Fig. S4.

NRX1 regulates catalase activity. (A) Protein extracts from untreated WT and nrx1-1 plants were desalted on NAP-5 columns and protein concentrations equalized. Decomposition of added H₂O₂ (5 mM) was measured at A₂₄₀ and leaf catalase activity (mmol H₂O₂·mg·protein⁻¹·min⁻¹) calculated using the extinction coefficient of 0.036 cm²/µmol. Error bars represent SE (n = 3). Asterisks indicate statistically significant differences between samples (Student’s t test, P < 0.05). (B) Catalase protein abundance does not differ between WT and nrx1 mutant lines. Protein was extracted from untreated, MV-treated (5 µM), or Psm ES4326- (5 × 10⁵ cells) treated WT, nrx1-1, and cat2 cat3 plants. Analysis was performed by Western blotting using an anti-CAT antibody and an anti-HSP90 antibody as loading control. (C) Protein extract from untreated WT and nrx1-1 plants was desalted on NAP-5 columns and protein concentrations equalized. Extracts were incubated with either 4 µM recombinant NRX1 or NRX1(C55,58,375,378S) and 0.33 mM DTT. Decomposition of added H₂O₂ (5 mM) was measured at A₂₄₀ and leaf catalase activity (mmol H₂O₂·mg·protein⁻¹·min⁻¹) calculated using the extinction coefficient of 0.036 cm²/µmol. Error bars represent SE (n = 3). Asterisks indicate significant differences between WT and mutant recombinant NRX1 proteins (Student’s t test, P < 0.05).