title: Genetic dissection of trophic interactions in the larval optic neuropil of Drosophila melanogaster.
abstract: The larval visual system of Drosophila melanogaster consists of two bilateral clusters of 12 photoreceptors, which express Rhodopsin 5 and 6 (Rh5 and Rh6) in a non-overlapping manner. These neurons send their axons in a fascicle, the larval optic nerve (LON), which terminates in the larval optic neuropil. The LON is required for the development of a serotonergic arborization originating in the central brain and for the development of the dendritic tree of the circadian pacemakers, the small ventral lateral neurons (LNv) [Malpel, S., Klarsfeld, A., Rouyer, F., 2002. Larval optic nerve and adult extra-retinal photoreceptors sequentially associate with clock neurons during Drosophila brain development. Development 129, 1443-1453; Mukhopadhyay, M., Campos, A.R., 1995. The larval optic nerve is required for the development of an identified serotonergic arborization in Drosophila melanogaster. Dev. Biol., 169, 629-643]. Here, we show that both Rh5- and Rh6-expressing fibers overlap equally with the 5-HT arborization and that it, in turn, also contacts the dendritic tree of the LNv. The experiments described here aimed at determining whether Rh5- or Rh6-expressing fibers, as well as the LNv, influence the development of this serotonergic arborization. We conclude that Rh6-expressing fibers play a unique role in providing a signal required for the outgrowth and branching of the serotonergic arborization. Moreover, the innervation of the larval optic neuropil by the 5-HT arborization depends on intact Rac function. A possible role for these serotonergic processes in modulating the larval circadian rhythmicity and photoreceptor function is discussed.
authors.affiliation: Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON, Canada.
authors.forename: Verónica G
authors.initials: VG
authors.lastname: Rodriguez Moncalvo
authors.forename: Ana Regina
authors.initials: AR
authors.lastname: Campos
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D003712:Dendrites; D029721:Drosophila Proteins / Q000032:analysis*; D004331:Drosophila melanogaster / Q000254:growth & development*; D005123:Eye / Q000737:chemistry / Q000196:embryology*; D007814:Larva; D009412:Nerve Fibers / Q000737:chemistry; D009474:Neurons; D019581:Neuropil / Q000737:chemistry*; D009900:Optic Nerve / Q000196:embryology*; D012243:Rhodopsin / Q000032:analysis*; D012701:Serotonin / Q000502:physiology*; D020744:rac GTP-Binding Proteins / Q000502:physiology
chemical_list: D029721:Drosophila Proteins; C105578:Rh6 protein, Drosophila; D012701:Serotonin; D012243:Rhodopsin; D020744:rac GTP-Binding Proteins