The use of carbon and phenol sources in the medium for optimal induction of virulence genes promoter in Agrobacterium tumefaciens

The virulence genes (vir) of Agrobacterium tumefaciens induces by many factors such as specific plant phenolic metabolites and sugars. A number of these factors act synergistically with acetosyringone and causing high expression levels of vir genes. In present research, the induction of virB2 and virD2 gene promoters, were investigated in A348 (MX311) and A348 (MX243) Agrobacterium variants, respectively. The promoter sequences from these vir genes have been fused with a promoterless lacZ gene in a cassettes carrying Tn3. A three-day culture of Agrobacterium was performed, which was included a vegetative growth followed by an induction step. Sugar treatment of glucose, mannose and deoxymannose were used in combination with different concentrations of acetosyringone in the two biological and three technical replications. According to the results, the highest activity of β-galactosidase enzyme attained when the mannose of sugar was used in combination with 50 µM acetosyringone for bacterial strain carrying virB2::lacZ construct. The mannose of sugar treatment in combination with 100 µM acetosyringone treatment, for bacterial strain carrying virD2:: lacZ, induced the highest enzyme activity. The monosaccharides in order of descending vir::lacZ activity in the absence of acetosyringone: glucose > mannose > deoxymannose. According to our observations, we suggested that the mannose of sugar treatment with 100 µM acetosyringone could be utilized for obtaining strong induction of Agrobacterium vir genes in an induction medium.