Ammonium induction of PKA activity depends on Tor1p, Ras2p and Sch9p regulation. Trehalase activity of cells nonstarved or starved for leucine, histidine, or lysine, individually or in different combinations, of (a) wild-type S. cerevisiae (BY4742) and of mutant deleted strains (b) tor1Δ, (c) ras2Δ, and (d) sch9Δ; before being, transferred to water (T0h) and after 2 hours in water (T2h H2O) or water with (NH4)2SO4, 0.5% (T2h H2O + NH4
+). In all the cultures, starting cell density was about 3.8 × 107 cells/mL, and the initial pH was adjusted to 7.0. Values are means ± SEM (n = 3–4). (a) *P < 0.05 (aa-starved T0h versus aa-starved T2h H2O + NH4
+), **P < 0.01 (Leu-starved T0h versus Leu-starved T2h H2O + NH4
+), **P < 0.01 (Leu-starved T2h H2O + NH4
+ versus His-starved T2h H2O + NH4
+), **P < 0.01 (Leu-starved T2h H2O + NH4
+ versus Lys-starved T2h H2O + NH4
+), *P < 0.05 (Leu-starved T2h H2O + NH4
+ versus His-Lys-starved T2h H2O + NH4
+); (c) ***P < 0.001 (nonstarved T0h versus nonstarved H2O + NH4
+); (d) *P < 0.05 (aa-starved T0h versus aa-starved T2h H2O + NH4
+). Statistical analysis was performed by two-way and one-way ANOVA.