Soybean ureide transporters play a critical role in nodule development, function and nitrogen export
Article first published online: 9 AUG 2012
© 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd
The Plant Journal
Volume 72, Issue 3, pages 355–367, November 2012
How to Cite
Collier, R. and Tegeder, M. (2012), Soybean ureide transporters play a critical role in nodule development, function and nitrogen export. The Plant Journal, 72: 355–367. doi: 10.1111/j.1365-313X.2012.05086.x
- Issue published online: 29 OCT 2012
- Article first published online: 9 AUG 2012
- Accepted manuscript online: 23 JUN 2012 10:52AM EST
- Received 30 April 2012; revised 17 June 2012; accepted 19 June 2012; published online 9 August 2012.
- allantoic acid;
- nodule development;
- nitrogen fixation;
- ureide export
Legumes can access atmospheric nitrogen through a symbiotic relationship with nitrogen-fixing bacteroids that reside in root nodules. In soybean, the products of fixation are the ureides allantoin and allantoic acid, which are also the dominant long-distance transport forms of nitrogen from nodules to the shoot. Movement of nitrogen assimilates out of the nodules occurs via the nodule vasculature; however, the molecular mechanisms for ureide export and the importance of nitrogen transport processes for nodule physiology have not been resolved. Here, we demonstrate the function of two soybean proteins – GmUPS1-1 (XP_003516366) and GmUPS1-2 (XP_003518768) – in allantoin and allantoic acid transport out of the nodule. Localization studies revealed the presence of both transporters in the plasma membrane, and expression in nodule cortex cells and vascular endodermis. Functional analysis in soybean showed that repression of GmUPS1-1 and GmUPS1-2 in nodules leads to an accumulation of ureides and decreased nitrogen partitioning to roots and shoot. It was further demonstrated that nodule development, nitrogen fixation and nodule metabolism were negatively affected in RNAi UPS1 plants. Together, we conclude that export of ureides from nodules is mediated by UPS1 proteins, and that activity of the transporters is not only essential for shoot nitrogen supply but also for nodule development and function.