Fig. 4

Nitrate inhibits the accumulation of ROS through the GAF domain of AtNLP7. A, B NBT and DAB staining showed that nitrate treatment significantly reduced the contents of ROS in the primary root of nlp7-1 and AtNLP7^ΔGAF plants. Bar = 100 μm. Plants growing on medium with 10 mM KNO₃ for five days were transferred to N-free medium for two days then treated with 10 mM KCl or KNO₃ for one hour. C, D Quantification of NBT and DAB intensities by Image J. Data are mean ± SD (n = 10). The letters indicate significant differences (P < 0.05). E ROS treatment attenuated nitrate-induced nuclear localization of AtNLP7 but not AtNLP7^ΔGAF. Plants growing on medium with 10 mM KNO₃ for five days were transferred to N-free medium for two days then treated with 10 mM KNO₃ or 10 mM KNO₃ + 0.5 mM H₂O₂ for one hour. Bar = 50 μm