Specificity of signal molecules in the activation of Agrobacterium virulence gene expression

• Published in: Molecular microbiology Vol. 3; no. 7; p. 969
• Main Authors: Melchers, L S, Regensburg-Tuïnk, A J, Schilperoort, R A, Hooykaas, P J
• Format: Journal Article
• Language: English
• Published: England 01.07.1989
• Subjects: Acetophenones - pharmacology; Gene Expression Regulation; Hydrogen-Ion Concentration; Kinetics; Molecular Structure; Mutation; Rhizobium - genetics; Rhizobium - physiology; Sodium Chloride - pharmacology; Structure-Activity Relationship; Temperature
• ISSN: 0950-382X
• DOI: 10.1111/j.1365-2958.1989.tb00246.x

The activation of the Agrobacterium virulence system is known to be induced by certain phenolic compounds. We have tested the vir-inducing ability of fifty compounds, by using a virB-lacZ gene fusion, and analysed the relationship between structure and activity of these compounds. In this way we have identified several new vir-inducers: coniferylalcohol, 3,5-dimethoxy-4-hydroxybenzene, homovanillic acid, ferulic acid, 3-ethoxy-4-hydroxybenzaldehyde and guaiacol, all of which are compounds with strong or moderate activity and four compounds with weak vir-inducing activity. In view of the specificity of vir-inducers, our data extended observations of others and enabled us to define the specific structural features of a vir-inducer molecule. In addition we show here that induction of the octopine Ti vir-genes is (i) optimal at 29 degrees C and totally abolished at 37 degrees C, and (ii) strongly inhibited at low concentrations of sodium chloride. The implications for plant transformation are discussed.