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Stress responses of Synechocystis sp strain PCC 6803 mutants impaired in genes encoding putative alternative sigma factors
Autor: Huckauf, J; Nomura, C; Forchhammer, K; Hagemann, M
In:
Microbiology-SGM
Bandangabe: 146
ISBN: ISSN:1350-0872
Seite: 2877 - 2889
Jahr: 2000
Einordung:
Institut: Professur Agrobiotechnologie
Abstract:
In the complete genome sequence of the cyanobacterium Synechocystis sp.
strain PCC 6803 [Kaneko et al. (1996). DNA Res 3, 109–136] genes were
identified encoding putative group 3 r-factors SigH (Sll-0856), SigG (Slr-1545)
and SigF (Slr-1564) and the regulatory protein RsbU (Slr-2031). Mutations in
these genes were generated by interposon mutagenesis to study their
importance in stress acclimation. For the genes sigH, sigF and rsbU, the loci
segregated completely. However, attempts to mutagenize the sigG locus
resulted in merodiploids. Under standard growth conditions only minor
differences were detected between the mutants and wild-type. However, cells
of the RsbU mutant showed a clear defect in regenerating growth after a
nitrogen- and sulphur-starvation-induced stationary phase. After applying salt,
heat and high-light shocks, stress protein synthesis was analysed by means of
one- and two-dimensional electrophoresis. Cells of the SigF mutant showed a
severe defect in the induction of salt stress proteins. Although the acclimation
to moderate salt stress up to 684 mM NaCl was not significantly changed in
this mutant, its ability to acclimate to higher concentrations of NaCl was
reduced. Northern blot experiments showed a constitutive expression of the
rsbU and sigF genes. The expression of the sigH gene was found to be stressstimulated,
particularly in heat-shocked cells, whilst that of sigG was
transiently decreased under stress conditions. Possible functions of these
regulatory proteins in stress acclimation of Synechocystis cells are discussed. Ansprechpartner
Zur Publikation: Mitarbeiter,
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Letzte Änderung des Eintrages:
04.05.2010
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