The zygotic control of Drosophila pair-rule gene expression. I. A search for new pair-rule regulatory loci.
The examination of pair-rule gene expression in wild-type and segmentation mutant embryos has identified many, but not necessarily all, of the elements of the regulatory system that establish their periodic patterns. Here we have conducted a new type of search for previously unknown regulators of these genes by examining pair-rule gene expression in blastoderm embryos lacking parts of or entire chromosomes. This method has the advantage of direct inspection of abnormal pair-rule gene patterns without relying upon mutagenesis or interpretation of larval phenotypes for the identification of segmentation genes. From these experiments we conclude that: (i) most zygotically required regulators of the fushi tarazu (ftz), even-skipped (eve) and hairy (h) pair-rule genes have been identified, except for one or more loci we have uncovered on chromosome arm 2L; (ii) the repression of the ftz and eve genes in the anterior third of the embryo is under maternal, not zygotic control; and (iii) there are no general zygotically required activators of pair-rule gene expression. The results suggest that the molecular basis of pair-rule gene regulation can be pursued with greater confidence now that most key trans-acting factors are already in hand.
Vavra
S H
SH
Laboratory of Molecular Biology, University of Wisconsin, Madison 53706.
Carroll
S B
SB
D000818:Animals; D002872:Chromosome Deletion; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D004330:Drosophila / Q000196:embryology* / Q000235:genetics; D005809:Genes, Regulator / Q000235:genetics*; D009154:Mutation; D015053:Zygote / Q000502:physiology*