title: Comprehensive screening of Arabidopsis mutants suggests the lysine histidine transporter 1 to be involved in plant uptake of amino acids.
abstract: Plant nitrogen (N) uptake is a key process in the global N cycle and is usually considered a "bottleneck" for biomass production in land ecosystems. Earlier, mineral N was considered the only form available to plants. Recent studies have questioned this dogma and shown that plants may access organic N sources such as amino acids. The actual mechanism enabling plants to access amino acid N is still unknown. However, a recent study suggested the Lysine Histidine Transporter 1 (LHT1) to be involved in root amino acid uptake. In this study, we isolated mutants defective in root amino acid uptake by screening Arabidopsis (Arabidopsis thaliana) seeds from ethyl methanesulfonate-treated plants and seeds from amino acid transporter T-DNA knockout mutants for resistance against the toxic D-enantiomer of alanine (Ala). Both ethyl methanesulfonate and T-DNA knockout plants identified as D-Ala resistant were found to be mutated in the LHT1 gene. LHT1 mutants displayed impaired capacity for uptake of a range of amino acids from solutions, displayed impaired growth when N was supplied in organic forms, and acquired substantially lower amounts of amino acids than wild-type plants from solid growth media. LHT1 mutants grown on mineral N did not display a phenotype until at the stage of flowering, when premature senescence of old leaf pairs occurred, suggesting that LHT1 may fulfill an important function at this developmental stage. Based on the broad and unbiased screening of mutants resistant to D-Ala, we suggest that LHT1 is an important mediator of root uptake of amino acids. This provides a molecular background for plant acquisition of organic N from the soil.
authors.affiliation: Umea Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umea, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Svennerstam
authors.forename: Ulrika
authors.initials: U
authors.lastname: Ganeteg
authors.forename: Catherine
authors.initials: C
authors.lastname: Bellini
authors.forename: Torgny
authors.initials: T
authors.lastname: Näsholm
mesh_terms: D026923:Amino Acid Transport Systems, Basic / Q000235:genetics / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics; D009154:Mutation; D030821:Plants, Genetically Modified
chemical_list: D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids; D029681:Arabidopsis Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; C110638:LHT1 protein, Arabidopsis; C036483:T-DNA