FIG. 5.

Primer extension analysis of the expression of the P_ntcA-gfp fusion in strains CSEL6, CSEL10, CSEL11, and CSEL12. Primer extension was carried out with primer GFP4 and RNA isolated from filaments grown with ammonium (lanes labeled 0) or from filaments grown with ammonium, washed, and incubated for 6, 12, or 24 h in the absence of combined nitrogen. The positions of TSPs −49, −136, and −180, which were generated from promoters P₁, P₂, and P₃, respectively, are indicated. The results shown in panels A and B correspond to two different step-down experiments.