School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA.
J Exp Bot. 2014 Apr;65(7):1865-78. doi: 10.1093/jxb/eru012. Epub 2014 Jan 31.
In most plant species, amino acids are the predominant chemical forms in which nitrogen is transported. However, in nodulated tropical or subtropical legumes, ureides are the main nitrogen transport compounds. This review describes the partitioning of amino acids and ureides within the plant, and follows their movement from the location of synthesis (source) to the sites of usage (sink). Xylem and phloem connect source and sink organs and serve as routes for long-distance transport of the organic nitrogen. Loading and unloading of these transport pathways might require movement of amino acids and ureides across cell membranes, a task that is mediated by membrane proteins (i.e. transporters) functioning as export or import systems. The current knowledge on amino acid and ureide transporters involved in long-distance transport of nitrogen is provided and their importance for source and sink physiology discussed. The review concludes by exploring possibilities for genetic manipulation of organic nitrogen transporter activities to confer increases in crop productivity.
在大多数植物物种中，氨基酸是氮运输的主要化学形式。然而，在根瘤热带或亚热带豆科植物中，尿素是主要的氮运输化合物。本文综述了氨基酸和尿素在植物体内的分配，并追踪了它们从合成部位（源）到使用部位（汇）的移动。木质部和韧皮部连接源和汇器官，并作为有机氮长距离运输的途径。这些运输途径的加载和卸载可能需要氨基酸和尿素穿过细胞膜的运动，这一任务由作为出口或进口系统的膜蛋白（即转运蛋白）介导。本文提供了参与氮长距离运输的氨基酸和尿素转运蛋白的最新知识，并讨论了它们对源和汇生理学的重要性。本文最后探讨了通过遗传操纵有机氮转运体活性来提高作物生产力的可能性。
