Salt-dependent expression of glucosylglycerol-phosphate synthase, involved in osmolyte synthesis in the cyanobacterium Synechocystis sp strain PCC 6803

Autor: Marin, K; Huckauf, J; Fulda, S; Hagemann, M
In:

Journal of Bacteriology

Bandangabe: 148
Auflage: 11
ISBN: ISSN:0021-9193
Seite: 2870 - 2877
Jahr: 2002

Einordung:
Institut: Professur Agrobiotechnologie

Abstract:
The cyanobacterium Synechocystis sp. strain PCC 6803 is able to acclimate to levels of salinity ranging from
freshwater to twice the seawater concentrations of salt by accumulating the compatible solute glucosylglycerol
(GG). Expression of the ggpS gene coding for the key enzyme (glucosylglycerol-phosphate synthase) in GG
synthesis was examined in detail. Under control conditions, the GgpS protein is stable, so that weak constitutive
transcription of the ggpS gene resulted in a significant protein content. However, the enzyme activity was
biochemically switched off, and no GG was detectable. After a salt shock, an immediate increase in mRNA
content proportional to the salt content occurred, while the GgpS protein and GG contents rose in a linear
manner. Furthermore, the stability of the ggpS mRNA increased transiently. In salt-acclimated cells expression
of the ggpS gene, the GgpS protein content, and the amount of accumulated GG depended linearly on the
external salt concentration. Mapping of the 5
end of the ggpS transcript revealed a long nontranslated 5

sequence and a putative typical cyanobacterial promoter, which did not show any obvious salt-regulatory
element. The alternative
factor
F was found to be involved in salt-dependent regulation of ggpS, since in a

F mutant induction of this gene was strongly reduced. The present study demonstrated that in addition to
biochemical regulation of GgpS activity, alterations of ggpS expression are involved in regulation of GG
synthesis in Synechocystis sp. strain PCC 6803. A model showing the interaction of the two regulatory levels is
presented.

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