(NAS Colloquium) Vision From Photon to Perception (1999) / Chapter Skim
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The biology of vision in Drosophila
The biology of vision in Drosophila
Pages 15-20
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From page 15... ...
Each photoreceptor cell contains a specialization of the plasma membrane, known as a rhabdomere, composed of ~60,000 microvilla; these are the functional equivalent of the discs in the rod outer segments and contain rhodopsin and the machinery involved in phototransduction (the large increase in surface area provided by the rhabdomeres allows the photoreceptor neurons to pack >100 million molecules of rhodopsin per cell)
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From page 16... ...
Not only is the system amenable to molecular genetic analysis but also it can report activity with exquisite sensitivity and specificity: photoreceptor cells are sensitive to single photons, and the signaling pathway can be turned on and off with millisecond kinetics (phototransduction in Drosophila is the fastest known G protein cascade, taking just a few tens of milliseconds to go from light activation of rhodopsin to the generation of a receptor potential)
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From page 17... ...
Although the messengers that actually gates the plasma membrane ion channels remains elusive, patch clamp studies have provided strong evidence implicating calcium in the regulation of the light response (18, 25, 26~. For example, extracellular calcium influx is both sufficient and necessary to regulate activation and deactivation kinetics of the light-activated conductance.
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From page 18... ...
To enhance signals above noise, we time averaged images from five identical flash trials, and each resulting image was subjected to spatial averaging. The bottom, right-hand panel shows a black and white photograph of the same cell at low contrast levels to emphasize the difference between cell body and rhabdomere.
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From page 19... ...
The study of this signaling cascade in the fruit fly Drosophila melanogaster makes it possible to use powerful molecular genetic techniques to identify novel transduction molecules and then to examine the function of these molecules in vivo, in their normal cellular and organismal environment. Recent advances in mouse knockout technology also offer an exciting opportunity for a genetic dissection of this process in vertebrates.
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From page 20... ...
(1979) in Neurogenetics, Genetic Approaches to the Nervous System, ed.
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