Phosphorylation of heptahelical receptor molecules is an important process in termination of phototransduction cascade and regeneration of the receptor molecule. Rhodopsin in the eye of genetically modified fruit fly (Drosophila melanogaster) is an appropriate model for studying phosphorylation characteristics. We brought up two strains for research purposes of the central photoreceptor R8, which contains only rhodopsin Rh6. We achieved this by two double crossbreeds sev;rdgC and control strain sev;ninaE (sev - sevenless, absence of R7 photoreceptor cells; rdgC - non-functional RdgC phosphatase and ninaE - non-functional, absent rhodopsin Rh1). Central classes of photoreceptor cells R7 and R8 are pairing up, with regard to containment of two different rhodopsins, always the same way: if R7 contains Rh3, then R8 holds Rh5 rhodopsin and if R7 contains Rh4, then R8 holds Rh6 rhodopsin. When R7 cells are absent (sevenless), then R8 cells will express only Rh6. Fruit fly photoreceptors, with degenerated RdgC phosphatase, are subjected to light dependent degeneration. Degeneration is incomplete, so it is possible to measure residual ERG in fruit flies of different ages. It is reported that central photoreceptor cell R8 contribute to residual ERG from degenerated sev;rdgC fruit flies. Comparison of sev;rdgC mutant's spectral sensitivity with sev;ninaE (mutants without R7 cells, with non-functional gene for Rh1 rhodopsin and consequently with only functional R8 photoreceptor cells), indicates that we can study characteristics of individual photoreceptor cells in vivo, in our case on central photoreceptor R8 cells. Our crossbreed contains sev, therefore all R8 cells express only Rh6 rhodopsin, what we have managed to prove with our research.
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