UASz sequences are fused upstream of a genomic fragment that extends from the start of the nanos 5'UTR to 500bp downstream of the end of the nanos 3'UTR. Mutations have been introduced into the two smg-response elements (SREs) present in the nanos 3'UTR. 24 repeats of the SunTag(v4) peptide have been inserted at the N-terminal end of the nanos coding sequence.