3. Courtship in Drosophila Flashcards
what courtship parameters can we study? (4)
- total time courting during the observation period
- latency to initiate courtship
- latency to copulate
- order of courtship steps
what does the female receive that allows them to make a decision as to whether they want to copulate
volatile pheromones and vibrations
what type of receptor is the sex peptide receptor
a GPCR
what does sex peptide contain
two anti-aphrodisiac pheromones
cVa
7-T
how does sex peptide regulate female receptivity
modulates the properties of fruitless neurons via a monophosphate signalling pathway
what is sex peptide released alongside
the sperm
what is the action of sex peptide
sex peptide receptors in the uterus which activate uterine neurons that project to the abdominal ganglia and SOG. this pathway alters the pheromones and behaviours the female produces to warn other males that the y do not wish to mate.
describe the order of the courtship ritual
- orientation
- wing extension
- licking
- copulation
- repetitive process that continues until the female becomes receptive.
what neuron is responsible for the courtship song production in males
the mesothoracic ganglion
what happens when fragments of the D. simulans period gene are expressed in D. melanogaster?
D. melanogaster produces the species specific song of D. simulans
the courtship song is species specific, what gene controls it?
period gene
where is the SOG located
in the protocerebrum
describe the process of licking in the courtship ritual
gustatory receptor neurons on the foreleg tarsi and mouthparts detect non-volatile pheromones which enter the sensilla via single cuticle pore.
the female pheromone info is then relayed via a single axon to the SOG, and the male decides whether or not to act
what wing produces a series of species-specific vibrations = courtship song
the ipsilateral wing
a specific class of visual projection neurons are dedicated to courtship, what are these called?
LC10 visual projection neurons
what are LC10 visual projection neurons required for
tracking a fly size object
where do flies secrete pheremones?
what does this allow?
the cuticle
allows species recognition
name a female fly pheremone
7,11-HD and 7,11-ND
what can happen when males secrete cVa?
elicits aggression in other males
in some cases, young males respond to these pheromones and attempt to court elder males
name a male pheromone
cVA and 7-t and 7-p
name the receptor responsible for detecting these auditory vibrations
stretch receptors
what receptor is involved in the female perception of male pheromones?
Or83b: Or67d receptor
what OBP is involved in detection of male pheremones
Lush
how does the female fly receive the courtship song
through her antennae - Johnstons organ in the Artista
describe the evidence showing how Or67d was implicated in courtship behaviour
Jallon et al., 1981 = males lacking or67d display increased courtship toward males compared to wild-type controls.
describe the process of how males receive non-volatile pheromones
non-volatile pheromones are detected by gustatory receptor neurons of the foreleg tarsi and mouthparts
gustatory information is relayed from the SOG to a region of the lateral protocerebrum
describe the process of how females receive volatile pheromones:
- cVa enters the sensillar lymph via cuticle pores
- cVa binds to Lush (OBP) to create a conformational change
- activated lush binds to Or83b:0r67d receptor of olfactory sensory neurons
- OSNs project to the Da1 or Va1m glomerulus of the antennal lobe
- spatial info is conveyed to mushroom bodies via olfactory projection neurons
describe how the LC10 visual input is integrated to initiate courtship
LC10 input is integrated into the higher order brain centre called the command centre - these project to the P1 cluster of neurons
if the higher order brain centre decides to initiate courtship:
- descending neurons project to the ventral ganglia to initiate song production.
how does Johnstons organ trigger motor action
via the antennal mechanosensory and motor cortex
where does Fruitless transcripts work
in the nervous system
where does doublesex transcripts work
in neural and non-neuronal tissues
what is sex lethal protein
an RNA binding protein that regulates the splicing of itself and downstream transformer genes mRNA
what does action of sex lethal protein result in
translation of transformer
what does transformer do?
regulates the splicing of two downstream genes in females : doublesex and fruitless
how is sex lethal protein activated
the additional female X chromosome regulates splicing to produce sex lethal protein
what happens in the absence of the female XX genotype
in males, the presence of only one X chromosome results in default splicing patterns - this means sex Lethal protein is not produced
what happens in default splicing in males
yields functional Dsx male protein and Fru male protein
how were the functions of fruitless and doubles assessed?
using mutants
what happens in Dsx KO mutants
produce most aspects of courtship - except one part of the courtship song
what happens if male Dsx is expressed in females
somatic differentiation - they transformed into males, but they could not perform courtship (Dsx not required for courtship behaviour)
what happens to fru KO flies
phenotypically male but show no courtship behaviour
what produces sex specific transcripts
P1 promoter
what happens if these promoters are knocked out
it can be lethal
how have fruitless proteins been studied in the CNS
using antibodies tagged with a fluorescent dye
where has male fruitless been identified
brain, ventral ganglia, antennal lobe, SOG, lateral regions
sensory neurons
what were first used to identify sexually dimorphic CNS regions involved in male courtship
gynandromorphs
how has the GAL4/UAS system been used to study sexually dimorphic brain circuitry?
using UAS-traF (female transformer) driven by GAL4 lines with distinct patterns in the CNS
ER! What have gynandromorph studies revealed about the male courtship song?
only a single region in the dorsal protcerebrum must be genetically male for a fly to sing (this being a region rich in fruitless neurons
if a small set of approx 20 fruitless neurons from a normal female are masculinised, then the female will sing
what happens when the male GR32a receptor is mutated, and what does GR32a do
and what happens to the wing
males with this mutation show increases courtship towards males and mated females
the wings simultaneously extend during the courtship ritual
name the OBP used in detecting female pheremones
OBP57d
