title: UMAMIT14 is an amino acid exporter involved in phloem unloading in Arabidopsis roots.
abstract: Amino acids are the main form of nitrogen transported between the plant organs. Transport of amino acids across membranes is mediated by specialized proteins: importers, exporters, and facilitators. Unlike amino acid importers, amino acid exporters have not been thoroughly studied, partly due to a lack of high-throughput techniques enabling their isolation. Usually Multiple Acids Move In and out Transporters 14 (UMAMIT14) from Arabidopsis shares sequence similarity to the amino acid facilitator Silique Are Red1 (UMAMIT18), and has been shown to be involved in amino acid transfer to the seeds. We show here that UMAMIT14 is also expressed in root pericycle and phloem cells and mediates export of a broad range of amino acids in yeast. Loss-of-function of UMAMIT14 leads to a reduced shoot-to-root and root-to-medium transfer of amino acids originating from the leaves. These fluxes were further reduced in an umamti14 umamit18 double loss-of-function mutant. This study suggests that UMAMIT14 is involved in phloem unloading of amino acids in roots, and that UMAMIT14 and UMAMIT18 are involved in the radial transport of amino acids in roots, which is essential for maintaining amino acid secretion to the soil.
authors.affiliation: Department of Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg 24061, VA, USA.
authors.forename: Julien
authors.initials: J
authors.lastname: Besnard
authors.affiliation: Department of Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg 24061, VA, USA.
authors.forename: Réjane
authors.initials: R
authors.lastname: Pratelli
authors.affiliation: Department of Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg 24061, VA, USA.
authors.forename: Chengsong
authors.initials: C
authors.lastname: Zhao
authors.affiliation: Department of Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg 24061, VA, USA.
authors.forename: Unnati
authors.initials: U
authors.lastname: Sonawala
authors.affiliation: Department of Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg 24061, VA, USA.
authors.forename: Eva
authors.initials: E
authors.lastname: Collakova
authors.affiliation: Department of Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg 24061, VA, USA gpilot@vt.edu sokumoto@tamu.edu.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Pilot
authors.affiliation: Department of Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg 24061, VA, USA gpilot@vt.edu sokumoto@tamu.edu.
authors.forename: Sakiko
authors.initials: S
authors.lastname: Okumoto
mesh_terms: D026905:Amino Acid Transport Systems / Q000378:metabolism / Q000502:physiology*; D017360:Arabidopsis / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism / Q000502:physiology*; D018613:Microscopy, Confocal; D052585:Phloem / Q000378:metabolism / Q000502:physiology*; D018517:Plant Roots / Q000378:metabolism / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D036226:Seedlings / Q000378:metabolism / Q000502:physiology
chemical_list: D026905:Amino Acid Transport Systems; D029681:Arabidopsis Proteins; C000624649:UMAMIT14 protein, Arabidopsis
keywords: Amino acids; Arabidopsis; membrane export; nitrogen; phloem; transporter.