AAP1 transports uncharged amino acids into roots of Arabidopsis
Article first published online: 5 APR 2007
The Plant Journal
Volume 50, Issue 2, pages 305–319, April 2007
How to Cite
Lee, Y.-H., Foster, J., Chen, J., Voll, L. M., Weber, A. P.M. and Tegeder, M. (2007), AAP1 transports uncharged amino acids into roots of Arabidopsis. The Plant Journal, 50: 305–319. doi: 10.1111/j.1365-313X.2007.03045.x
- Issue published online: 5 APR 2007
- Article first published online: 5 APR 2007
- Received 22 September 2006; revised 22 November 2006; accepted 12 December 2006.
- amino acid transport;
- root uptake;
- nitrogen partitioning
Amino acids are available to plants in some soils in significant amounts, and plants frequently make use of these nitrogen sources. The goal of this study was to identify transporters involved in the uptake of amino acids into root cells. Based on the fact that high concentrations of amino acids inhibit plant growth, we hypothesized that mutants tolerating toxic levels of amino acids might be deficient in the uptake of amino acids from the environment. To test this hypothesis, we employed a forward genetic screen for Arabidopsis thaliana mutants tolerating toxic concentrations of amino acids in the media. We identified an Arabidopsis mutant that is deficient in the amino acid permease 1 (AAP1, At1g58360) and resistant to 10 mm phenylalanine and a range of other amino acids. The transporter was localized to the plasma membrane of root epidermal cells, root hairs, and throughout the root tip of Arabidopsis. Feeding experiments with [14C]-labeled neutral, acidic and basic amino acids showed significantly reduced uptake of amino acids in the mutant, underscoring that increased tolerance of aap1 to high levels of amino acids is coupled with reduced uptake by the root. The growth and uptake studies identified glutamate, histidine and neutral amino acids, including phenylalanine, as physiological substrates for AAP1, whereas aspartate, lysine and arginine are not. We also demonstrate that AAP1 imports amino acids into root cells when these are supplied at ecologically relevant concentrations. Together, our data indicate an important role of AAP1 for efficient use of nitrogen sources present in the rhizosphere.