Endocrinology Abstracts

Molecular aspects of juvenile hormone action upon vitellogenin production in insects

X. Bellés, D. Comas, D. Martín & M. D. Piulachs

Department of Physiology and Molecular Biodiversity, Instituto de Biología Molecular de Barcelona (CID, CSIC), Jordi Girona 18, 08034 Barcelona, Spain

Juvenile hormone (JH) is the master vitellogenic and gonadotrophic factor in many insect orders. However, molecular aspects of JH action upon vitellogenesis have been mainly studied in less modified insect groups, like locusts or cockroaches. Cloning of the complete or partial cDNA for vitellogenin in the locust Locusta migratoria and the cockroach Blattella germanica has facilitated molecular analysis of the vitellogenic action of JH. In L. migratoria, most of the results available have been described by G. R. Wyatt and associates. For example, they have shown that this species requires quite a high doses of JH III (higher than 100 ? g) or JH analog (10 ? g of pyriproxyfen) to stimulate vitellogenin production in allatectomized females. In addition, the same authors have shown that induction of vitellogenin transcription by JH or JH analog administered to allatectomized locusts is delayed about 24 hours In contrast, results obtained in our laboratory with B. germanica, indicate that a dose as low as 0.1 ? g of JH III induces clearly detectable amounts of vitellogenin mRNA in the fat body of allatectomized females as early as 2 hours after the administration of the hormone. Experiments carried out on fat body tissue of B. germanica incubated in vitro also show the high sensitivity and rapidity of response of this species to the vitellogenic action of JH. The gene or the cDNA for vitellogenin has been cloned in other insect species in which vitellogenesis is apparently governed by JH, like the cockroach Periplaneta americana, the hemipterans Riptortus clavatus, Plautia stali and Graptopsaltria nigrofuscata, the coleopteran Anthonomus grandis or the hymenopterans Athalia rosae and Pimpla nipponica. However, the hormonal control of vitellogenin expression in these species has not yet been reported. In any case, the substantial differences encountered when comparing two relatively close related species, such as the orthopteran L. migratoria and the dictyopteran B. germanica, promises a great diversity of vitellogenin regulation modes within the insect class.

Acknowledgements: Financial support from the DGICYT, Spain (project No PB98-0472) and from the CIRIT, Catalonia (1999 SGR 00186) is gratefully acknowledged.

Index terms: Blattella germanica, Locusta migratoria, vitellogenesis.

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