Equilibrative nucleoside transporter 1 (ENT1) is critical for pollen germination and vegetative growth in Arabidopsis

J Exp Bot. 2011 Aug;62(13):4627-37. doi: 10.1093/jxb/err183. Epub 2011 Jun 3.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine / metabolism
  • Adenosine Triphosphate / metabolism
  • Arabidopsis / genetics
  • Arabidopsis / growth & development*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Cyclic AMP / metabolism
  • Equilibrative Nucleoside Transport Proteins / genetics
  • Equilibrative Nucleoside Transport Proteins / metabolism*
  • Equilibrative Nucleoside Transporter 1 / genetics
  • Equilibrative Nucleoside Transporter 1 / metabolism*
  • Extracellular Space / metabolism
  • Gene Expression Regulation, Plant
  • Germination / physiology*
  • Intracellular Space / metabolism
  • Models, Biological
  • Mutation / genetics
  • Organ Specificity / genetics
  • Pollen / anatomy & histology
  • Pollen / genetics
  • Pollen / growth & development*
  • Pollen / physiology
  • Protein Transport
  • RNA Interference
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Subcellular Fractions / metabolism
  • Vacuoles / metabolism

Substances

  • Arabidopsis Proteins
  • ENT1 protein, Arabidopsis
  • Equilibrative Nucleoside Transport Proteins
  • Equilibrative Nucleoside Transporter 1
  • RNA, Messenger
  • Adenosine Triphosphate
  • Cyclic AMP
  • Adenosine