NtHSP101 activity is repressed by amino starvation. SL304A(pTPI–NtHSP101) containing either pGAL1–Ω-luc (•) or pGAL1–luc (○) was grown to an early exponential stage in SGM before introduction into SGM containing (A) 95 μm, 19 μm, 5 μm, or no histidine or (B) 230 μm, 2.3 μm, or no leucine. The expression from pGAL1–Ω-luc, pGAL1–luc, and their expression ratio (i.e., NtHSP101 activity as indicated by the ratio, Ω-luc/luc) are shown below each panel. See A for symbol designation.