scholarly journals 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.

1996 ◽  
Vol 178 (14) ◽  
pp. 4248-4257 ◽  
Author(s):  
J Alt-Mörbe ◽  
J L Stryker ◽  
C Fuqua ◽  
P L Li ◽  
S K Farrand ◽  
...  
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Ti Plasmid ◽  
Conjugal Transfer ◽  
Transfer System ◽  
Ti Plasmids ◽  
Vir Genes

scholarly journals TraG from RP4 and TraG and VirD4 from Ti Plasmids Confer Relaxosome Specificity to the Conjugal Transfer System of pTiC58

2000 ◽  
Vol 182 (6) ◽  
pp. 1541-1548 ◽  
Author(s):  
Claire M. Hamilton ◽  
Hyewon Lee ◽  
Pei-Li Li ◽  
David M. Cook ◽  
Kevin R. Piper ◽  
...  
Keyword(s):  
Mating Systems ◽  
Pair Formation ◽  
Ti Plasmid ◽  
Dna Transfer ◽  
Conjugal Transfer ◽  
Transfer System ◽  
Essential Factor ◽  
Ti Plasmids ◽  
Coupling Protein ◽  
Formation System

ABSTRACT Plasmid conjugation systems are composed of two components, the DNA transfer and replication system, or Dtr, and the mating pair formation system, or Mpf. During conjugal transfer an essential factor, called the coupling protein, is thought to interface the Dtr, in the form of the relaxosome, with the Mpf, in the form of the mating bridge. These proteins, such as TraG from the IncP1 plasmid RP4 (TraGRP4) and TraG and VirD4 from the conjugal transfer and T-DNA transfer systems of Ti plasmids, are believed to dictate specificity of the interactions that can occur between different Dtr and Mpf components. The Ti plasmids of Agrobacterium tumefaciens do not mobilize vectors containing the oriT of RP4, but these IncP1 plasmid derivatives lack the trans-acting Dtr functions and TraGRP4. A. tumefaciensdonors transferred a chimeric plasmid that contains theoriT and Dtr genes of RP4 and the Mpf genes of pTiC58, indicating that the Ti plasmid mating bridge can interact with the RP4 relaxosome. However, the Ti plasmid did not mobilize transfer from an IncQ relaxosome. The Ti plasmid did mobilize such plasmids if TraGRP4 was expressed in the donors. Mutations intraG RP4 with defined effects on the RP4 transfer system exhibited similar phenotypes for Ti plasmid-mediated mobilization of the IncQ vector. When provided with VirD4, thetra system of pTiC58 mobilized plasmids from the IncQ relaxosome. However, neither TraGRP4 nor VirD4 restored transfer to a traG mutant of the Ti plasmid. VirD4 also failed to complement a traG RP4 mutant for transfer from the RP4 relaxosome or for RP4-mediated mobilization from the IncQ relaxosome. TraGRP4-mediated mobilization of the IncQ plasmid by pTiC58 did not inhibit Ti plasmid transfer, suggesting that the relaxosomes of the two plasmids do not compete for the same mating bridge. We conclude that TraGRP4 and VirD4 couples the IncQ but not the Ti plasmid relaxosome to the Ti plasmid mating bridge. However, VirD4 cannot couple the IncP1 or the IncQ relaxosome to the RP4 mating bridge. These results support a model in which the coupling proteins specify the interactions between Dtr and Mpf components of mating systems.

scholarly journals Transsexuality in the Rhizosphere: Quorum Sensing Reversibly Converts Agrobacterium tumefaciens from Phenotypically Female to Male

2009 ◽  
Vol 191 (10) ◽  
pp. 3375-3383 ◽  
Author(s):  
Hongbaek Cho ◽  
Uelinton M. Pinto ◽  
Stephen C. Winans
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Quorum Sensing ◽  
Host Cell ◽  
Ti Plasmid ◽  
Conjugative Plasmids ◽  
Acylhomoserine Lactone ◽  
Ti Plasmids ◽  
Quorum Sensing Signals

ABSTRACT Conjugative plasmids generally encode proteins that block the conjugative entry of identical or similar plasmids into the host cell, a phenomenon known as entry exclusion. Here, we demonstrate that two Ti plasmids of Agrobacterium tumefaciens encode robust entry exclusion functions. Two proteins, TrbJ and TrbK, can each mediate entry exclusion and act synergistically. The trbJ and trbK genes are included within the trb operon, which is tightly regulated by the quorum-sensing regulator TraR and the cognate acylhomoserine lactone. In the absence of quorum-sensing signals, these proteins are not significantly expressed, and cells lacking TrbJ and TrbK are efficient Ti plasmid recipients. In the presence of these signals, these strains block the entry of Ti plasmids and instead become efficient conjugal donors.

scholarly journals Opines stimulate induction of the vir genes of the Agrobacterium tumefaciens Ti plasmid.

1989 ◽  
Vol 171 (7) ◽  
pp. 3696-3703 ◽  
Author(s):  
K Veluthambi ◽  
M Krishnan ◽  
J H Gould ◽  
R H Smith ◽  
S B Gelvin
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Ti Plasmid ◽  
Vir Genes

scholarly journals Opine Catabolic Loci from Agrobacterium Plasmids Confer Chemotaxis to Their Cognate Substrates

1998 ◽  
Vol 11 (2) ◽  
pp. 131-143 ◽  
Author(s):  
Heenam Kim ◽  
Stephen K. Farrand
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Transport System ◽  
Hairy Roots ◽  
Binding Protein ◽  
Ti Plasmid ◽  
Periplasmic Binding Protein ◽  
Metabolic Intermediates ◽  
Condensation Products ◽  
Ti Plasmids ◽  
Carbon Compounds

Opines are carbon compounds produced by crown galls and hairy roots induced by Agrobacterium tumefaciens and A. rhizogenes, respectively. These novel condensation products of plant metabolic intermediates are utilized as nutritional sources by the Agrobacterium strains that induced the growths. Thus, opines are thought to favor the propagation of agrobacteria in the tumorsphere. Certain Agrobacterium strains were chemoattracted to opines. The chemotactic activities to octopine, to nopaline, to manno-pine, and to agrocinopines A+B were dependent on the type of the Ti plasmid present in the bacterium. The determinants for chemotaxis to these opines were localized to the regions of the octopine- and nopaline-type Ti plasmids coding for transport and catabolism of that opine. An insertion in accA, which encodes the periplasmic binding protein for agrocinopines A+B, abolished chemotaxis while an insertion in accC, which encodes a component of the transport system, and an insertion in accF, which encodes a function required for agrocinopine catabolism, did not affect chemotaxis to this opine. Thus, transport and catabolism of these opines are not required for the chemo-tactic activity. Analyses of subclones of the acc region confirmed that accA is the only gene required from the Ti plasmid for chemotaxis to agrocinopines A+B.

scholarly journals Essential Components of the Ti Plasmidtrb System, a Type IV Macromolecular Transporter

1999 ◽  
Vol 181 (16) ◽  
pp. 5033-5041 ◽  
Author(s):  
Pei-Li Li ◽  
Ingyu Hwang ◽  
Heather Miyagi ◽  
Heather True ◽  
Stephen K. Farrand
Keyword(s):  
Insertion Site ◽  
Ti Plasmid ◽  
Conjugal Transfer ◽  
Insertion Mutation ◽  
Type Iv ◽  
System A ◽  
Catabolic Plasmid ◽  
Ti Plasmids ◽  
Essential Components ◽  
Insertion Mutations

ABSTRACT The trb operon from pTiC58 is one of three loci that are required for conjugal transfer of this Ti plasmid. The operon, which probably codes for the mating bridge responsible for pair formation and DNA transfer, contains 12 genes, 11 of which are related to genes from other members of the type IV secretion system family. The 12th gene, traI, codes for production ofAgrobacterium autoinducer (AAI). Insertion mutations were constructed in each of the 12 genes, contained on a full-length clone of the trb region, using antibiotic resistance cassettes or a newly constructed transposon. This transposon, called mini-Tn5Ptrb, was designed to express genes downstream of the insertion site from a promoter regulated by TraR and AAI. Each mutation could trans complement downstream Tn3HoHo1 insertions in the trb operon of full-sized Ti plasmids. When marker-exchanged into the transfer-constitutive Ti plasmid pTiC58ΔaccR mutations intrbB, -C, -D, -E, -L, -F, -G, and -Habolished conjugal transfer from strain UIA5, which lacks the 450-kb catabolic plasmid pAtC58. However, these mutants retained residual conjugal transfer activity when tested in strain NT1, which contains this large plasmid. The trbJ mutant failed to transfer at a detectable frequency from either strain, while the trbImutant transferred at very low but detectable levels from both donors. Only the trbK mutant was unaffected in conjugal transfer from either donor. Transfer of each of the marker-exchange mutants was restored by a clone expressing only the wild-type allele of the corresponding mutant trb gene. An insertion mutation intraI abolished the production of AAI and also conjugal transfer. This defect was restored by culturing the mutant donor in the presence of AAI. We conclude that all of the trb genes except trbI and trbK are essential for conjugal transfer of pTiC58. We also conclude that mutations in any one of thetrb genes except traI and trbJ can be complemented by functions coded for by pAtC58.

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