Drosophila Olfaction

Abstract

We have designed a system for targeted gene expression that allows the selective activation of any cloned gene in a wide variety of tissue-and cell-specific patterns. The gene encoding the yeast transcriptional activator GAL4 is inserted randomly into the Drosophila genome to drive GAL4 expression from one of a diverse array of genomic enhancers. It is then possible to introduce a gene containing GAL4 binding sites within its promoter, to activate it in those cells where GAL4 is expressed, and to observe the effect of this directed misexpression on development. We have used GAL4-directed transcription to expand the domain of embryonic expression of the homeobox protein even-skipped. We show that even-skipped represses wingless and transforms cells that would normally secrete naked cuticle into denticle secreting cells. The GAL4 system can thus be used to study regulatory interactions during embryonic development. In adults, targeted expression can be used to generate dominant phenotypes for use in genetic screens. We have directed expression of an activated form of the Dras2 protein, resulting in dominant eye and wing defects that can be used in screens to identify other members of the Dras2 signal transduction pathway.

A Population of Interneurons Signals Changes in the Basal Concentration of Serotonin and Mediates Gain Control in the Drosophila Antennal Lobe

“…Interestingly, 5-HT7R-expressing LNs in the R70A09 promoter line do not appear to express any other 5-HTRs, thus suggesting they may be dedicated cellular sensors of low 5-HT levels. LNs are an ideal target for modulation as they influence several aspects of olfactory coding in both flies [30,31] and mice [32,33]. Serotonin is also a potent modulator of GABAergic transmission in vertebrates [34], and 5-HT targets local interneurons in the olfactory bulb (OB) as well [6,35,36].…”

Paracrine and Synaptic Serotonin Have Opposite Effects on Olfactory Processing in Drosophila Via Distinct Signaling Pathways

“…We propose that paracrine 5-HT binds to excitatory 5-HT7Rs on these cells to boost their activity and suppress PN output ( Figure 7B). LNs are an ideal target for modulation as they can influence several aspects of olfactory coding in both flies [49,50] and mice [51,52]. Serotonin is also a potent modulator of GABAergic transmission in vertebrates [53] and 5-HT targets local interneurons in the olfactory bulb (OB) as well [54][55][56].…”

Early Draper-mediated glial refinement of neuropil architecture and synapse number in the Drosophila antennal lobe

“…neuron (ORN), with its cell body in either the antennae or maxillary palps, is activated by an odor that binds and activates its uniquely expressed olfactory receptor (Vosshall and Stocker, 2007). In the antennal lobe, approximately 1,300 cholinergic input ORNs synapse with output projection neurons as well as interneurons in about fifty distinct glomeruli each with stereotyped synapse numbers (Guven-Ozkan and Davis, 2014;Gaudry and Schenk, 2018). Glomeruli can be assigned functions based on the classes of odors which activate the ORN subtype that provides presynaptic input to each.…”