Figure 1. HopM1 suppresses Pph-induced PR-1 expression without reducing accumulation of SA.

A) Col-0 leaves were infiltrated with buffer, Pph, or Pph (HopM1), sprayed with 500 µM SA, or left untreated. Quantitative real time PCR (qRT-PCR) was used to measure the amount of PR-1 transcript (relative to actin) at 12, 24, and 48 hai. The graph shows combined values from three independent biological replicates normalized with Pph in Col-0 at 24 hai set to 1. Error bars represent standard deviations. Paired two-tailed t-tests indicate that Pph (HopM1) induced less PR-1 transcript than Pph at 24 (*, P = 0.0001) and 48 (**, P = 0.004) hai. PR-1 accumulation with SA treatment was also significantly higher compared to Pph infiltration at 12 hai (***, P = 0.02). B) From leaves treated as in (A), total protein was extracted at 24 and 48 hai and subjected to anti-PR-1 immunoblotting. PR-1 protein in each sample was quantified and normalized with the value for Pph at 48 hai set to 1. The numbers shown below the blots indicate the average and standard deviation of combined data from three independent biological replicates. Paired two-tailed t-tests indicate that Pph (HopM1) induce less PR-1 protein than Pph at both 24 and 48 hai (P≤0.05). The cross-reacting band above PR-1 and ponceau staining of RuBisCo indicate equal loading of samples. C) From leaves treated as in (A), SA was extracted at 6, 12, 24, and 48 hai and measured by HPLC. Shown is the combined data from three biological replicates and error bars represent standard deviations. Samples marked with asterisks (*) contained too little SA for accurate quantification.