(040529 revised, 040529 created)
Noguchi H,
Hayakawa Y. (2001)
Dopamine is a key factor for the induction of egg diapause of the silkworm,
Bombyx mori.
Eur J Biochem. 2001 Feb;268(3):774-80.
The silkworm, Bombyx mori, enters diapause in the early embryonic
stage. Embryonic diapause is induced by incubating eggs of the maternal
generation at high temperature (diapause type), whereas incubation at low
temperature results in non-diapausing progeny (non-diapause type). Measurement of catecholamine concentrations in haemolymph and brain-
subesophageal ganglia (Br-SGs) showed that only dopamine concentrations in
both tissues are consistently higher in diapause-type than non-diapause-
type larvae and pupae. In particular, the difference in dopamine concentrations in both tissues increases around pupal ecdysis. During the
early pupal stage, Dopa decarboxylase activities and mRNA concentrations in
Br-SGs were also much higher in diapause-type than non-diapause-type
insects. Elevation of dopamine levels induced by feeding Dopa to penultimate-instar and last-instar larvae, and by injecting Dopa or dopamine into pupae 2 days after pupation made the non-diapause-destined
insects lay diapause-destined eggs at 59% and approximately 70% frequencies, respectively. Furthermore, injection of Dopa or dopamine
elevated mRNA levels of the diapause hormone in the Br-SGs of non-diapause-type pupae 1 day after injection. Incubation of Br-SGs isolated
from non-diapause-type day-2 pupae with Dopa or dopamine also stimulated
the expression of diapause hormone mRNA. These data indicate that environmental stimuli during embryonic development increase dopamine
levels in both hemolymph and Br-SGs from the larval stage to early pupal
stage, which results in laying of diapause-destined eggs by female adults
through enhanced expression of the diapause hormone gene.
Bombyx mori : English name: Japanese name: