Journal Article

Plant RelA/SpoT Homolog Confers Salt Tolerance in <i>Escherichia coli</i> and <i>Saccharomyces cerevisiae</i>

Akiyo Yamada, Kouichi Tsutsumi, Shizufumi Tanimoto and Yoshihiro Ozeki

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 1, pages 3-9
Published in print January 2003 | ISSN: 0032-0781
Published online January 2003 | e-ISSN: 1471-9053 | DOI:
Plant RelA/SpoT Homolog Confers Salt Tolerance in Escherichia coli and Saccharomyces cerevisiae

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry


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To analyze the mechanisms of salt tolerance in the halophyte Suaeda japonica, Escherichia coli was used as a host organism to undertake functional screening of cDNAs encoding proteins that may play an important role for the salt-tolerance mechanisms. A transformant expressing RelA/SpoT homolog (Sj-RSH) was found to have enhanced salt tolerance. In E. coli, RelA/SpoT controlled the amount of guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp), which are the effectors of the bacterial stringent response. Complementation analysis using the relA mutant of E. coli showed that Sj-RSH conferred the phenotype associated with (p)ppGpp synthesis. Furthermore, expression of Sj-RSH driven by the GAL1 promoter also gave rise to enhanced salt tolerance in yeast. Northern blot analyses of the yeast transformant revealed that the transcriptional levels of stress responsive genes including GPD1, VMA6, BMH1, HYP1 and HOG1 were clearly enhanced in the Sj-RSH transformant when compared with an empty vector transformant under stress-free and 1.5 M NaCl stress conditions. These results suggest that (p)ppGpp synthesis mediated by plant RelA/SpoT homologs plays a critical role for the transcriptional induction of several stress responsive genes, directly or indirectly in yeast, and that the conserved stress-resistance system may exist in higher plants.

Keywords: Keywords: Guanosine tetraphosphate — RelA — Salt-tolerance — SpoT — Suaeda japonica.; Abbreviations: ppGpp, guanosine tetraphosphate; pppGpp, guanosine pentaphosphate.

Journal Article.  3727 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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