Fig. 2

dAtg1 is required for complete tissue regeneration in response to apoptosis. a–c’ Late third instar eye discs, anterior is to the left. ELAV labels photoreceptor neurons and is used to outline the shape of the posterior part of the discs. Conditional expression of dAtg1 ^RNAi (a, a’), hid (b, b’), or hid and dAtg1 ^RNAi (c, c’) was under control of DE-Gal4 and tub-Gal80 ^ts (DE ^ts) and indicated by GFP. A temperature shift to 29 °C for 12 h during second instar larval stage induced expression of these transgenes which is followed by a recovery period of 72 h at 18 °C (R72h). (a, a’) Following such a temperature shift procedure, expression of dAtg1 ^RNAi alone (DE ^ts  > dAtg1 ^RNAi) does not affect the eye disc morphology indicated by the normal ELAV pattern in the dorsal half of the eye disc (red in a, grey in a’). (b, b’) DE ^ts  > hid induced massive apoptosis (GFP puncta and aggregates, arrow in b), which results in loss of bilateral symmetry of the disc 24 h after the temperature shift [52]. However, as indicated by the largely normal ELAV pattern in late third instar eye discs, the apoptosis-induced tissue damage has fully recovered after 72 h recovery (R72h) at 18 °C. (c, c’) A DE ^ts  > hid eye disc that was simultaneously treated with dAtg1 ^RNAi (DE ^ts  > hid-dAtg1 ^RNAi). The arrow in (c’) highlights the incomplete ELAV pattern on the dorsal half of the disc indicating that the regenerative response was partially impaired by reduction of dAtg1; 79 % (n = 28) of DE ^ts  > hid-dAtg1 ^RNAi eye discs showed incomplete regeneration. (d) Quantification of the dorsal/ventral size ratio (mean ± SE) in eye discs of various genotypes. One-way ANOVA with Bonferroni multiple comparison test was used to compute P values. Asterisks indicate a statistically significant change on dorsal/ventral size ratio compared to the control DE ^ts  > hid. Compared to DE ^ts  > hid, expression of dAtg1 ^RNAi or dAtg1 ^DN significantly (****P < 0.0001 and **P < 0.01, respectively) reduces the size of the dorsal half of the eye disc. As the controls, disc sizes of DE ^ts  > dAtg1 ^RNAi and DE ^ts  > dAtg1 ^DN are not significantly (n.s.) different from those of DE ^ts  > hid