EXPRESSION OF THE GPDH-4 ISOZYME OF SN-GLYCEROL-3-PHOSPHATE DEHYDROGENASE IN 3 DROSOPHILA SPECIES

A fourth recently discovered isozyme of sn-glycerol-3-phosphate dehydr ogenase (GPDH-4) in Drosophila melanogaster is shown to be a translati onal product of the Gpdh transcript which contains exons 1 through 7. This transcript was also found in two other Drosophila species, D. bus ckii and D. virilis. In contrast to D. melanogaster and D. busckii, th e Gpdh transcript containing exons 1-6 is absent in D. virilis adults. The reason for this difference between D. virilis and the two other s pecies is intriguing but remains elusive. We have ruled out the possib ility that a replacement of an amino acid residue in exon 7 played any role in generating this interspecific variation.