Originally published as Genetics Published Articles Ahead of Print on June 24, 2008.

Genetics, Vol. 179, 1785-1793, August 2008, Copyright © 2008
doi:10.1534/genetics.108.087072

Cytotype Regulation of P Transposable Elements in Drosophila melanogaster: Repressor Polypeptides or piRNAs?

Philip A. Jensen, Jeremy R. Stuart, Michael P. Goodpaster, Joseph W. Goodman and Michael J. Simmons1

Department of Genetics, Cell Biology, and Development, University of Minnesota, St. Paul, Minnesota 55108-1095

1 Corresponding author: Department of Genetics, Cell Biology, and Development, 250 BioScience Center, University of Minnesota, 1445 Gortner Ave., St. Paul, MN 55108-1095.
E-mail: simmo004{at}umn.edu

The telomeric P elements TP5 and TP6 are associated with the P cytotype, a maternally inherited condition that represses P-element-induced hybrid dysgenesis in the Drosophila germ line. To see if cytotype repression by TP5 and TP6 might be mediated by the polypeptides they could encode, hobo transgenes carrying these elements were tested for expression of mRNA in the female germ line and for repression of hybrid dysgenesis. The TP5 and TP6 transgenes expressed more germ-line mRNA than the native telomeric P elements, but they were decidedly inferior to the native elements in their ability to repress hybrid dysgenesis. These paradoxical results are inconsistent with the repressor polypeptide model of cytotype. An alternative model based on the destruction of P transposase mRNA by Piwi-interacting (pi) RNAs was supported by finding reduced P mRNA levels in flies that carried the native telomeric P elements, which are inserted in a known major piRNA locus.