Regulation of enzyme activities inDrosophila: I. The detection of regulatory loci by gene dosage responses

Abstract

In order to detect regulatory genetic sites in the autosomes of Drosophila melanogaster, the levels of X-linked glucose-6-phosphate dehydrogenase and autosomally linked a-glycerophosphate and isocitrate dehydrogenases have been monitored in extracts of flies aneuploid for regions of chromosomes II and III. In addition to expected structural gene dosage responses of a-GPDH and IDH, flies hyperploid for several autosome regions were found to display altered levels of one or more of the enzymes studied. While IDH activity was increased in flies hyperploid for segments of both chromosomes II and III, a-GPDH activity was decreased in specific hyperploids for chromosome II regions only. The latter group of segmental aneuploids were normal with respect to levels of chromosome II-linked alcohol dehydrogenase. To test if the observed responses were due to dosage changes of discrete genes lying within the larger effective segments, flies aneuploid for subdivisions of the chromosome segments 21A-25CD, 35A-40, and 70CD-71B were assayed. For two of these large segments so analysed, the apparent effects were attributable to specific small subdivisions, suggesting the presence of discrete regulatory sites within the latter. For the 35A-40 region the a-GPDH effect observed for subdivisions was not sufficient to account for the large a-GPDH decrease seen in flies hyperploid for the large, inclusive region. These observations are discussed with respect to the possible bases of effect of regulatory elements on enzyme activity.

Autosomal dosage compensation Drosophila melanogaster strains trisomic for the left arm of chromosome 2.

“…Indeed, changes in enzyme activity associated with aneuploids are often used to locate the structural gene of an enzyme or a dose-dependent locus regulating its expression (2,15). Because little is known about the effect of autosomal trisomy on gene expression, we examined seven gene-enzyme systems located within and outside a trisomic region, namely chromosome 2L.…”

“…Experiments are in progress to test the application of these two models to autosomal dosage compensation. Indeed, Rawls and Lucchesi (15) Further evidence for autosomal dosage compensation may be found within the evolutionary history of the genus Drosophila. Fusion of autosomal and X chromosome arms to form X chromosomes of varying size and shape has occurred in the genus Drosophila (29) and appears to be a common mechanism of speciation.…”

Inheritance of protein amounts: comparison of two-dimensional electrophoresis patterns of leaf sheaths of two maize lines (Zea maysL.) and their hybrids

“…The closely located elements, which can even be inside the structural gene, are cw-acting and exhibit additive inheritance (Lalley & Shows, 1977;Allendorf, Knudsen & Phelps, 1982;Chandlee & Scandalios, 1984); in all cases examined, the proteins were affected at the synthesis level (Bernstine & Koh, 1980;Shaffer & Bewley, 1983;Sano, 1984). The distantly located elements seem to be numerous, and have been found whenever looked for (Rawls & Lucchesi, 1974;Laurie-Ahlberg et al 1980Colas des Francs & Thiellement, 1985;Thiellement et al 1986). When studied, their inheritance is mostly non-additive (Abraham & Doane, 1978;McDonald & Ayala, 1978;King & McDonald, 1983;Maroni & Laurie-Ahlberg, 1983;Gibson et al 1986, but see Scandalios et al 1980).…”

Gene balance hypothesis: Connecting issues of dosage sensitivity across biological disciplines

“…This effect is quite common in the data for trisomic segments in other species. including Datura, barley, Arabidopsis, Drosophila, and human trisomic cells (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32). The ability to recover corresponding monosomics in maize facilitated the finding that this effect can be proportional through one, two, and three doses.…”