Effect of the fungal metabolite mixtures on caspase 3-like activity, chromatin condensation and ultrastructure of soybean cells. Panel a and b: caspase 3-like activity in cells treated for 30 min with >3 kDa (a, black boxes) and <3 kDa (b, grey boxes) fractions of the metabolite mixtures. Control cells (Co, white boxes) were incubated with culture medium only. All the abbreviations used for the treatments (wt Tr, Bo, Δech42) are as in Fig. 3. Data are means ± SD of three independent experiments. Bars labeled with a different letter differ significantly (P < 0.05) by Student's t test. Panel c: cells were treated with <3 kDa culture filtrates, stained with HO and PI, and observed under a fluorescence microscope. Pictures represent typical examples. nu, nucleus. Bars: 5 μm. Panel d: ultrastructural observations of control cells and cells incubated for 15 min with <3 kDa fungal metabolites. cc, chromatin condensation, chl, chloroplast, cw, cell wall, nu, nucleus, v, vacuole. Bars: 1 μm.