Figure 1.

High-resolution kinetics of transcriptome responses to NO₃^- treatment. (a) Levels of mRNA for nitrogen-responsive sentinel genes in Arabidopsis roots in response to NO₃^- treatment. Fourteen-day-old plants grown in the presence of ammonium succinate were treated with 1 mM KNO₃ or KCL (as a mock treatment). Plants were collected at 0 minutes (before treatment) and 3, 6, 9, 12, 15, 20, 25, 35, 45, and 60 minutes after treatment. Sentinel transcripts were measured in RNA from roots using RT-QPCR and normalized to two housekeeping genes (see Materials and methods). The insets show the Affymetrix MAS5 normalized signal for the sentinel genes on the 0- to 20-minute samples. The data represent the mean ± standard error of three and two biological replicates for QPCR and Affymetrix measurements, respectively. (b) Percentage of genes not detected as NO₃^- regulated in Wang et al. [6]. (c) Overall behavior (relative expression) of 550 regulated genes (Log base 2(Signal KNO₃/Signal KCl)) between 0 and 20 minutes. These data correspond to ATH1 measurement of the samples collected for the RT-PCR presented in (a) (grey shades; see also Materials and methods for further details).