ATPα is essential for the function and survival of Drosophila photoreceptors. A, ERG recordings failed to reveal any light response in 1-day-old and 10-day-old knockdown flies. The event markers underneath represent 5-sec orange light pulses. B, In optical neutralization assays, severe loss of peripheral rhabdomeres was detected in 10-day-old knockdown flies but not in 1-day-old knockdown flies. C, Quantification and comparison of ERG response amplitudes. D, Based on optical neutralization assays, the rhabdomere integrity index (Materials and Methods) was dramatically decreased in 10-day-old but not in 1-day-old knockdown flies. E, The light-off stimulation elicited a large peak of giant fiber response within 40 ms in the control lGMR-Gal4 flies. No visually elicited giant fiber response was observed in ATPα knockdown flies. F and G, Both phototaxis and the motion-dependent walking optomotor response in ATPα knockdown flies were severely impaired. Asterisk (*): p< 0.01; Two-tailed t-test. Error bars denote S.E.M.