Terpenoid omega-hydroxylase (CYP4C7) messenger RNA levels in the corpora allata: a marker for ovarian control of juvenile hormone synthesis in Diploptera punctata
Td. Sutherland et al., Terpenoid omega-hydroxylase (CYP4C7) messenger RNA levels in the corpora allata: a marker for ovarian control of juvenile hormone synthesis in Diploptera punctata, J INSECT PH, 46(8), 2000, pp. 1219-1227
Ribonuclease protection assays were used to measure changes in allatal tran
script levels of the CYP4C7 gene which encodes a cytochrome P450 terpenoid
omega-hydroxylase thought to play a role in the metabolism of JH and its pr
ecursors. Denervation of the corpora allata does not affect the pattern of
expression of the CYP4C7 gene. Transplantation experiments show that CYP4C7
mRNA levels are dependent on a humoral factor characteristic of the reprod
uctive state of the insect. Messenger RNA levels rise substantially in mate
d or denervated females, or in mated or virgin females treated with hydropr
ene, when the follicle length is over 1.5 mm. Vitellogenic ovaries however
exert a negative influence on CYP4C7 expression, as ovariectomy in mated fe
males causes a premature rise in CYP4C7 mRNA levels. The half-life of the C
YP4C7 transcript is approx. 2 h when the corpora allata are incubated in vi
tro. Under these conditions, coincubation with a post-vitellogenic ovary ma
intains high CYP4C7 transcript levels in the glands. Excess juvenile hormon
e or analog applied at the end of vitellogenesis blocks ovulation or causes
abortion of embryos deposited in the brood sac. We conclude that expressio
n of the CYP4C7 gene is tightly controlled by the ovary, and it coincides w
ith the ovarian signal to rum off juvenile hormone synthesis. The role of t
he CYP4C7 enzyme may be to ensure the clearance of allatal juvenile hormone
and its precursors at the end of the gonotrophic cycle. (C) 2000 Elsevier
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