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

February 1998 , Volume 11 , Number  2
Pages  131 - 143

Heenam Kim 1 and Stephen K. Farrand 1 , 2

Department of 1Microbiology and 2Crop Sciences, University of Illinois at Urbana-Champaign, Urbana 61801, U.S.A.

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Accepted 25 October 1997.

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.

Additional keywords: ABC-type transport system, moc, noc, occ.

© 1998 The American Phytopathological Society