Influence of a crown-gall tumor initiation enhancer on bacterial attachment to the host plant cell wall.

The competitive activities of different plant cell walls upon Agrobacterium tumefaciens attachment have been studied in vitro by means of two crown-gall tumor initiation assays. The low or high susceptibility of different plant species is independent of their capacity to cause bacterial cells to adhere to specific sites on the plant cell walls. However, the attachment properties of cell wall fragments derived from Helianthus cotyledons seem to be age-dependent. It is found that a tumor initiation enhancer, present in extract fractions derived from highly susceptible plants and closely related with the competence for tumor formation, does not influence bacterial adherence. The two steps, attachment and the step by which the tumor initiation enhancer is involved, clearly differ in the processes leading to the transformation of a normal cell into a tumor cell.