Affiliation:
1. Laboratory of Applied Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, Tsutsumidori Amamiya-machi 1-1, Aoba-ku, Sendai 981-8555, Japan
Abstract
ABSTRACT
Pectobacterium carotovorum
subsp.
carotovorum
strain Er simultaneously produces the phage tail-like bacteriocin carotovoricin (Ctv) and pectin lyase (Pnl) in response to DNA-damaging agents. The regulatory protein RdgB of the Mor/C family of proteins activates transcription of
pnl
through binding to the promoter. However, the optimal temperature for the synthesis of Ctv (23°C) differs from that for synthesis of Pnl (30°C), raising the question of whether RdgB directly activates
ctv
transcription. Here we report that RdgB directly regulates Ctv synthesis. Gel mobility shift assays demonstrated RdgB binding to the P
0
, P
1
, and P
2
promoters of the
ctv
operons, and DNase I footprinting determined RdgB-binding sequences (RdgB boxes) on these and on the
pnl
promoters. The RdgB box of the
pnl
promoter included a perfect 7-bp inverted repeat with high binding affinity to the regulator (
K
d
[dissociation constant] = 150 nM). In contrast, RdgB boxes of the
ctv
promoters contained an imperfect inverted repeat with two or three mismatches that consequently reduced binding affinity (
K
d
= 250 to 350 nM). Transcription of the
rdgB
and
ctv
genes was about doubled at 23°C compared with that at 30°C. In contrast, the amount of
pnl
transcription tripled at 30°C. Thus, the inverse synthesis of Ctv and Pnl as a function of temperature is apparently controlled at the transcriptional level, and reduced
rdgB
expression at 30°C obviously affected transcription from the
ctv
promoters with low-affinity RdgB boxes. Pathogenicity toward potato tubers was reduced in an
rdgB
knockout mutant, suggesting that the RdgAB system contributes to the pathogenicity of this bacterium, probably by activating
pnl
expression.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
3 articles.
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