OPINE CATABOLIC LOCI FROM AGROBACTERIUM PLASMIDS CONFER CHEMOTAXIS TOTHEIR COGNATE SUBSTRATES

Opines are carbon compounds produced by crown galls and hairy roots in duced by Agrobaeterium tumefaciens and A, rhizogenes, respectively, Th ese novel condensation products of plant metabolic intermediates are u tilized as nutritional sources by the Agrobacterium strains that induc ed the growths, Thus, opines are thought to favor the propagation of a grobacteria in the tumorsphere, Certain Agrobacterium strains were che moattracted to opines, The chemotactic activities to octopine, to nopa line, to mannopine, and to agrocinopines A+B were dependent on the typ e of the Ti plasmid present in the bacterium, The determinants for che motaxis to these opines were localized to the regions of the octopine- and nopaline-type Ti plasmids coding for transport and catabolism of t hat opine. An insertion in accA, which encodes the periplasmic binding protein for agrocinopines A+B, abolished chemotaxis while an insertio n in accC, which encodes a component of the transport system, and an i nsertion in accF, which encodes a function required for agrocinopine c atabolism, did not affect chemotaxis to this opine, Thus, transport an d catabolism of these opines are not required for the chemotactic acti vity, Analyses of subclones of the acc region confirmed that accA is t he only gene required from the Ti plasmid for chemotaxis to agrocinopi nes A+B.