gstD-GFP transgenic larval imaginal discs, imaged for gstD-GFP (green). (A–D) Representative images of eye imaginal discs incubated in control culture media (A, B), or with that containing the ER-stress-causing chemical DTT (C, D). Anti-Elav (red) labeling shows photoreceptor nuclei. Shown are images of two different focal planes: (A, C) The support cell layer focal plane that does not include Elav-positive nuclei. (B, D) The Elav-positive focal plane. Note that gstD-GFP is induced primarily in the Elav-negative cell layer. (E, H) Eye discs incubated with tunicamycin dissolved in DMSO (G, H), or just with DMSO (E, F). Shown are two different focal planes, the Elav-negative (E, G) and Elav-positive cell layers (F, H). (I, J) Wing imaginal discs incubated with control culture media (I), or with media containing 2 mM DTT for 4 hr (J). Anti-Wg (magenta) was used for counterstaining. (A’, B’, C’, D’, E’, F’, G’, H’, I’, J’) gstD-GFP single channels. Scale bar in H’ = 50 μm.