HW - Sexual Dimorphism Flashcards
What triggers sex determination in fruit flies?
The X to autosome ratio is the main determinant, which then triggers alternative gender-dependent splicing cascades controlling both dosage compensation and somatic and neural sex determination
What regulates the male-specific splicing of the fruitless (fru) gene
In the absence of functional TRA protein, TRANSFORMER 2 (TRA2) regulates male-specific splicing of the fruitless (fru) gene in a subset of CNS neurons, which leads to the production of BTB-zinc finger FRUM protein isoforms
What occurs when stimulating fru neurons in a single male?
Male engages in courtship actions even in the absence of a female
What do fru mutations affect?
Other fru mutants affect courtship song, transfer of sperm & seminal fluid
Targeted reporter gene expression is created by two transgenes:
- P-Gal4, expressing the foreign transcription factor GAL4 in the pattern of promotor P
- UAS-Transgene, which uses GAL4 binding sites (UAS) to produce transgene expression
What do FruM olfactory receptor neurons process?
FruM olfactory receptor neurons process cues that Inhibit male-mated female courtship and promote male-virgin female courtship
What does stimulation of P1 cells cause?
Activation ol the P1 cluster FruM neurons Is sufficient to elicit many aspects of courtship behavior
Requirements for male courtship behaviour? (4)
- Male-specific organs?
- Male-specific neurons?
- Male-specific molecular signals?
- Male-specific patterns of neural activity?
What are 4 features for male-like courtship behaviour?
- The female brain is equipped with latent circuitry underlying male-like behavior
- Females with activated dsxf brain neurons court males and females and other Drosophila species
- This function maps to dsx-pC1 brain neurons.
- Cuticular methyl pheromones trigger male courtship behaviors in activated females
Drosophila Male Courtship circuit
Fru+ neurons participate in different aspects of courtship
Sensory Input
- Auditory (courtship song)
- Olfactory (pheromones, food-associated aphrodisiacs)
- Gustatory (pheromones)
- Visual
P1 cluster: central control of ♂ courtship
Integrates sensory and dopaminergic (motivational) input)
Controls output via Descending Neurons > Ventral Nerve Cord
- Courtship song
- Copulation
What does activation of vGlut Dsxm Neurons during copulation cause?
Male genitalia are unable to release clasp from the female abdomen
What does inhibition of GABA Dsxm Neurons during copulation cause?
Male genitalia are unable to clasp onto female abdomen
What doublesex-expressing neurons are involved in copulation? (3)
- Glutamatergic motor neurons that coordinate the joining of genitals
- GABA-ergic inhibitory interneurons that promote release of genitals by opposing the motor neurons
- mechanosensory neurons that connect to brain and abdominal ganglion
How is female mating receptivity controlled?
In virgin females, pC1 neurons integrate auditory, olfactory, and somatosensory inputs and in turn activate vpoDNs
- vpoDNs project axons to the ventral nerve cord to promote vaginal plate opening, which is essential for copulation
pC1 neurons receive tonic excitation from SAG neurons of the ventral nerve cord, which are activated by sex peptide sensory neurons (SPSNs) in the reproductive tract.
- After mating, the sex peptide inhibits SPSNs, thereby reducing the excitatory drive onto SAG neurons and pC1 neurons
Courtship receptivity and conditioning (5)
- Drosophila virgin ♀ has Fru-Gal4-marked sensory neurons that promote receptivity.
- Courtship song and cVA promote receptivity via pC1 neurons.
- Transfer of Sex Peptide during mating reduces receptivity in mated ♀ by inactivating the SAG neurons, which connect to pC1.
- pC1 connect to vaginal plate opening descending neurons.
- Repeated rejection by mated ♀ conditions ♂ to reduce courtship via their FruM mushroom body gamma neurons.
