Targeted expression of Sk2 leads to photoreceptor degeneration and decrease in Rh1 and TRP levels. (A) 7-d-old photoreceptors overexpressing Sk1 show a mild effect on rhabdomeres, whereas photoreceptors overexpressing Sk2 show severe degeneration. The percentage of intact rhabdomeres for w¹¹¹⁸ is 100%, for Sk1 overexpression is 80%, and for Sk2 overexpression is 4%. R1–R7 label the rhabdomeres of R1–R7 photoreceptor cells; N represents the nucleus, M represents mitochondria, and black arrows show adherens junctions. (B) Sk2 overexpression results in decreased Rh1 and TRP levels in 7-d-old flies. The TRP blot is reprobed with an antibody to IPP as a loading control. Sk2 overexpression is also seen in blots probed with an Sk2 antibody. (C) A 65–70% reduction in Rh1 level and a 60% reduction in TRP level are observed in Sk2 overexpressors compared with w¹¹¹⁸. (D) Graph shows the extent of Sk2 overexpression compared with w¹¹¹⁸. (E) Photoreceptors expressing Sk2 at 30°C degenerate, whereas those at 18°C expressing Gal80^ts do not degenerate. (F) TRP level is reduced at 30°C compared with 18°C. Sk2 overexpressor (Sk2 OE) represents GMR-Gal4–driven Sk2 at 25°C. The middle blot shows Sk2 overexpression, and the bottom blot shows loading controls. (G and H) Quantitation of TRP bands (G) and Sk2 (H) at permissive and nonpermissive temperature, and Sk2 overexpression at 25°C. n = 3; bars denote standard deviation.