Journal
JOURNAL OF EXPERIMENTAL BOTANY
Volume 62, Issue 13, Pages 4627-4637Publisher
OXFORD UNIV PRESS
DOI: 10.1093/jxb/err183
Keywords
Arabidopsis thaliana L; equilibrative nucleoside transporter; pollen; purine; pyrimidine; salvage pathway; vacuole
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Funding
- Deutsche Forschungsgemeinschaft [MO 1032/3-1, STE A455/4-A]
- 'Research Initiative Membrane Biology' at the University of Kaiserslautern
- Alexander von Humboldt-Foundation
- Human Frontier Science Program
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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.
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