Functional expression of a locust visual pigment in transgenic Drosophila melanogaster

The cDNA encoding a visual pigment of the locust Schistocerca gregaria has been inserted into the germline of the ninaE mutant of Drosophila melanogas ter by P-element-mediated transformation. Functional expression has been do cumented by recording light-regulated electroretinograms in transgenic flie s. The spectral properties of the expressed visual pigment were determined with detergent-solubilized material, prepared from the eyecups of the trans genic D. melanogaster. The recombinant locust pigment, as well as the genui ne pigment of the fruitfly (Rh1) that served as a control for transformatio n/expression, showed photoreversibility between the pigment and metapigment forms. The absorptions of the difference spectra identify the locust visua l pigment as a short wavelength-absorbing, blue-light-sensitive photorecept or. The absorption maxima are similar to those recorded on living locust an imals. These results show that, although locust visual pigments contain 11- cis retinal as chromophore, the expressed protein is able to adopt 3-hydrox yretinal that is provided by the transgenic fruitflies. The electrophysiolo gical recordings reveal that the locust visual pigment is able to induce ph ototransduction in the fruitfly. The reported results have two important co nsequences: On the one hand, the binding site of the locust opsin is appare ntly able to interact with the 3-hydroxyretinal from Drosophila in a way th at the biological signal generated by the photoisomerization of the chromop hore can be used by the protein to adopt a physiologically active conformat ion. On the other hand, despite the relatively large phylogenetic distance between both insect species, the extent of conservation between the protein domains thought to be involved in G-protein activation is striking.