Nitrogen (N)-fixing soybean plants use the ureides allantoin and allantoic acid as major long-distance transport forms of N, but in non-fixing, non-nodulated plants amino acids mainly serve in source-to-sink N allocation. However, some ureides are still synthesized in roots of non-fixing soybean, and our study addresses the role of ureide transport processes in those plants. In previous work, legume ureide permeases (UPSs) were identified that are involved in cellular import of allantoin and allantoic acid. Here, UPS1 from common bean was expressed in the soybean phloem, which resulted in enhanced source-to-sink transport of ureides in the transgenic plants. This was accompanied by increased ureide synthesis and elevated allantoin and allantoic acid root-to-sink transport. Interestingly, amino acid assimilation, xylem transport, and phloem partitioning to sinks were also strongly up-regulated. In addition, photosynthesis and sucrose phloem transport were improved in the transgenic plants. These combined changes in source physiology and assimilate partitioning resulted in increased vegetative growth and improved seed numbers. Overall, the results support that ureide transport processes in non-fixing plants affect source N and carbon acquisition and assimilation as well as source-to-sink translocation of N and carbon assimilates with consequences for plant growth and seed development.

中文翻译：

---

酰脲在非固色大豆光同化物从源到库的运输中的作用。


固氮（N）大豆植物使用尿囊素和尿囊酸作为氮的主要长距离运输形式，但在非固氮、非结瘤植物中，氨基酸主要用于源到库的氮分配。然而，一些脲化物仍然在非固定大豆的根部合成，我们的研究解决了脲化物运输过程在这些植物中的作用。在之前的工作中，豆科植物酰脲渗透酶（UPS）被发现参与尿囊素和尿囊酸的细胞输入。在这里，来自普通豆的UPS1在大豆韧皮部中表达，这导致转基因植物中酰脲从源到库的运输增强。这伴随着脲化物合成的增加以及尿囊素和尿囊酸从根到库的运输的增加。有趣的是，氨基酸同化、木质部运输和韧皮部库分配也被强烈上调。此外，转基因植物的光合作用和蔗糖韧皮部运输也得到改善。这些来源生理学和同化物分配的综合变化导致了营养生长的增加和种子数量的增加。总体而言，结果支持非固定植物中的脲化物运输过程影响源氮和碳的获取和同化以及氮和碳同化物的源到库的易位，从而对植物生长和种子发育产生影响。