Characteristics of the structural organization of the DIP1 gene in Drosophila melanogaster strains mutant for the flamenco gene

Molecular cloning of the DIP1 gene located in the 20A4-5 region has been performed from the following strains with the flamenco phenotype: flamSS (SS) and flamMS (MS) characterized by a high transposition rate of retrotransposon gypsy (mdg4), flampy + (P) carrying the insertion of a construction based on the P element into the region of the flamenco gene, and flamenco+. The results of restriction analysis and sequencing cloned DNA fragments has shown that strains flamSS, flamMS, flampy +(P), and flamenco+ considerably differ from one another in the structure of DIP1. Strains flamss and flamMS have no Dral restriction site at position 1765 in the coding region of the gene, specifically, in the domain determining the signal of the nuclear localization of the DIP1 protein. This mutation has been found to consist in a nucleotide substitution in the recognition site of DraI restriction endonuclease, which is transformed from TTTAAA into TTTAAG and, hence, is not recognized by the enzyme. This substitution changes codon AAA into AAG and is translationally insignificant, because both triplets encode the same amino acid, lysine. The Dral gene of strainsflamSS andflamMS has been found to contain a 182-bp insertion denoted IdSS (insertion in DIP1 strain SS); it is located in the second intron of the gene. The IdSS sequence is part of the open reading frame encoding the putative transposase of the mobile genetic element HB1 belonging to the Tcl/mariner family. This insertion is presumed to disturb the conformations of DNA and the chromosome, in particular, by forming loops, which alters the expression of DIPI and, probably, neighboring genes. In strains flamenco+ and flampy + (P), the IdSS insertion within the HB1 sequence is deleted. The deletion encompasses five C-terminal amino acid residues of the conserved domain and the entire C-terminal region of the putative HB1 transposase. The obtained data suggest that DIP1 is involved in the control of gypsy transpositions either directly or through interaction with other elements of the genome.     

Retrotransposon gtwin: structural analysis and distribution in Drosophila melanogaster strains

A search for noncanonical variants of the gypsy retrotransposon (MDG4) in the genome of the Drosophila melanogaster strain G32 led to the cloning of four copies of the poorly studied 7411-bp gtwin element. Sequence analysis showed that gtwin belongs to a family of endogeneous retroviruses, which are widespread in the Drosophila genome and have recently been termed insect erantiviruses. The gtwin retrotransposon is evolutionarily closest to MDG4, as evident from a good alignment of their nucleotide sequences including ORF1 (the pol gene) and ORF3 (the env gene), as well as the amino acid sequences of their protein products. These regions showed more than 75% homology. The distribution of gtwin was studied in several strains of the genus Drosophila. While strain G32 contained more than 20 copies of the element, ten other D. melanogaster strains carried gtwin in two to six copies per genome. The gtwin element was not detected in D. hydei or D. virilis. Comparison of the cloned gtwin sequences with the gtwin sequence available from the D. melanogaster genome database showed that the two variants of the mobile element differ by the presence or absence of a stop codon in the central region of ORF3. Its absence from the gtwin copies cloned from the strain G32 may indicate an association between the functional state of ORF3 and amplification of the element.     

Mating success and courtship ritual in strains of Drosophila melanogaster carrying mutation flamenco

Mating success was examined in groups of Drosophila melanogaster carrying mutation flamMS (SS, MSn1-2, and MSn1-3) and in wild-type flies. The proportion of normally copulating males was significantly lower in the mutant strains. The reduction in mating efficiency was caused by changes in male behavior rather than in female attractiveness. Individual analyses showed that male mating behavior in strains carrying flamMS was qualitatively and quantitatively different from that in the wild-type strain Canton S. The proportion of males that performed consecutive courtship stages was significantly lower in the mutant strains. The sequence and duration of some courtship stages (in particular, orientation and wing vibration) in mutant flies was shown to be altered. The significance of the flamenco locus in regulation of processes occurring at the organismal level are discussed.     

Male reproductive behavior in Drosophila melanogaster strains with different alleles of the flamenco gene

The allelic state of gene flamenco has been determined in a number of Drosophila melanogaster strains using the ovoD test. The presence of an active copy of gypsy in these strains was detected by restriction analysis. Then male reproduction behavior was studied in the strains carrying a mutation in gene flamenco. In these experiments mating success has been experimentally estimated in groups of flies. It has been demonstrated that the presence of mutant allele flamMS decreases male mating activity irrespective of the presence or absence of mutation white. The active copy of gypsy does not affect mating activity in the absence of the mutation in gene flamenco. Individual analysis has demonstrated that that mutation flamMS results in characteristic changes in courtship: flamMS males exhibit a delay in the transition from the orientation stage to the vibration stage (the so-called vibration delay). The role of locus flamenco in the formation of male mating behavior in Drosophila is discussed.     

Frequency-dependent viability in mutant strains of Drosophila melanogaster

We investigated the effects of genotypic frequencies on egg-to-adult viabilities in pairwise combinations of four strains of Drosophila melanogaster. The experiments involved mixture of a total of 42,000 eggs in varying proportions under controlled densities and observation of surviving adults. Viabilities were found to depend on frequencies in several genotypic combinations. In the most extreme case, the absolute viability of cn;bw females increased monotonically from 54% when common to 70% when rare. The results illustrate several statistical and methodological problems that might explain why some experiments have failed to detect frequency-dependent viabilities. These problems include heterogeneity between replications, sex differences in susceptibility to competition, and strong dependence of the experimental outcome on the choice of competitor genotypes.     

Structural organization of the Amy locus in seven strains of Drosophila melanogaster.

Restriction maps were made by Southern blot analysis of the Amy (alpha-amylase) region in 7 strains of D. melanogaster using endonucleases SalI, XhoI and EcoRI. These were compared to the map of lambda Dm65 which contains the cloned Amy region. Strains used produce either two amylase variants, a single variant, or no amylase, yet all 7 strains carry two Amy genes as inverted repeats at the Amy locus. This and the orientation of the repeats resembles the situation in lambda Dm65. Most restriction sites mapped are conserved but two strains contain a large insertion which differs in size and position between strains. A complex anomaly, probably an inversion, exists at the Amy locus in a null strain. Maps for our Amy1,3 strain and the lambda Dm65 clone are identical, the DNA of each having been derived from a Canton-S wild stock. Restriction and genetic maps of the Amy region were aligned and alleles assigned to the proximal and distal genes, Amy-p and Amy-d.     

Fertile heteroallelic combinations of mutant alleles of the otu locus of Drosophila melanogaster

Summary This paper describes the ovarian pathologies observed when 108 different heteroallelic combinations were made involving 17 independent mutations at the ovarian tumor (otu) locus. Most of the mutant phenotypes can be explained as graded responses by individual germ cells to different levels of functionally active otu gene product (OGP) synthesized by the mutant cells themselves. The lowest and highest levels of OGP appear to be produced by otu ¹⁰ and otu ¹⁴, respectively. In most heteroallelic ovaries the alleles have additive effects, and hybrid germ cells reach a developmental stage more advanced than the weaker homozygote but less advanced than the stronger homozygote. However, examples of both positive and negative complementation also have been found, and these suggest that the products encoded by different mutant alleles can combine to form dimers or multimers which may be superior or inferior to the homodimers. In flies homozygous for otu ¹¹ most ovarioles contain tumors, but some germ cells are able to develop further than those in otu ¹⁴ homozygotes. This suggests that, while otu ¹¹ produces intermediate levels of OGP, it also produces a second product (which otu ¹⁴ cannot make) that is utilized at the period in oogenesis when development in cells homozygous for otu ¹⁴ is blocked. When otu ¹¹ is combined with any one of eight specific alleles, it allows oocyte/nurse cell syncytia to differentiate that can complete development and undergo embryogenesis, if fertilized. The endopolyploid nurse cells of these hybrids have giant polytene chromosomes, and the presence of GPCs in functionally active, germ-line derived cells provides an interesting new system for experimental study. Analysis of the characteristic ovarian pathologies produced by flies of different genotypes leads to the conclusion that the products of the otu ⁺ gene are utilized during at least six different periods in Drosophila oogenesis.     

Mating behavior in mutant strains of Drosophila melanogaster at different population densities

The effects of mutations and genetic background on the mating activity of males and receptivity of females Drosophila melanogaster have been studied at different population densities. Population density, as well as its combinations with other factors, significantly affects mating behavior of D. melanogaster. There are two distinct trends in the effect of this factor on mating behavior: the maximum larval overpopulation may cause either a significant suppression of the behaviors studied or an increase in their expressivity. The mating behaviors of w ^a and cn mutants against a certain genetic background changed similarly in response to varying population density.     

Mating behavior in mutant strains of Drosophila melanogaster at different population densities

The effects of mutations and genetic background on the mating activity of male and receptivity of female Drosophila melanogaster have been studied at different population densities. Population density, as well as its combinations with other factors, significantly affects mating behavior of D. melanogaster. There are two distinct trends in the effect of this factor on mating behavior: the maximum larval overpopulation may cause either a significant suppression of the behaviors studied or an increase in their expressivity. The mating behaviors of wa and cn mutants against a certain genetic background changed similarly in response to varying population density.     

Apoptotic activities of wild-type and Alzheimer's disease-related mutant presenilins in Drosophila melanogaster.

Mutant human presenilins cause early-onset familial Alzheimer's disease and render cells susceptible to apoptosis in cultured cell models. We show that loss of presenilin function in Drosophila melanogaster increases levels of apoptosis in developing tissues. Moreover, overexpression of presenilin causes apoptotic and neurogenic phenotypes resembling those of Presenilin loss-of-function mutants, suggesting that presenilin exerts a dominant negative effect when expressed at high levels. In Drosophila S2 cells, Psn overexpression leads to reduced Notch receptor synthesis affecting levels of the intact approximately 300-kD precursor and its approximately 120-kD processed COOH-terminal derivatives. Presenilin-induced apoptosis is cell autonomous and can be blocked by constitutive Notch activation, suggesting that the increased cell death is due to a developmental mechanism that eliminates improperly specified cell types. We describe a genetic model in which the apoptotic activities of wild-type and mutant presenilins can be assessed, and we find that Alzheimer's disease-linked mutant presenilins are less effective at inducing apoptosis than wild-type presenilin.     

Regulation of white locus expression: the structure of mutant alleles at the white locus of Drosophila melanogaster

We have analyzed the structures of 19 mutant alleles at the white locus of Drosophila melanogaster. Thirteen of the mutant alleles in our selected sample arose spontaneously, and of these, seven are associated with insertions of non-white-region DNA sequence elements. Several lines of evidence strongly suggest that these insertions are responsible for their associated mutant alleles, and further suggest that most or all of these insertions are transposons. Moreover, the white locus DNA sequences can be divided into two nonoverlapping domains on the basis of the properties of the two domains as mutational targets. One of these domains behaves, in this regard, in the manner expected of functional coding sequences, whereas the other does not. We propose a model for the nature and function of the presumptive noncoding white locus genetic elements. The two domains of the white locus defined by our studies are approximately coextensive with the functionally distinct subintervals of the locus defined by previous genetic analysis. Lastly, our results strongly suggest that the dominant, mutable wDZL allele results from the insertion of a transposon outside of, but near, the white locus. This putative transposon apparently carries genetic elements that act at a distance to repress expression of the white locus.     

Transposition of the bobbed locus in Drosophila melanogaster

Due to the complete absence of ribosomal DNA (genetic symbol bb-), the Xbb- chromosome of Drosophila is lethal both in homozygous conditions and in compound with the Xbb- chromosome. However, in the cross between the C(1)RM/Ybb- females and the Xbb-/BSYbb+ males, characterized by the development of lethal Xbb-/Ybb- zygotes, two fertile males were detected. These males possessed all the markers of the Xbb- chromosome but lacked the Y chromosome BS marker. Genetic analysis of their progeny showed that genes responsible for restoration of viability and fertility of these exceptional males were associated with the X chromosome. The crossover tests showed that in one case these genes were tightly linked to the w locus (the bbAM1 allele), and in the second case they were located 12.6 map units to the right of the Tu locus (the bbAM7 allele). It has also been shown that the bb locus was transposed to the X chromosome within the short arm of Y chromosome. Transposition of the BSYbb+ chromosome-specific rDNA sequences to the X chromosome was confirmed by means of Southern blotting. These data indicate that replacement of the bb locus is realized by transposition rather than recombination.     

Age Dependence of the Level ofcopia Retrotransposon Expression in the Testes of Drosophila melanogaster

Expression of the lacZ reporter gene controlled by various deletion derivatives of the regulatory region of the copia retrotransposon was studied in the testes of adult transgenic males of the Drosophila melanogaster y ¹ w ^67c23(2) strain at the age of 3, 6–9, 12–15, 18–21, and 24–27 days. When the construct contained the full-length regulatory region, which included the 5-long terminal repeat (LTR) and the 5-untranslated region (UTR), expression was the lowest in males aged 12–15 days and the highest in males aged 3 or 24–27 days. A similar V-shaped age dependence was previously observed for the copia transposition rate and RNA content in a strain with a high rate of copia transposition. Thus, the V-shaped age dependence of expression, which is unusual for Drosophila, proved to be characteristic of copiaregardless of its transposition rate. Deletion of the 5 or 3 end of the LTR, but not of the UTR, changed the age dependence of the level of reporter gene expression. In this case, expression was the highest in 3-day-old males and gradually decreased with age, as typical for many Drosophila genes. It was assumed that the 5- and 3-terminal regions of the copiaLTR contain regulatory elements responsible for the V-shaped age dependence of expression, while the expression level depends to a greater extent on the regulatory elements of UTR.