184(2):340-352. doi: 10.1111/j.1469-8137.2009.02966.x. Epub 2009 Jul 27.
*The main steps of nitrogen (N) metabolism were characterized in the developing ear of the two maize (Zea mays) lines F2 and Io, which were previously used to investigate the genetic basis of nitrogen use efficiency (NUE) in relation to yield. *During the grain-filling period, we monitored changes in metabolite content, enzyme activities and steady-state levels of transcripts for marker genes of amino acid synthesis and interconversion in the cob and the kernels. *Under low N fertilization conditions, line Io accumulated glutamine, asparagine and alanine preferentially in the developing kernels, whereas in line F2, glutamine and proline were the predominant amino acids. Quantification of the mRNA-encoding enzymes involved in asparagine, alanine and proline biosynthesis confirmed that the differences observed between the two lines at the physiological level are likely to be attributable to enhanced expression of the cognate genes. *Integrative analysis of physiological and gene expression data indicated that the developing ear of line Io had higher N use and transport capacities than line F2. Thus, in maize there is genetic and environmental control of N metabolism not only in vegetative source organs but also in reproductive sink organs.
*本研究以先前用于研究氮利用效率（NUE）与产量关系的遗传基础的两个玉米（Zea mays）品系 F2 和 Io 的发育穗为材料，对氮代谢的主要步骤进行了特征描述。*在灌浆期，我们监测了穗部和籽粒中氨基酸合成和相互转化标记基因的转录本的代谢物含量、酶活性和稳态水平的变化。*在低氮施肥条件下，品系 Io 优先在发育的籽粒中积累谷氨酰胺、天冬酰胺和丙氨酸，而在品系 F2 中，谷氨酰胺和脯氨酸是主要的氨基酸。参与天冬酰胺、丙氨酸和脯氨酸生物合成的编码酶的 mRNA 定量证实，两条品系在生理水平上观察到的差异可能归因于同源基因的表达增强。*生理和基因表达数据的综合分析表明，与 F2 相比，Io 品系的发育穗具有更高的氮利用和运输能力。因此，在玉米中，氮代谢不仅在营养源器官中受到遗传和环境控制，而且在生殖汇器官中也受到遗传和环境控制。
