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At least 271 records · Page 15Linked to original sources
PubMed2005

Loss of function of MULTICOPY SUPPRESSOR OF IRA 1 produces nonviable parthenogenetic embryos in Arabidopsis.

In sexually reproducing species, fertilization brings together in the zygote the genomes of the female and male gametes. In several animal species, female gametes are able to initiate embryogenesis in the absence of fertilization, a process referred to as parthenogenesis. Parthenogenesis has been engineered in mice by tampering with expression of loci under epigenetic controls [1]. In plants, embryo development in the absence of fertilization has been reported in cases in which meiosis is bypassed leading to apomictic development, and parthenogenetic development from a reduced egg cell has been only reported in rare accidental cases [2]. We report that single mutations in the gene MULTICOPY SUPPRESSOR OF IRA 1 (MSI1) are able to initiate parthenogenetic development of the embryo in Arabidopsis thaliana from eggs cells produced by meiosis. The WD40 repeat protein MSI1 is part of the evolutionarily conserved Polycomb group (PcG) chromatin-remodeling complexes [3] and is homologous to the Retinoblastoma binding proteins P55 in Drosophila and RbAp48 in mammals [4]. Nonviable haploid parthenogenetic msi1 embryos express molecular markers and polarity similar to diploid wild-type (wt) embryos produced by fertilization, indicating a maternal contribution to early patterning of the Arabidopsis embryo.

Arabidopsis↗
PubMed1998

Recent studies on the reproductive biology of the schistosomes and their relevance to speciation in the Digenea.

The members of the family Schistosomatidae, dioecious Digenea, are discussed with regard to their distribution, intermediate and definitive host-parasite relationships. The biological species concept is considered together with the difficulties of its application to Schistosoma spp. and the Digenea. The correlation between pairing of adult schistosomes, physical and sexual development and the maintenance of reproductive potential is emphasised. Development of the female reproductive system does not depend upon species-specific pairing. In some combinations, e.g., Schistosoma haematobium/Schistosoma intercalatum and Schistosoma bovis/Schistosoma curassoni, a specific mate choice system apparently does not exist, whereas it does in other combinations, e.g., Schistosoma mansoni/Schistosoma intercalatum. In mixed infections change of mate may occur and when the opportunity arises heterospecific pairs of worms will change partners to conspecific pairs. Interspecific pairing in adult schistosomes will lead to either hybridisation or parthenogenesis. Yet the majority of schistosomes that inhabit the same definitive host maintain their genetic identity: specific mate recognition, site selection within the host and heterologous immunity have been suggested as isolating mechanisms. Experimental intraspecific crosses have enabled evaluation of the degree to which some populations separated and became reproductively isolated through pre-mating isolating mechanisms, indicative of incipient speciation, e.g., the Lower Guinea and Zaire strains of S. intercalatum. The occurrence and significance of parthenogenesis in schistosomes and other species of Digenea are discussed. The consequences of interspecific mating interactions in schistosomes with regard to parasite epidemiology, interspecific competition and genetic heterogeneity are debated. Geographical isolation and host specificity represent important pre-zygotic isolating mechanisms. It is suggested that site selection within the host and heterologous immunity may both reduce interspecific genetic interchange when digenean parasites utilise the same definitive host.

Animals↗
PubMed1993

In vivo parthenogenetic activation of ovulated oocytes in a marsupial, Sminthopsis crassicaudata.

The occurrence of in vivo parthenogenesis is documented for laboratory-bred individuals of the Australian dasyurid marsupial, Sminthopsis crassicaudata. About 30% of females that had been isolated from males for a greater period of time than the length of pregnancy were found, on dissection of their uteri, to have embryos present. The embryos were surrounded by a mucoid coat and shell membrane and at least the first two cleavage divisions occurred normally. After this time, however, unequal cleavage divisions appeared to result. The parthenogenesis that takes place may be initiated as a result of activation of ageing ovulated oocytes. Its frequent occurrence may prove useful in a study of maternal and paternal contributions to early embryonic development in the species.

Animals↗
PubMed1999

The kinetics of oocyte activation and dynamics of polar body formation in Calomys musculinus and Calomys laucha (Rodentia-Sigmodontinae).

The objective of this study was to determine whether Calomys laucha and Calomys musculinus superovulated oocytes undergo parthenogenetic activation following activation stimuli. Cumulus-intact or denuded oocytes were treated with medium containing ethanol (7%), medium containing strontium chloride, or medium alone. They were then incubated for 6-8 h to allow for activation. A group of oocytes was fixed immediately after maturation to serve as a control. The nuclear status of the oocytes was examined after staining with Hoechst 33342, to determine the timing of pronuclear progression from metaphase II to anaphase II or telophase II or to the pronuclear stage. The proportion of oocytes that underwent activation was higher for oocytes treated with ethanol or strontium chloride than in those incubated in medium alone, for the two species studied (p < 0.001). There was little evidence of spontaneous activation occurring in oocytes during the treatments. Most of the activated oocytes contained a single haploid pronucleus, but it was possible to find immediate cleavage and two pronuclei. The different classes of activated oocytes were cultured for 5 days. The type of activating treatment had a marked effect on the ability of the resulting C. musculinus and C. laucha parthenogenetic embryos to develop to the preimplantation stages. Incubation with ethanol produced only 8-cell embryos while the embryos induced with strontium chloride reached the blastocyst stage. This is the first report of parthenogenesis in C. musculinus and C. laucha. The ability of strontium ions to induce matured secondary oocytes to initiate parthenogenesis and obtain further development of Calomys provides opportunities to use Calomys oocytes in vitro and, therefore, to study the genetics, cell biology and virology of development.

Animals↗
PubMed2004

Birth of parthenogenetic mice that can develop to adulthood.

Only mammals have relinquished parthenogenesis, a means of producing descendants solely from maternal germ cells. Mouse parthenogenetic embryos die by day 10 of gestation. Bi-parental reproduction is necessary because of parent-specific epigenetic modification of the genome during gametogenesis. This leads to unequal expression of imprinted genes from the maternal and paternal alleles. However, there is no direct evidence that genomic imprinting is the only barrier to parthenogenetic development. Here we show the development of a viable parthenogenetic mouse individual from a reconstructed oocyte containing two haploid sets of maternal genome, derived from non-growing and fully grown oocytes. This development was made possible by the appropriate expression of the Igf2 and H19 genes with other imprinted genes, using mutant mice with a 13-kilobase deletion in the H19 gene as non-growing oocytes donors. This full-term development is associated with a marked reduction in aberrantly expressed genes. The parthenote developed to adulthood with the ability to reproduce offspring. These results suggest that paternal imprinting prevents parthenogenesis, ensuring that the paternal contribution is obligatory for the descendant.

Animals↗
PubMed2006

Genetic variability and adaptive evolution in parthenogenetic root-knot nematodes.

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.

Adaptation, Physiological↗
PubMed2006

Paternal inheritance in parthenogenetic forms of the planarian Schmidtea polychroa.

Parthenogenesis usually includes clonal inheritance, which is thought to increase the risk of the clonal populations' extinction. Yet many parthenogenetic organisms appear to have survived for extended periods. A possible explanation is that parthenogens occasionally reproduce through sex-like processes. Although there is indirect evidence for occasional sex, the underlying mechanisms are currently unknown. In the present study, we examined sex-like processes in the planarian flatworm Schmidtea (Dugesia) polychroa. Parthenogenetic forms of this species are simultaneous hermaphrodites that require sperm to trigger embryogenesis, whereas paternal genetic material is usually excluded from the oocyte (sperm-dependent parthenogenesis). Based on a comparison of parents and offspring, using highly polymorphic microsatellites, we demonstrate the incorporation of paternal alleles in about 5% of the offspring. We detected two distinct processes: chromosome addition and chromosome displacement. Such rare sexual processes may explain the long-term persistence of the many purely parthenogenetic populations of S. polychroa in northern Europe.

Animals↗
PubMed2000

Evidence for predominant clones in a cyclically parthenogenetic organism provided by combined demographic and genetic analyses.

Aphids are particularly interesting models in the study of genetic and demographic components of plant adaptation because of their breeding system which combines parthenogenesis and sexual reproduction (i.e. cyclical parthenogenesis), and the frequent emergence of host-adapted races reported in this group. In this paper, patterns of host adaptation were assessed on local populations of the aphid Sitobion avenae by following their demographic and genetic structure in a maize field for two consecutive years. The existence of putative generalist (polyphagous) or specialized (host-adapted) genotypes was also investigated by comparing the genotypic distribution of this aphid on maize and other cultivated host plants, using five microsatellite loci. Although population dynamics revealed strong variation in aphid abundance during the colonization period on maize, two genotypes identified at seven additional microsatellite loci were predominant and exhibited stable frequencies over cropping season and between years. Based on present and earlier studies, these two prevalent genotypes were shown to survive on different host plants other than maize, to colonize large geographical zones and to persist parthenogenetically for several years. All these data strongly suggest that these two genotypes are asexual generalist clones that could have been favoured by agricultural practices encountered in western Europe. Besides these two clones, a continual replacement of rare genotypes was observed on maize in both years. Hypotheses involving selection via aphid-plant interactions and natural enemies were proposed for explaining the disappearance of these genotypes on maize.

Alleles↗
PubMed2003

Nonhuman primate parthenogenetic stem cells.

Parthenogenesis is the biological phenomenon by which embryonic development is initiated without male contribution. Whereas parthenogenesis is a common mode of reproduction in lower organisms, the mammalian parthenote fails to produce a successful pregnancy. We herein describe in vitro parthenogenetic development of monkey (Macaca fascicularis) eggs to the blastocyst stage, and their use to create a pluripotent line of stem cells. These monkey stem cells (Cyno-1 cells) are positive for telomerase activity and are immunoreactive for alkaline phosphatase, octamer-binding transcription factor 4 (Oct-4), stage-specific embryonic antigen 4 (SSEA-4), tumor rejection antigen 1-60 (TRA 1-60), and tumor rejection antigen 1-81 (TRA 1-81) (traditional markers of human embryonic stem cells). They have a normal chromosome karyotype (40 + 2) and can be maintained in vitro in an undifferentiated state for extended periods of time. Cyno-1 cells can be differentiated in vitro into dopaminergic and serotonergic neurons, contractile cardiomyocyte-like cells, smooth muscle, ciliated epithelia, and adipocytes. When Cyno-1 cells were injected into severe combined immunodeficient mice, teratomas with derivatives from all three embryonic germ layers were obtained. When grown on fibronectin/laminin-coated plates and in neural progenitor medium, Cyno-1 cells assume a neural precursor phenotype (immunoreactive for nestin). However, these cells remain proliferative and express no functional ion channels. When transferred to differentiation conditions, the nestin-positive precursors assume neuronal and epithelial morphologies. Over time, these cells acquire electrophysiological characteristics of functional neurons (appearance of tetrodotoxin-sensitive, voltage-dependent sodium channels). These results suggest that stem cells derived from the parthenogenetically activated nonhuman primate egg provide a potential source for autologous cell therapy in the female and bypass the need for creating a competent embryo.

Animals↗
PubMed1998

Incongruence between morphological and mitochondrial-DNA characters suggests hybrid origins of parthenogenetic weevil lineages (Genus aramigus).

An expanded matrix of morphological characters for the genus Aramigus (Coleoptera: Curculionidae), which includes numerous polyploid parthenogenetic lineages, was compared and combined with a published matrix of mitochondrial DNA (mtDNA) characters. The matrix of morphological characters provides little resolution of the A. tessellatus and A. uruguayensis species complexes but does resolve previously unresolved relationships among other morphologically defined species (A. globoculus + A. intermedius, A. curtulus + A. planioculus). The morphological and mtDNA characters are significantly incongruent (0.435 < or = IM < or = 0.463; IMF = 0.0735), according to the tests of Farris et al. (P = 0.010) and Templeton (P < 0.005), probably because of hybrid origins of polyploid parthenogenetic lineages. For the few sexual lineages included in both matrices, morphology and mtDNA provide congruent estimates of phylogeny. In spite of recent injunctions against combining data sets that are incongruent because of differing histories, the results of the combined analyses were used to select one of the most-parsimonious mtDNA trees as the best estimate of maternal-lineage genealogy and to reconstruct the evolution of parthenogenesis under the assumption that transitions from sexuality to parthenogenesis are irreversible. Where cytogenetically justified, as in weevils, the irreversibility assumption is useful for producing conservative estimates of the age of parthenogenetic lineages in spite of potential sampling bias against sexuals.

Animals↗
PubMed2005

Increased capacity for sustained locomotion at low temperature in parthenogenetic geckos of hybrid origin.

The evolution of parthenogenesis is typically associated with hybridization and polyploidy. These correlates of parthenogenesis may have important physiological consequences that need be taken into account in understanding the relative merits of sexual and parthenogenetic reproduction. We compared the thermal sensitivity of aerobically sustained locomotion in hybrid/triploid parthenogenetic races of the gecko Heteronotia binoei and their diploid sexual progenitors. Endurance times at low temperature (10 degrees , 12.5 degrees , and 15 degrees C, 0.05 km h(-1)) were significantly greater in parthenogenetic females than in sexual females. Comparison of oxygen consumption rates during sustained locomotion at increasing speeds (0.05, 0.10, 0.15, 0.20, 0.25, and 0.30 km h(-1), 25 degrees C) indicated that parthenogenetic lizards have higher maximum oxygen consumption rates and maximum aerobic speeds than do female sexual geckos. In addition, parthenogenetic geckos showed greater levels of voluntary activity at 15 degrees C than did sexual geckos, although this pattern appears strongest in comparison to male sexual forms. Parthenogenetic lineages of Heteronotia thus have an advantage over sexual lineages in being capable of greater aerobic activity. This result is opposite of that found in prior studies of parthenogenetic teiid lizards (genus Cnemidophorus) and highlights the idiosyncratic nature of phenotypic evolution in parthenogens of hybrid origin.

Analysis of Variance↗
PubMed1974

Enzyme variability in natural populations of Daphnia magna. II. Genotypic frequencies in permanent populations.

In permanent habitats populations of the cyclical parthenogen, Daphnia magna, reproduce by continued parthenogenesis and are subject to only sporadic sexual recruitment. The genetic effects of this breeding system have been investigated by analyzing allozyme frequencies in thirteen populations of D. magna.-Genotypic frequencies at polymorphic loci characteristically deviated markedly from Hardy-Weinberg proportions and gametic phase imbalance between loci was frequent. Genotypic frequencies were subject to violent, selectively determined oscillations over short periods of time. These observations suggest that permanent populations of D. magna ordinarily consist of a limited number of highly structured genotypes. The adaptational advantages offered by such structuring may have been a major selective factor favoring the evolution of cyclical parthenogenesis.

Animals↗
PubMed1975

Genetic polymorphism and evolution in parthenogenetic animals. II. Diploid and polyploid Solenobia triquetrella (Lepidoptera: Psychidae).

Genic polymorphism at sixteen enzyme loci of four different chromosomal races of Solenobia triquetrella (bisexual, two diploid parthenogenetic races and tetraploid parthenogentiic) has been studied by starch gel electrophoresis. Isolated small diploid bisexual populations have rather uniform allele frequencies at all loci which we have studied. Diploid and tetraploid parthenogenetic individuals of this species are in general as heterozygous as bisexual ones. All parthenogenetic local populations are different from each other in the Alps. These parthenogenetic genotypes cannot be derived from a common ancestor through single mutations but rather bear evidence for a polyphyletic origin of parthenogenesis in Solenobia triquetrella. In the marginal distribution areas of the species in northern Europe single genotypes are spread over far larger areas than in the mountain regions of central Europe. This may be due to the old origin of parthenogenesis and polyploidy in northern Europe. No new parthenogenetic and polyploid strains have lately arisen in the regions outside of the Alps.

Alcohol Oxidoreductases↗
PubMed2003

A bacterial symbiont in the Bacteroidetes induces cytoplasmic incompatibility in the parasitoid wasp Encarsia pergandiella.

Vertically transmitted symbionts of arthropods have been implicated in several reproductive manipulations of their hosts. These include cytoplasmic incompatibility (CI), parthenogenesis induction in haplodiploid species (PI), feminization and male killing. One symbiont lineage in the alpha-Proteobacteria, Wolbachia, is the only bacterium known to cause all of these effects, and has been thought to be unique in causing CI, in which the fecundity of uninfected females is reduced after mating with infected males. Here, we provide evidence that an undescribed symbiont in the Bacteroidetes group causes CI in a sexual population of the parasitic wasp Encarsia pergandiella. Wasps were crossed in all four possible combinations of infected and uninfected individuals. In the cross predicted to be incompatible, infected (I) males x uninfected (U) females, progeny production was severely reduced, with these females producing only 12.6% of the number of progeny in other crosses. The incompatibility observed in this haplodiploid species was the female mortality type; dissections showed that most progeny from the incompatible cross died as eggs. The 16S rDNA sequence of this symbiont is 99% identical to a parthenogenesis-inducing symbiont in other Encarsia, and 96% identical to a feminizing symbiont in haplodiploid Brevipalpus mites. Thus, this recently discovered symbiont lineage is capable of inducing three of the four principal manipulations of host reproduction known to be caused by Wolbachia.

Animals↗
PubMed2004

Characterization of a 'Bacteroidetes' symbiont in Encarsia wasps (Hymenoptera: Aphelinidae): proposal of 'Candidatus Cardinium hertigii'.

Previously, analysis of 16S rDNA sequences placed a newly discovered lineage of bacterial symbionts of arthropods in the 'Bacteroidetes'. This symbiont lineage is associated with a number of diverse host reproductive manipulations, including induction of parthenogenesis in several Encarsia parasitoid wasps (Hymenoptera: Aphelinidae). In this study, electron microscopy and phylogenetic analysis of the 16S rRNA and gyrB genes of symbionts from Encarsia hispida and Encarsia pergandiella are used to describe and further characterize these bacteria. Phylogenetic analyses based on these two genes showed that the Encarsia symbionts are allied with the Cytophaga aurantiaca lineage within the 'Bacteroidetes', with their closest described relative being the acanthamoeba symbiont 'Candidatus Amoebophilus asiaticus'. The Encarsia symbionts share 97 % 16S rDNA sequence similarity with Brevipalpus mite and Ixodes tick symbionts and 88 % sequence similarity with 'Candidatus A. asiaticus'. Electron microscopy revealed that many of the bacteria found in the ovaries of the two Encarsia species contained a regular, brush-like array of microfilament-like structures that appear to be characteristic of the symbiont. Finally, the role of this bacterium in parthenogenesis induction in E. hispida was confirmed. Based on phylogenetic analyses and electron microscopy, classification of the symbionts from Encarsia as 'Candidatus Cardinium hertigii' is proposed.

Animals↗
PubMed1975

Multiple-yolked eggs from a parthenogenetic stock of chickens.

The frequency of double-yolked eggs in a parthenogenetic Dark Cornish line of chickens was increased in certain birds. A line was selected that had a higher frequency of parthenogenesis and double yolks than the High parthenogenetic group. Selection within the double-yolked line appeared to have reached its maximum. The amount of parthenogenesis was higher in the offspring groups with embryos in both single and double-yolked eggs. The number of eggs and yolks from birds that laid a large number of double-yolked eggs did not differ significantly from the number from birds that laid only a few double-yolked eggs. Many triple-yolked eggs were seen in this stock as well as one quadruple-yolked egg. High frequency, double-yolked egg layers laid the same number of eggs, therefore, multiple ovulations may be due to a hormone or enzyme effect.

Animals↗
PubMed1982

The relationship of parthenogenetic development in Broad Breasted White turkey eggs to level of production and environmental factors.

One hundred and twenty Broad Breasted White turkey hens were taken through two production periods with a 10-week dark house treatment between cycles. Incidence of parthenogenesis was established on each virgin female prior to artificial insemination to determine fertility and hatch of fertile eggs. Following the dark house treatment, the hens were again checked for incidence of parthenogenetic development assuming that no viable spermatozoa remained in the oviduct. A number of environmental factors affecting the hens and their egg production were checked to determine the effect on parthenogenesis. There was a strong correlation between the incidence of parthenogenetic development in the two cycles. In addition, incidence of parthenogenetic development was correlated with low ambient temperature at time of ovulation. Parthenogenetic development had a heritability of .2 and a sizable genetic correlation with both production and hatch of fertile eggs. All other relationships showed little or no correlation.

Animals↗
PubMed1978

[Research on the artificial regulation of sex in animals in the USSR].

The problem of artificial sex control was cardinally solved only for the silkworm among the domestic animals. The artificial sex control is realized by means of several methods. The artificial ameiotic parthenogenesis allows to obtain isogenic parthenogenetic progeny of only female sex. The meiotic parthenogenesis, on the contrary, gives only male progeny characterized by homozygosis by all genes. As a result of androgenesis with the participation of ooplasm and male nuclear material, only male progeny develops as well. Sex marked strains in which the female and male eggs are coloured in different may were obtained by means of translocation of the dominant genes controlling the egg colour on W chromosome determining the female sex. This allows readily to pick out the eggs of desirable sex only with the help of photoelectric equipment. The males of a specially raised strain balanced by two non-allelic sex-linked lethals, when being crossed with the females of any other strain, give male progeny only. The developed methods of sex control have found wide application in theoretical investigations of various directions and practical sericulture.

Animals↗