Adult and larval photoreceptors use different mechanisms to specify the same Rhodopsin fates

  1. Simon G. Sprecher,
  2. Franck Pichaud1, and
  3. Claude Desplan2
  1. Center for Developmental Genetics, Department of Biology, New York University, New York, New York 10003, USA

Abstract

Although development of the adult Drosophila compound eye is very well understood, little is known about development of photoreceptors (PRs) in the simple larval eye. We show here that the larval eye is composed of 12 PRs, four of which express blue-sensitive rhodopsin5 (rh5) while the other eight contain green-sensitive rh6. This is similar to the 30:70 ratio of adult blue and green R8 cells. However, the stochastic choice of adult color PRs and the bistable loop of the warts and melted tumor suppressor genes that unambiguously specify rh5 and rh6 in R8 PRs are not involved in specification of larval PRs. Instead, primary PR precursors signal via EGFR to surrounding tissue to develop as secondary precursors, which will become Rh6-expressing PRs. EGFR signaling is required for the survival of the Rh6 subtype. Primary precursors give rise to the Rh5 subtype. Furthermore, the combinatorial action of the transcription factors Spalt, Seven-up, and Orthodenticle specifies the two PR subtypes. Therefore, even though the larval PRs and adult R8 PRs express the same rhodopsins (rh5 and rh6), they use very distinct mechanisms for their specification.

Keywords

Footnotes

  • 1 Present address: Medical Research Council Laboratory for Molecular and Cell Biology and Cell Biology Unit, Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom.

  • 2 Corresponding author.

    2 E-MAIL cd38{at}nyu.edu; FAX (212) 995-4710.

  • Supplemental material is available at http://www.genesdev.org.

  • Article is online at http://www.genesdev.org/cgi/doi/10.1101/gad.1565407

    • Received April 26, 2007.
    • Accepted July 16, 2007.
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