Ca2+ limits the development of the light response in Drosophila photoreceptors.
The development of the light response was followed in Drosophila photoreceptors at 25 degrees C. In whole-cell recordings from dissociated ommatidia, responses to light were first detected at 82 h post-puparium formation; over the next 8 h sensitivity to light increased exponentially by 5 or 6 orders of magnitude. The end of this phase coincided with the maturation of the rhabdomere as measured by whole-cell capacitance. There was a modest 5-10fold further increase in sensitivity over the final 10 h of pupal development (90-100 h). During a narrow developmental time window (82-87 h) no responses could be detected using non-invasive recording techniques (electroretinogram or suction electrode), and responses to light could only be elicited in whole-cell recordings when micromolar concentrations of Ca2+ are included in the pipette. It seems unlikely that cytosolic Ca2+ per se is the limiting factor, and we suggest instead that the failure to respond to light is due to the lack of Ca2+ in the InsP3-sensitive intracellular stores and that the presence of Ca2+ in these stores is an absolute requirement for phototransduction in Drosophila.
Department of Physiology, Hadassah Medical School, Hebrew University, Jerusalem, Israel.
R C
RC
Hardie
A
A
Peretz
J A
JA
Pollock
B
B
Minke
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D004331:Drosophila melanogaster / Q000502:physiology*; D004596:Electroretinography; D005123:Eye / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects; D005260:Female; D006737:Horseshoe Crabs / Q000502:physiology; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology*; D010786:Photoreceptor Cells / Q000187:drug effects* / Q000528:radiation effects; D011679:Pupa; D015398:Signal Transduction / Q000187:drug effects*; D013045:Species Specificity
D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium