AbstractChemotaxis in bacteria is an excellent model for signal transduction processes. InAgrobacterium tumefaciens, the causative agent of crown gall tumour on wounded plants, it is a vital part of the organism's biology. A chromosomally‐determined chemotaxis system causes the bacterium to be attracted into the rhizosphere by chemoattractants in plant exudates. By interfacing with this system, the multifunctional products of two Tiplasmid encoded genes,virAandvirG, allow the sensing of specific wound phenolics such as acetosyringone. This attracts Ti‐plasmid harbouring A.tumefaciensto wound sites, where the higher acetosyringone concentrations lead tovirAandvirG‐mediated induction of thevir‐genes. The products of the induced genes, act in concert to effect transfer of the T‐DNA to the p