Figure 1.

MAMP Activity from Xac.

(A) Preparations of living Xac bacteria or bacteria after sonication induce extracellular alkalinization in cultured cells of the Arabidopsis double mutant fls2 efr (Col-0 background). The activity is strongly impaired by heating (95°, 10 min) or by digestion with Proteinase K. The data show continuous pH tracings of representative examples from n > 5 repetitions of these experiments. The pH at the start of the experiment was 5.3, and scaling of time (x axis) and pH (y axis) were as indicated by the arrows.

(B) Partial purification of the activity in the Xac extract by anion exchange chromatography at pH 8.0. Eluate obtained by increasing NaCl concentration (x axis) was analyzed for OD₂₈₀ and OD₂₁₅. Fractions with highest activity (measured by ethylene emission from leaf pieces of fls2 efr plants; y axis) were pooled and denominated eMax as indicated.

(C) Dose dependency for ethylene induction. Leaf pieces of fls2 efr plants were treated with different concentrations of eMax. Values represent mean and sd of three replicates.

(D) Ethylene production of Col-0 leaf pieces treated with eMax (2 μg/mL), heat-treated eMax (2 μg/mL), or the fungal preparation Pen (90 µg/mL) as positive control. Bars and error bars represent mean and sd of n = 3 replicates. Asterisks show results that differ significantly from control treatment (Student's t test, P < 0.01).

(E) PTI against P. syringae pv tomato strain DC3000 (Pst DC3000). Arabidopsis fls2 efr leaves were pretreated by pressure infiltration of leaves with 100 μL of buffer (0.4 mM Tris, pH 8.0, with 5 mM NaCl) or buffer with eMax (0.6 µg protein) for 12 h before pressure infiltration with P. syringae pv tomato strain DC3000. Bars and error bars show mean and sd of bacterial numbers (measured as colony-forming units [CFU], at the indicated days after infection [dpi]) from n = 8 replicates. Asterisks mark significant induction over control based on a Student’s t test, P value < 0.01.

(F) PTI against B. cinerea. Arabidopsis fls2 efr plants were sprayed with eMax or buffer and 12 h later infected by spotting 5 μL drops containing ∼500 spores of B. cinerea. Photographs were taken 4 d after infection.