title: Recycling of pyridoxine (vitamin B6) by PUP1 in Arabidopsis.
abstract: Vitamin B6 is a cofactor for more than 140 essential enzymatic reactions and was recently proposed as a potent antioxidant, playing a role in the photoprotection of plants. De novo biosynthesis of the vitamin has been described relatively recently and is derived from simple sugar precursors as well as glutamine. In addition, the vitamin can be taken up from exogenous sources in a broad range of organisms, including plants. However, specific transporters have been identified only in yeast. Here we assess the ability of the family of Arabidopsis purine permeases (PUPs) to transport vitamin B6. Several members of the family complement the growth phenotype of a Saccharomyces cerevisiae mutant strain impaired in both de novo biosynthesis of vitamin B6 as well as its uptake. The strongest activity was observed with PUP1 and was confirmed by direct measurement of uptake in yeast as well as in planta, defining PUP1 as a high affinity transporter for pyridoxine. At the tissue level the protein is localised to hydathodes and here we use confocal microscopy to illustrate that at the cellular level it is targeted to the plasma membrane. Interestingly, we observe alterations in pyridoxine recycling from the guttation sap upon overexpression of PUP1 and in a pup1 mutant, consistent with the role of the protein in retrieval of pyridoxine. Furthermore, combining the pup1 mutant with a vitamin B6 de novo biosynthesis mutant (pdx1.3) corroborates that PUP1 is involved in the uptake of the vitamin.
authors.affiliation: Department of Botany and Plant Biology, University of Geneva, 1211, Geneva, Switzerland.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Szydlowski
authors.affiliation: ETH Zurich, Institute of Agricultural Sciences, 8092, Zurich, Switzerland.
authors.forename: Lukas
authors.initials: L
authors.lastname: Bürkle
authors.affiliation: Department of Botany and Plant Biology, University of Geneva, 1211, Geneva, Switzerland.
authors.forename: Lucille
authors.initials: L
authors.lastname: Pourcel
authors.affiliation: Department of Botany and Plant Biology, University of Geneva, 1211, Geneva, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Moulin
authors.affiliation: Lehrstuhl für Ernährungsphysiologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung (ZIEL) - Abteilung Biochemie, Wissenschaftszentrum Weihenstephan, Technische Universität München, 85350, Freising, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Stolz
authors.affiliation: Department of Botany and Plant Biology, University of Geneva, 1211, Geneva, Switzerland.
authors.forename: Teresa B
authors.initials: TB
authors.lastname: Fitzpatrick
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D018613:Microscopy, Confocal; D005810:Multigene Family; D009154:Mutation; D033702:Nucleobase Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D019441:Plant Epidermis / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D053147:Plant Exudates / Q000032:analysis; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D011736:Pyridoxine / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D033702:Nucleobase Transport Proteins; C586645:PUP1 protein, Arabidopsis; D053147:Plant Exudates; D011993:Recombinant Fusion Proteins; C022483:purine permease; D011736:Pyridoxine