Characterization of <i>Gfat1</i> (<i>zeppelin</i>) and <i>Gfat2</i>, Essential Paralogous Genes Which Encode the Enzymes That Catalyze the Rate-Limiting Step in the Hexosamine Biosynthetic Pathway in <i>Drosophila melanogaster</i>
Shawn Cotsworth,
Catherine J. Jackson,
Graham Hallson,
Kathleen A. Fitzpatrick,
Monika Syrzycka,
Alistair B. Coulthard,
Amy Bejsovec,
Marcella Marchetti,
Sergio Pimpinelli,
Simon J. H. Wang,
Robert G. Camfield,
Esther M. Verheyen,
Donald A. Sinclair,
Barry M. Honda,
Arthur J. Hilliker
Affiliations
Shawn Cotsworth
Department of Molecular Biology and Biochemistry (MBB), Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
Catherine J. Jackson
Department of Molecular Biology and Biochemistry (MBB), Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
Graham Hallson
Department of Molecular Biology and Biochemistry (MBB), Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
Kathleen A. Fitzpatrick
Department of Molecular Biology and Biochemistry (MBB), Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
Monika Syrzycka
Department of Molecular Biology and Biochemistry (MBB), Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
Alistair B. Coulthard
Department of Biology, York University, Toronto, ON M3J 1P3, Canada
Amy Bejsovec
Department of Biology, Duke University, Durham, NC 27708, USA
Marcella Marchetti
Department of Biology and Biotechnology “C. Darwin”, “Sapienza” University of Rome, 00185 Rome, Italy
Sergio Pimpinelli
Department of Biology and Biotechnology “C. Darwin”, “Sapienza” University of Rome, 00185 Rome, Italy
Simon J. H. Wang
Department of Molecular Biology and Biochemistry (MBB), Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
Robert G. Camfield
BC Genome Science Centre, 675 West 10th Avenue, Vancouver, BC V5Z 1L3, Canada
Esther M. Verheyen
Department of Molecular Biology and Biochemistry (MBB), Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
Donald A. Sinclair
Department of Molecular Biology and Biochemistry (MBB), Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
Barry M. Honda
Department of Molecular Biology and Biochemistry (MBB), Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
Arthur J. Hilliker
Department of Biology, York University, Toronto, ON M3J 1P3, Canada
The zeppelin (zep) locus is known for its essential role in the development of the embryonic cuticle of Drosophila melanogaster. We show here that zep encodes Gfat1 (Glutamine: Fructose-6-Phosphate Aminotransferase 1; CG12449), the enzyme that catalyzes the rate-limiting step in the hexosamine biosynthesis pathway (HBP). This conserved pathway diverts 2%–5% of cellular glucose from glycolysis and is a nexus of sugar (fructose-6-phosphate), amino acid (glutamine), fatty acid [acetyl-coenzymeA (CoA)], and nucleotide/energy (UDP) metabolism. We also describe the isolation and characterization of lethal mutants in the euchromatic paralog, Gfat2 (CG1345), and demonstrate that ubiquitous expression of Gfat1+ or Gfat2+ transgenes can rescue lethal mutations in either gene. Gfat1 and Gfat2 show differences in mRNA and protein expression during embryogenesis and in essential tissue-specific requirements for Gfat1 and Gfat2, suggesting a degree of functional evolutionary divergence. An evolutionary, cytogenetic analysis of the two genes in six Drosophila species revealed Gfat2 to be located within euchromatin in all six species. Gfat1 localizes to heterochromatin in three melanogaster-group species, and to euchromatin in the more distantly related species. We have also found that the pattern of flanking-gene microsynteny is highly conserved for Gfat1 and somewhat less conserved for Gfat2.
