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 Periplasmic binding protein dependent transport system for maltose and maltodextrins: some recent studies

1989 ◽  
Vol 63 (1-2) ◽  
pp. 53-60
Author(s):  
W. Saurin ◽  
E. Francoz ◽  
P. Martineau ◽  
A. Charbit ◽  
E. Dassa ◽  
...  
Keyword(s):  
Transport System ◽  
Binding Protein ◽  
Periplasmic Binding Protein ◽  
Dependent Transport

Periplasmic binding protein-dependent transport systems: the membrane-associated components

1990 ◽  
Vol 326 (1236) ◽  
pp. 353-365 ◽  
Keyword(s):  
Transport System ◽  
Atp Hydrolysis ◽  
Binding Protein ◽  
Primary Source ◽  
Energy Coupling ◽  
Transport Systems ◽  
Common Mechanism ◽  
Atp Binding ◽  
Periplasmic Binding Protein ◽  
Dependent Transport

Periplasmic binding protein-dependent transport systems are multicomponent, consisting of several inner membrane-associated proteins and a periplasmic component. The membrane-associated components of different systems are related in organization and function suggesting that, despite different substrate specificities, each transport system functions by a common mechanism. Current understanding of these components is reviewed. The nature of energy coupling to periplasmic transport systems has long been debated. Recent data now demonstrate that ATP hydrolysis is the primary source of energy for transport. The ATP-binding transport components are the best characterized of a family of closely related ATP-binding proteins believed to couple ATP hydrolysis to a variety of different biological processes. Intriguingly, systems closely related to periplasmic binding protein-dependent transport systems have recently been identified in several Gram-positive organisms (which lack a periplasm) and in eukaryotic cells. This class of transport system appears to be widespread in nature, serving a variety of important and diverse functions.

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 The Agrobacterium tumefaciens rndHomolog Is Required for TraR-Mediated Quorum-Dependent Activation of Ti Plasmid tra Gene Expression

2001 ◽  
Vol 183 (13) ◽  
pp. 3919-3930 ◽  
Author(s):  
Zhao-Qing Luo ◽  
Stephen K. Farrand
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Quorum Sensing ◽  
Homoserine Lactone ◽  
Ti Plasmid ◽  
Detectable Effect ◽  
Wild Type ◽  
Reading Frame ◽  
Gene Coding ◽  
Ti Plasmids ◽  
Induced Mutants

ABSTRACT Conjugal transfer of Agrobacterium tumefaciens Ti plasmids is regulated by quorum sensing via TraR and its cognate autoinducer, N-(3-oxo-octanoyl)-l-homoserine lactone. We isolated four Tn5-induced mutants of A. tumefaciens C58 deficient in TraR-mediated activation oftra genes on pTiC58ΔaccR. These mutations also affected the growth of the bacterium but had no detectable influence on the expression of two tester gene systems that are not regulated by quorum sensing. In all four mutants Tn5 was inserted in a chromosomal open reading frame (ORF) coding for a product showing high similarity to RNase D, coded for by rnd ofEscherichia coli, an RNase known to be involved in tRNA processing. The wild-type allele of the rnd homolog cloned from C58 restored the two phenotypes to each mutant. Several ORFs, including a homolog of cya2, surround A. tumefaciens rnd, but none of these genes exerted a detectable effect on the expression of the tra reporter. In the mutant,traR was expressed from the Ti plasmid at a level about twofold lower than that in NT1. The expression of tra, but not the growth rate, was partially restored by increasing the copy number of traR or by disrupting traM, a Ti plasmid gene coding for an antiactivator specific for TraR. The mutation in rnd also slightly reduced expression of two tested vir genes but had no detectable effect on tumor induction by this mutant. Our data suggest that the defect intra gene induction in the mutants results from lowered levels of TraR. In turn, production of sufficient amounts of TraR apparently is sensitive to a cellular function requiring RNase D.

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