The extraretinal eyelet of Drosophila: Development, ultrastructure, and putative circadian function

Helfrich-Foerster, Charlotte and Edwards, Tara and Yasuyama, Kouji and Wisotzki, Barbara and Schneuwly, Stephan and Stanewsky, Ralf and Meinertzhagen, Ian A. and Hofbauer, Alois (2002) The extraretinal eyelet of Drosophila: Development, ultrastructure, and putative circadian function. JOURNAL OF NEUROSCIENCE, 22 (21). pp. 9255-9266. ISSN 0270-6474

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Abstract

Circadian rhythms can be entrained by light to follow the daily solar cycle. In Drosophila melanogaster a pair of extraretinal eyelets expressing immunoreactivity to Rhodopsin 6 each contains four photoreceptors located beneath the posterior margin of the compound eye. Their axons project to the region of the pacemaker center in the brain with a trajectory resembling that of Bolwig's organ, the visual organ of the larva. A lacZ reporter line driven by an upstream fragment of the developmental gap gene Kruppel is a specific enhancer element for Bolwig's organ. Expression of immunoreactivity to the product of lacZ in Bolwig's organ persists through pupal metamorphosis and survives in the adult eyelet. We thus demonstrate that eyelet derives from the 12 photoreceptors of Bolwig's organ, which entrain circadian rhythmicity in the larva. Double labeling with anti-pigment-dispersing hormone shows that the terminals of Bolwig's nerve differentiate during metamorphosis in close temporal and spatial relationship to the ventral lateral neurons (LNv), which are essential to express circadian rhythmicity in the adult. Bolwig's organ also expresses immunoreactivity to Rhodopsin 6, which thus continues in eyelet. We compared action spectra of entrainment in different fly strains: in flies lacking compound eyes but retaining eyelet (so(1)), lacking both compound eyes and eyelet (so(1);gl(60j)), and retaining eyelet but lacking compound eyes as well as cryptochrome (so(1);cry(b)). Responses to phase shifts suggest that, in the absence of compound eyes, eyelet together with cryptochrome mainly mediates phase delays. Thus a functional role in circadian entrainment first found in Bolwig's organ in the larva is retained in eyelet, the adult remnant of Bolwig's organ, even in the face of metamorphic restructuring.

Item Type: Article
Uncontrolled Keywords: DEVELOPING OPTIC LOBES; VISUAL-SYSTEM; EXTRAOCULAR PHOTORECEPTORS; PHASE-SHIFTS; SINE OCULIS; ECTOPIC EXPRESSION; LATERAL NEURONS; NERVOUS-SYSTEM; TIMELESS GENES; GANGLION-CELLS; Drosophila melanogaster; circadian rhythm; Bolwig's organ; extraretinal photoreceptors; compound eye; insect; rhodopsin
Subjects: 500 Science > 590 Zoological sciences
Divisions: Biology, Preclinical Medicine > Institut für Zoologie > Alumni or Retired > Organisation der inneren Uhr auf neuronaler Ebene (Prof. Dr. Charlotte Förster)
Biology, Preclinical Medicine > Institut für Zoologie > Entwicklungsbiologie (Prof. Dr. Stephan Schneuwly)
Depositing User: Dr. Gernot Deinzer
Date Deposited: 04 Oct 2021 06:00
Last Modified: 04 Oct 2021 06:00
URI: https://pred.uni-regensburg.de/id/eprint/39739

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