title: Equilibrative nucleoside transporter 1 (ENT1) is critical for pollen germination and vegetative growth in Arabidopsis.
abstract: ENT1 of Arabidopsis thaliana was the first member of the equilibrative nucleoside transporter (ENT) family to be identified in plants and characterized as a cellular, high-affinity nucleoside importer. Evidence is presented here for a tonoplast localization of ENT1 based on proteome data and Western blot analyses. Increased export of adenosine from reconstituted tonoplast preparations from 35S:ENT1 mutants compared with those from the wild type and ENT1-RNAi mutants support this view. Furthermore, increased vacuolar adenosine and vacuolar 2'3'-cAMP (an intermediate of RNA catabolism) contents in ENT1-RNAi mutants, but decreased contents of these metabolites in 35S:ENT1 over-expresser mutants, were observed. An up-regulation of the salvage pathway was detected in the latter mutants, leading to the conclusion that draining the vacuolar adenosine storage by ENT1 over-expression interferes with cellular nucleotide metabolism. As a consequence of the observed metabolic alterations 35S:ENT1 over-expresser mutants exhibited a smaller phenotypic appearance compared with wild-type plants. In addition, ENT1:RNAi mutants exhibited significantly lower in vitro germination of pollen and contained reduced internal and external ATP levels. This indicates that ENT1-mediated nucleosides, especially adenosine transport, is important for nucleotide metabolism, thus influencing growth and pollen germination.
authors.affiliation: Pflanzenphysiologie, Fachbereich Biologie, Universität Kaiserslautern, Erwin-Schrödinger-Strasse, Postfach 3049, D-67663 Kaiserslautern, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Bernard
authors.forename: Michaela
authors.initials: M
authors.lastname: Traub
authors.forename: H-Henning
authors.initials: HH
authors.lastname: Kunz
authors.forename: Stefanie
authors.initials: S
authors.lastname: Hach
authors.forename: Oliver
authors.initials: O
authors.lastname: Trentmann
authors.forename: Torsten
authors.initials: T
authors.lastname: Möhlmann
mesh_terms: D000241:Adenosine / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D033705:Equilibrative Nucleoside Transport Proteins / Q000235:genetics / Q000378:metabolism*; D033721:Equilibrative Nucleoside Transporter 1 / Q000235:genetics / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000502:physiology*; D042541:Intracellular Space / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D009928:Organ Specificity / Q000235:genetics; D011058:Pollen / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D021381:Protein Transport; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C569097:ENT1 protein, Arabidopsis; D033705:Equilibrative Nucleoside Transport Proteins; D033721:Equilibrative Nucleoside Transporter 1; D012333:RNA, Messenger; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D000241:Adenosine