FIG. 3.

The AMT1 and AMT2 genes are required for growth under low-ammonium conditions and are differently regulated in response to nitrogen availability. (A) Wild-type MATα (H99) and MATa (KN99) and isogenic amt1Δ, amt2Δ, and amt1Δ amt2Δ strains were grown overnight in YPD medium, washed, serially diluted and plated on YPD and low-ammonium (50 μM) medium, and grown for 2 days at 30°C. (B) Overnight cultures of H99 wild-type cells and isogenic amt1Δ, amt2Δ, and amt1Δ amt2Δ cells were washed and spotted onto complete synthetic medium (CMD) and grown for 2 weeks at room temperature. The white lines represent the diameter of the wild-type colony for comparison purposes. (C) Northern analysis of the levels of AMT1 and AMT2 transcripts in wild-type (H99) cells grown CMD or synthetic medium with limiting quantities of glutamine (Glu), proline (Pro), or ammonium (Am) (50 μM). Levels of ACT1 transcripts served as the loading control.