Identification of the signal molecules produced by wounded plant cells that activate T-DNA transfer in Agrobacterium tumefaciens

We show here that Agrobacterium tumefaciens virulence (Vir) gene expression is activated specifically by the plant molecules acetosyringone (AS) and α-hydroxyacetosyringone (OH-AS). These molecules induce the entire vir regulon in Agrobacterium as well as the formation of T-DNA intermediate molecules. AS and OH-AS occur specifically in exudates of wounded and metabolically active plant cells and probably allow Agrobacterium to recognize susceptible cells in nature.