Cloning and characterization ofbicaudal, a maternal effect mutation of Drosophila melanogaster

[摘要] The Drosophila maternal effect mutant, bicaudal (bic), affects the anterior-posterior axis of the embryo. It is incompletely penetrant, producing a variety of lethal embryonic phenotypes, the most severe of which is replacement of the anterior half with a mirror image duplication of the posterior half. Genetic mapping has placed this locus within a region defined by the overlap of two chromosomal deficiencies on the second chromosome. Indirect genetic evidence has suggested that a lethal mutation that maps to the same region, $vr22sp{P3}$ may represent a more severe allele of the bicaudal locus. A chromosome walk was performed in this region and over 65 kb of overlapping clones isolated. The location of the P-element insertion responsible for the $vr22sp{P3}$ mutation was localized in the walk, and cDNAs corresponding to two adjacent transcription units isolated. These clones have been analyzed and sequenced, and one shows at least a 65% identity with eukaryotic release factor.Recombination work with bicaudal mutant stocks has improved penetrance of the mutation to a level allowing genetic analysis. These stocks were used in genetic rescue experiments to determine the locations of bic and $vr22sp{P3}.$ The results of genetic rescue and polymorphism mapping provide good evidence that $vr22sp{P3}$ and bicaudal are in fact alleles at the same locus, and the gene codes for a protein with strong homology to release factor. The bic protein most likely plays a role in negative regulation of translation of downstream maternal genes such as nanos.

[发布机构] Rice University

[效力级别] biology