title: AAP1 transports uncharged amino acids into roots of Arabidopsis.
abstract: 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 [(14)C]-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.
authors.affiliation: School of Biological Sciences, Center for Integrated Biotechnology, Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA.
authors.forename: Yong-Hwa
authors.initials: YH
authors.lastname: Lee
authors.forename: Justin
authors.initials: J
authors.lastname: Foster
authors.forename: Janet
authors.initials: J
authors.lastname: Chen
authors.forename: Lars M
authors.initials: LM
authors.lastname: Voll
authors.forename: Andreas P M
authors.initials: AP
authors.lastname: Weber
authors.forename: Mechthild
authors.initials: M
authors.lastname: Tegeder
mesh_terms: D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D000596:Amino Acids / Q000378:metabolism* / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D001692:Biological Transport / Q000187:drug effects; D002250:Carbon Radioisotopes; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D005816:Genetic Complementation Test; D008954:Models, Biological; D009154:Mutation; D010649:Phenylalanine / Q000378:metabolism / Q000494:pharmacology; D019441:Plant Epidermis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000378:metabolism
chemical_list: C420564:AAP1 protein, Arabidopsis; D026921:Amino Acid Transport Systems, Neutral; D000596:Amino Acids; D029681:Arabidopsis Proteins; D002250:Carbon Radioisotopes; D010649:Phenylalanine