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  • 1
    Electronic Resource
    Electronic Resource
    Molecular characteristics of the heterochromatic I elements from a reactive strain ofDrosophila melanogaster (1990)
    Springer
    Journal of molecular evolution 31 (1990), S. 424-431 
    Details
    ISSN: 1432-1432
    Keywords: Drosophila melanogaster ; Evolution ; Hybrid dysgenesis ; I elements ; Transposons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary There are two categories of strains inDrosophila melanogaster with respect to the I-R system of hybrid dysgenesis. The inducer strains contain particular transposable elements named I factors. They are not present in the strains of the other category called reactive (R) strains. Defective I elements are present in the pericentromeric regions of both categories of strains. This last subfamily of I sequences has not yet been described in detail and little is known about its origin. In this paper, we report that the defective I elements display an average of 94% of sequence identity with each other and with the transposable I factor. The results suggest that they cannot be the progenitors of the present day I factors, but that each of these two subfamilies started to evolve independently several million years ago. Furthermore, the sequence comparison of these I elements with an active I factor fromDrosophila teissieri provides useful information about when the deleted I elements became immobilized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02106056
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    I transposable elements and I-R hybrid dysgenesis in Drosophila
    Amsterdam : Elsevier
    Trends in Genetics 6 (1990), S. 16-21 
    Details
    ISSN: 0168-9525
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0168-9525(90)90044-7
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A cloned I-factor is fully functional in Drosophila melanogaster (1988)
    Springer
    Molecular genetics and genomics 214 (1988), S. 533-540 
    Details
    ISSN: 1617-4623
    Keywords: Transposition ; Retroposon ; Reverse transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary I-R hybrid dysgenesis in Drosophila melanogaster occurs in female progeny of crosses between reactive strain females and inducer strain males, and is controlled by transposable elements called I-factors. These are 5.3 kb elements that are structurally similar to mammalian LINE elements and other retroposons. We have tested the activity of an I-factor directly, by introducing it into the genome of a reactive strain, using P-element mediated transformation. It confers the complete inducer phenotype on the reactive strain, and can stimulate dysgenesis when transformed males are mated with reactive females. It has transposed in the transformed lines, and we have cloned one of the transposed copies. This is the first time that it has been possible to demonstrate that a particular retroposon is transposition proficient, and to compare donor and transposed elements. We propose a mechanism for I-factor transposition based on these results, and the coding capacity of these elements. We have been unable to detect either autonomous transposition of a complete I-factor from a plasmid injected into reactive strain embryos, or transposition of a marked I-factor when co-injected with a complete element.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330491
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  • 4
    Electronic Resource
    Electronic Resource
    I elements and the Drosophila genome (1992)
    Springer
    Genetica 86 (1992), S. 175-190 
    Details
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract LINEs are a large class of transposable elements in eukaryotes. They transpose by reverse transcription of an RNA intermediate. I elements of Drosophila melanogaster belong to this class and are responsible for the I-R system of hybrid dysgenesis. Many results indicate that at the beginning of the century natural populations of this species were devoid of active I elements and that they were invaded by functional I elements in the last decades. Many Drosophila species contain both defective and active I elements. It seems that the latter were lost in Drosophila melanogaster before its spread throughout the world, and that the recent invasion results from the spread of functional elements originating either from another species by horizontal transfer or from an isolated population of the same species. These data are discussed, as well as their significance in evolutionary processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00133719
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  • 5
    Electronic Resource
    Electronic Resource
    About the origin of retroviruses and the co-evolution of the gypsy retrovirus with the Drosophila flamenco host gene (1997)
    Springer
    Genetica 100 (1997), S. 29-37 
    Details
    ISSN: 1573-6857
    Keywords: envelope ; LTR-retrotransposon ; phylogeny ; polymorphism ; Ty3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The gypsy element of Drosophila melanogaster is the first retrovirus identified so far in invertebrates. According to phylogenetic data, gypsy belongs to the same group as the Ty3 class of LTR-retrotransposons, which suggests that retroviruses evolved from this kind of retroelements before the radiation of vertebrates. There are other invertebrate retroelements that are also likely to be endogenous retroviruses because they share with gypsy some structural and functional retroviral-like characteristics. Gypsy is controlled by a Drosophila gene called flamenco, the restrictive alleles of which maintain the retrovirus in a repressed state. In permissive strains, functional gypsy elements transpose at high frequency and produce infective particles. Defective gypsy proviruses located in pericentromeric heterochromatin of all strains seem to be very old components of the genome of Drosophila melanogaster, which indicates that gypsy invaded this species, or an ancestor, a long time ago. At that time, Drosophila melanogaster presumably contained permissive alleles of the flamenco gene. One can imagine that the species survived to the increase of genetic load caused by the retroviral invasion because restrictive alleles of flamenco were selected. The characterization of a retrovirus in Drosophila, one of the most advanced model organisms for molecular genetics, provides us with an exceptional clue to study how a species can resist a retroviral invasion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018336303298
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    Paper (German National Licenses)
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