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Journal of Bacteriology, June 2001, p. 3310-3317, Vol. 183, No. 11
Plant Science Institute, Department of
Biology, University of Pennsylvania, Philadelphia, Pennsylvania
19104-6018,1 and Department of Biology,
Swarthmore College, Swarthmore, Pennsylvania 190812
Received 30 November 2000/Accepted 6 March 2001
A yeast two-hybrid screen searching for chromosomally encoded
proteins that interact with the Agrobacterium tumefaciens
VirB8 protein was carried out. This screen identified an interaction candidate homologous to the partial sequence of a gene that had previously been identified in a transposon screen as a potential regulator of virG expression, chvD. In this
report, the cloning of the entire chvD gene is described
and the gene is sequenced and characterized. Insertion of a
promoterless lacZ gene into the chvD locus
greatly attenuated virulence and vir gene expression. Compared to that of the wild-type strain, growth of the
chvD mutant was reduced in rich, but not minimal, medium.
Expression of chvD, as monitored by expression of
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.11.3310-3317.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
ChvD, a Chromosomally Encoded ATP-Binding Cassette
Transporter-Homologous Protein Involved in Regulation of Virulence Gene
Expression in Agrobacterium tumefaciens

-galactosidase activity from the chvD-lacZ fusion,
occurred in both rich and minimal media as well as under conditions
that induce virulence gene expression. The ChvD protein is highly
homologous to a family of ATP-binding cassette transporters involved in
antibiotic export from bacteria and has two complete Walker box motifs.
Molecular genetic analysis demonstrated that disruption of either
Walker A box, singly, does not inactivate this protein's effect on
virulence but that mutations in both Walker A boxes renders it
incapable of complementing a chvD mutant strain.
Constitutive expression of virG in the chvD
mutant strain restored virulence, supporting the hypothesis that ChvD
controls virulence through effects on virG expression.
*
Corresponding author. Mailing address: Plant Science
Institute, Department of Biology, University of Pennsylvania,
Philadelphia, PA 19104-6018. Phone: (215) 898-8684. Fax: (215)
898-8780. E-mail: abinns{at}sas.upenn.edu.
Present address: Agricultural Products Group, FMC Corporation,
Philadelphia, PA 19103.
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