Biology Reference
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Figure 2.2
Model of transcriptional regulation of the
ggpS
gene for glucosylglycerol
(GG) synthesis (left panels) in
Synechocystis
6803 in comparison to experimental data
(right panels). In low-salt grown cells, the
ggpS
gene is repressed leading to GG-free
cells. Salt-shock treatments induce the highest
ggpS
expression and quick GG accumu-
lation because the influx of inorganic ions releases the repressor GgpR from the
ggpS
promoter in salt-stressed cells. In long-term salt-acclimated cells, the
ggpS
expression
remains active but depends on the external salinity. Moreover, the
ggpS
expression in
salt-acclimated cells seems to be driven by SigF instead of SigA because a SigF dele-
tion abolishes
ggpS
expression to a large extent. Possibly, additional regulatory factors
(marked by ?) are also involved. See the colour plate.
AqpZ affected not only water flow and turgor, but also the expression
of many salt-regulated genes was changed as well in
Synechocystis
6803
(
Shapiguzov et al., 2005
).
Analyses of the impact of mutations of two component systems in
Syn-
echocystis
6803 on salt-regulated gene expression revealed that defined groups
of these genes are controlled by pairs of histidine kinases and their cognate
response regulators (
Marin et al., 2003
;
Shoumskaya et al., 2005
). However,
none of the genes involved in GG synthesis or transport showed changes in
the salt regulation in any of these mutants. Other candidates for regulating
