Fig 5.

Regulation of P2 and P1 in mutant strain MN52. (A) Membranes m1, m2, and m3, containing RNA from cells of the WT or mutant strain MN52 cultured in medium containing ammonium (a) or nitrate (n) as a nitrogen source, as indicated, were hybridized with internal probes of the genes indicated at the right of each panel. Hybridization with rnpB was used as a control for RNA loading. (B) RNA from cells of the WT and strain MN52 cultured with ammonium or nitrate as a nitrogen source was subjected to primer extension with the primers indicated at the right. Arrowheads point to extension products at the expected positions for transcripts initiating at Pnir (red), P2 (blue), or P1 (brown).