Ectopic expression of ultraviolet-rhodopsins in the blue photoreceptor cells of Drosophila: visual physiology and photochemistry of transgenic animals

Abstract

We have generated transgenic flies expressing R7 cell-specific opsins in the major class of photoreceptor cells of the Drosophila retina and characterized their spectral properties using high-resolution microspectrophotometry and sensitivity recordings. We show that the Rh3 and Rh4 opsin genes encode UV-sensitive opsins with similar spectral properties (lambda max = 345 nm and 375 nm), and that Rh3 corresponds to the R7p and R7marg class of visual pigments. We have also generated Rh3 and Rh4 isoform-specific antibodies and present an R7 cell map of the Drosophila retina. In a related set of experiments, we show that it is possible to coexpress two different visual pigments functionally in the same cell and produce photoreceptors that display the summed spectral response of the individual pigments. These findings open up the possibility of tuning an animal's visual behavior by targeted expression of combinations of opsin genes to selective types of photoreceptors.

The Drosophila ninaG Oxidoreductase Acts in Visual Pigment Chromophore Production

“…To discount this possibility, the profile of retinoids in flies expressing Rh4 in place of Rh1 (referred to here as pRh1:Rh4, see Ref. 35) was examined. Earlier (Fig.…”

Phototransduction and retinal degeneration in Drosophila

“…The minor rhodopsins are also bistable pigments. Misexpression of a minor opsin in the R1-6 photoreceptor cells, in the absence of Rh1, results in the production of a PDA according to the spectral characteristics of the minor rhodopsin [54,56,101]. For example, introduction of Rh2 in the R1-R6 cells results in a PDA that is produced at ∼420 nm and terminated at ∼520 nm, respectively.…”

Insect retinal pigments: Spectral characteristics and physiological functions

“…The situation for R7y and R8y is quite different, however. R7y has a violet rhodopsin (R430-M510) and its companion R8y a green rhodopsin (R520); (Hardie 1985(Hardie , 1986Feiler et al, 1992). Like the visual pigment in the R1-6 cells, that of R7y binds 3-hydroxy-retinol and this also acts as a sensitizer here, thus boosting ultraviolet sensitivity (Hardie, 1985(Hardie, , 1986.…”

“…Ectopic expression of the ultraviolet rhodopsins in the R1-6 cells combined with a thorough physiological analysis of these Stavenga amenable cells (Feiler et al, 1992) demonstrated that the Rhl gene expresses the main blue-green rhodopsin, R480, of photoreceptors R1-6; the Rh2 gene codes the violet rhodopsin, R420, of the ocelli; the Rh3 and Rh4 genes code two distinct ultraviolet rhodopsins, R345 and R375, respectively, expressed in nonoverlapping sets of R7 cells (Montell et al, 1987;Pollock and Benzer, 1988;Carulli et al, 1994). The resulting spectral sensitivities resemble those of the Musca R7p and R7y cells, respectively.…”

“…Although the organization of the photoreceptors and their visual, sensitizing and carotenoid pigments appears to be rather similar among the different flies, certain subtle variations exist, e.g. the UV-absorbing sensitizing pigment seems to be absent in Drosophila 7y cells (see Feiler et al, 1992).…”