Affiliation:
1. Institut für Genetik, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle, Germany
Abstract
ABSTRACT
The pathogenicity of the plant-pathogenic bacterium
Xanthomonas campestris
pv. vesicatoria depends on a type III secretion system which is encoded by the 23-kb
hrp
(
h
ypersensitive
r
esponse and
p
athogenicity) gene cluster. Expression of the
hrp
operons is strongly induced in planta and in a special minimal medium and depends on two regulatory proteins, HrpG and HrpX. In this study, DNA affinity enrichment was used to demonstrate that the AraC-type transcriptional activator HrpX binds to a conserved
cis
-regulatory element, the plant-inducible promoter (PIP) box (TTCGC-N
15
-TTCGC), present in the promoter regions of four
hrp
operons. No binding of HrpX was observed when DNA fragments lacking a PIP box were used. HrpX also bound to a DNA fragment containing an imperfect PIP box (TTCGC-N
8
-TTCGT). Dinucleotide replacements in each half-site of the PIP box strongly decreased binding of HrpX, while simultaneous dinucleotide replacements in both half-sites completely abolished binding. Based on the complete genome sequence of
Xanthomonas campestris
pv. vesicatoria, putative plant-inducible promoters consisting of a PIP box and a −10 promoter motif were identified in the promoter regions of almost all HrpX-activated genes. Bioinformatic analyses and reverse transcription-PCR experiments revealed novel HrpX-dependent genes, among them a NUDIX hydrolase gene and several genes with a predicted role in the degradation of the plant cell wall. We conclude that HrpX is the most downstream component of the
hrp
regulatory cascade, which is proposed to directly activate most genes of the
hrpX
regulon via binding to corresponding PIP boxes.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference47 articles.
1. Bogdanove, A. J., S. V. Beer, U. Bonas, C. A. Boucher, A. Collmer, D. L. Coplin, G. R. Cornelis, H. C. Huang, S. W. Hutcheson, N. J. Panopoulos, and F. Van Gijsegem. 1996. Unified nomenclature for broadly conserved hrp genes of phytopathogenic bacteria. Mol. Microbiol. 20 : 681-683.
2. Bonas, U., R. Schulte, S. Fenselau, G. V. Minsavage, B. J. Staskawicz, and R. E. Stall. 1991. Isolation of a gene cluster from Xanthomonas campestris pv. vesicatoria that determines pathogenicity and the hypersensitive response on pepper and tomato. Mol. Plant-Microbe Interact. 4 : 81-88.
3. Browning, D. F., and S. J. Busby. 2004. The regulation of bacterial transcription initiation. Nat. Rev. Microbiol. 2 : 57-65.
4. Busby, S., and R. H. Ebright. 1997. Transcription activation at class II CAP-dependent promoters. Mol. Microbiol. 23 : 853-859.
5. Canteros B. J. 1990. Diversity of plasmids and plasmid-encoded phenotypic traits in Xanthomonas campestris pv. vesicatoria. Ph.D. thesis. University of Florida Gainesville.
Cited by
136 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献