FIG. 4.

Expression analysis of A. nidulans ammonium permease genes in wild-type background. (A) Northern analysis of ammonium permease gene expression from the wild-type (MH1) strain. RNAs were isolated from mycelia grown in 1% glucose-ANM medium, pH 6.5, with 20 mM ammonium (NH₄⁺) at 37°C for 16 h and then transferred to fresh medium that was nitrogen- and/or carbon-free, as indicated, for 4 hours. Alternatively, RNAs were isolated from mycelia grown for 16 h at 37°C in 1% glucose medium, pH 6.5, with 10 mM glutamine (gln), glutamate (glu), proline (pro), alanine (ala), or nitrate (NO₃⁻), as indicated. Northern blots were hybridized with probes specific for meaA, mepA, mepB, and mepC (see Materials and Methods) or A. nidulans histone H3 as a loading control (13), as indicated. Sizes to the right (in kb) represent the approximate sizes of the respective transcripts. (B) Multiplex RT-PCR analysis of meaA, mepA, mepB, and mepC gene expression. The sizes of the AMT/MEP products (upper bands) and the benA loading control (lower bands) are indicated, and the name of the respective AMT/MEP gene is shown at the top of each gel picture. The growth conditions were the same as those for panel A. RT-PCR conditions and primer details are described in Materials and Methods.