Biology Reference
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up-regulated and some down-regulated. At present, the function of immunity
genes in mating behavior is not known. One of the genes identified was
glucose
dehydrogenase
, which facilitates sperm storage in mated females, suggesting
that transcriptional changes associated with mating may begin during courtship
in advance of egg fertilization.
The
fruitless
+
gene is involved in both sex determination and courtship behav-
ior and is active in the central nervous system (
Hall 1994, Ryner et al. 1996,
Goodwin 1999, Baker et al. 2001
). Males with a mutation in
fruitless
may court
both females and males without copulating. Male flies expressing this mutated
gene are unable to bend their abdomens in the presence of females they are
courting because they lack a male-specific Muscle of Lawrence (MOL). Some
mutant alleles of
fruitless
cause males to be homosexual (they court only males),
while others cause males to be bisexual (they court both males and females)
(
Yamamoto et al. 1997
).
The
fruitless
+
gene is the first gene in the sex-determination hierarchy func-
tioning specifically in the central nervous system, with mutants of this gene
affecting nearly all aspects of male sexual behavior (
Ryner et al. 1996, Villella
et al. 1997, Goodwin et al. 2000
). It is at least 140 kb long and produces a com-
plex array of transcripts by using four promoters and alternative splicing; the
male-specific transcripts are only expressed in a small fraction of the central
nervous system (
Goodwin et al. 2000
).
Ito et al. (2012)
showed that
fruitless
+
encodes a set of transcription factors that promote male sexual behavior by
forming a complex with a transcriptional cofactor, which recruits two chromatin
regulators. This combination masculinizes individual sexually dimorphic neurons.
Another gene,
dissatisfaction
+
, is necessary for some aspects of sex-specific
courtship behavior and neural differentiation in
D. melanogaster
of both sexes.
Mutant males are bisexual but, unlike
fruitless
males, attempt to copulate.
Males with the mutant
dissatisfaction
phenotype take longer to copulate with
females and females with the mutant
dissatisfaction
phenotype are unrecep-
tive to male advances during courtship and do not lay mature eggs (
Goodwin
1999
). Mating behavior of normal females involves the following sequence: stop
moving
→
offer the courting male a chance to lick the female's genitalia
→
allow
males to attempt copulation. Nonreceptive females leave the courting male, and
if the male pursues her, she may kick him. Nonreceptive virgin females persis-
tently repel male approaches by lifting their abdomens up to block any physical
contact with males. Nonreceptive fertilized females lower their abdomen,
extrude their ovipositors and eggs to repel males. Thus, female receptivity var-
ies with age, diet, hormonal condition, and mating experience. A mutation of
