THE BINDING-SITE OF THE TRANSCRIPTIONAL ACTIVATOR VIRG FROM AGROBACTERIUM COMPRISES BOTH CONSERVED AND SPECIFIC NONCONSERVED SEQUENCES

Virulence genes of Agrobacterium tumefaciens are transcriptionally act ivated in response to phenolic compounds and certain sugars. The trans criptional activator VirG specifically binds to fragments containing t he conserved vir box sequence present in the promoter region of all vi r genes. This study shows that both the vir box as well as specific no nconserved sequences downstream of the vir box are required for VirG b inding and transcriptional activation. Insertion of the identified Vir G binding site into the lac promoter resulted in transcriptional activ ation of this heterologous promoter in response to the plant phenolic signal molecule acetosyringone.