Figure 3.

Comparison of the various TAs. (A) Western blot analysis of TA levels. Equivalent amounts of total extract protein from flies carrying one copy of the various TAs were probed with a TetR-specific antibody. All TAs were expressed from the actin5C promoter. Wild-type flies (−) without any TA and flies containing an unaltered Tet-Off (tTA), unaltered Tet-On (rtTA), altered Tet-On (rtTA-alt), and altered M2 (rtTA-M2-alt) TAs were compared. (B) Comparison of TA activity using in vitro luciferase assays. Double transgenic Tet-On flies were fed dox-containing food (1 mg/ml) for 24 h, then assayed for luciferase activity. Double transgenic Tet-Off flies were maintained on regular food before luciferase measurements. Flies containing the unaltered, original Tet-On TA (rtTA) produced no detectable luciferase induction, and this value was set to one. All other values are relative to this amount of luciferase.