Figure 1.

Dependence of the rate of H₂O₂ release by transgenic tomato suspension cultures on time following inoculation with P. syringae pv. tomato. Twenty-five milliliters of the desired tomato suspension culture (± Pto) was inoculated with 10⁷ colony-forming units/ml Pst or Pst (avrPto). Aliquots (1.5 ml) were then taken out at the appropriate times, transferred to a fluorimeter cuvette and treated with 7 μl pyranine. The fluorescence quenching due to H₂O₂ catalyzed oxidation of pyranine was then monitored for 15 min. The initial rate of H₂O₂ production was calculated and plotted as a function of time after inoculation with bacteria. Ten units of fluorescence corresponds to 1 μmol of H₂O₂. Similar profiles were seen in at least two independent experiments. (A) BC-R + Pst (avrPto); (B) BC-R + Pst; (C) BC-S + Pst (avrPto); (D) BC-S + Pst.