<p>The genomic structures of the transgenes pGFP-Zenv and pGFP-Idgag used in this study are presented at the tops of both panels: The grey boxes correspond to the UASt promoter, the dotted boxes to the GFP gene, and the white box to the <i>env</i> fragment of <i>ZAM</i> or the <i>gag</i> fragment of <i>Idefix</i>. Triangles indicate the FRT sites. Focal plane of the follicles dissected from a line in which the pGFP-Zenv transgene is driven by the ubiquitous Actin-Gal4 driver. Expression of the pGFP-Zenv transgene in an S genetic background before (A) or after (B) <i>flp</i>-recombinase action, or in a U genetic background before the <i>flp</i> treatment (C). GFP expression in the ovarioles of a transgenic line bearing the pGFP-Idgag transgene driven by the ubiquitous Actin-Gal4 driver. Expression of the pGFP-Idgag transgene in an S genetic background before (D) or after (E) <i>flp</i>-recombinase action, or in a U genetic background before the <i>flp</i> treatment (F). No GFP is detected in ovaries of the S lines. Its expression is recovered after the flp treatment or when the COM locus is mutated, as in the U genetic background.</p
