Molecular cloning of alpha-amylase genes from Drosophila melanogaster. II. Clone organization and verification.

Restriction maps of an alpha-amylase structural gene clone, lambda Dm65, and of four putative alpha-amylase pseudogene clones are presented. Two alpha-amylase structural genes, inverted with respect to each other, are contained in lambda Dm65. Subregions of internal DNA sequence homology within lambda Dm65 and of cross-homology between the presumptive pseudogene clones and lambda Dm65 were determined. Subregions of cross-homology between the Drosophila clones and the mouse alpha-amylase cDNA clone, pMSa104, were also determined. The presence of functional alpha-amylase structural genes in lambda Dm65 was verified by injection of appropriate subclones into the germinal vesicle of Xenopus oocytes, followed by incubation of the oocytes under conditions that allowed coupled transcription and translation of injected genes to occur. Subclones of the 3.8- and 5.6-kb EcoRI fragments of lambda Dm65 were shown to code for alpha-amylase isozymes 1 and 3, respectively, of Drosophila melanogaster Canton-S. Both subclones are homologous to RNA of a size sufficient to accommodate the alpha-amylase-coding information. No RNA species homologous to other subcloned EcoRI fragments of lambda Dm65 was detected.