Figure 3.

RTP protein is exclusively found in the rhabdomeres of photoreceptors. A, A frontal section through the adult head shows RTP-GFP is only detected within the retina when the rtp promoter controls expression. B, A cross-section through the retina demonstrates that RTP-GFP is expressed in the rhabdomeres of all photoreceptor cells. C–H, The coexpression of RTP-RFP and RH1-GFP under pRh1-Gal4 control in photoreceptor cells R1–R6 shows RTP-RFP colocalized with RH1-GFP within the photoreceptor rhabdomere. C–E show two isolated ommatidial bundles of photoreceptors, and F–H show deep pseudopupil images taken from living flies. RFP, GFP, and merged channel images are shown. I, Photoreceptors coexpressing both GFP-RTP and PDI-RFP under pRh1-GAL4 in photoreceptor cells R1–R6 showed GFP-RTP also localized to rhabdomere and showed no overlap with cytoplasmic PDI-RFP. J, Photoreceptors coexpressing both GFP-RTP and PDI-RFP under GMR-GAL4 in all retinal cells showed only photoreceptor rhabdomeres retain RTP while PDI expression was expanded to other cell types of retina. K, pRh1-Gal4-driven expression of a ΔN-terminal RTP-RFP protein showed that RTP protein lacking the N-terminal domain was not stable in photoreceptor rhabdomere. The signal was very weak at young ages and lost by 1 d of age. L, RH1-GFP expression in the same eye displayed in K. The Rh1 rhodopsin localizes within the rhabdomere.