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Molecular cloning of a family of xenobiotic-inducible drosophilid cytochrome P450s: Evidence for involvement in host-plant allelochemical resistance

  1. James C. Fogleman*
  1. *Department of Biological Sciences, 2101 East Wesley Avenue, University of Denver, Denver, CO 80208; and ‡Section of Genetics and Development, 407 Biotechnology Building, Cornell University, Ithaca, NY 14853

  1. Edited by May R. Berenbaum, University of Illinois, Urbana, IL, and approved July 31, 1997 (received for review March 10, 1997)

Abstract

Cytochrome P450s constitute a superfamily of genes encoding mostly microsomal hemoproteins that play a dominant role in the metabolism of a wide variety of both endogenous and foreign compounds. In insects, xenobiotic metabolism (i.e., metabolism of insecticides and toxic natural plant compounds) is known to involve members of the CYP6 family of cytochrome P450s. Use of a 3′ RACE (rapid amplification of cDNA ends) strategy with a degenerate primer based on the conserved cytochrome P450 heme-binding decapeptide loop resulted in the amplification of four cDNA sequences representing another family of cytochrome P450 genes (CYP28) from two species of isoquinoline alkaloid-resistant Drosophila and the cosmopolitan species Drosophila hydei. The CYP28 family forms a monophyletic clade with strong regional homologies to the vertebrate CYP3 family and the insect CYP6 family (both of which are involved in xenobiotic metabolism) and to the insect CYP9 family (of unknown function). Induction of mRNA levels for three of the CYP28 cytochrome P450s by toxic host-plant allelochemicals (up to 11.5-fold) and phenobarbital (up to 49-fold) corroborates previous in vitro metabolism studies and suggests a potentially important role for the CYP28 family in determining patterns of insect–host-plant relationships through xenobiotic detoxification.

Footnotes

    • ↵† To whom reprint requests should be addressed.

    • This paper was submitted directly (Track II) to the Proceedings Office.

    • Abbreviations: RACE, rapid amplification of cDNA ends; rp49, ribosomal protein 49.

    • Data deposition: The sequences reported in this paper have been deposited in the GenBank database [accession nos. U89746 (CYP28A1), U89747 (CYP28A2), U91565 (CYP28A3), and U91566 (CYP28A4)].

    • Received March 10, 1997.

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