Drosophila Subject

Clos, J., Westwood, J.T., Becker, P.B., Wilson, S., Lambert, K., Wu, C. (1990). Molecular cloning and expression of a hexameric Drosophila heat shock factor subject to negative regulation. Cell 63, 1085-1097. 

The interaction between Drosophila, yeasts and columnar cacti of the Sonoran Desert has been the subject of much recent interest (37) As a coevolved system, perhaps more is known about this interaction than any other. The chemistry of the cacti (70 spp.) has been postulated to play a significant role in the establishment of this system (38 ), but this was based upon reports of a relatively small number of relatively simple alkaloids, and a small number of terpenoid compounds. Only recently, the diversification of plant compounds has been discovered to be much greater (5). In their section on alkaloids in the above work, BajaJ and McLaughlin report the presence of some thirty-five structures. In addition, I have been able to isolate some sixty triterpenoid glycosides (structures were not determined) and more were detected but not Isolated. 

The first unequivocal demonstration that environmental agents could produce mutations came with the work of H. J. Muller293 that showed that x rays are mutagenic in Drosophila. L. J. Stadler1 31 independently discovered x-ray mutagenesis in barley. In his earliest writings on this subject,... 

Group A in Table 9-3 consists of 33 chemicals that would have been classified as presumed mammalian mutagens on the basis of Tier I testing. Hie internal consistency of Tier I tests in this group is high for example, only three of the 33 chemicals had negative results in the Salmonella/microsome test. Of the 33 chemicals, 20 were subjected to the Drosophila X-linked recessive lethal test, and 19 had positive results. Note that there are only two cases of a discrepancy between L51 and V79. 

Fluothane was negative in two Tier I tests (and not subjected to the third), but was positive in the Drosophila test. If fluothane had also had a negative result in the mammalian cytogenetic test, it would be the only example in this series of a substance that was mutagenic according to the Tier II test but was not detected in Tier I. 

Although the subject is in its infancy, it is already clear that a substantial fraction, possibly a majority, of spontaneous mutations in Drosophila have such a cause. If that turns out to be true and generalizable to mammals (there is reason to believe that such elements are present in mice and humans), it will require a revision in our thinking about mutation and mutagens, and it would mean that the kinds of mutagenic mechanisms discussed in this report account for only a part of the spontaneous-mutation rate. On the one hand, we can conclude optimistically that classical mutagens are relatively less important. On the other hand, we cam assume pessimistically that chemicals not detectable with existing test systems increase the rate of transposon-induced mutations. 

Fig. (2). Strategy for the identification of gel-separated (2D-SDS-PAGE) proteins that are part of the immune response of Drosophila. Blood from control and immune-challenged flies was collected and subjected to 2D-SDS-PAGE, immune-induced (-I-) or repressed (-) stained spots were excised, subjected to proteolysis e.g. trypsin), and the peptides fragments analyzed by MS and/or MS/MS.

In a landmark paper, Muller (1964) demonstrated that clonal lineages may be subject to reduce fitness due to a relentless increase in the load of deleterious mutations, and that sexual recombination would tend to reduce that load. The progressive increase in deleterious mutations has become known as Muller s ratchet, and there is evidence for the ratchet in nonrecombining genomes present in eukaryotic cells, namely, mitochondrial DNA (Lynch, 1997 Moran, 1996), sex chromosomes, and Drosophila chromosomes that are prevented from recombining (Rice, 1994). A potential consequence of the ratchet is extinction of clonal lineages (Lynch et al., 1993). Some models indicate that clonal species... 

Some types of cultured cells, such as Drosophila Schneider cells, can be grown directly on glass microscope cover slips. Such cells can be subjected to FISH procedures as easily as they can be immunostained. Here is a simple procedure for fixation ... 

Biochemical analyses can be performed in parallel with or instead of morphological studies. At various time points during the course of in vitro disassembly, aliquots of the reaction mixture should be separated into supernatant and pellet fractions by sedimentation at 12,000 g and proteins subjected to SDS-PAGE and immunoblot analysis. An extract of stage 14 Drosophila oocytes contains only lamin Dm i, (Smith and Fisher, 1989 see also Lin and Fisher, 1990 Mans et at., 1995). Purified Drosophila nuclei contain lamins Dmi and Dm2 (Smith et al, 1987 see also Lin and Fisher, 1990 Maus et al, 1995). Lamin Dmmit migrates with a gel mobility intermediate to lamins Dm, and Dm2 (Fig. 4). 

An exhaustive bibliography of papers dealing with the biology and genetics of Drosophila was commenced by Muller (1939) and continued in four more volumes by Herskowitz (1952, 1958, 1963, 1969). These volumes include an author and subject and species index. Most of the technical and research notes in DIS are also indexed in these volumes, as is also much of the literature on chemical mutagenesis in Drosophila, Finally, books by Auerbach (1962) and by Loveless (1966) are useful surveys of the field of chemical mutagenesis. 

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