Figure 2.

P. syringae T3E polymutants display differential activities with regard to manipulation of the Arabidopsis actin cytoskeleton. A, Type three-secretion system effector Pst DC3000 polymutants show a differential growth response in Col-0. Bacterial growth of Pst DC3000 and the suite of Pst DC3000 effector polymutants were enumerated at 24 h after dip-inoculation with Pst DC3000 polymutant strains at a concentration of 3 × 10⁷ cfu ml⁻¹. Shaded boxes indicate the presence of the described effector gene clusters. Error bars, representing mean ± se, were calculated from five (n = 15) biological replicates for Pst DC3000, and from two (n = 6) for each of the Pst DC3000 polymutants. Bacterial growth was enumerated based on cfu per mg fresh weight. Statistical significance was determined using a one-way ANOVA, Tukey test; P < 0.01. B, Pst DC3000 in planta growth correlates with the degree of modulation of host actin architecture. Actin skewness and density values were determined in Col-0/GFP-fABD2 seedlings at 24 hpi. Representative micrographs (left) from n = 80–90 are shown. Quantification of actin bundling (center) and density (right) indicates a bacterial density-dependent alteration in host actin cytoskeleton architecture after inoculation. Wild-type Col-0 plants and Col-0/GFP-fABD2 plants were dip-inoculated with Pst DC3000 at concentrations of 3 × 10⁷ cfu ml⁻¹, 3 × 10⁶ cfu ml⁻¹, and 10⁶ cfu ml⁻¹. Mock = MgCl₂ dip-inoculated. **, P < 0.001. Bar = 20 μm. C, In planta bacterial growth enumeration of Pst DC3000 D28E and the ∆hrcC mutant. Bacterial growth was enumerated at 24 hpi with Pst DC3000 at three separate initial inoculation concentrations; concentrations of 3 × 10⁷ cfu ml⁻¹, 3 × 10⁶ cfu ml⁻¹, and 10⁶ cfu ml⁻¹. Pst DC3000 D28E and the ∆hrcC mutant were inoculated at 3 × 10⁷ cfu ml⁻¹. Bacterial growth assays were repeated twice. Error bars, representing mean ± se, were calculated from three (n = 9) technical replicates. Statistical significance was determined using a one-way ANOVA; P < 0.01.