STRUCTURE, EXPRESSION AND DUPLICATION OF GENES WHICH ENCODE PHOSPHOGLYCEROMUTASE OF DROSOPHILA-MELANOGASTER

We report here the isolation and characterization of genes from Drosop hila that encode the glycolytic enzyme phosphoglyceromutase (PGLYM). T wo genomic regions have been isolated that have potential to encode PG LYM. Their cytogenetic localizations have been determined by in situ h ybridization to salivary gland chromosomes. One gene, Pglym78, is foun d at 78A/B and the other, Pglym87, at 87B4,5 of the Drosophila polyten e map. Pglym78 transcription follows a developmental pattern similar t o other glycolytic genes in Drosophila, i.e., substantial maternal tra nscript deposited during oogenesis; a decline in abundance in the firs t half of embryogenesis; a subsequent increase in the second half of e mbryogenesis which continues throughout larval life; a decline in pupa e and a second increase to a plateau in adults. This transcript has be en mapped by cDNA and genomic sequence comparison, RNase protection, a nd primer extension. Using similar analyses transcripts of Pglym87 cou ld not be detected. Pglym78 has two introns which interrupt the coding region, while the Pglym87 gene lacks introns. This and other features support a model of retrotransposition mediated gene duplication for t he origin of Pglym87. The apparent absence of a complete, intact codin g frame and transcript suggest that Pglym87 is a pseudogene. However, retention of reading frame and codon bias suggests that Pglym87 may re tain coding function, or may have been inactivated recently, substanti ally after the time of duplication, or that the molecular evolution of Pglym87 is unusual. Similarities of the unusual molecular evolution o f Pglym87 and other proposed pseudogenes are discussed.