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J. Bacteriol., Nov 1995, 6518-6526, Vol 177, No. 22
P Crouzet and L Otten
The grapevine is the natural host of the tumorigenic bacterium
Agrobacterium vitis. Most of the A. vitis isolates can use tartrate, an
unusually abundant compound in grapevine. The nopaline strain, AB4,
contains a 170-kb conjugative plasmid (pTrAB4) encoding tartrate
utilization. A 5.65-kb pTrAB4 region which enables non-tartrate- utilizing
Agrobacterium tumefaciens to grow on tartrate was sequenced and mutagenized
with the transcriptional fusion transposon Tn5-uidA1. This DNA fragment
contains four intact open reading frames (ORFs) (ttuABCD) required for
tartrate-dependent growth. The mutant phenotypes of each ORF, their
homologies to published sequences, and their induction patterns allowed us
to propose a model for tartrate utilization in A. vitis. ttuA encodes a
LysR-like transcriptional activator and is transcribed in the absence of
tartrate. ttuB codes for a protein with homology to transporter proteins
and is required for entry of tartrate into bacteria. ttuC codes for a
tartrate dehydrogenase, while ttuD lacks homology to known sequences; the
growth properties of ttuD mutants suggest that TtuD catalyzes the second
step in tartrate degradation. A fifth incomplete ORF (ttuE) encodes a
pyruvate kinase which is induced by tartrate and required for optimal
growth. Although the ttuABCD fragment allows growth of A. tumefaciens on
tartrate, it does not provide full tartrate utilization in the original A.
vitis background.
Copyright © 1995, American Society for Microbiology
Sequence and mutational analysis of a tartrate utilization operon from Agrobacterium vitis
Department of Phytopathology, Plant Molecular Biology Institute of Centre National de la Recherche Scientifique, Strasbourg, France.
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