Microscopy of multiple visual receptor types in Drosophila

[摘要] Purpose: To take advantage of specialized microscopic methods andtransgenic stocks, to understand the properties of each rhodopsin nowthat Drosophila's six rhodopsins (Rh1-Rh6) have been isolated.Methods: The visual pigment containing organelles, the rhabdomeres,were imaged in live flies with the pseudopupil in standard and confocalmicroscopes. Five transgenic Drosophila strains in which Rh2-Rh6replaced the native Rh1 in R1-6 receptors were compared with normalcontrols (Rh1 in R1-6) for two lines of work: (1) autofluorescence ofrhodopsin; and (2) imaging rhodopsin. Other transgenic Drosophila inwhich the Rh1, Rh3, and Rh4 promoters drive the green fluorescentprotein (GFP) reporter were used for other purposes, especiallydistinguishing the R7/8 types.Results: We show, for the first time, that visual pigment appearspink in white light, especially for Rh1 and Rh6. While showing thatrhodopsin-metarhodopsin conversions were understood by their respectivewavelengths, we discovered that, for Rh6, rhodopsin and metarhodopsincould not be spectrally separated. Relative fluorescent emission,Rh1=Rh5>Rh6>Rh2>Rh4>Rh3, was of little value in explainingdifferences between bright and dim autofluorescence in R7. Rather,analysis of GFP driven by Rh3 and Rh4 promoters show that therhabdomeres with bright autofluorescence are the ones that contain Rh4.Conclusions: Careful imaging provides a useful approach to analyzingDrosophila rhodopsins. Amid a considerable body of microscopic data,we identify the sources of bright and dim R7 rhabdomeres, and wedemonstrate the unique properties of Rh6.

[学科分类] 生物化学/生物物理