A Ti-plasmid determined function is responsible for chemotaxis of Agrobacterium tumefaciens towards the plant wound product acetosyringone

Agrobacterium tumefaciens C58C¹[pTiB6S3] harbouring the octopine Ti-plasmid pTiB6S3, showed positive chemotaxis towards the phenolic plant wound exudate acetosyringone (AS). Maximal attraction was observed at 10⁻⁷ M. In contrast, A. tumefaciens C58C¹ lacking a Ti-plasmid, exhibited no chemotactic response to AS. However, chemotaxis did occur towards the plant phenolic vanillyl alcohol, but at higher concentrations (10⁻² M) and in both Ti-plasmid-containing and cured A. tumefaciens.These results indicate that at least one Ti-plasmid function is involved in the specific chemotactic response to AS, although chemotaxis per se is not Ti-plasmid-encoded. This correlates well with the specific induction of vir-operons mediated by this plant wound product [1].