Genetics of esterases in Drosophila. VI. Gene system regulating the phenotypic expression of the organ-specific esterase in Drosophila virilis.

It is shown that the gene controlling the synthesis of the organ-specific S-esterase of Drosophila virilis ejaculatory bulbs is located on the second chromosome (at approximate position 192.1 +/- map units). The cells of the genital imaginal disks are determined for the synthesis of S-esterase 10-12 hr after the second molt. The organ-specific esterase can be detected after adult emergence only. It is preceded by an increase in RNA content and by enhancement of RNA synthesis in the cells of the ejaculatory bulbs. Interstock differences were found in the level of the activity of S-esterase, which is under the control of the X chromosome, as well as in the time of expression of enzyme activity, which is controlled by the fifth chromosome. It is suggested that the specific phenotypic expression of this enzyme depends on the system of genes with regulatory expression at both the transcriptional and posttranscriptional levels. The genetic control of the synthesis of the S-esterase described is a convenient model for studying mechanisms of gene activity regulation in eukaryotes.