Carotenoid replacement inDrosophila: freeze-fracture electron microscopy

Abstract

Because of the consequent lack of photopigment chromophore, carotenoid/ retinoid (vitamin A) deprivation during the larval period of Drosophila leads to decreased rhodopsin in adult photoreceptors. Decreased density of P-face particles in photoreceptor membrane (rhabdomeric microvilli) is a prominent ultrastructural feature of this rhodopsin deficiency. When adults are fed carotenoid, the rhabdomeric P-face particle density-which reflects the concentration of rhodopsin-increases halfway to the replete control level during the first 12 hours, and is fully restored by 2 days. Based on freeze-fracture replicas, there is a continuity of membrane between rhabdomeric microvilli and the parent retinula cell. That confluence is relevant to turnover of photoreceptive membrane. Microvillar and retinula cell P-face particle densities covary. The relevance of the demonstration of rapid recovery from chromophore depletion is discussed in relation to hypotheses that the chromophore and/or related retinoids regulate opsin gene transcription, and/or post-translational processing and deployment from the endoplasmic reticulum to the rhabdomere.

Receptor demise from alteration of glycosylation site in Drosophila opsin: Electrophysiology, microspectrophotometry, and electron microscopy

“…The Drosophila mutant outer rhabdomeres absent (ora) also has such membranes ; ora is an allele of ninaE (the Rl-6 opsin gene, see also below), hence the name ninaE ora (Washburn & OTousa, 1992). The site of zipper accumulation is directly confluent with rhabdomeric microvilli (Stark et al, 1992). Thus, the abnormality could reflect a defect of opsin deployment which results in a "storage disease."…”

Control ofDrosophilaRetinoid and Fatty Acid Binding Glycoprotein Expression by Retinoids and Retinoic Acid: Northern, Western and Immunocytochemical Analyses

“…Previously, we had shown a decrease in visual sensitivity, visual pigment and P-face particle density in retinoid deprived Drosophila Stark, 1977 ;Stark, Ivanyshyn and Hu, 1976 ;Stark and Zitzmann, 1976) followed by fast recovery upon chromophore replacement (Chen and Stark, 1992 ;Sapp et al, 1991 ;Stark and White, 1996). Opsinpromoter-CAT-reporter analyses in Drosophila and Northern blot analyses in flies * For correspondence and reprint requests.…”

Appearance of Opsin-containing Vesicles as Rhabdomeric Precursors and Their Incorporation into the Rhabdom around Dusk in the Compound Eye of the Crab, Hemigrapsus sanguineus

“…These turnover processes are controlled by ambient light conditions (Eguchi and Waterman, 1967;White, 1967;Blest et al, 1993;Blest and Stowe, 1997) though they are also modulated by factors such as the biological clock and the supply of material for rhodopsin biosynthesis (Barlow et al, 1980;White and Bennet, 1992;Ozaki et al, 1993;Huber et al, 1994;Stark and White, 1996).…”