Transgenic construct used in a pairing-sensitive repression (PSR) assay. Generated by inserting a 1 kb AvrII-KpnI fragment from upstream of ph-p (nucleotides 72,024 to 70,973 of AE003423) fragment into pCaSpeR4 (which contains the w+mC minigene). The orientation of the fragment relative to the w ORF is the reverse of its normal orientation relative to the ph-p transcription unit.