A chromosomal Agrobacterium tumefaciens gene required for effective plant signal transduction.
The vir gene products of Agrobacterium tumefaciens carry out the transfer of T-DNA to the plant genome. Effective transcriptional induction of the vir genes by plant signal molecules is controlled by two vir gene products, VirA and VirG. In this study we have identified and cloned a chromosomal region which is also required for vir gene induction. Transposon insertions within this region reduce induction significantly and strongly attenuate virulence, resulting in a restricted host range for infection. The reduction in vir gene transcription can be partially overcome by high concentrations of the inducer molecule acetosyringone. Expression of virG at low pH and low phosphate concentrations, which is independent of plant signals, is not affected by these mutations. Sequence analysis of the region revealed two divergent open reading frames, which we have designated chvE and ORF1. Several transposon insertions mapped in chvE; this resulted in attenuated virulence. chvE codes for a putative protein which is homologous to two periplasmic receptor proteins involved in chemotaxis and uptake of sugars. Whether ORF1 is required for virulence is uncertain. One transposon insertion resulting in avirulence maps in or near the 5' end of ORF1, and several which do not affect virulence map in its 3' end. ORF1 codes for a putative protein which is homologous to a family of transcriptional activator proteins.
Huang
M L
ML
Department of Botany, University of Washington, Seattle 98195.
Cangelosi
G A
GA
Halperin
W
W
Nester
E W
EW
D000098:Acetophenones / Q000494:pharmacology; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics; D002876:Chromosomes, Bacterial; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial / Q000187:drug effects; D005838:Genotype; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D033902:Periplasmic Binding Proteins; D018521:Plant Physiological Phenomena; D010944:Plants / Q000235:genetics*; D010957:Plasmids; D015183:Restriction Mapping; D012231:Rhizobium / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology; D012266:Ribose / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction; D014774:Virulence / Q000235:genetics
D000098:Acetophenones; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D033902:Periplasmic Binding Proteins; C028003:RbsB protein, E coli; D012266:Ribose; C051667:acetosyringone