Figure 5. A. tumefaciens strains lacking virG and pTi are able to suppress SA production in N. tabacum.

Tobacco leaves were inoculated with wild type A. tumefaciens A348 (dark grey bars), A348 (virG-) (pale grey bars), the pTi lacking derivative A136 (white bars) (all at 10⁷ cfu/ml) or 10 mM MgCl₂(AS) (black bars), followed by inoculation with P. syringae pv. tabaci 11528 (Pta) or P. s. pv. tomato DC3000 (Pto) (10⁵ cfu/ml) after 48 hours. The SA biosensor ADPWH-lux was inoculated into leaves 24 hours after infiltration with P. syringae. SA-induced luminescence was measured one hour after biosensor inoculation using a photon-counting camera and absolute lux values were normalized against the infiltrated area. Error bars show standard error of the mean. General Linear Model (GLM) analysis revealed statistical differences between treatments (F = 21.0735; p<0.0001; df = 50). Means with the same letter were not significantly different at the 5% confidence level based on least square (LS) means using Student's t-test. The experiment was performed at least twice with similar results.