Wound-Released Chemical Signals May Elicit Multiple Responses from an Agrobacterium tumefaciens Strain Containing an Octopine-Type Ti Plasmid
AUTOR(ES)
Kalogeraki, Virginia S.
FONTE
American Society for Microbiology
RESUMO
The vir regions of octopine-type and nopaline-type Ti plasmids direct the transfer of oncogenic T-DNA from Agrobacterium tumefaciens to the nuclei of host plant cells. Previous studies indicate that at least two genetic loci at the left ends of these two vir regions are sufficiently conserved to form heteroduplexes visible in the electron microscope. To initiate an investigation of these genetic loci, we determined the DNA sequences of these regions of both Ti plasmids and identified both conserved loci. One of these is the 2.5-kb virH locus, which was previously identified on the octopine-type Ti plasmid but thought to be absent from the nopaline-type Ti plasmid. The virH operon contains two genes that resemble P-450-type monooxygenases. The other locus encodes a 0.5-kb gene designated virK. In addition, we identified other potential genes in this region that are not conserved between these two plasmids. To determine (i) whether these genes are members of the vir regulon and, (ii) whether they are required for tumorigenesis, we used a genetic technique to disrupt each gene and simultaneously fuse its promoter to lacZ. Expression of these genes was also measured by nuclease S1 protection assays. virK and two nonconserved genes, designated virL and virM, were strongly induced by the vir gene inducer acetosyringone. Disruptions of virH, virK, virL, or virM did not affect tumorigenesis of Kalanchöe diagramontiana leaves or carrot disks, suggesting that they may play an entirely different role during pathogenesis.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=107625Documentos Relacionados
- Relationship between the limited and wide host range octopine-type Ti plasmids of Agrobacterium tumefaciens.
- VirA and VirG activate the Ti plasmid repABC operon, elevating plasmid copy number in response to wound-released chemical signals
- Competition of Octopine-Catabolizing Pseudomonas spp. and Octopine-Type Agrobacterium tumefaciens for Octopine in Chemostats
- The octopine-type Ti plasmid pTiA6 of Agrobacterium tumefaciens contains a gene homologous to the chromosomal virulence gene acvB.
- The conjugal transfer system of Agrobacterium tumefaciens octopine-type Ti plasmids is closely related to the transfer system of an IncP plasmid and distantly related to Ti plasmid vir genes.