[Notch122, mutation of Notch locus Abruptex type in Drosophila virilis: characteristics of genetic interactions].

A Drosophila virilis Notch122 mutant has been isolated and genetically identified which is similar to Notch Drosophila melanogaster Abruptex type alleles. Some possible peculiarities of genetic interactions of Notch alleles of Abruptex type are discussed.

[Drosophila genes that encode LIM-domain containing proteins: their organization, functions, and interactions].

Diverse sets of developmental programs including cytoskeleton organization, cell lineage specification, muscle and neuron differentiation, limb and eye formation, imaginal disk development are controlled by LIM-homeobox genes encoding LIM-homeodomain (LIM-HD) transcription factors. LIM-domains are known as adaptors and functional modifiers of the protein-protein interactions and of the specific contacts between the members of functional complexes mediating activation of some constitutive proteins. Primary structure of LIM-HD proteins is remarkably evolutionary conserved in vertebrates and invertebrates. Though the genome size of Drosophila is about 5 % of the mammal genome the majority of its gene families and signaling pathways are similar to those of the mammals. There are some well known LIM-domain-containing proteins in Drosophila: Arrowhead, Apterous, Islet, dLim and Lim3 transcription factors; DLMO and Prickle proteins, as well as Chip, RLIM, Ssdp cofactors that modulate the LIM-HD function. Drosophila is a unique model system to analyze genetic interactions and transcription complexes in vivo. Genetic and molecular approaches including isolation of extragenic supressors of mutations in LIM-HD proteins may be used for identification of target genes which interact directly with LIM-HD proteins and that are necessary for specification of cell identity.

[Novel miniature-like m42 mutant of Drosophila virilis. Unusual microstructure of wing fibres]. / Novyi miniature-podobnyi mutant m42 u Drosophila virilis. Neobychnaia mikrostruktura zhilok kryla.

Distinctive defects of cuticular wing vein microstructure in Drosophila virilis miniature-like m42 allele and the possible role of m42 locus in cytoskeleton reorganization during of wing morphogenesis are discussed.

[Locus Delta in the Notch signaling system: organization and pleiotropic function during Drosophila development]. / Lokus Delta v Notch signal'noi sisteme: organizatsiia i pleiotropnaia funktsiia v razvitii drozofily.

Delta locus is the important component of the Delta-Notch signaling system implicating in a general mechanism of local cell signaling. Delta and Notch encode the evolutionary conserved cell surface proteins that interact and function as ligand (DELTA) and receptor (NOTCH) in a wide variety of cell fate specification events during oogenesis, embryogenesis and metamorphosis.

[Genetic characteristics of the wing mutation Odd(22) and its interaction with alleles of the Delta locus in Drosophila virilis]. / Geneticheskaia kharakteristika krylovoi mutatsii Odd(22) i ee vzaimodeistvii s alleliami lokusa Delta u Drosophila virilis.

The dominant sex-linked semilethal mutation Odd22 was isolated from progeny of a dysgenic cross of Drosophila virilis lines. Flies homozygous, heterozygous, and hemizygous for Odd22 displayed multiple wing defects, including enlargements and gaps on the veins; irregularly thickened, branched, shortened, or completely reduced veins; and cuts on the wing margin. The most remarkable feature of the Odd22 expression was a combination of both an increase and a reduction of the wing vein material simultaneously present in the same wing, which is commonly associated with suppression and hyperfunction, respectively, of genes of the Notch (N) signaling system. Phenotypic analysis revealed the interaction of Odd22 with alleles of the Delta (Dl) locus, which codes for the ligand of the NOTCH receptor. Based on these data, Odd22 was assumed to directly or indirectly affect the activity of the genes involved in Dl-N signaling.

[The Delta locus in Drosophila virilis: alleles, wing phenotypes and genetic interactions]. / Lokus Delta u Drosophila virilis: alleli, fenotipy kryla, geneticheskie vzaimodeistviia.

A considerable number of Delta (D1) alleles resulting from spontaneous mutation or induced by following X-ray irradiation have been isolated on the basis of the dominant phenotype consisting of disrupted wing venation and associated with heterozygosity for different D1 alleles. The L2 "delta" forming at the wing margin is the most characteristic fully penetrant phenotype of D1-heterozygous adults. The structure disruption of all other longitudinal (L3-L5) and cross (C1 and C2) veins including formation of "deltas" and other additional vein material, have been characterized as the irregular bilaterally asymmetrical nondirectional fluctuations of D1 phenotype expression. The phenotypic interactions between Delta and two D1 phenotype enhancer mutations, L2 fork and gap L2, have been found. Possible participation of Delta, one of the elements of Notch signaling system, in the structure formation is discussed.

Characterization of the progeny of X-ray irradiated males from two Drosophila virilis strains differing in genetic instability.

Significant effects of X-ray treatment on the increase in the number of phenotypic variations, two visible mutations, and chromosome aberrations were found in the progeny of irradiated males from the D. virilis laboratory stock that is capable of hybrid dysgenesis syndrome induction. This effect is much more pronounced than in the progeny of irradiated males from strong wild-type strains studied. A correlation between genetic instability and chromosome radiosensitivity was outlined. The mechanism of this phenomenon and the possibilities of using the property of genome instability for the productive induction of gene and chromosome damage in radiation mutagenesis experiments are discussed.

[An "unusual" stress-activated Drosophila virilis 20CD puff: cytologic localization of the thermostable locus and characteristics of the reaction to heat shock]. / "Neobychnyi" aktiviruemyi v usloviiakh stressa puf 20CD Drosophila virilis: tsitologicheskaia lokalizatsiia teplochuvstvitel'nogo lokusa i osobennosti reaktsii na teplovoi shok.

Using a series of chromosome aberrations heat shock (hs) inducible site of 20CD Drosophila virilis hs puff was cytologically localized in distal 20C subdivision: the hs puff was not observed in chromosome 2 carrying Df(2)eb deficiency; the bands in proximal 20D subdivision are unable to provide autonomous activation by hs in aberrant chromosomes having this deficiency or the In(2)eb inversion. Electron microscopical analysis of successive stages of 20CD development showed the hs puff to be initially formed from the right part of 20C 6-7 band. Neighbouring bands of 20C and 20D regions in the most developed puff are only partially decondensed and were detected as discrete compact chromatin clumps.

Unusual Drosophila virilis stress-puff at 20CD: cytological localization of a heat sensitive locus and some peculiarities of the heat shock response.

Using a series of chromosome aberrations a heat shock (hs) inducible site of the Drosophila virilis heat shock puff 20CD has been cytologically localized in the distal 20C subdivision: the hs puff was not observable in chromosome 2 carrying the Df(2)ebTG-52 deficiency; the bands in the proximal 20D subdivision could not autonomously be activated by hs in aberrant chromosomes that have this deficiency or the In(2)ebPC-19 inversion. An electron microscopy (EM) analysis of the successive stages of puff development in the 20CD and 20F regions shows that the 20CD puff is intially formed from the right part of the 20C6-7 band. In the maximally developed puff, the neighboring bands of the 20C and 20D regions are only partially decondensed; they are seen as discrete compact chromatin clumps. Specific differences in the ultrastructural organization and in response to hs have been found between the D. virilis "unusual" 20CD and typical 20F hs puffs.

[Mutation variability and instability in the Drosophila melanogaster thickened 2 strain and its derivatives]. / Mutatsionnaia izmenchivost' i nestabil'nost' v linii thickened 2 Drosophila melanogaster i ee proizvodnykh.

Mutations in Drosophila melanogaster thi2 strain obtained using exogenous viral DNA, and in the thi2 derivatives, have been studied. Revertants to the wild type arose with high frequency (1-2.10(-2)) in both 83f-7 (1-2.6-5.3) and the initial thi2 (2-71.4) strains. New mutations of chromosome 2, non-allelic to the thi2, though with thi2-like phenotypic effects, and some lethal alleles of these mutations have been found in the progeny of the revertants from the thi2 to the wild type in 83f-7 strain. Cytological analysis has failed to disclose large chromosome aberrations of salivary gland chromosomes carrying the mutations r83f-3 (1-54.5), 83f-7, 83f-21 (3-67.1) originated from the thi2 strain. The data are consistent with possibility that mutations from the thi2 strain and its derivatives were formed by means of a small insertion sequence.