Fig. 3.

Nitrate response of the OBP4 transcription factor is altered in nac4 mutants. WT Col-0, nac4-1, and nac4-2 mutant plants were grown in ammonium succinate for 2 wk and then treated with 5 mM KNO₃ or 5 mM KCl for 1, 2, and 4 h. RNA levels of the OBP4 and the bHLH128 transcription factors were measured using qRT-PCR. Values are mean ± SE of three biological replicates. Gray bars represent time 0 (before treatment), white bars represent KCl treatment, and black bars represent KNO₃ treatment. Asterisks denote means that are statistically different between the KCl and KNO₃ treatments (P < 0.05).