FIGURE 6.

Alkalinization of the incubation medium by cultured tomato cells in response to CS-20 proteins contained in fraction V, which reduced Fusarium wilt severity in tomato seedlings. (A) Profiles of extracellular pH change in suspensions of two cell lines after addition of the lyophilized fraction V to a final concentration of 10 μg/ml. Cell response (line β) to the fraction pretreated with proteinase K shown by dotted line. The solid line shows extracellular pH of non-treated cells. (B) Dose-rate effect of the fraction V isolated from CS-20 on tomato cell line γ. Numerals near curves show final concentrations (μg per ml) of the lyophilized fraction V in the tomato cell suspension. Re-stimulation of the reversible response is exemplified for a concentration of 2.5 μg/ml. Dotted line illustrates the irreversibility of alkalinization response to preparation from the pathogenic FOL (strain F37), obtained by the same procedures that were applied to isolate fraction V from CS-20. (C) The extracellular pH values after addition of inactive fractions III (white circles) or IV (white triangles) at a concentration of 10 μg/ml. Asterisks show extracellular pH of non-treated cells. Arrows indicated starting point of treatments. The representative data are out of one of three experiments with the protein fraction V samples independently isolated from CS-20 culture.