FIGURE 4.

The arr1¹ photoreceptors require fewer light pulses to initiate PDA. A, representative ERG recordings of arr2¹ (top panel), arr1¹ (middle), and wild-type (wt) (bottom) flies by repetitive blue light pulses for generating PDA. PDA were reversed by orange light stimulation. Light pulses (blue or orange) are indicated below. B, a comparison of the number of blue light pulses needed for generating PDA in various mutants. Data are represented as the mean ± S.E. from several experiments as indicated under “Results.” ***, p < .0001, compared with wild type. The p value equals 0.23 when arr1¹;Rh1CT S>A was compared with Rh1CT S>A. C, Western blotting analysis of arr2¹. Head extracts from 1-day-old and 3-day-old arr2¹ flies were analyzed. arr2¹ expresses a truncated Arr2. Anti-InaD was used as a control. D, Western blotting shows arr1¹ contains a reduced level of Arr1, compared with wild type. M, mass markers.