The maternally active αTub84B promoter drives expression of a version of the precursor hairpin of mir-308 carrying compensatory mutations to restore binding to the cadM1 3' UTR contained in P{αTub84B-nEGFP.cad-M1}, with additional changes to preserve the secondary structure of the precursor. The mir-308 mutant sequence is flanked by 50 nucleotides of genomic sequence and the SV40 3'UTR, and is downstream of a human H2B-mRFPruby fusion.