title: Evidence for indirect control of phospholipase C (PLC-beta) by retinoids in Drosophila phototransduction.
abstract: OBJECTIVE
  To determine how retinoids regulate the phospholipase C (PLC) gene in the Drosophila visual system.
  
  
  METHODS
  Western blotting, activity analyses and immunocytochemistry were applied to Drosophila reared on various diets.
  
  
  RESULTS
  Western blots and activity analyses showed that retinoid deprivation decreases PLC, the product of the norpA gene, by approximately 1/3 to 1/2 in Drosophila. Immunocytochemistry using standard and confocal fluorescence microscopy confirmed the expectation that PLC is localized to the photoreceptive rhabdomeres. Rhabdomeres of flies that were retinoid deprived, or reared on other diets devoid of chromophore precursors, fluoresced brightly. These observations are consistent with earlier morphometric analyses showing that retinoid deprivation decreases the size of rhabdomeres. In a separate control, rhabdomeric PLC was shown to be virtually eliminated by retinoid deprivation in transgenic Drosophila where the norpA coding sequence was driven by the opsin promoter.
  
  
  CONCLUSIONS
  PLC is decreased by retinoid deprivation. Retinoid control of PLC is indirect, as expected, since the norpA promoter is so different from the promoter for rhodopsin's gene. PLC is not eliminated by deprivation but decreases in proportion to the associated decrease in rhabdomere size which, in turn, is caused by the opsin decrease. By contrast, opsin is controlled by retinoids both translationally by chromophore availability and transcriptionally. The fact that PLC is eliminated by retinoid deprivation when opsin's promoter drives the PLC gene is important evidence substantiating retinoid control via opsin's promoter.
authors.affiliation: Department of Biology, Saint Louis University, St. Louis, MO 63103-2010, USA. kshim@im.wustl.edu
authors.forename: K
authors.initials: K
authors.lastname: Shim
authors.forename: K M
authors.initials: KM
authors.lastname: Zavarella
authors.forename: C F
authors.initials: CF
authors.lastname: Thomas
authors.forename: R D
authors.initials: RD
authors.lastname: Shortridge
authors.forename: W S
authors.initials: WS
authors.lastname: Stark
mesh_terms: D000818:Animals; D015153:Blotting, Western; D004331:Drosophila melanogaster; D019084:Fluorescent Antibody Technique, Indirect; D007527:Isoenzymes / Q000378:metabolism*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D054799:Phospholipase C beta; D017956:Photoreceptor Cells, Invertebrate / Q000201:enzymology*; D012176:Retinoids / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism*; D014785:Vision, Ocular / Q000502:physiology*; D014802:Vitamin A Deficiency / Q000201:enzymology*
chemical_list: D007527:Isoenzymes; D012176:Retinoids; D010738:Type C Phospholipases; D054799:Phospholipase C beta