Suppression of JH biosynthesis by JH analog treatment: Mechanism of suppression and roles of allatostatins and nervous connections in the cockroach Diploptera punctata

Juvenile hormone analogs are known to inhibit the production of juvenile hormone (JH) by the corpora allata (CA). However, the mechanism of this inhibition remains undefined. We have used two JH mimics, fenoxycarb and pyriproxyfen, to examine the mechanism of suppression in the cockroach, Diploptera...

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Published in:	Journal of insect physiology Vol. 55; no. 11; pp. 967 - 975
Main Authors:	Lenkic, Lisa E., Tiu, Shirley H.K., Tobe, Stephen S.
Format:	Journal Article
Language:	English
Published:	England Elsevier Ltd 01-11-2009
Subjects:	Allatostatin allostatins animal tissue extracts Animals biochemical pathways Biosynthesis brain Brain - drug effects Brain - metabolism Cockroach Cockroaches - drug effects Cockroaches - genetics Cockroaches - metabolism corpora allata Corpora Allata - drug effects Corpora Allata - metabolism Diploptera punctata Down-Regulation Female Fenoxycarb gene expression Gene Expression - drug effects hormone antagonists Hormone Antagonists - pharmacology in vitro studies insect pests Juvenile hormone juvenile hormone analogs juvenile hormones Juvenile Hormones - biosynthesis mechanism of action midgut neurons Neuropeptides - pharmacology polymerase chain reaction Pyriproxyfen receptors synthesis vitellogenesis Cockroach Pyriproxyfen Fenoxycarb Biosynthesis Allatostatin Juvenile hormone
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Summary:	Juvenile hormone analogs are known to inhibit the production of juvenile hormone (JH) by the corpora allata (CA). However, the mechanism of this inhibition remains undefined. We have used two JH mimics, fenoxycarb and pyriproxyfen, to examine the mechanism of suppression in the cockroach, Diploptera punctata. Denervation experiments demonstrated the importance of nervous connections between the brain and CA for the inhibition of JH biosynthesis by fenoxycarb. Fenoxycarb treatment alters the sensitivity of CA to allatostatin treatment in vitro. Suppression of JH biosynthesis by fenoxycarb following denervation of the CA showed that innervation was in part responsible for the inhibition. Similarly, maximal inhibition by Dippu-AST7 requires intact nervous connections between the brain and CA, particularly during rapid vitellogenesis. qPCR analysis of brain, CA, ovary and midgut extracts revealed that both allatostatin and its receptor Dippu-ASTR2 show increased levels of expression following topical fenoxycarb treatment, particularly in brain tissue on days 4 and 5 of the first gonadotrophic cycle and in CA on day 4. The correlation between inhibition of JH biosynthesis and increased expression of AST and ASTR2 in brains and CA, together with increased sensitivity of CA to allatostatin in vitro, suggests that allatostatin may be one of the effectors by which fenoxycarb inhibits JH biosynthesis.
Bibliography:	http://dx.doi.org/10.1016/j.jinsphys.2009.06.008 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0022-1910 1879-1611
DOI:	10.1016/j.jinsphys.2009.06.008