Ten copies of the UAS site followed by an Hsp70 basal promoter are fused upstream of EGFP which has been optimised for Drosophila codon usage. A small intron derived from the Mhc gene followed by a synthetic AT-rich 21bp sequence made by combining the Cavener consensus sequence with elements from the Malacosoma neustria nucleopolyhedrovirus (MnNPV) polyhedrin gene has been inserted between the promoter and EGFP sequences. The 3' UTR (666bp) from the Autographa californica nucleopolyhedrovirus (AcNPV) p10 gene is present downstream of the EGFP sequences.