Functional activity of dEsyt ^CaBM . (A) Representative optical neutralization (ON) images showing rhabdomere structure of the indicated genotypes. Rearing conditions and the age of the flies are indicated on top. (*CL–Constant Light). Scale bar: 20 pixels (corresponds to ∼5 µm). (B) Quantification of the time course taken for retinal degeneration. 50 ommatidia were scored from five flies of each genotype and plotted. (N = 5; n = 50). (C) Confocal images showing the localization of RDGB in Rh1>, Rh1>dEsyt::GFP and Rh1>dEsyt^CaBM::GFP photoreceptors of flies which are (i) 1-day-old dark reared (ii) 6-day-old exposed to constant illumination (5,000 Lux). For (i) and (ii), RDGB visualized is detected using an antibody against the endogenous protein (Cyan). Rhabdomeres are outlined using phalloidin which marks F-actin (Red). A single ommatidium is shown. Scale bar: 2 µm. (D) TEM images of a single ommatidium from photoreceptors of flies reared in dark, 1-day-old (i) Rh1>, (iv) Rh1>dEsyt::GFP, (vii) Rh1>dEsyt^CaBM::GFP and (x) dEsyt^KO. Scale bar: 1 µm. (* - R7 photoreceptor). (ii, v, viii, and xi) Magnified image showing a single photoreceptor from the ommatidium image shown on the left. Scale bar: 200 nm. (iii, vi, ix, and xii) Magnified image showing the MCS distance (yellow arrows highlight the distance between ER and PM) of the photoreceptor image shown on the left. Scale bar: 100 nm. (E) Quantification of the contact site distance between the apical PM and the associated SMC, X-axis indicates the genotypes and Y-axis indicates the contact site distance in nm, 75 data points from 25 photoreceptors of three separate flies (R1–R6). (N = 3; n = 25). (F) Quantification of the MCS density per photoreceptor, X-axis indicates the genotype and Y-axis indicates the MCS density/photoreceptor, n = 25 photoreceptors from three separate flies (R1–R6). (N = 3; n = 25) (B) XY plots with mean ± SD are shown. (E and F) Violin plots with mean ± SD are shown. Statistical tests: (E and F) One-way ANOVA with post hoc Tukey’s multiple pairwise comparison. ns - Not significant; **P value <0.01; ****P value <0.0001.