a Experimental designs for assessing activation of defense pathways and resistance to nematodes and bacteria. b Enhanced resistance to virulent P. syringae pv. tomato (Pst) DC3000 does not require acx1 acx5. Bacterial growth was assayed 3 days post inoculation. Data are averages ± SEM (n = 17). c ascr#18 increases resistance of Arabidopsis wildtype, but not acx1 acx5 mutants, to plant-parasitic nematodes (M. incognita). Arabidopsis seedlings were treated with buffer or the indicated concentrations of ascr#18 for 48 h before inoculation with ~300 freshly hatched M. incognita J2 larvae. The numbers of root galls of infected plants were counted 6 weeks post inoculation. Data are averages ± SEM (n ≥ 15). d, e ascr#18 treatment of Arabidopsis wildtype, but not acx1 acx5 mutants results in deterrence of M. incognita J2 larvae resistance. Arabidopsis seedlings were treated with the indicated concentrations of ascr#18 for 48 h before transfer into 12-well plates containing Pluronic F-127 gel with ̴~200 freshly hatched M. incognita J2 larvae. Larvae touching root tips (d) or the whole area of roots (e) were counted at 6 h post seedling transfer. Data are average ± SEM (n = 12). f Induction of defense–response genes in Arabidopsis leaves 24 h after root treatment with 1000 nM ascr#18. Transcript levels were determined by qRT-PCR. Data are mean ± SEM (n ≥ 6). Adjusted p-values were calculated by two-way ANOVA followed by Tukey multiple comparisons post hoc test. n.s. = not significant. Source data are provided as a source data file.