SMP domain is dispensable for supporting dEsyt function at the ER-PM interface. (A) Schematic of (i) dEsyt- wild type (ii) dEsyt∆SMP mutant protein structure showing the distribution of conserved domains spread through the length of the protein (Image generated using IBS, Illustrator for Biological sciences Version 1.0 software http://ibs.biocuckoo.org/) (Liu et al., 2015). (B) Western blot from head extracts of the genotypes as indicated on the top of the blot. The blot was probed with antibody against mcherry. Tubulin was used as the loading control. (Mr: Molecular weight). (C) Confocal images showing the localization of exogenously expressed mcherry::dEsyt and mcherry::dEsytΔSMP driven using eye-specific Rh1-Gal4 in 1-day-old dark reared flies. Rh1-Gal4 is shown as a control. Transverse sections of an individual ommatidium are shown. Phalloidin marks F-actin staining and highlights rhabdomeres R1–R7 (Magenta), red indicates the localization of exogenously expressed dEsyt and dEsytΔSMP protein tagged to mcherry, cyan represents RDGB localization at the base of the rhabdomere (marker for SMC). Scale bar: 2 µm. (D) Representative optical neutralization (ON) images showing rhabdomere integrity 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). (E) Quantification of the time course of retinal degeneration. 10 ommatidia from 5 separate flies of each genotype were scored and plotted. Y-axis is the number of intact rhabdomeres/ommatidium. The maximum value possible is 7. X-axis is the age of the flies after eclosion. (N = 5; n = 50). Source data are available for this figure: SourceData FS4.