ORGANIZATION OF THE ROSY LOCUS IN DROSOPHILA MELANOGASTER: EVIDENCE FOR A CONTROL ELEMENT ADJACENT TO THE XANTHINE DEHYDROGENASE STRUCTURAL ELEMENT

Abstract

From a collection of electrophoretic variants of XDH obtained from laboratory strains and natural populations, a stock was isolated that was associated with much greater than normal levels of XDH activity. Preliminary recombination experiments demonstrated that this character maps to the rosy locus. While a series of observations failed to relate this phenotype to alteration in the structure of the XDH polypeptide, kinetic and immunological experiments did succeed in associating this character with variation in number of molecules of XDH/fly. Large scale fine structure recombination experiments locate the genetic basis for this variation in number of molecules of XDH/fly to a site very close to, but definitely outside of, the genetic boundaries of the XDH structural information. Observations are described which eliminate the possibility that we are dealing with a tandem duplication of the XDH structural element. Turning to a regulatory role for this genetic element located adjacent to the XDH structural information, a simple experiment is described which demonstrates that it functions as a "cis-acting" regulator of the XDH structural element.

SPONTANEOUS UNEQUAL EXCHANGE IN THE ROSY REGION OF DROSOPHILA MELANOGASTER

“…Background: The fine-structure mating described in this report were designed to localize the site responsible for a two-fold increase in XDH levels detectable in strains bearing the r y f 4 isoallele (CHOVNICK et al 1976). Preliminary mapping experiments indicated that the site responsible for this increased activity (designated 2 0 9 ) resided in the 0.3 map unit interval from karriioisin to rosy, but at or to the left of all markers in the XDH structural element.…”

“…During the fine-structure mapping of a putative xanthine dehydrogenase regulatory element (CHOVNICK et al 1976), one series of crosses afforded an opportunity to detect some of these unusual events. In particular, triploid and partially trisomic individuals (these latter bearing tandem direct duplications of the rosy region) were recovered at unexpectedly high frequencies.…”

P-Element-Induced Control Mutations at the r gene of Drosophila melanogaster

“…Selective screens have been available to recover regulatory mutations at the rosy (xanthane dehydrogenase), adh (alcohol dehydrogenase), and rudimentary (carbamylphosphate synthetase [CPSase]-aspartate transcarbamylase [ATCase]-dihydroorotase [DHOase]) loci; however, no regulatory mutations have been recovered in screens with conventional mutagens such as ethyl methanesulfonate (EMS) and X-rays. In fact the only putative control mutations at these loci have been isolated either from natural populations (6,33) or as spontaneous mutations (35). Hence, it could be argued that control regions of Drosophila genes and perhaps genes of other eucaryotes may be refractory to many of the standard mutagens and that it would be worthwhile employing a somewhat different approach for the generation of regulatory mutations.…”

HIDDEN ELECTROPHORETIC VARIATION AT THE XANTHINE DEHYDROGENASE LOCUS IN A NATURAL POPULATION OF DROSOPHILA MELANOGASTER

“…This locus is an appropriate one to screen for evidence of loci affecting protein mobility. There is evidence for a cis-acting control site (i409) for Xdh immediately to the left of the structural gene (CHOVNICK et al 1976;MCCARRON et al 1979). In addition three other loci, low xanthine dehydrogenase (Jxd, 3-33.9), maroon-like (ma-I, 2-64.8) and cinnamon (cin, 1-0.0) also affect XDH activity (MACINTYRE and O'BRIEN 1976).…”