drp2b single mutants are more susceptible to Pseudomonas syringae pv. tomato (Pto) DC3000 and Pto hrcC− infection.
(A) In planta growth of Pto DC3000 LuxCDABE (DC3000lux) in 4–5 week old Col-0, drp2b-2 (2b-2), and sid2-2 plants. Plants were imaged at 3 days post infiltration (dpi) after syringe-infiltration with DC3000lux (OD600 = 0.0005) by bright field or with a Photek camera. A representative plant is shown for each genotype and treatment. Color scale bar indicates increasing photon intensity. (n = 4 plants/genotype and treatment). (B) Compared to Col-0 (white bars), bacterial growth was significantly increased in drp2b-2 plants (black bar) (P<0.0065) at 3 dpi with DC3000lux (OD600 = 0.0005) as measured by serial dilution plating. sid2-2 served as control (gray bars; sid2-2 to Col-0: P<0.0001; to drp2b-2: P<0.02). (n = 7-12/genotype and treatment). (C) Compared to Col-0 (white bars), bacterial growth was significantly increased in drp2b-2 plants (black bar) (P<0.01) at 3 dpi with Pto hrcC- (OD600 = 0.02) as measured by serial dilution planting. sid2-2 served as control (gray bars; sid2-2 to Col-0: P<0.0001; to drp2b-2: P = 0.0005). (n = 6/genotype and treatment). (D) Using qRT-PCR, no difference in PR1 mRNA levels was observed between drp2b-2, sid2-2 and Col-0 24 hrs after treatment with 50 µM exogenous SA (black bars). Treatment with water (H2O; white bars) served as mock control. (n = 4/genotype an treatment). (E) Levels of SA in drp2b-2 (black bars) compared to Col-0 (white bars) at 24 hr post infection (hpi) with Pto DC3000lux (OD600 = 0.02) (P = 0.375). Treatment with water (H2O; white bars) served as mock control (P = 0.91). (n = 4/genotype and treatment; with each n containing 6 seedlings). Experiments in (A-C) and in (D-E) utilized 4–5 week or 2 week old plants, respectively. All experiments were repeated three times with similar results. Values are mean ± SE. Statistical analysis was done as in Fig. 1.
