FIG 2.

Expression of the nasA gene was induced by nitrate and repressed by ammonium. RNA was extracted from wild-type R. solanacearum cells incubated for 3 h at a density of 2 × 10⁸ CFU/ml in either minimal medium (with no nitrogen, ammonium, nitrate, or both ammonium and nitrate) or in 1:10-diluted xylem sap. After cDNA synthesis, gene expression levels were determined with relative value quantitative real-time PCR using rplM for normalization. The data are presented relative to nasA expression in wild-type R. solanacearum cells in minimal medium with no nitrogen source. Bars indicate the standard errors; n = 9 biological replicates for each treatment.