Cis-acting sequences sufficient for correct tissue and temporal specificity of larval serum protein 1 genes of Drosophila.

We have constructed hybrid genes in which the coding region of the bacterial gene chloramphenicol acetyl transferase (CAT) has been linked to varying lengths of upstream sequences of Drosophila genes for larval serum sequence 1 (LSP1). These have been inserted into a P-element transformation vector and subsequently transferred into the germ-line of recipient flies. Transformants carrying the CAT gene linked to 1650 bp, 570 bp or 377 bp of upstream LSP1alpha sequences, or 745 bp or 471 bp of upstream beta sequences express CAT with the same developmental and tissue specificity as the endogenous LSP1 genes. Constructs having only 66 bp of upstream LSP1beta sequences, however, show extremely low levels of CAT expression in tissues and at developmental stages in which LSP1 is not expressed. We discuss the significance of short regions of homology between the DNA upstream of the alpha and beta genes, which lie within the regions identified by the transformation experiments as being required for the cis-regulation of LSP1 synthesis.