QUEMAO, A DROSOPHILA BRISTLE LOCUS, ENCODES GERANYLGERANYL PYROPHOSPHATE SYNTHASE

The quemao (qm) locus of Drosophila melanogaster is characterized by a P-element-associated mutant lacking most of the large bristles on the thorax and by several EMS-induced recessive lethals. quemao was clone d using a transposon tagging strategy. P-element-mediated transformati on demonstrated that the cloned qm DNA sequence (from the 65F cytologi cal region) rescues the mutant phenotype. A 2.3-kb qm transcript was i dentified by Northern blot analysis by sequencing of the isolated qm c DNA clones and by 5' rapid amplification cDNA end (RACE). The predicte d amino acid sequence (338 residues) of the coding region of the qm tr anscript shares 42, 31, 13, 20, and 12% identical amino acid sequences with the geranylgeranyl pyrophosphate synthase (GGPPS) of fungi, yeas t, plants, archaebacteria, and eubacteria, respectively. It also conta ins five highly conserved domains common among all known isoprenyl pyr ophosphate synthases. The P element associated with the original qm mu tant is inserted in the 5' untranslated region of the transcript. An E MS-induced qm nonsense mutation at the 12th codon leads to recessive l ethality at the first larval instar, indicating the essential role of qm in the isoprenoid biosynthesis of insects.