Fig. 2.
Precocious E93 provides an instructive cue to deactivate and activate specific enhancers. (A,C,E,G) Schematic of spatiotemporal enhancer activity alongside immunofluorescence examples. (A) brdisc is active in wing discs and inactive in pupal wings. (B) Confocal image depicting brdisc activity (green) in control genotypes lacking the UAS-E93 transgene (left panels). brdisc remains active (green) after a 5 h E93 (magenta) induction (middle panels). brdisc activity (green) is lost in E93-expressing cells (magenta) after a 24 h induction (right panels). Green arrows indicate comparable locations in the anterior wing after 5 h and 24 h of E93 expression. (C) tncblade (cyan) is inactive in wing discs but is active in pupal wings in the body wall (arrows) marked by Tsh (yellow), and in intervein cells of the blade. (D) tncblade is inactive in control genotypes lacking the UAS-E93 transgene (left panels). ci-GAL4 pattern is indicated in yellow (GFP). tncblade is active (green) in E93-expressing cells (left of red dashed line) also expressing Tsh (magenta) (right panels). Green arrows indicate colocalization of Tsh expression and precocious activation of tncblade. (E) tncwv (cyan) is inactive in wing discs but is active in pupal wings along longitudinal veins marked by pMad (yellow). Cyan arrows indicate high level tncwv activity in the marginal and L5 veins. Yellow arrows indicate high pMad levels in the marginal and L5 veins. (F) tncwv is inactive in control genotypes lacking the UAS-E93 transgene (left panels). ci-GAL4 pattern is indicated in yellow (GFP). tncwv is active (green) in E93-expressing cells (left of dashed red line) with high pMad levels (magenta) (right panels). Green arrows indicate colocalization of high pMad signal and precocious activation of tncwv. (G) nubvein (green) is inactive in wing discs, but is active in pupal wings along the longitudinal veins. E93 expression is shown in magenta. (H) nubvein (green) is inactive in wing discs regardless of E93 expression (magenta). Dashed white lines outline wing tissue. Red dashed lines indicate the boundary of ci-GAL4 activity, as determined by GFP expression. Scale bars: 100 µm.