János Szidonya

The DrosDel Deletion Collection: A Drosophila Genomewide Chromosomal Deficiency Resource

We describe a second-generation deficiency kit for Drosophila melanogaster composed of molecularly mapped deletions on an isogenic background, covering ∼77% of the Release 5.1 genome. Using a previously reported collection of FRT-bearing P-element insertions, we have generated 655 new deletions and verified a set of 209 deletion-bearing fly stocks. In addition to deletions, we demonstrate how the P elements may also be used to generate a set of custom inversions and duplications, particularly useful for balancing difficult regions of the genome carrying haplo-insufficient loci. We describe a simple computational resource that facilitates selection of appropriate elements for generating custom deletions. Finally, we provide a computational resource that facilitates selection of other mapped FRT-bearing elements that, when combined with the DrosDel collection, can theoretically generate over half a million precisely mapped deletions.

Mutations at the fat locus interfere with cell proliferation control and epithelial morphogenesis in Drosophila

Lethal mutations at the fat locus in Drosophila cause imaginal discs to continue to grow by cell proliferation far beyond their normal final size. During a greatly extended larval period, the overgrowing imaginal discs develop additional folds and lobes, but retain a single-layered epithelial structure. In the wing disc, the additional lobes originate in the proximal fold area, and in the extra tissue the cells are less columnar than normal. Mutant disc cells lack zonulae adherents as well as associated microtubules and microfilaments, and they show an abnormal distribution and reduced density of gap junctions. The effect on growth is disc-autonomous as shown by transplantation experiments. The overgrown imaginal discs retain the ability to differentiate adult cuticular structures, as shown by metamorphosis of discs after transplantation into wild-type larval hosts and by the ability of some mutant animals to develop to the pharate adult stage. The structures differentiated by mutant discs show many abnormalities including ingrowths, outgrowths, separated cuticular vesicles, and areas of reversed bristle polarity; some of these abnormalities suggest that the mutations interfere with cell adhesion as well as the control of cell proliferation. The fat locus is located in cytogenetic interval 24D5.6-7, and 18 alleles are known including spontaneous, chemically induced, X-ray-induced, and dysgenic mutations.

Cytogenetic analysis of the echinoid (ed), dumpy (dp) and clot (cl) region in Drosophila melanogaster

The chromosomal region surrounding the ed, dp and cl genes has been studied cytogenetically (24–26 on 2L chromosome). It contains three Minutes and a haplo-sterile function. For isolation of deficiencies and mutations these haplo-insufficient functions were covered by an insertional translocation of 24D4-25F2 into the X chromosome, or by tandem duplications. 112 lethal and visible mutations induced by EMS and X-rays have been localized by deficiency mapping to 20 subregions. They specify 42 loci in a 48 band interval consistent with the notion that most of the bands encode a single lethal function. The dp, DTS, tkv and suppressor/enhancer loci for position-effect variegation were studied in detail. A dominant suppressor function was localized within the structural part of the dp complex. New non-conditional lethals have been isolated for the DTS locus. Complementation analysis with the previously identified dominant heat-sensitive alleles places the site for heat sensitivity in the middle of the locus. Two haplo-abnormal enhancers of position-effect variegation were localized in the region 25F2–26A1. A triplo-abnormal suppressor function maps to 26B2–5; 26B9. The dose-dependent functions of these loci were studied by the use of deficiencies and duplications.

Cytogenetic analysis of variegation suppressors and a dominant temperature-sensitive lethal in region 23-26 of chromosome 2L in Drosophila melanogaster

Three suppressor loci for position-effect variegation, one dominant temperature-sensitive (DTS), three Minute genes, and two recessive visible mutants (ed, tkv) have been cytogenetically localized by using duplicatons and deficiencies in regions 23–25 of chromosome arm 2L of Drosophila melanogaster. Two of the suppressor loci studied proved to represent haplo-abnormal genes localized in regions 23A6-23F6 and 24E2-25A1, respectively. The third one is a strong triplo-abnormal suppressor mapping in 25F4-26B9 which affects white variegation in wm4h when present in three doses. The l(2)2DTS mutation, which belongs to a group of noncomplementing dominant temperature-sensitive mutations, is localized in the 25A4-B1 region. Furthermore, two Minute genes have been localized in region 24 that are included in Df (2L)M11 and can be separated employing translocation (Y;2)P8 (24E2–4): M(2)LS2 in 24D3-4-24E2-4, and M(2)z in 24E4-5-24F5-7. A third Minute gene (M(2)S1) is localized in 25C3-8-25C9-D1. The usefulness of the isolated chromosomal rearrangements for further genetic studies of region 23–26 is discussed.

The fatty acid constitution and ordering state of membranes in dominant temperature-sensitive lethal mutation and wild-type Drosophila melanogaster larvae

The ordering state and changes in fatty acid composition of microsomal (MS) and mitochondrial (MC) membranes of two dominant temperature-sensitive (DTS) lethal mutations and the wild-type Oregon-R strain larvae ofDrosophila melanogaster have been studied at 18 and 29°C and after temperature-shift experiments. The membranes of wild-type larvae have a stable ordering state, with “S” values between 0.6 (18°C) and 0.5 (29°C) in both membranes which remained unchanged in shift experiments, although the ratios of saturated/unsaturated fatty acids were changed as expected. The stronglyDTS mutation1(2)10DTS forms very rigid membranes at the restrictive temperature (29°C) which cannot be normalized after shift down, while shift up or development at the permissive temperature results in normal ordering state. This mutant is less able to adjust MS and MC fatty acid composition in response to the growth temperature than the wild type. The less temperature-sensitive1(2)2DTS allele occupies an intermediate state between Oregon-R and1(2)10DTS in both respects. We assume and the genetical data suggest that the DTS mutant gene product is in competition with the wild-type product, resulting in a membrane structure which is not able to accommodate to the restrictive temperature.

Developmental Analysis of fs(1)1867 , an Egg Resorption Mutation of Drosophila Melanogaster

The X-linked 1867+ gene seems to be a pleiotropic one. Mutation in this gene causes delay in development and abnormal bristle morphology. These phenotypes are expressed autonomously in genetic mosaics. There is no focus for the delay. The female sterility could be localized to the ovary (based on ovary transplantations). It seems that the 1867+ gene is expressed in the follicular cells at one of the last steps of oogenesis. This is suggested by the results of mosaic analysis based on mitotic recombination. Possible drawbacks of the mitotic recombination type of analyses are also discussed.