Visual receptor cycle in normal and period mutant Drosophila: microspectrophotometry, electrophysiology, and ultrastructural morphometry.
Visual pigment, sensitivity, and rhabdomere size were measured throughout a 12-h light/12-h dark cycle in Drosophila. Visual pigment and sensitivity were measured during subsequent constant darkness [dark/dark (D/D)]. MSP (microspectrophotometry) and the ERG (electroretinogram) revealed a cycling of visual pigment and sensitivity, respectively. A visual pigment decrease of 40% was noted at 4 h after light onset that recovered 2-4 h later in white-eyed (otherwise wild-type, w per+) flies. The ERG sensitivity [in w per+ flies in light/dark (L/D)] decreased by 75% at 4 h after light onset, more than expected if mediated by visual pigment (MSP) changes alone. ERG sensitivity begins decreasing 8 h before light onset while decreases in visual pigment begin 2 h after light onset. These cycles continue in constant darkness (D/D), suggesting a circadian rhythm. White-eyed period (per) mutants show similar cycles of visual pigment level and sensitivity in L/D; per's alterations, if any on the D/D cycles were subtle. The cross-sectional areas of rhabdomeres in w per+ were measured using electron micrographic (EM) morphometry. Area changed little through the L/D cycle.
Chen
D M
DM
Division of Biological Sciences, University of Missouri-Columbia 65211.
Christianson
J S
JS
Sapp
R J
RJ
Stark
W S
WS
D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D003623:Dark Adaptation; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology*; D004596:Electroretinography; D007091:Image Processing, Computer-Assisted; D008027:Light; D009154:Mutation; D010786:Photoreceptor Cells / Q000502:physiology* / Q000648:ultrastructure; D012684:Sensory Thresholds; D013053:Spectrophotometry