Affiliation:
1. Department of Plant Pathology, University of Nebraska, Lincoln, Nebraska 68583
Abstract
ABSTRACT
Sclerotinia sclerotiorum
acidifies its ambient environment by producing oxalic acid. This production of oxalic acid during plant infection has been implicated as a primary determinant of pathogenicity in this and other phytopathogenic fungi. We found that ambient pH conditions affect multiple processes in
S. sclerotiorum
. Exposure to increasing alkaline ambient pH increased the oxalic acid accumulation independent of carbon source, sclerotial development was favored by acidic ambient pH conditions but inhibited by neutral ambient pH, and transcripts encoding the endopolygalacturonase gene
pg1
accumulated maximally under acidic culture conditions. We cloned a putative transcription factor-encoding gene,
pac1
, that may participate in a molecular signaling pathway for regulating gene expression in response to ambient pH. The three zinc finger domains of the predicted Pac1 protein are similar in sequence and organization to the zinc finger domains of the
A. nidulans
pH-responsive transcription factor PacC. The promoter of
pac1
contains eight PacC consensus binding sites, suggesting that this gene, like its homologs, is autoregulated. Consistent with this suggestion, the accumulation of
pac1
transcripts paralleled increases in ambient pH. Pac1 was determined to be a functional homolog of PacC by complementation of an
A. nidulans pacC
-null strain with
pac1
. Our results suggest that ambient pH is a regulatory cue for processes linked to pathogenicity, development, and virulence and that these processes may be under the molecular regulation of a conserved pH-dependent signaling pathway analogous to that in the nonpathogenic fungus
A. nidulans
.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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