Letteratura scientifica selezionata sul tema "Diploidy restoration"

Parthenogenesis induced by cytoplasmatically inherited Wolbachia bacteria has been found in a number of arthropod species, mainly Hymenoptera. Previously, two different forms of diploidy restoration have been reported to underlie parthenogenesis induction in Hymenoptera by Wolbachia. Both are a form of gamete duplication, but each differs in their timing. We investigated the cytology of the early embryonic development of a Wolbachia-infected strain of the parasitoid wasp Leptopilina clavipes and compared it with that of an uninfected sexual strain. Both strains have a similar meiosis. In the infected parthenogenetic strain, diploidy is restored by anaphase restitution during the first somatic mitosis, similar to Trichogramma, but not to Muscidifurax. Our results confirm the occurrence of different cytological mechanisms of diploidy restoration associated with parthenogenesis-inducing Wolbachia in the order Hymenoptera.Key words: gamete duplication, Leptopilina clavipes, parthenogenesis, thelytoky, Wolbachia.

Interspecific androgenetic rosy barb (Puntius conchonius) was generated using its cadaveric (-20 °C) or fresh sperm to activate nuclear genome inactivated oocytes of gray tiger barb (Puntius tetrazona). UV irradiation was used to inactivate nuclear genome of tiger barb oocytes. Thermal shock restored diploidy of rosy barb in the oocytes of tiger barb. Survival of androgenotes was 14% or 7% when fresh or cadaveric sperm was used. The diploid or haploid nuclear genome of rosy barb, individually or jointly with that of tiger barb, regulated the time sequence of embryonic development in an alien cytoplasm of tiger barb oocytes. Androgenetic males (Y2Y2) attained sexual maturity earlier and had significantly higher gonadosomatic index and sperm concentration, albeit suffering a slight decrease in fertilizing ability. Conversely, androgenetic females (X2X2) suffered extended interspawning period, reduced fecundity, and poor hatchability of their progenies. These results are discussed with respect to their significance for conservation biology.Key words: nuclear genome inactivation, tiger barb, cadaveric sperm, rosy barb, interspecific androgenotes, Tc1 transposon.

Intraspecific ploidy variation is an important component of angiosperm biodiversity; however, this variation is rarely considered in conservation programs. This is of particular concern when conservation activities include augmentation, reintroduction or ecological restoration because there are potentially negative consequences when ploidy variants are unintentionally mixed within populations. We surveyed regional ploidy variation in the Lepidosperma costale Nees species complex (Schoeneae: Cyperaceae) in the South West Australian Floristic Region, an international biodiversity hotspot. Several L. costale sensu lato populations are threatened by iron-ore extraction, including the rare L. gibsonii R.L.Barrett, and these populations are the subject of ecological restoration programs. The DNA ploidy of 2384 individuals from 28 populations across the range of the species complex was determined and four DNA ploidy levels were discovered, namely, diploid, triploid, tetraploid and pentaploid. Diploids and tetraploids were the most common cytotypes and were largely geographically segregated, even at an exhaustively studied contact zone. Triploids were found at a low frequency in two populations. The rarity of triploids suggests substantial interploidy sterility, and that mixing of ploidy variants should, therefore, be avoided when restoring L. costale s.l. populations. These data provide a guide for L. costale s.l. germplasm collection and suggest that polyploidy may be an important driver of diversification in these sedges.

Abstract In Zea mays L. plants carrying the S-type of sterility-inducing cytoplasm, male fertility is determined by a gametophytic, nuclear restoration-of-fertility gene. Haploid pollen carrying the fertility-restoring allele (historically designated Rf3) is starch-filled and functional, whereas pollen carrying the nonrestoring allele (historically designated rf3) is shrunken and nonfunctional. Because restoration of fertility occurs in haploid tissue, the dominance relationship of restoring and nonrestoring alleles is unknown. We have tested the dominance relationship of the restoring and nonrestoring alleles at the rf3 locus in diploid pollen. The meiotic mutant elongate was used to generate tetraploid plants carrying both Rf3 and rf3 alleles in the S cytoplasm. These plants shed predominantly starch-filled pollen, consistent with dominance of the restoring allele. Restriction fragment length polymorphisms linked to the rf3 locus demonstrated cotransmission of rf3 and Rf3 alleles through heterozygous diploid pollen, providing conclusive genetic evidence that the restoring allele is the dominant or functional form of this restoration-of-fertility gene. We suggest that other Scytoplasm restorers result from loss-of-function mutations and propose analysis of unreduced gametes as a test of this model.

Background: The human heart has limited capacity to generate new cardiomyocytes and this capacity declines with age. Because loss of cardiomyocytes may contribute to heart failure, it is crucial to explore stimuli of endogenous cardiac regeneration to favorably shift the balance between loss of cardiomyocytes and the birth of new cardiomyocytes in the aged heart. We have previously shown that cardiomyogenesis can be activated by exercise in the young adult mouse heart. Whether exercise also induces cardiomyogenesis in aged hearts, however, is still unknown. Here, we aim to investigate the effect of exercise on the generation of new cardiomyocytes in the aged heart. Methods: Aged (20-month-old) mice were subjected to an 8-week voluntary running protocol, and age-matched sedentary animals served as controls. Cardiomyogenesis in aged hearts was assessed on the basis of 15 N-thymidine incorporation and multi-isotope imaging mass spectrometry. We analyzed 1793 cardiomyocytes from 5 aged sedentary mice and compared these with 2002 cardiomyocytes from 5 aged exercised mice, followed by advanced histology and imaging to account for ploidy and nucleation status of the cell. RNA sequencing and subsequent bioinformatic analyses were performed to investigate transcriptional changes induced by exercise specifically in aged hearts in comparison with young hearts. Results: Cardiomyogenesis was observed at a significantly higher frequency in exercised compared with sedentary aged hearts on the basis of the detection of mononucleated/diploid 15 N-thymidine–labeled cardiomyocytes. No mononucleated/diploid 15 N-thymidine–labeled cardiomyocyte was detected in sedentary aged mice. The annual rate of mononucleated/diploid 15 N-thymidine–labeled cardiomyocytes in aged exercised mice was 2.3% per year. This compares with our previously reported annual rate of 7.5% in young exercised mice and 1.63% in young sedentary mice. Transcriptional profiling of young and aged exercised murine hearts and their sedentary controls revealed that exercise induces pathways related to circadian rhythm, irrespective of age. One known oscillating transcript, however, that was exclusively upregulated in aged exercised hearts, was isoform 1.4 of regulator of calcineurin, whose regulation and functional role were explored further. Conclusions: Our data demonstrate that voluntary running in part restores cardiomyogenesis in aged mice and suggest that pathways associated with circadian rhythm may play a role in physiologically stimulated cardiomyogenesis.

The diploid (2n = 20) wild species of Arachis are the potential sources of resistance to many pests and diseases. The diploid wild sp. A. cardenasii was hybridized with CV. VRI 2 of A. hypogaea (2n = 40) The resultant triploids (2n = 30) were partially fertile. The pollen of the triploids were utilised for back crossing again with A. hypogaea. There were three distinct form of plants obtained in BC1F1. The pollen of the BC1F1 were utilized for back crossing again with A. hypogaea. The resultant BC1F1 were studied. The complete fertility restoration Iwas observed in form I in the immediate back cross, whereas it was observed in the second back cross in form II. Hence, triploids is also a potential source for genetic introgression in groundnut.

Les mitochondries ont la particularité de posséder leur propre génome, l'ADN mitochondrial (ADNmt), transmis exclusivement par la mère via le cytoplasme de l'ovocyte. Les mutations pathogènes au sein de l'ADNmt sont à l'origine des maladies mitochondriales. Le transfert de pronoyaux (TPN), non autorisé en France, est une technique proposée depuis 2016 par le Royaume Uni afin de substituer le génome mitochondrial muté d'un zygote par un autre non muté. Cette méthode reste largement débattue sur le plan international en termes d'efficacité et de sécurité. L'objectif de nos travaux était d'évaluer la faisabilité clinique et technique du TPN. Nos recherches ont confirmé que les femmes porteuses d'un variant pathogène de l'ADNmt présentaient des critères de réponse ovarienne à la stimulation comparable à un groupe contrôle. Grâce à une étude sociologique nous avons également montré que cette technique recevait une adhésion par la grande majorité des femmes interrogées principalement car elle permet de maintenir un lien génétique entre une femme et son enfant. Puis nous avons mis au point la technique de TPN en utilisant des zygotes triploïdes (3PN) donnés à la recherche et après autorisation de l'Agence de Biomédecine. Enfin, nous avons évalué la pertinence de l'utilisation des 3PN et démontré leurs limites en termes de développement et de statut chromosomique, même lorsque la diploïdie était rétablie. Ces travaux ouvrent des perspectives sur la faisabilité et l'acceptation du TPN. De futures recherches sont nécessaires pour explorer la sécurité de cette technique
Mitochondria have the unique characteristic of possessing their own genome, mitochondrial DNA (mtDNA), which is exclusively transmitted by the mother through the cytoplasm of the oocyte. Pathogenic mutations in mtDNA are responsible for mitochondrial diseases. Pronuclear transfer (PNT), not authorized in France, is a technique proposed by the United Kingdom since 2016 to replace the mutated mitochondrial genome of a zygote with a non-mutated one. This method remains widely debated internationally regarding its efficacy and safety. The aim of our work was to evaluate the clinical and and technical feasibility of PNT. Our research confirmed that women carrying a pathogenic variant of mtDNA exhibited ovarian response criteria to stimulation comparable to a control group. Through a sociological study, we also showed that this technique received support from the majority of women surveyed, primarily because it maintains a genetic link between a woman and her child. Subsequently, we developed the PNT technique using triploid zygotes (3PN) donated for research, following authorization from the Biomedicine Agency. Finally, we assessed the relevance of using 3PN and demonstrated their limitations in terms of development and chromosomal status, even when diploidy was restored. This work opens up perspectives on the feasibility and acceptance of PNT. Future research is necessary to explore the safety of this technique

A large proportion of stock improvement in agriculture and more recently aquaculture has come through breeding strategies that work to isolate and fix favourable characters and eliminate undesirable genetic qualities in the target species. The development of homozygous breeding lines, which allow fixing of desirable traits need to be progressed to enhance the effectiveness of breeding strategies. Such lines would also be a valuable research tool for examining genetic versus environmental influence on reproductive biology and stock performance. One potentially rapid and effective method that may produce 100% homozygous individuals is to create what are known as "double-haploids", by suppressing the 1st cell cleavage in haploid zygotes. This project investigated the efficacy of haploid production in the Pacific oyster, Crassostrea gigas, by examining UV irradiation of the paternal DNA, and restoration to the diploid state using the chemicals 6-dimethylaminopurine (6-DMAP) or Cytochalasin B (CB) to suppress either polar body I, polar body II or 1st Cleavage of activated eggs. Additionally, the use of a recessive colour phenotype was examined as a marker to identify parentage of putative gynogen offspring. Sperm Viability via a membrane integrity test ranged between 78-80% viable for controls (no UV exposure) and was significantly greater than all treatment exposures except 60 second low energy exposure (601±22μWcm⁻²s⁻¹), with 300 second high energy exposure (1063±15μWcm⁻²s⁻¹) causing the greatest reduction in sperm viability, ranging between 32-52%. There was no significant difference in egg activation between controls and treatments. In contrast, there was a significant reduction in development of embryos to D larvae with controls averaging approximately 40% development to D stage and the lowest energy treatment (60 seconds @ 601±22μWcm⁻²s⁻¹) averaging a little over 1%. UV radiation of sperm had a significant effect on embryo ploidy levels, with all treatments 180 seconds or longer resulting in less than 20% of cells being diploid or some level of aneuploidy between haploid and diploid. However other published work indicated that, sperm densities and treatment depths are likely to be as important as energy levels when developing irradiation protocols. Survival of putative diploid gynogens was extremely low in all experiments, with the best results yielding 3.9% recovery to D stage larvae and 0.04% recovery to settled spat assessed at 34 days post spawning. Suppression of PB II or 1st Cleavage with CB resulted in the greatest proportion of diploid cells (37.3% and 28.9% respectively) compared with CB suppression of PB I which resulted in the majority of cells produced being tetraploid (35.7%). Microsatellite (mSAT) analysis of these putative gynogen spat revealed a greater level of homozygosity in their genome relative to normal diploid controls; however the presence of null alleles and a lack of genetic variability at some mSAT loci reduced the power of these tools to fully distinguish parentage and validate the production of meiotic or mitotic gynogens. In a direct comparison of 6-DMAP and CB to restore the diploid state by suppression of 1st Cleavage, CB provided a greater percentage of diploid cells (28.4%) compared with 6-DMAP (23.7%) and significantly lower subsequent mortality of larvae. However using 6-DMAP to suppress PB I and II, survival and percentage of diploid cells produced was comparable to that obtained for similar trials using CB. The use of eggs obtained from recessive gold phenotype females crossed with inactivated sperm from homozygous wild type males was investigated to help elucidate the parentage of putative meiotic and mitotic gynogens. Survival of these putative gynogens was lower than for wild type female progeny however gold offspring were produced in both forms of gynogen induction and were not found in corresponding diploid controls. In summary, effective sperm deactivation for subsequent haploid gynogen production can be achieved by exposure to UV radiation for 5 minutes at energy levels ranging between 600 and 1000 μWcm⁻²s⁻¹. Restoring the diploid state of zygotes for meiotic gynogen production can be achieved through the addition of Cytochalasin B or 6-dimethylaminopurine targeting Polar body II suppression, however Cytochalasin B is recommended over 6-dimethylaminopurine for the production of putative mitotic gynogens through 1st cleavage suppression. Mitotic gynogens may be particular useful in the production of genetically identical lines, as they have the potential to be homozygous at every locus.

Wolbachia are intracellular bacteria known to cause reproductive and sex ratio disorders in many insects. In various parasitic Hymenoptera, Wolbachia induce thelytokous reproduction. The overall goal of this research was the improvement of biological control agents by reversion of their mode of reproduction. This was attempted from two directions: 1) studying the effect of naturally occurring Wolbachia on the thelytokous species Muscidifuraxuniraptor and 2) trying to transmit thelytoky-inducing Wolbachia to Nasoniavitripennis. In M. uniraptor, gamete duplication was found to be the mode of diploidy restoration and Wolbachia density had a strong effect on sex ratio but not on host fitness. Studies on the natural horizontal transmission of Wolbachia between Nasonia wasps and their Protocalliphora hosts using the Wolbachia Outer Surface Protein (WOSP) gene revealed that (a) two Nasonia species (N. giraulti and N. longicornis) possess closely related strains of B-group Wolbachia, but N. vitripennisapparently acquired B Wolbachia by horizontal transmission from an unknown source, (b) Nasonia and its Protocalliphora host have similar Wolbachia, and (c) the Protocalliphora Wolbachia WOSP gene is a recombinant between the one found in N. giraulti/longicornis and N. vitripennis. Results show parasitoid-host insect transmission of Wolbachia and recombination among Wolbachia strains. Results from gynandromorph studies suggest a novel mechanism of sex determination in Nasonia.

The long-term motivation for this research is to transfer useful traits from a broad based gene pool of wild species into the narrow base of a cultivated crop in Cucumis. Our primary focus was to use polyploid prior to fertilization as a tool to overcome fertility barriers in the cross between C. melo and C. metuliferus. In conducting this research, we explored all combinations of tetraploid and diploid parents, in reciprocal combinations. Pollinations were made in both the field and greenhouse, using emasculated flowers, moneocious females, and open pollination by insect vectors, with morphological selection criteria. After observations of thousands of ovaries, we still have no definitive proof that this hybridization yielded viable embryos. The most promising results came from using tetraploid C. metuliferus, as the maternal parent in the interspecific hybridization, that set fruit were seeds contained small embryos that did not germinate. To obtain fruit set, it was important to rear plants in a cooler sunny greenhouse, as would be found in late winter/early spring. A second interspecific hybrid between wild and cultivated Cucumis, C. hystrix x C. sativus, yielded fertile progeny for the first time, while concomitantly working toward our primary goal. Two distinct treatments were necessary; 1) special plant husbandry was necessary to have the wild species produce fruit in cultivation, and 2) embryo rescue followed by chromosome doubling in vitro was required for fertility restoration. Backcrosses to crop species and resistance to nematodes are compelling areas for further work.