Fig. 6. LLG1 genetically functions downstream of MEKK2.

a The llg1-1 mutant partially suppresses the mkk1/2 cell death. The seedlings grown on ½MS plate were photographed at 2-weeks post-germination. The leaves from the individual plants were placed with the order of age (from oldest to youngest, right panels). Scale bar, 0.5 cm. b llg1-1 increases the fresh weight of mkk1/2. The data are shown as mean ± SE (n = 4). P = 1.46 × 10⁻² (column 3 and 5). The asterisk indicates statistical significance by using two-sided two-tailed Student’s t test (*P < 0.05). c The llg1-1 mutant reduces the expression of PR1 in mkk1/2. The expression of PR1 was determined with the plants in a and normalized to the expression of UBQ10. The data are shown as the mean ± SE of four biological repeats (n = 4). P = 2.06 × 10⁻⁵ (column 3 and 5). The different letters indicate the significant difference determined by one-way ANOVA followed by the Tukey test (P < 0.05). d The llg1-1 mutant partially suppresses the mpk4 cell death. The plants grown on soil were photographed at 4-weeks after germination. Scale bar, 1 cm. e llg1-1 increases the fresh weight of mpk4. The data are shown as mean ± SE (n = 4). P = 4.69 × 10⁻³ (column 3 and 5). The asterisk indicates statistical significance by using two-sided two-tailed Student’s t test (***P < 0.01). f The llg1-1 mutant reduces the expression of PR1 in mpk4. The expression of PR1 was determined with the plants in d and normalized to the expression of UBQ10. The data are shown as the mean ± SE of four biological repeats (n = 4). P = 6.78 × 10⁻⁸ (column 3 and 5). The different letters indicate the significant difference determined by one-way ANOVA followed by the Tukey test (P < 0.05). g Overexpressing MEKK2 triggers growth defects in WT, but not in llg1-1. Three representative lines were used to indicate the phenotype of transgenic lines in WT Col-0 and llg1-1 with different MEKK2-HA expression level. The pictures were taken with 4-week-old soil-grown plants. Scale bar, 1 cm. h The protein accumulation of MEKK2-HA in WT and llg1-1 transgenic plants. Total proteins were isolated from plants in g and immunoblotted using an α-HA antibody (top panel). CBB staining of RBC is shown as the loading control (bottom panel). i The elevated expression of PR1 triggered by overexpressing MEKK2 in WT (Lines 1, 2, and 3) is reduced in llg1-1 (Lines 4, 5, and 6). The expression of PR1 was normalized to the expression of UBQ10 and the data are shown as the mean ± SE of four biological repeats (n = 4). The different letters indicate the significant difference determined by one-way ANOVA followed by the Tukey test (P < 0.05). To measure the weight of mkk1/2 and mpk4 mutants, 10 plants were pooled and the weight of individual plants was averaged. The above experiments were repeated three times with similar results.