Tracking fly movement and gene expression using GFP. (A) A young 3xP3-GFP male fly was tracked for 120 seconds using GFP, and the 3D trajectory is indicated in red. (B) A male hsp70-GFP fly (40 days old, strain 2MI4) was tracked for 120 seconds, flanking a transition from motionless to sustained activity. Activity is expressed as distance moved per second (blue) and GFP intensity is expressed as average pixel intensity per second (green). (C-E) Single flies of the indicated age were tracked for 48 hours. Black/white bars indicate the light/dark cycle the flies were cultured under prior to the beginning of the experiment. Activity is expressed as distance moved per hour (blue) and GFP intensity is expressed as average pixel intensity per hour (green). (C) 3xP3-GFP, transgenic strain M1, 37 days old. (D) hsp70-GFP, transgenic strain 2MI4. (E) hsp22-GFP, transgenic strain 1MI1. Arrows indicate the last time point at which the 48-day-old animals displayed spontaneous movement; these animals were scored as dead at the end of the experiment based on lack of movement in response to stimulation.