Biology Reference
In-Depth Information
P
-element-mediated transformation (
Wheeler et al. 1991
). The
D. simulans per
+
gene restored a rhythm in
D. melanogaster
and transgenic
D. melanogaster
males produced song cycles characteristic of
D. simulans
males.
Wheeler et al.
(1991)
concluded that substitutions in four or fewer amino acids in the
per
+
locus are responsible for the species-specific courtship behavior.
11.5.1.3 Other Effects of
per
per
alleles affect locomotion, cellular rhythms, and development time. Flies
with
per
S
develop faster than wild-type flies, and
per
L
flies develop more slowly
than the wild type (
Kyriacou 1990, 1993
). It has long been thought that circa-
dian oscillations provided the clock for photoperiodically induced
diapause
in
insects (
Takeda and Skopik 1997
). Diapause is a genetically determined state
of arrested development that is induced before the onset of detrimental con-
ditions. Hibernal diapause, which allows insects to survive overwinter, can
be induced when insects develop during a period of cool temperatures under
a short daylength, which means they must be able to measure light and dark
cycles. However,
per
+
appears to have no influence on the photoperiodic clock
in
D. melanogaster
(
Saunders 1990
). Females of a wild-type strain of
D. mela-
nogaster
(Canton-S) and strains with
per
mutations were able to discriminate
between diapause-inducing short days and noninductive daylengths. Adult
females of
D. melanogaster
exhibit an ovarian diapause when reared and held
under short days and low temperature (12°C). Females exposed to long days
at the same temperature reproduce. The critical daylength (the photoperiod
at which 50% of the individuals enter diapause) for Canton-S females at
12°C is
≈
14 hours of light per 24 hours. Photoperiodic response curves for
the
per
S
,
per
L
, and Canton-S strains were almost identical, although
per
0
flies showed shortened critical daylengths. However,
per
0
females are able to
discriminate between a long and a short day.
Ikeno et al. (2011)
, however, found that the circadian clock genes
period
+
and
cycle
+
regulate reproductive diapause in males of the bean bug
Riptortus pedes-
tris
(
Ikeno et al. 2011
). RNA interference (RNAi) analyses showed that disruption
of
per
+
and
cycle
+
disrupted the rhythm of cuticle deposition. RNAi of
per
+
also
induced development of male reproductive organs even under diapause-induc-
ing short-day conditions. RNAi of
cycle
+
suppressed development of the repro-
ductive organs even under diapause-preventing long-day conditions. Larval
diapause in
Chymomyza costata
also is affected by mutations affecting the
photoperiodic clock (
Kostal and Shimada 2001
).
Many behaviors, including learning, involve temporally patterned events. The
interval between presentation of the conditioned stimulus and reinforcement is
