The molecular basis of instability of the singedvery weak mutation in Drosophila melanogaster

SummaryThe singedvery weak mutation was created by the sequential addition of two P transposable elements to the singed gene. The mutation can be somatically unstable through the action of a dominant maternal effect mutation on the second chromosome. It is also unstable in the germ line in these conditions. Sequencing of the region of the P insertions in the mutation reveals that the two inserted elements have single internal deletions, and the larger of the two is a copy of the KP element. The mutation will generate, at high frequencies, strongly singed and pseudo-wild type products by reversions occurred in the germline. These are the result of the precise excision of the smaller and the larger elements respectively. By PCR amplification of dissected thoraces we show that the somatic instability of the mutation, from a weak to a strong singed phenotype, is also caused by the excision of the smaller of the two elements.

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Germ-Line Effects of a Mutator, mu2, in Drosophila melanogaster

Genetics ◽

10.1093/genetics/146.4.1381 ◽

1997 ◽

Vol 146 (4) ◽

pp. 1381-1397 ◽

Cited By ~ 1

Author(s):

James M Mason ◽

Lany E Champion ◽

Graham Hook

Keyword(s):

Drosophila Melanogaster ◽

Germ Line ◽

Wild Type ◽

Cell Stage ◽

Chromosomal Structure ◽

High Frequencies ◽

Female Germ Line ◽

Γ Rays ◽

Sperm Chromosomes ◽

Mutant Frequency

A mutator, mu2a, in Drosophila melanogaster potentiates terminal deficiencies. In the female germ line the y mutant frequency induced by irradiation of mature oocytes with 5 Gy increases approximately twofold in heterozygotes and 20-fold in homozygotes compared with wild type. The recovery of terminal deficiencies is not limited to breaks close to chromosome ends; high frequencies of deficiencies can be recovered with breakpoints located in centric heterochromatin or near the middle of a chromosome arm. Lesions induced by γ-rays are repaired slowly in mu2a oocytes, but become “fixed” as terminal deficiencies upon fertilization. A few lesions induced in wild-type females also produce terminal deficiencies. Mutator males do not exhibit an increase in terminal deletions, regardless of the germ cell stage irradiated. In addition, there is no increase in the mutant frequency when mature sperm are irradiated and fertilize eggs produced by mu2a females. The data are consistent with the hypothesis that lesions induced in sperm chromosomes are repaired after fertilization, while lesions induced in oocyte chromosomes are shunted instead to a mechanism that stabilizes broken chromosome ends. We propose that mu2 affects chromosomal structure during oogenesis, thereby modulating DNA repair.

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Sex determination in the germ line of Drosophila melanogaster: activation of the gene Sex-lethal

Development ◽

10.1242/dev.118.3.813 ◽

1993 ◽

Vol 118 (3) ◽

pp. 813-816 ◽

Cited By ~ 9

Author(s):

B. Granadino ◽

P. Santamaria ◽

L. Sanchez

Keyword(s):

Drosophila Melanogaster ◽

Germ Cells ◽

Germ Line ◽

Wild Type ◽

Female Development ◽

Pole Cell ◽

Somatic Tissues ◽

Wild Type Female ◽

Sex Lethal ◽

Pole Cell Transplantation

The germ line exhibits sexual dimorphism as do the somatic tissues. Cells with the 2X;2A chromosome constitution will follow the oogenic pathway and X;2A cells will develop into sperm. In both somatic and germ-line tissues, the sexual pathway chosen by the cells depends on the gene Sex-lethal (Sxl), whose function is continuously needed for female development. In the soma, the sex of the cells is autonomously determined by the X:A signal while, in the germ line, the sex is determined by cell autonomous (the X:A signal) and somatic inductive signals. Three X-linked genes have been identified, scute (sc), sisterless-a (sis-a) and runt (run), that determine the initial functional state of Sxl in the soma. Using pole cell transplantation, we have tested whether these genes are also needed to activate Sxl in the germ line. We found that germ cells simultaneously heterozygous for sc, sis-a, run and a deficiency for Sxl transplanted into wild-type female hosts develop into functional oocytes. We conclude that the genes sc, sis-a and run needed to activate Sxl in the soma seem not to be required to activate this gene in the germ line; therefore, the X:A signal would be made up by different genes in somatic and germ-line tissues. The Sxlf7M1/Sxlfc females do not have developed ovaries. We have shown that germ cells of this genotype transplanted into wild-type female hosts produce functional oocytes. We conclude that the somatic component of the gonads in Sxlf7M1/Sxlfc females is affected, and consequently germ cells do not develop.(ABSTRACT TRUNCATED AT 250 WORDS)

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A Genetically Marked I Element in Drosophila melanogaster Can Be Mobilized When ORF2 Is Provided in trans

Genetics ◽

10.1093/genetics/148.1.267 ◽

1998 ◽

Vol 148 (1) ◽

pp. 267-275

Author(s):

Isabelle Busseau ◽

Sophie Malinsky ◽

Maria Balakireva ◽

Marie-Christine Chaboissier ◽

Danielle Teninges ◽

...

Keyword(s):

Drosophila Melanogaster ◽

Heat Shock ◽

Reverse Transcriptase ◽

Germ Line ◽

Ltr Retrotransposons ◽

Low Frequencies ◽

High Frequencies ◽

In Trans ◽

Very High Frequencies ◽

Very High

Abstract I factors in Drosophila melanogaster are non-LTR retrotransposons similar to mammalian LINEs. They transpose at very high frequencies in the germ line of SF females resulting from crosses between reactive females, devoid of active I factors, and inducer males, containing active I factors. The vermilion marked IviP2 element was designed to allow easy phenotypical screening for retrotransposition events. It is deleted in ORF2 and therefore cannot produce reverse transcriptase. IviP2 can be mobilized at very low frequencies by actively transposing I factors in the germ line of SF females. This paper shows that IviP2 can be mobilized more efficiently in the germ line of strongly reactive females in the absence of active I factors, when it is trans-complemented by the product of ORF2 synthesized from the hsp70 heat-shock promoter. This represents a promising step toward the use of marked I elements to study retrotransposition and as tools for mutagenesis.

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The distribution of transposable elements within and between chromosomes in a population of Drosophila melanogaster. I. Element frequencies and distribution

Genetics Research ◽

10.1017/s0016672300030792 ◽

1992 ◽

Vol 60 (2) ◽

pp. 103-114 ◽

Cited By ~ 65

Author(s):

Brian Charlesworth ◽

Angela Lapid ◽

Darlene Canada

Keyword(s):

Population Dynamics ◽

Drosophila Melanogaster ◽

Linkage Disequilibrium ◽

Transposable Elements ◽

Copy Number ◽

Polytene Chromosomes ◽

Chromosome Band ◽

High Frequencies ◽

Copy Numbers

SummaryData were collected on the distribution of nine families of transposable elements among second and third chromosomes isolated from a natural population of Drosophila melanogaster, by means of in situ hybridization of element probes to polytene chromosomes. It was found that the copy numbers per chromosome in the distal sections of the chromosome arms followed a Poisson distribution. Elements appeared to be distributed randomly along the distal sections of the chromosome arms. There was no evidence for linkage disequilibrium in the distal sections of the chromosomes, but some significant disequilibrium was detected in proximal regions. There were many significant correlations between different element families with respect to the identity of the sites that were occupied in the sample. There were also significant correlations between families with respect to sites at which elements achieved relatively high frequencies. Element frequencies per chromosome band were generally low in the distal sections, but were higher proximally. These results are discussed in the light of models of the population dynamics of transposable elements. It is concluded that they provide strong evidence for the operation of a force or forces opposing transpositional increase in copy number. The data suggest that the rate of transposition perelement per generation is of the order of 10−4, for the elements included in this study.

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Ds-INDUCED ALLELES AT THE OPAQUE-2 LOCUS OF MAIZE

Genetics ◽

10.1093/genetics/112.1.121 ◽

1986 ◽

Vol 112 (1) ◽

pp. 121-133

Author(s):

Mario Motto ◽

Renzo Marotta ◽

Natale Di Fonzo ◽

Carlo Soave ◽

Francesco Salamini

Keyword(s):

Transposable Elements ◽

Transposon Mutagenesis ◽

Dna Fragments ◽

Wild Type ◽

Genetic Analyses ◽

Somatic Instability ◽

Mutable Allele ◽

Recessive Phenotype ◽

Maize Plants ◽

Ds Element

ABSTRACT Transposon mutagenesis has been used to isolate mutable alleles at the Opaque-2 (O2) locus of maize. Plants with the Activator-Dissociation (Ac-Ds) system of transposable elements and O2 were crossed as males to a stable o2 tester line. Among a population of 200,000 kernels, 198 exceptional kernels with somatic instability were recovered. In four cases, designated O2-m1, o2-m2, O2-m3 and O2-m4, variegated phenotypes appeared in F2 and subsequent generations. Genetic analyses indicated that the presence of Ds near or within the O2 gene was responsible for the observed somatic instability at the O2 locus. The phenotypes of the newly induced alleles were of two types. Alleles O2-m1, O2-m3 and O2-m4, in the absence of Ac, were characterized by kernel phenotypes indistinguishable from the wild type; in the presence of Ac they generated kernels with opaque sectors interspersed within a vitreous background. In contrast, the mutable allele o2-m2, in the absence of Ac, was characterized by kernels with a recessive phenotype similar to o2 recessive mutants. In the presence of Ac, it reverted somatically to wild-type-producing kernels with vitreous spots in an o2 background. The association of the Ds element with the O2 locus may prove a valuable tool directed to the isolation of DNA fragments bearing the O2 gene.

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Genetic and molecular analyses of vgal: a spontaneous and unstable mutation at the vestigial locus in Drosophila melanogaster

Genetics Research ◽

10.1017/s0016672300029384 ◽

1991 ◽

Vol 57 (3) ◽

pp. 235-243 ◽

Cited By ~ 2

Author(s):

Claude Bazin ◽

Françoise Lemeunier ◽

Georges Periquet ◽

Joël Silber

Keyword(s):

Drosophila Melanogaster ◽

Low Temperature ◽

Germ Line ◽

The Other ◽

Wild Type ◽

Male Germ Line ◽

Molecular Analyses ◽

Dna Insertion ◽

Unstable Mutation

SummaryWe describe herein, a new unstable mutant of the vestigial locus, isolated from a French natural population. From this mutant vestigialalmost (vgal) wild-type flies (vgal+) and extreme vg phenotypes (vge) arose spontaneously without genomic shock. The occurrence of vgal+ or vge alleles depends mostly on the breeding temperature; vgal+ revertants arose principally at low temperature (21 °C) and vge at 28 °C. These events occur mainly in the male germ line and the phenomenon appears to be premeiotic. Our results with in situ hybridization experiments and Southern blots show that the vgal mutation is due to a 2 kb DNA insertion, which is a deleted hobo element. Genetic and molecular analyses show that two distinct events may underly the wild-type revertants. One is the excision of the resident hobo element, the other a further deletion (about 300 bp in the example characterized herein). The vge mutation is probably due to a deletion of vestigial sequences flanking the hobo insertion.

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New Insights on Homology-Dependent Silencing of I Factor Activity by Transgenes Containing ORF1 in Drosophila melanogaster

Genetics ◽

10.1093/genetics/156.3.1147 ◽

2000 ◽

Vol 156 (3) ◽

pp. 1147-1155 ◽

Cited By ~ 1

Author(s):

Sophie Malinsky ◽

Alain Bucheton ◽

Isabelle Busseau

Keyword(s):

Drosophila Melanogaster ◽

Germ Line ◽

Ltr Retrotransposons ◽

Factor Activity ◽

Hsp70 Promoter ◽

Transgene Copy Number ◽

High Frequencies ◽

I Factor ◽

Very High Frequencies ◽

Very High

Abstract I factors in Drosophila melanogaster are non-LTR retrotransposons that transpose at very high frequencies in the germ line of females resulting from crosses between reactive females (devoid of active I factors) and inducer males (containing active I factors). Constructs containing I factor ORF1 under the control of the hsp70 promoter repress I factor activity. This repressor effect is maternally transmitted and increases with the transgene copy number. It is irrespective of either frame integrity or transcriptional orientation of ORF1, suggesting the involvement of a homology-dependent trans-silencing mechanism. A promoterless transgene displays no repression. The effect of constructs in which ORF1 is controlled by the hsp70 promoter does not depend upon heat-shock treatments. No effect of ORF1 is detected when it is controlled by the I factor promoter. We discuss the relevance of the described regulation to the repression of I factors in I strains.

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Maternal Effect for DNA Mismatch Repair in the Mouse

Genetics ◽

10.1093/genetics/160.1.271 ◽

2002 ◽

Vol 160 (1) ◽

pp. 271-277

Author(s):

Vanessa E Gurtu ◽

Shelly Verma ◽

Allie H Grossmann ◽

R Michael Liskay ◽

William C Skarnes ◽

...

Keyword(s):

Mismatch Repair ◽

Maternal Effect ◽

Genome Stability ◽

Germ Line ◽

Dna Mismatch Repair ◽

Surprising Result ◽

Wild Type ◽

Repair Gene ◽

Dna Mismatch ◽

Dna Repair Gene

Abstract DNA mismatch repair (DMR) functions to maintain genome stability. Prokaryotic and eukaryotic cells deficient in DMR show a microsatellite instability (MSI) phenotype characterized by repeat length alterations at microsatellite sequences. Mice deficient in Pms2, a mammalian homolog of bacterial mutL, develop cancer and display MSI in all tissues examined, including the male germ line where a frequency of ~10% was observed. To determine the consequences of maternal DMR deficiency on genetic stability, we analyzed F1 progeny from Pms2−/− female mice mated with wild-type males. Our analysis indicates that MSI in the female germ line was ~9%. MSI was also observed in paternal alleles, a surprising result since the alleles were obtained from wild-type males and the embryos were therefore DMR proficient. We propose that mosaicism for paternal alleles is a maternal effect that results from Pms2 deficiency during the early cleavage divisions. The absence of DMR in one-cell embryos leads to the formation of unrepaired replication errors in early cell divisions of the zygote. The occurrence of postzygotic mutation in the early mouse embryo suggests that Pms2 deficiency is a maternal effect, one of a limited number identified in the mouse and the first to involve a DNA repair gene.

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REGULATION OF RIBOSOMAL RNA GENE MULTIPLICITY IN DROSOPHILA MELANOGASTER

Genetics ◽

10.1093/genetics/73.1.57 ◽

1973 ◽

Vol 73 (1) ◽

pp. 57-71

Author(s):

Kenneth D Tartof

Keyword(s):

Drosophila Melanogaster ◽

Ribosomal Rna ◽

Homologous Chromosome ◽

Germ Line ◽

Rrna Genes ◽

Rrna Gene ◽

Wild Type ◽

Wild Type Level ◽

New Genotype ◽

Successive Generations

ABSTRACT The ribosomal RNA (rRNA) genes of Drosophila melanogaster can undergo a disproportionate replication of their number. This occurs when the cluster of rRNA genes (rDNA) of one chromosome is maintained with a homologous chromosome that is completely or partially deficient in its rDNA. Under appropriate genetic conditions, it appears that disproportionate rDNA replication can be generated at the level of both somatic and germ line cells. In the latter case, mutants partially deficient for rDNA can increase their rRNA gene number to the wild type level and transmit this new genotype to successive generations.

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piRNA pathway is not required for antiviral defense in Drosophila melanogaster

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1607952113 ◽

2016 ◽

Vol 113 (29) ◽

pp. E4218-E4227 ◽

Cited By ~ 56

Author(s):

Marine Petit ◽

Vanesa Mongelli ◽

Lionel Frangeul ◽

Hervé Blanc ◽

Francis Jiggins ◽

...

Keyword(s):

Drosophila Melanogaster ◽

Germ Line ◽

Fruit Fly ◽

Antiviral Response ◽

Antiviral Defense ◽

Wild Type ◽

Cellular Processes ◽

Pirna Pathway ◽

Interfering Rna ◽

Sirna Pathway

Since its discovery, RNA interference has been identified as involved in many different cellular processes, and as a natural antiviral response in plants, nematodes, and insects. In insects, the small interfering RNA (siRNA) pathway is the major antiviral response. In recent years, the Piwi-interacting RNA (piRNA) pathway also has been implicated in antiviral defense in mosquitoes infected with arboviruses. Using Drosophila melanogaster and an array of viruses that infect the fruit fly acutely or persistently or are vertically transmitted through the germ line, we investigated in detail the extent to which the piRNA pathway contributes to antiviral defense in adult flies. Following virus infection, the survival and viral titers of Piwi, Aubergine, Argonaute-3, and Zucchini mutant flies were similar to those of wild type flies. Using next-generation sequencing of small RNAs from wild type and siRNA mutant flies, we showed that no viral-derived piRNAs were produced in fruit flies during different types of viral infection. Our study provides the first evidence, to our knowledge, that the piRNA pathway does not play a major role in antiviral defense in adult Drosophila and demonstrates that viral-derived piRNA production depends on the biology of the host–virus combination rather than being part of a general antiviral process in insects.

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