FIGURE 2:

Differential gene expression as a function of nitrogen source in nutrient-limited chemostats. (A) The nitrogen-responsive NCR-A, NCR-P, and SPS regulons respond specifically to nitrogen limitation, whereas the GAAC and UPR regulons are not differentially expressed in nitrogen-limited chemostats compared with carbon, sulfur, phosphorus, leucine, and uracil growth limitation. Gene expression values in Brauer et al. (2008) were relative to a common reference taken from a glucose-limited chemostat grown at a dilution rate of 0.25 h⁻¹. (B) A small number of nitrogen-regulated genes respond significantly to variation in nitrogen source in nitrogen-limited conditions. Regulon membership of genes is denoted by color corresponding to A (NCR-A, green; GAAC, orange; NCR-P, blue; UPR, red). GDH2 has been proposed to be a member of both NCR-A and GAAC regulons (Godard et al., 2007). Filled symbols represent significant effects as determined by permutation testing. Gene expression values are relative to gene expression in an ammonium-limited chemostat growing at a dilution rate of 0.12 h⁻¹.