The Behavior of a Daphnia pulex Transposable Element in Cyclically and Obligately Parthenogenetic Populations

Sullender, Barry W.; Crease, Teresa J.

doi:10.1007/s002390010193

Cited by 27 publications

(25 citation statements)

References 29 publications

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“…Future work should therefore focus on a higher resolution study of the underlying rDNA motif structure, which would involve sequencing of the IGS region and potentially the examination of patterns of methylation (i.e., effects on gene expression; Sardana et al 1993) and transposable element load (e.g., gene silencing by retro-transposons; Sullender and Crease 2001). Such genomic-level studies coupled with more extensive studies of growth rate and biochemical and C : N : P parameters should be a fertile field for future research efforts.…”

Section: Discussionmentioning

confidence: 99%

Associations among ribosomal (r)DNA intergenic spacer length, growth rate, and C:N:P stoichiometry in the genus Daphnia

Weider

Glenn

Kyle

et al. 2004

Limnology & Oceanography

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The growth rate hypothesis (GRH) proposes that variation in organismal C : N : P ratios is associated with growth rate due to differential allocation to P-rich ribosomal RNA to support growth. A further extension of the GRH proposes that this variation is associated with the structure of ribosomal (r)DNA genes (e.g., promoter-enhancer sequences in the rDNA intergenic spacer [IGS]) that influence the production rate of rRNA. To test these ideas, we examined growth rate, rDNA structure, RNA : DNA ratios, and elemental composition (C : N : P) in multiple clones of three Daphnia species (pulex, pulicaria, magna) in controlled laboratory experiments. Results show that a portion of the rDNA motif, consisting primarily of the IGS, shows considerable interspecific and intraspecific length variation. Significant interspecific differences in all parameters were found, while significant intraspecific (clone) effects were detected only for RNA : DNA ratios and growth rate. As predicted by the GRH, there were significant positive correlations between RNA : DNA ratio and either growth rate or rDNA/IGS length, and a significant positive correlation between rDNA/IGS length and growth rate, when clonal means for all three species were examined. However, no clear-cut relationships between RNA : DNA and either C : P or N : P were observed for any of the three species. Likewise, no discernible intraspecific relationships between growth rate and either C : P or N : P were detected. These preliminary findings suggest that further study of elemental composition, nucleic acid content, and growth rates of organisms may lead to a clearer understanding of the role of stoichiometric constraints in influencing the ecology and evolution of natural populations.

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Section: Discussionmentioning

confidence: 99%

Associations among ribosomal (r)DNA intergenic spacer length, growth rate, and C:N:P stoichiometry in the genus Daphnia

Weider

Glenn

Kyle

et al. 2004

Limnology & Oceanography

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“…The spread of Ty1 LTR-retroelements in sexually and asexually reproducing laboratory populations of Saccharomyces cerevisiae, as expected, was more efficient in sexuals (Zeyl et al, 1996). In cyclically and obligately parthenogenetic populations of Daphnia pulex, a DNA transposon named Pokey exhibited pronounced differences in mobility, being virtually immobilized in obligate parthenogens and exhibiting a high degree of variability in cyclic parthenogens (Sullender and Crease, 2001). Analogous studies with the unicellular green alga Chlamydomonas, however, did not yield any differences in mobility for two transposons studied, TOC1 and Gulliver (Zeyl et al, 1994).…”

Section: Transposon Dynamics Under Different Reproductive Modesmentioning

confidence: 91%

Mobile genetic elements and sexual reproduction

Arkhipova

2005

Cytogenet Genome Res

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Transposable elements (TE) are prominent components of most eukaryotic genomes. In addition to their possible participation in the origin of sexual reproduction in eukaryotes, they may be also involved in its maintenance as important contributors to the deleterious mutation load. Comparative analyses of transposon content in the genomes of sexually reproducing and anciently asexual species may help to understand the contribution of different TE classes to the deleterious load. The apparent absence of deleterious retrotransposons from the genomes of ancient asexuals is in agreement with the hypothesis that they may play a special role in the maintenance of sexual reproduction and in early extinction for which most species are destined upon the abandonment of sex.

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“…In parthenogenetic organisms, theoretical predictions suggest that transposable elements could be beneficial in the short-term, but deleterious if present and still active in the long-term (Nuzhdin and Petrov, 2003). Indeed, it was shown that obligately parthenogenetic populations of Daphnia pulex contain only fixed (ie inactive) transposons (Sullender and Crease, 2001) and that ancient asexual bdelloid rotifers have lost all of the retrotransposables elements (Arkhipova and Meselson, 2000). Similarly, a molecular survey revealed that the genome of M. incognita totally lack sequences homologous to the Tc(s) transposable elements of Caenorhabditis elegans (Abad et al, 1991).…”

Section: Putative Mechanisms Of Genome Evolution In Parthenogenetic Rknmentioning

confidence: 99%

Genetic variability and adaptive evolution in parthenogenetic root-knot nematodes

2006

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Root-knot nematodes (RKN) of the genus Meloidogyne are biotrophic plant parasites of major agricultural importance, which exhibit very variable modes of reproduction, from classical amphimixis to mitotic parthenogenesis. This review focuses on those RKN species that reproduce exclusively by mitotic parthenogenesis (apomixis), in contrast to those that have meiotic/amphimitic events in their life cycle. Although populations of clonal organisms are often represented as being ecologically isolated and evolutionary inert, a considerable volume of literature provides evidence that asexual RKN are neither: they are widely distributed, extremely polyphagous, and amenable to selection and adaptive variation. The ancestors of the genus are unknown, but it is assumed that the parthenogenetic RKN have evolved from amphimictic species through hybridization and subsequent aneuploidization and polyploidization events. Molecular studies have indeed confirmed that the phylogenetic divergence between meiotic and mitotic RKN lineages occurred early, and have revealed an unexpected level of clonal diversity among populations within apomictic species. Laboratory experiments have shown that asexual RKN can rapidly adapt to new environmental constraints (eg host resistance), although with some fitness costs. Lastly, the molecular and chromosomal mechanisms that could contribute to genome plasticity leading to persistent genetic variation and adaptive evolution in apomictic RKN are discussed. It is concluded that RKN provide an excellent model system in which to study the dynamic nature and adaptive potential of clonal genomes.

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The Behavior of a Daphnia pulex Transposable Element in Cyclically and Obligately Parthenogenetic Populations

Cited by 27 publications

References 29 publications

Associations among ribosomal (r)DNA intergenic spacer length, growth rate, and C:N:P stoichiometry in the genus Daphnia

Associations among ribosomal (r)DNA intergenic spacer length, growth rate, and C:N:P stoichiometry in the genus Daphnia

Mobile genetic elements and sexual reproduction

Genetic variability and adaptive evolution in parthenogenetic root-knot nematodes

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