Abstract

Chemotaxis in bacteria is an excellent model for signal transduction processes. In Agrobacterium 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, virA and virG, allow the sensing of specific wound phenolics such as acetosyringone. This attracts Ti‐plasmid harbouring A. tumefaciens to wound sites, where the higher acetosyringone concentrations lead to virA and virG‐mediated induction of the vir‐genes. The products of the induced genes, act in concert to effect transfer of the T‐DNA to the plant cell.