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PubMed1980

Human parthenogenesis: a fascinating single event.

Ovarian teratomas and complete hydatidiform moles are considered as two forms of parthenogenetic development in humans. The diploid chromosome complement is entirely of material origin in the first, and of paternal origin in the second.

Animals↗
PubMed1994

[Production of partial blastulas by parthenogenesis in Xenopus].

In mature Xenopus eggs, the cell cycle can be triggered by pricking the egg or by an electric shock. However, no cleavage occurs unless centriole-containing fractions or isolated centrosomes are injected at the time of egg activation. We have obtained for an average of one heterologous centrosome injected per oocyte a complete parthenogenetic development. We also observed that the success rate of blastula formation declined linearly with the time elapsing between oocyte activation and centrosome injection. Moreover, in most cases, large areas of the blastulas remained uncleaved, interfering with gastrulation and blocking further development.

Animals↗
PubMed2001

How does infection with parthenogenesis-inducing Wolbachia reduce the fitness of Trichogramma?

We analyzed the survival rate of the immature stages of Trichogramma species and lines that differed in their mode of reproduction. Specifically, we compared the mortality of arrhenotokous (W(-)), irrevertable thelytokous (W(-)), and Wolbachia-associated thelytokous (W(+)) forms. The embryonic mortality of the W(+) strains was significantly higher than that of the W(-) lines. The embryonic mortality was negligible for the arrhenotokous Trichogramma evanescens and the thelytokous Trichogramma cacoeciae, which is not infected with Wolbachia. Only 30% of the eggs of the Wolbachia-infected strains developed to adults, while the emergence rate of the Wolbachia-free strains was more than 78%, irrespective of the origin of the strains. More than 78% of the overall mortality in W(+) strains happened during the early stages of development. About 35% of embryos of W(+) strains remain in the mitotic stage even 48 h after oviposition. Most embryos of W(-) strains had already developed to cellular blastoderm after 6 h, regardless of strains. The mortality of immature stages in W(+) strains was mainly caused by the failure of the mitotic divisions.

Animals↗
PubMed1998

Distribution of parthenogenesis-inducing symbionts in ovaries and eggs of Aphytis (Hymentoptera: Aphelinidae).

In parasitic Hymenoptera, severe sex ratio distortions are sometimes associated with the presence of symbiotic microorganisms. Symbiont-induced uniparental reproduction is found in several species of the genus Aphytis and is suspected in others. These intracellular bacteria (called Wolbachia) reside within the egg cytoplasm. In order to follow their vertical transmission, the distribution pattern of the symbionts in ovaries and eggs of two uniparental lines (A. lingnanensis and A. yanonensis) was studied by electron, confocal, and two-photon microscopy. The results obtained suggest that Wolbachia move from nurse cells to developing oocytes. In freshly laid eggs, the symbionts are concentrated in the posterior pole, away from the micropyle, and in later stages of embryogenesis they are found surrounding nuclei throughout the embryo.

Animals↗
PubMed2004

The Inheritance of apomixis in Poa pratensis confirms a five locus model with differences in gene expressivity and penetrance.

The genetic control of apomixis was studied in numerous segregating progenies originated from intercrossing and selfing of obligate sexual and facultative apomictic parents in Poa pratensis by means of the flow cytometric seed screen. The data support a novel model with five major genes required to control asexual seed formation: the Apospory initiator (Ait) gene, the Apospory preventer (Apv) gene, a Megaspore development (Mdv) gene, the Parthenogenesis initiator (Pit) gene, and the Parthenogenesis preventer (Ppv) gene. Differences in expressivity and interactions of these genes are responsible for the wide variation of the mode of reproduction. Apospory and parthenogenesis as well as the initiator and preventer genes of these components segregate independently. The genotypes with the highest expressivity of apospory and parthenogenesis were assigned as Ait-/apvapv/Pit-/ppvppv, those with intermediate expressivity as Ait-/Apv-/Pit-/Ppv-, and those with low expressivity as aitait/apvapv/pitpit/ppvppv. Among the self progenies of obligate sexual individuals, plants with a low capacity for apospory and/or parthenogenesis occurred, indicating that the sexual parents were heterozygous for the preventer genes and homozygous for the recessive initiator alleles (aitait/Apv-/pitpit/Ppv-). The dominant allele Ait exhibits incomplete penetrance. The degree of expressivity of apospory and parthenogenesis was constant among several harvest years of F1 plants.

Gene Expression Regulation, Plant↗
PubMedDate not supplied

Evolutionary implications of developmental instability in parthenogenetic drosophila mercatorum. I. Comparison of several strains with different genotypes.

Natural populations of sexually reproducing Drosophila mercatorum are capable of a very low rate of parthenogenesis, but this mode of reproduction has apparently never characterized an entirely asexual population in this species. The high abortion rate observed in laboratory parthenogenetic lines suggests that developmental constraints may cause the failure of this trait to spread in nature. To investigate the basis of this developmental instability and how it may affect the evolution of parthenogenesis in natural populations, early embryonic development was compared between one sexual and four parthenogenetic laboratory strains of D. mercatorum. There is a large amount of variation within a given parthenogenetic strain, suggesting that parthenogenesis is associated with a general breakdown of developmental stability. There is relatively little variation among different parthenogenetic strains, suggesting that most abortions are due to a feature inherent to parthenogenetic reproduction rather than a feature of a particular genome. Likewise, there is little variation between parthenogenetic and sexual strains in the causes of abortions, suggesting that the developmental problems encountered by parthenogenetic lineages are not unique to parthenogens. Thus, the failure of parthenogenesis to spread within D. mercatorum can be attributed to no particular developmental constraint per se operating after the initiation of embryogenesis. However, the overall increase in all developmental problems that occurs with the transition from sexual to parthenogenetic development suggests that the high degree of developmental instability associated with parthenogenesis may be considered a developmental constraint in its own right.

Animals↗
PubMed2006

Aseptic vitrification of human germinal vesicle oocytes using dimethyl sulfoxide as a cryoprotectant.

OBJECTIVE: To evaluate the viability of vitrified human germinal vesicle (GV)-oocytes to mature to metaphase II (MII) stage after "rapid" cooling directly in liquid nitrogen in comparison with "slow" cooling in a closed 0.5-mL straw (aseptic system), with or without dimethyl sulfoxide (DMSO) in vitrification solution. The possibility of avoiding parthenogenesis of the oocytes after vitrification using DMSO was investigated. DESIGN: In vitro maturation after vitrification. SETTING: Assisted reproduction centers. PATIENT(S): Patients undergoing standard superovulation treatment and having GV-oocytes after follicular puncture. INTERVENTION(S): The GV-oocytes were vitrified with long/short exposure to DMSO using slow or rapid cooling, then warmed and matured in vitro. MAIN OUTCOME MEASURE(S): Maturation after warming. RESULT(S): Oocyte development up to MII stage after vitrification with DMSO was 71% in the group with "rapid" cooling, and in groups with "slow" cooling, 68% and 72% for long and short exposure to DMSO, respectively. The maturation rate of GV-oocytes after slow cooling without DMSO was 51%. In the vitrification with long-term contact of oocytes with DMSO group, a high rate of parthenogenesis was observed. When vitrification with short-term contact of oocytes with DMSO at room temperature was used, no parthenogenesis was observed. CONCLUSION(S): Cryopreservation of human GV-oocytes in open-pulled straws OPS) using an aseptic slow cooling method gives high maturation rates but only in combination with DMSO. To avoid spontaneous parthenogenesis, the exposure to DMSO must occur for a reduced time and at room temperature.

Asepsis↗
PubMed2004

Developmental success, stability, and plasticity in closely related parthenogenetic and sexual lizards (Heteronotia, Gekkonidae).

The developmental trajectory of an organism is influenced by the interaction between its genes and the environment in which it develops. For example, the phenotypic traits of a hatchling reptile can be influenced by the organism's genotype, by incubation temperature, and by genetically coded norms of reaction for thermally labile traits. The evolution of parthenogenesis provides a unique opportunity to explore such effects: a hybrid origin of this trait in vertebrates modifies important aspects of the genotype (e.g., heterozygosity, polyploidy) and may thus impact not only on the phenotype generally, but also on the ways in which incubation temperature affects expression of the phenotype. The scarcity of vertebrate parthenogenesis has been attributed to developmental disruptions, but previous work has rarely considered reaction norms of embryogenesis in this respect. We used closely related sexual and asexual races of the Australian gecko Heteronotia binoei, which include those with multiple origins of parthenogenesis, to explore the ways in which reproductive modes (sexual, asexual), incubation temperatures (24, 27, and 30 degrees C), and the interaction between these factors affected hatchling phenotypes. The hatchling traits we considered included incubation period, incidence of deformities, hatchling survivorship, body size and shape, scalation (including fluctuating asymmetry), locomotor performance, and growth rate. Developmental success was slightly reduced (higher proportion of abnormal offspring) in parthenogenetic lineages although there was no major difference in hatching success. Incubation temperature affected a suite of traits including incubation period, tail length, body mass relative to egg mass, labial scale counts, running speed, growth rate, and hatchling survival. Our data also reveal an interaction between reproductive modes and thermal regimes, with the phenotypic traits of parthenogenetic lizards less sensitive to incubation temperature than was the case for their sexual relatives. Thus, the evolution of asexual reproduction in this species complex has modified both mean hatchling viability and the norms of reaction linking hatchling phenotypes to incubation temperature. Discussions on the reasons why parthenogenetic organisms are scarce in nature should take into account interactive effects such as these; future work could usefully try to tease apart the roles of parthenogenesis, its hybrid origin (and thus effects on ploidy and heterozygosity, etc.), and clonal selection in generating these divergent embryonic responses.

Analysis of Variance↗