title: Capacities and constraints of amino acid utilization  in Arabidopsis.
abstract: Various amino acids, including both L- and D-enantiomers, may be present in soils, and recent studies have indicated that plants may access such nitrogen (N) forms. Here, the capacity of Arabidopsis to utilize different L- and D-amino acids is investigated and the constraints on this process are explored. Mutants defective in the lysine histidine transporter 1 (LHT1) and transgenic plants overexpressing LHT1 as well as plants expressing D-amino acid-metabolizing enzymes, were used in studies of uptake and growth on various N forms. Arabidopsis absorbed all tested N-forms, but D-enantiomers at lower rates than L-forms. Several L- but no D-forms were effective as N sources. Plants deficient in LHT1 displayed strong growth reductions and plants overexpressing LHT1 showed strong growth enhancement when N was supplied as amino acids, in particular when these were supplied at low concentrations. Several D- amino acids inhibited growth of wild-type plants, while transgenic Arabidopsis-expressing genes encoding D-amino acid-metabolizing enzymes could efficiently utilize such compounds for growth. These results suggest that several amino acids, and in particular L-Gln and L-Asn, promote growth of Arabidopsis, and increased expression of specific amino acid transporters enhances growth on amino acids. The efficiency by which transgenic plants exploit D-amino acids illustrates how plants can be engineered to utilize specific N sources otherwise inaccessible to them.
authors.affiliation: Umeå Plant Science Centre, Department or Forest Genetics and Plant Physiology and.
authors.forename: Oskar
authors.initials: O
authors.lastname: Forsum
authors.affiliation: Umeå Plant Science Centre, Department or Forest Genetics and Plant Physiology and.
authors.forename: Henrik
authors.initials: H
authors.lastname: Svennerstam
authors.affiliation: Umeå Plant Science Centre, Department or Forest Genetics and Plant Physiology and.
authors.forename: Ulrika
authors.initials: U
authors.lastname: Ganeteg
authors.affiliation: Umeå Plant Science Centre, Department or Forest Genetics and Plant Physiology and.|Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden.
authors.forename: Torgny
authors.initials: T
authors.lastname: Näsholm
mesh_terms: D026923:Amino Acid Transport Systems, Basic / Q000235:genetics; D000596:Amino Acids / Q000737:chemistry / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics; D009584:Nitrogen / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism
chemical_list: D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids; D029681:Arabidopsis Proteins; D029968:Escherichia coli Proteins; D005656:Fungal Proteins; C110638:LHT1 protein, Arabidopsis; D009584:Nitrogen