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J Bacteriol, July 1998, p. 3629-3634, Vol. 180, No. 14
Department of Plant Pathology, University of
Missouri, Columbia, Missouri 652111;
Cancer Research Center, Columbia, Missouri
652013; and
Department of Molecular
Genetics, National Institute of Genetics, Mishima, Shizuoka 411, Japan2
Received 22 January 1998/Accepted 18 May 1998
RpoS (sigma-S or sigma-38) controls a large array of genes that are
expressed during stationary phase and under various stress conditions
in Escherichia coli and other bacteria. We document here
that plant pathogenic and epiphytic Erwinia species, such as E. amylovora; E. carotovora subsp.
atroseptica, betavasculorum, and
carotovora; E. chrysanthemi;
E. herbicola; E. rhapontici; and
E. stewartii, possess rpoS genes and
produce the alternate sigma factor. We show that rpoS
transcription in E. carotovora subsp.
carotovora is driven from a major promoter which
resides within the nlpD gene located upstream of
rpoS as in E. coli. RpoS
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
RpoS (Sigma-S) Controls Expression of rsmA, a Global
Regulator of Secondary Metabolites, Harpin, and Extracellular
Proteins in Erwinia carotovora
E. carotovora subsp. carotovoa strain
AC5061, constructed by marker exchange, is more sensitive to hydrogen
peroxide, carbon starvation, and acidic pH than its
RpoS+ parent strain, AC5006. The basal levels of
extracellular pectate lyase, polygalacturonase, and
cellulase as well as those of transcripts of E. carotovora subsp. carotovora hrpN
(hrpNEcc), the gene for the elicitor
of the hypersensitive reaction, are higher in the RpoS
strain than in the RpoS+ parent. Likewise,
compared to AC5006, AC5061 causes more extensive maceration of celery
petioles. Our findings with the RpoS
mutant and strains
carrying multiple copies rpoS+ DNA reveal that
rpoS positively controls rsmA expression. We also present evidence that supports the hypothesis that the RpoS effect
on extracellular enzyme levels, hrpNEcc
expression, and virulence manifests itself by the modulation of
rsmA expression.
*
Corresponding author. Mailing address: Department of
Plant Pathology, College of Agriculture, Food and Natural Resources, University of Missouri-Columbia, 108 Waters Hall, Columbia, Mo. 65211. Phone: (573) 882-2643. Fax: (573) 882-0588. E-mail:
achatterjee{at}psu.missouri.edu.
Journal series 12,671 of the Missouri Agricultural Experiment
Station.
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