STUDY ON ECDYSTEROID LEVELS AND GENE EXPRESSION OF ENZYMES RELATED TO ECDYSTEROID BIOSYNTHESIS IN THE LARVAL TESTIS OF Spodoptera littoralis

Authors

  • Masatoshi Iga,

    1. Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
    Current affiliation:
    1. Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
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  • Catherine Blais,

    1. UMR 1272, Physiologie de l'insecte, Signalisation et Communication, UPMC Université Paris 6, France
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  • Guy Smagghe

    Corresponding author
    • Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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  • Grant sponsor: Fund of Scientific Research (FWO-Vlaanderen, Belgium).

Correspondence to: Guy Smagghe, Department of Crop Protection, Ghent University, Coupure Links 653, 9000 Ghent, Belgium. E-mail: guy.smagghe@ugent.be

Abstract

We investigated here the ecdysteroid titers and the expression of six genes coding for known enzymes of the ecdysteroid biosynthesis in the testes of last instar larvae of the pest cotton leafworm, Spodoptera littoralis. We showed that the timing of the ecdysteroid profile was the same in testes and in hemolymph, with a small peak at day 2 and a large one at day 4 after ecdysis. Ecdysone and 20-hydroxyecdysone (20E) were detected in both tissues. 20E was the major ecdysteroid in testes and in hemolymph from day 4. Interestingly, the gene expression of the steroidogenetic enzymes, Neverland, and the five cytochrome P450 enzymes encoded by the Halloween genes was confirmed in the testes, and varied during the instar. However, from the data obtained so far, we cannot conclude that the measured ecdysteroids in the testes result from the activity of the genes under study. Indeed, it is suggested that the ecdysone produced centrally in the prothoracic glands, could have been transformed into 20E in the testes, where Sl-shade is well expressed.

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