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Journal of Bacteriology, December 2000, p. 6622-6629, Vol. 182, No. 23
Section of Microbiology, University of
California, Davis, Davis, California 95616
Received 8 May 2000/Accepted 21 September 2000
One of the earliest events in the Myxococcus xanthus
developmental cycle is production of an extracellular cell density
signal called A-signal (or A-factor). Previously, we showed that cells carrying an insertion in the asgE gene fail to produce
normal levels of this cell-cell signal. In this study we found that
expression of asgE is growth phase regulated and
developmentally regulated. Several lines of evidence indicate that
asgE is cotranscribed with an upstream gene during
development. Using primer extension analyses, we identified two 5' ends
for this developmental transcript. The DNA sequence upstream of one 5'
end has similarity to the promoter regions of several genes that are
A-signal dependent, whereas sequences located upstream of the second 5'
end show similarity to promoter elements identified for genes that are
C-signal dependent. Consistent with this result is our finding that
mutants failing to produce A-signal or C-signal are defective for
developmental expression of asgE. In contrast to developing
cells, the large majority of the asgE transcript found in
vegetative cells appears to be monocistronic. This finding suggests
that asgE uses different promoters for expression during
vegetative growth and development. Growth phase regulation of
asgE is abolished in a relA mutant, indicating
that this vegetative promoter is induced by starvation. The data
presented here, in combination with our previous results, indicate that
the level of AsgE in vegetative cells is sufficient for this protein to
carry out its function during development.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Control of asgE Expression during Growth
and Development of Myxococcus xanthus


*
Corresponding author. Mailing address: Section of
Microbiology, One Shields Ave., University of California, Davis, Davis, CA 95616. Phone: (530) 752-9005. Fax: (530) 752-9014. E-mail: mhsinger{at}ucdavis.edu.
Present address: Departments of Biochemistry and Developmental
Biology, Stanford University, Stanford, CA 94305.
Present address: Department of Biochemistry and Biophysics,
University of California, San Francisco, San Francisco, CA 94143.
§
Department of Microbiology and Molecular Genetics, The University
of Texas Medical School, Houston, TX 77225.
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