UASt regulatory sequences drive expression of HcRed1. Marker allele that forms part of a disruptive FRT cassette that is located between two Gateway cassettes in the pFRiPE RNAi cloning vector, and in between two inverted copies of a 'silencing' fragment that target a gene of interest in transgenic RNAi constructs derived from this vector. The HcRed1 coding sequence in the disruptive cassette is flanked by FRT sites and when the cassette is present, HcRed1 is expressed under the control of UASt and the transcription termination signal present downstream of the HcRed1 coding sequence prevents production of dsRNA. FLP-mediated recombination can be used to excise the cassette, removing the HcRed1 coding sequence and downstream transcription termination signal, and allowing production of dsRNA that targets the gene of interest. Clones in which the FRT cassette has been excised and RNAi against the gene of interest has been activated can be identified by lack of HcRed1 expression.