title: Circadian plasticity in photoreceptor cells controls visual coding efficiency in Drosophila melanogaster.
abstract: In the fly Drosophila melanogaster, neuronal plasticity of synaptic terminals in the first optic neuropil, or lamina, depends on early visual experience within a critical period after eclosion. The current study revealed two additional and parallel mechanisms involved in this type of synaptic terminal plasticity. First, an endogenous circadian rhythm causes daily oscillations in the volume of photoreceptor cell terminals. Second, daily visual experience precisely modulates the circadian time course and amplitude of the volume oscillations that the photoreceptor-cell terminals undergo. Both mechanisms are separable in their molecular basis. We suggest that the described neuronal plasticity in Drosophila ensures continuous optimal performance of the visual system over the course of a 24 h-day. Moreover, the sensory system of Drosophila cannot only account for predictable, but also for acute, environmental changes. The volumetric changes in the synaptic terminals of photoreceptor cells are accompanied by circadian and light-induced changes of presynaptic ribbons as well as extensions of epithelial glial cells into the photoreceptor terminals, suggesting that the architecture of the lamina is altered by both visual exposure and the circadian clock. Clock-mutant analysis and the rescue of PER protein rhythmicity exclusively in all R1-6 cells revealed that photoreceptor-cell plasticity is autonomous and sufficient to control visual behavior. The strength of a visually guided behavior, the optomotor turning response, co-varies with synaptic-terminal volume oscillations of photoreceptor cells when elicited at low light levels. Our results show that behaviorally relevant adaptive processing of visual information is performed, in part, at the level of visual input level.
authors.affiliation: Friedrich-Miescher-Laboratory of the Max-Planck Society (MPG), Tuebingen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Barth
authors.forename: Michael
authors.initials: M
authors.lastname: Schultze
authors.forename: Christoph M
authors.initials: CM
authors.lastname: Schuster
authors.forename: Roland
authors.initials: R
authors.lastname: Strauss
mesh_terms: D000818:Animals; D056926:CLOCK Proteins / Q000235:genetics / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology*; D005123:Eye / Q000294:innervation / Q000378:metabolism / Q000648:ultrastructure; D005260:Female; D008297:Male; D008854:Microscopy, Electron; D008959:Models, Neurological; D009154:Mutation; D009434:Neural Pathways / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D056950:Period Circadian Proteins / Q000235:genetics / Q000502:physiology; D017440:Photoperiod; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology / Q000502:physiology*; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology*
chemical_list: C120526:Clk protein, Drosophila; D029721:Drosophila Proteins; C539040:PER protein, Drosophila; D056950:Period Circadian Proteins; D056926:CLOCK Proteins