Effect of Acetosyringone on Growth and Oncogenic Potential of Agrobacterium tumefaciens

Expression of the virulence genes of Agrobacterium tumefaciens occurs in acidic media containing sugars and certain phenolics secreted at plant wounds. In some strains of A. tumefaciens , exposure to these inducing conditions leads to inhibition of bacterial growth, which can then be followed by the selection of avirulent mutants (1 ). Observation of this effect of vir gene induction depends on the use of particular experimental conditions. This chapter first specifies experimental parameters allowing to reveal, in A. tumefaciens , the modifications that accompany vir gene induction. Other parts of the chapter then describe how the mutants that are generated in the presence of acetosyringone are recognized and characterized. These protocols may prove useful to those with an interest in Agrobacterium biology. In addition, acetosyringone enhances the ability of A. tumefaciens to transform recalcitrant host plants, and as such has been incorporated in medium used for co-cultivation of bacteria and plant tissue (2 –5 ) or alternatively has been used to precondition explants prior to addition of bacteria (6 ). Hence, the possibility of side effects of acetosyringone on A. tumefaciens bears direct relevance to experiments dealing with transformation of crop plants.