Adenyl Cyclase and Its Relationship to Insect Diapause in the European Corn Borer, Ostrinia Nubilalis (Hubner)
Adenyl Cyclase and Its Relationship to Insect Diapause in the European Corn Borer, Ostrinia Nubilalis (Hubner)
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Date
1978
Authors
Gelman, Dale Berkman
Advisor
Lockard, J. David
Hayes, Dora K.
Hayes, Dora K.
Citation
DRUM DOI
Abstract
The purpose of this study was to determine if there
is a link between adenyl cyclase activity and the diapause
condition in the European corn borer, Ostrinia nubilalis.
Insects inhabiting those latitudes where cold and warm
seasons alternate with one another have evolved mechanisms
which allow them to remain dormant (in a state of diapause)
during the winter months of the year. Photoperiod, as well
as temperature and humidity, has been shown to control the
onset, maintenance and termination of insect diapause. In
recent years, evidence supporting a role for the cyclic
AMP system, including adenyl cyclase, as well as a role
for one or more biogenic amines in the pathway between
light reception and the neuroendocrine regulation of the
insect life cycle and in the multitude of neuroendocrine
pathways controlling insect growth and metamorphosis has
been accumulating. In light of this evidence, it was decided
to investigate the effects of two light regimens,
short day (diapausing-inducing) and long day (pupation-inducing),
on adenyl cyclase activity of various stages of fifth instar European corn borer larval heads, and to
determine the effects of the biogenic amine neurotransmitters,
norepinephrine, octopamine, and dopamine on this
activity. Adenyl cyclase activity was measured by a
modification of the method of Krishna, et al., (1968).
A summary of the results follows.
In head extracts of fifth instar European corn borer
larvae reared under both long day and short day photoperiodic
regimens, adenyl cyclase activity in the presence
of sodium fluoride increased as the larvae progressed
through early, middle and mature stages. In long day
larval heads, activity decreased in late prepupae and
reached a low in pharate pupae. In contrast, adenyl
cyclase activity in short day larval heads peaked in early
diapause and then returned to prediapause levels during
late diapause. Norepinephrine significantly enhanced
adenyl cyclase activity only in early diapause larval head
extracts, while octopamine significantly enhanced adenyl
cyclase activity in head extracts of late short day mature
and early diapause larvae. Dopamine was ineffective as
an activator. An analysis of the combined effect of
neurotransmitter and developmental stage revealed that in
general, a given neurotransmitter in combination with
short day larval head extracts resulted in higher adenyl
cyclase levels than that neurotransmitter in combination
with long day head extracts.