Affiliation:
1. Department of Agronomy
2. Department of Biological Sciences
3. USDA-ARS, Purdue University, West Lafayette, Indiana 47907
Abstract
ABSTRACT
The signals that control the transcription of osmoregulated genes are not understood satisfactorily. The “turgor control model” suggested that the primary osmoregulatory signal in
Enterobacteriaceae
is turgor loss, which induces the
kdp
K
+
transport operon and activates the Trk K
+
permease. The ensuing increase in cytoplasmic K
+
concentration was proposed to be the signal that turns on all secondary responses, including the induction of the
proU
(proline-glycine betaine transport) operon. The “ionic strength model” proposed that the regulatory signal for all osmotically controlled responses is the increase in the cytoplasmic ionic strength or macromolecular crowding after an osmotic upshift. The assumption in the turgor control model that the induction of
kdp
is a primary response to osmotic shock predicts that this response should precede all secondary responses. Both models predict that the induction of all osmotically activated responses should be independent of the chemical nature of the solute used to impose osmotic stress. We tested these predictions by quantitative real-time reverse transcription-PCR analysis of the expression of six osmotically regulated genes in
Salmonella enterica
serovar Typhimurium. After shock with 0.3 M NaCl,
proU
was induced at 4 min,
proP
and
rpoS
were induced at 4 to 6 min,
kdp
was induced at 8 to 9 min, and
otsB
and
ompC
were induced at 10 to 12 min. After an equivalent osmotic shock with 0.6 M sucrose,
proU
was induced with kinetics similar to those seen with NaCl, but induction of
kdp
was reduced 150-fold in comparison to induction by NaCl. Our results are inconsistent with both the turgor control and the ionic strength control models.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Reference51 articles.
1. Regulation of kdp operon expression in Escherichia coli: evidence against turgor as signal for transcriptional control
2. Balaji, B., D. B. Bucholtz, and J. M. Anderson. 2003. Barley yellow dwarf virus and cereal yellow dwarf virus quantification by real-time polymerase chain reaction in resistant and susceptible plants. Phytopathology93:1386-1392.
3. Booth, I. R., and C. F. Higgins. 1990. Enteric bacteria and osmotic stress; intracellular potassium glutamate as a secondary signal of osmotic stress. FEMS Microbiol. Rev.75:239-246.
4. Bremer, H., and P. P. Dennis. 1996. Modulation of chemical composition and other parameters of the cell by growth rate, p. 1553-1569. In F. C. Neidhardt, R. Curtiss III, J. L. Ingraham, E. C. C. Lin, K. B. Low, B. Magasanik, W. S. Reznikoff, M. Riley, M. Schaechter, and H. E. Umbarger (ed.), Escherichia coli and Salmonella: cellular and molecular biology, 2nd ed. American Society for Microbiology, Washington, D.C.
5. Burg, M. B., E. D. Kwon, and D. Kültz. 1996. Osmotic regulation of gene expression. FASEB J.10:1598-1606.
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