Figure 4.

Oxidative burst reactions in heterologous N. tabacum cell suspension cultures after elicitation with supernatants of X. campestris pv. campestris co-incubated with plant cell wall material. The production of hydrogen peroxide was quantified by means of an H₂O₂-dependent chemiluminescence reaction (A). For each measurement, 200 μl of the respective supernatants were added to the cell cultures. The hydrogen peroxide formation was monitored at different time intervals upon the addition of supernatants of C. annuum cell wall material (✶), supernatants of X. campestris pv. campestris cultures (▲), supernatants of X. campestris pv. campestris cultures co-incubated with C. annuum cell wall material (●), and for a negative control of 200 μl water (♦). There was a clear oxidative burst upon the addition of a supernatant of X. campestris pv. campestris co-incubated with cell wall material, but an almost similar explicit reaction when a supernatant of X. campestris pv. campestris was added that had not been co-incubated with cell wall material. (B) Supernatants of X. campestris pv. campestris cultures were treated with polymyxin B agarose to remove LPS. Then the effect of the purified supernatants on N. tabacum cell suspension cultures was analyzed. The formation of H₂O₂ was monitored upon the addition of supernatants of X. campestris pv. campestris cultures (▲), supernatants of X. campestris pv. campestris cultures co-incubated with C. annuum cell wall material (●), supernatants of X. campestris pv. campestris cultures purified from LPS (■), supernatants of X. campestris pv. campestris cultures co-incubated with C. annuum cell wall material and purified from LPS (✶), and after adding 200 μl water as a negative control (♦). Removing the LPS reduced the response to X. campestris pv. campestris supernatant to the level of the water control. In contrast to this, the removal of LPS reduced the amplitude of the cell culture response to X. campestris pv. campestris co-incubated with cell wall material, but this supernatant still evoked a clear oxidative burst reaction.