Figure 3.

Bacteria-induced gene expression and bacterial multiplication in systemic leaves of primary inoculated plants. A, Five-week-old Arabidopsis wild-type plants were pressure infiltrated on four lower leaves with suspensions of Pst avrRpt2 (optical density at 600 nm [OD₆₀₀] = 0.002), Psm ES4326 (OD₆₀₀ = 0.002), or Psp avrB (OD₆₀₀ = 0.002) in 10 mm MgCl₂. Control plants were infiltrated with 10 mm MgCl₂ in the absence of bacteria (mock). After 3 d, systemic leaves were assayed for the presence of HsfB1 transcripts by qRT-PCR. B, Five-week-old wild-type (WT), hsfb1-1, and hsfb1-3 plants were inoculated on four lower leaves with Psp avrB (OD₆₀₀ = 0.002). Three days later, systemic leaves were challenge inoculated with Psm ES4326 (OD₆₀₀ = 0.0002). After another 3 d, Psm ES4326 bacteria were isolated from a homogenized 0.5-cm disc from infected systemic leaves, spread on King’s B agar plates containing 100 µg mL⁻¹ streptomycin as a selection marker, incubated at 28°C for 2 d, and analyzed for the number of developing colonies. C, Five-week-old wild-type and hsfb1-3 plants were infiltrated on four lower leaves with Psp avrB (OD₆₀₀ = 0.002). Three days later, three systemic leaves were harvested from each plant and assayed for the presence of transcripts for PR1, PR2, and PR5 using gene-specific primers (Supplemental Table S1). In all experiments, plants were grown as described in Figure 1. In A and C, relative amounts were normalized to those of ACTIN2. Error bars indicate sd (n = 3). The experiments were repeated three times with similar results.