| Summary: | <p>Abstract</p> <p>Background</p> <p>AtNHX1, the most abundant vacuolar Na<sup>+</sup>/H<sup>+ </sup>antiporter in <it>Arabidopsis thaliana</it>, mediates the transport of Na<sup>+ </sup>and K<sup>+ </sup>into the vacuole, influencing plant development and contributing to salt tolerance. In this report, microarray expression profiles of wild type plants, a T-DNA insertion knockout mutant of <it>AtNHX1 </it>(<it>nhx1</it>), and a 'rescued' line (NHX1::<it>nhx1</it>) were exposed to both short (12 h and 48 h) and long (one and two weeks) durations of a non-lethal salt stress to identify key gene transcripts associated with the salt response that are influenced by <it>AtNHX1</it>.</p> <p>Results</p> <p>147 transcripts showed both salt responsiveness and a significant influence of AtNHX1. Fifty-seven of these genes showed an influence of the antiporter across all salt treatments, while the remaining genes were influenced as a result of a particular duration of salt stress. Most (69%) of the genes were up-regulated in the absence of AtNHX1, with the exception of transcripts encoding proteins involved with metabolic and energy processes that were mostly down-regulated.</p> <p>Conclusion</p> <p>While part of the <it>AtNHX1</it>-influenced transcripts were unclassified, other transcripts with known or putative roles showed the importance of <it>AtNHX1 </it>to key cellular processes that were not necessarily limited to the salt stress response; namely calcium signaling, sulfur metabolism, cell structure and cell growth, as well as vesicular trafficking and protein processing. Only a small number of other salt-responsive membrane transporter transcripts appeared significantly influenced by <it>AtNHX1</it>.</p>
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