Biology Reference
In-Depth Information
B
C
A
20E
Dopamine
sNPF
20E
Brain
Brain
Dopamine
cells
Brain
CC
sNPF
CA
JHAMT, etc.
BmDopR2
MeVK
HMGR
No JH
No JH
JH
Figure 3.4 Model for the mode of action of 20E (A), dopamine (B), and sNPF (C) on the
CA of the early fifth (last) instar stadium in Bombyx. See text for detailed explanations.
30
C; therefore, the trophic action of AT is sex-, stage-, and temperature
dependent, which might be the reason that many reports have failed to find
the activation of CA by AT. The reason for the temperature dependence of
the allatotropic action is unknown, and we have not determined this AT
action in
Bombyx
. AT has been found in other insect species such as
Aedes
aegypti
(
Li, Unnithan, Veenstra, Feyereisen, & Noriega, 2003
) and others
(
Stay, 2000
), but the roles of these peptides on insect molting and metamor-
phosis need to be studied.
Bombyx
AT is the same peptide as that of
Manduca
, and the receptor for
AT in
Bombyx
is not expressed in the CA but unexpectedly in the CC
(
Yamanaka et al., 2008
). This might be the reason that AT does not have
allatotropic action on
Bombyx
,
Manduca
, and other lepidopterans. As the
AT receptor is produced in the same cells as the sNPF-producing cells in
the CC (based on the
in situ
hybridization and immunohistochemistry
experiments—
Yamanaka et al., 2008
) and the developmental transcript fluc-
tuations of
sNPF
in the CC mirror those of the
AT
receptor (unpublished
data), it is possible that interactions exist between AT and sNPF. Surpris-
ingly,
in vitro
experiments showed that 1
m
M AT stimulated sNPF expres-
sion in the CC of day 1 fifth instar larvae (unpublished data), indicating that
AT is one of the stimulatory regulators for sNPF (
Fig. 3.3
C).
