Figure 1.
E. coli DH5α can trigger stomatal closure in V. faba.
A, Stomatal aperture in V. faba epidermal peels incubated with DH5α at the indicated concentrations; B, Stomatal aperture in V. faba epidermal peels incubated with mock or DH5α at 108 CFU/ml. Results represent means of three replicates ±SEM, (n = 120 stomata).
Figure 2.
DH5α-induced stomatal closure involves ROS accumulation in guard cells.
A, Stomatal aperture in V. faba epidermal peels incubated with different treatments. Data are means of 120 stomatal aperture measurements from three replicates ±SEM; B, ROS accumulation in intact guard cells detected by H2DCF-DA fluorescence. The microscopic images represent fluorescent and DIC images of peels treated with mock (upper left and right), fluorescent image of peels treated with DH5α at 108 CFU/ml (lower left), and fluorescent image of peels treated with 1 mM LPS (lower right). Bars = 50 µm; C, Quantitation of generated ROS in Vicia faba guard cells as shown in B. Asterisks denote significant differences as analyzed by two-tailed t-test (***, P<0.001; ns, no statistical difference).
Figure 3.
DH5α-elicited stomatal closure is abolished by low [CO2] or high RH treatment.
A and B, Stomatal aperture and conductance in V. faba leaves dip-inoculated with mock or DH5α at 108 CFU/ml under ambient or low CO2 concentrations; C and D, Stomatal aperture and conductance in V. faba leaves dip-inoculated with mock or DH5α at 108 CFU/ml under ambient and high RH conditions. Data from the epidermal bioassay are means of 120 stomatal aperture measurements from three replicates ±SEM. Data from the stomatal conductance experiment are means of measurements from 8–12 leaves (n = 4). Asterisks denote significant differences as analyzed by two-tailed t-test (***, P<0.001; **, P<0.01; *, P<0.05; ns, no statistical difference).
Figure 4.
DH5α-triggered stomatal closure is disguised by darkness or drought treatment.
A and B, Stomatal aperture and conductance in V. faba leaves dip-inoculated with mock or DH5α at 108 CFU/ml under light/dark transition; C and D, Stomatal aperture and conductance in V. faba leaves dip-inoculated with mock or DH5α at 108 CFU/ml under different field water content (FWC). Data from the epidermal bioassay are means of 120 stomatal aperture measurements from three replicates ±SEM. Data from the stomatal conductance experiment are means of measurements from 8–12 leaves (n = 4). Asterisks denote significant differences as analyzed by two-tailed t-test (***, P<0.001; *, P<0.05; ns, no statistical difference).
Figure 5.
Exogenous ABA can reduce stomatal aperture and inhibit foliar bacterial growth under high RH.
A, Stomatal aperture in V. faba leaves dip-inoculated with mock or DH5α (108 CFU/ml) supplemented with the indicated concentrations of ABA under ambient and high RH conditions. Results represent means of three replicates ±SEM, (n = 120 stomata). “+” and “−” represent presence or absence of DH5α cells in the inoculum. Asterisks denote significant differences as analyzed by two-tailed t-test (**, P<0.01; ns, no statistical difference); B, Bacterial population in V. faba leaves at day 3 after dip inoculation with DH5α. “+” and “−” represent presence or absence of ABA (20 µM) in the inoculum.
Figure 6.
Pathogenicity of DC3118 in Arabidopsis can be modulated by extrinsic factors.
A, Stomatal aperture in Col-0 leaves surface-inoculated with mock or DC3118 at 108 CFU/ml under ambient or high RH; B, Stomatal aperture in Col-0 leaves surface-inoculated with different treatments under high RH. Data in A and B represent means of 120 stomatal aperture measurements from three replicates ±SEM. Asterisks denote significant differences as analyzed by two-tailed t-test (***, P<0.001; ns, no statistical difference); C, Progression of disease symptom in Col-0 plants with the following treatments: (I) RH = 60%, mock; (II) RH≥90%, mock; (III) RH = 60%, DC3118 (108 CFU/ml); (IV) RH≥90%, DC3118 (108 CFU/ml); (V) RH≥90%, DC3118 (108 CFU/ml) + ABA (20 µM).