Genomic and cDNA clones of the homeotic locus Antennapedia in Drosophila.

Homeotic genes are involved in the control of developmental pathways: dominant mutations at the Antennapedia locus of Drosophila, for example, lead to replacement of the antennae on the head of the fly by mesothoracic legs. Using a combination of chromosome walking and jumping, we have cloned a DNA region from Drosophila containing Antennapedia. Five DNA inversion rearrangements which are associated with the Antennapedia mutant phenotype were localized within a 25-kb region. Genomic DNA sequences from this area were used as hybridization probes to screen cDNA libraries prepared from Drosophila embryonic and pupal poly(A)+ RNA. A 2.2-kb cDNA sequence (903) was isolated which appears to derive from at least four non-contiguous chromosomal regions that span 100 kb. It includes the positions of the inversion breakpoints. A second cDNA of 2.9 kb (909) is composed of sequences from at least three chromosomal regions, two of which are similar or identical to sequences contained in the 903 clone but the third is derived from genomic DNA within a putative 903 intron. The unusual size and complexity of this locus are discussed.     

The cloning and expression of the gene encoding organ-specific esterase S from the genome of Drosophila virilis

We have cloned the gene for the esterase S isozymes complex from the genome of Drosophila virilis in pBR322. Esterase S is an enzyme which is specifically synthesized in the ejaculatory bulbs of D. virilis adult males. The gene for the esterase S isozyme complex (estS) has been localized in band 2G5e of chromosome II. Poly(A)+ RNA prepared from ejaculatory bulbs actively hybridizes with this band. A cloned 15-kb fragment of D. virilis DNA (pVE9) also hybridizes with band 2G5e. The area encoding the poly(A)+ RNA is located in the middle part of the cloned fragment whose ends are not transcribed in vivo. Only one poly(A)+ RNA which is 1.9 kb long and complementary to pVE9 DNA can be revealed in the cytoplasm. The mRNA preselected by hybridization to pVE9 DNA was microinjected into the cytoplasm of Xenopus laevis oocytes. In other experiments, the pVE9 DNA itself was microinjected into oocyte nuclei. In both cases, esterase S is synthesized in the oocytes, and the major part of the protein is transported from the oocytes and accumulated in the incubation medium.     

Molecular analysis of the ecdysterone-inducible 2B5 "early'' puff in Drosophila melanogaster.

The 2B5 region of the X-chromosome in Drosophila melanogaster plays a developmentally important role in the ecdysterone-triggered response of the late third instar salivary gland. Using a combination of transposon-tagging and chromosomal walking techniques, we have isolated 231 kb of contiguous genomic DNA sequences corresponding to this region. We have more precisely aligned this DNA to the 2B1,2 to 2B5-6 interval of the cytogenetic map by locating the position of three well-characterized chromosomal breakpoints by in situ hybridization and genomic DNA blotting experiments. Labeled cDNA, synthesized from poly(A)+ RNA isolated from hormone-induced salivary gland and imaginal disc tissues and hybridized to the cloned DNA, demonstrated that the ecdysterone-inducible sequences mapped to DNA segments corresponding to the 2B3,4 to 2B5-6 interval. Although some of these sequences were inducible in only one tissue type, many were found to be inducible in both salivary glands and imaginal discs. RNA blotting experiments have detected a major 4.5-kb RNA which is hormone inducible in the larval salivary gland and whose quantitative induction is not inhibited by cycloheximide. Thus, the 4.5-kb RNA represents at least one product from the ecdysterone-responsive 2B5 "early' puff.