Biology Reference
In-Depth Information
2001; Noguchi & Hayakawa, 1997; Puiroux, Moreau, & Gourdoux, 1990
).
Interestingly, dormant pupae of
Antheraea pernyi
decrease the hemolymphatic
levels of DA when they are chilled (
Matsumoto &Takeda, 2002
), suggesting
that chilling is pivotal in removing the DA signal. This facilitates PTTH
signaling to inhibit dormancy and stimulate its prometamorphic function.
Consistent with this model, brainless diapausing pupae of
Hyalophora cecropia
break the “permanently induced” dormancy when they receive the brain of
“chilled-activated” pupae (
Smith & Rybczynski, 2012; Williams, 1946,
1947, 1952
).
Although PTTH and DA signaling appear import, the full regulatory
mechanism underlying pupal diapause is likely to be more complex, since
DH is also required to reactivate postdiapause growth in synergism with
PTTH. Such DH functions are well documented for the pupal diapause of
noctuids belonging to the Heliothis/Helicoverpa complex (
Sun, Zhang,
Zhang, & Xu, 2003; Sun et al., 2005; Zhang, Sun, Zhang, Shen, & Xu,
2004; Zhang, Sun, Zhang, Xu, et al., 2004
). In these moths, DH injections
into “nonchilled” diapausing pupae induce them to break dormancy (
Xu &
Denlinger, 2003; Zhang, Nachman, Kaczmarek, Zabrocki, & Denlinger,
2011; Zhang, Sun, Zhang, Shen, et al., 2004; Zhang, Sun, Zhang, Xu,
et al., 2004; Zhang, Zdarek, Nachman, & Denlinger, 2008
)ina
temperature-dependent way: it is unable to break diapause at 20
C, but does
so in dormant pupae shifted to 25
C(
Zhang, Sun, Zhang, Shen, et al., 2004;
Zhang, Sun, Zhang, Xu, et al., 2004
).
Consistent with these observations, DH gene expression declines during
of the mid-early pupal stages in diapausing pupae of
Helicoverpa zea
and
Man-
duca sexta
, whereas it is upregulated in nondiapausing pupae (
Xu &
Denlinger, 2004; Zhang & Denlinger, 2012
). Moreover, 1-year-old “chil-
led” pupae (activated) of
Helicoverpa zea
break dormancy when they perceive
optimal temperatures (
25
C) in coincidence of an upregulation of DH
gene expression (
Zhang & Denlinger, 2012
).
DH also seems to control the modifications of larval development that
are coincident to diapause trajectory. Larvae of
Helicoverpa armigera
set for
the direct development delay larval development when injected with DH
(
Sun et al., 2005
). Similarly, larvae of
B. mori
set to develop into “diapause”
moths prolong their feeding period coincidentally to an upregulation of
BmDH
gene (
Xu et al., 1995a
). Interestingly, a conserved role of DH on
diapause response in a variety of Lepidoptera suggests that this hormone
might be pivotal in evolution of the diapause response in synergism with
the hormones PTTH and ECD.
