9.9kb fragment of vas promoter drives expression of a 4.5kb fragment from P\TIVS3.Hsp83.βgeo containing the ATG codon, translation start site and NLS driving the expression of a P\T fragment containing the third intron (IVS3) and flanking exons fused in frame to a 3.4kb ClaI XhoI fragment carrying the 3' half of Ecol\lacZ fused to Tn\neoR (Friedrich and Soriano, 1991, Genes Dev 5: 1513-1523) from P\TIVS3.Hsp83.βgeo