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At least 19 recordsLinked to original sources

PubMed1979

Origins of polyploids.

1. Polyploidy is a conspicuous feature of chromosomal evolution in higher plants. It is common in many genera, and numerous species are characterized by diploid and polyploid races. 2. Polyploid evolution is a process not an event. 3. Polyploid may involve somatic chromsome doubling or sexual functioning of cytologically non-reduced gametes. 4. Spontaneous chromosome doubling, either in the zygote to produce a polyploid is plant or in apical meristem to produce a polyploid chimera, is a rare event. 5. The common mode of polyploidy is through the formation and sexual functioning of cytologically non-reduced gametes. Increased in chromosome number can occur in the first or later hybrid generations. 6. Polyploid via cytologically non-reduced gametes is commonly a two step process. A diploid (2n) female gamete is fertilized by a haploid (n) male gamete to produce a triploid (3x), which in turn produces cytologically non-reduced triploid (3n) female gametes that are fertilized by haploid (n) gametes of the diploid parents and result in tetraploid (4x) offspring. 7. Fertilization of a rare diploid (2n) female gamete by an equally rare diploid (2n) male gamete to directly produce a tetraploid (4x) is extremely rare but does occur. 8. Polyploidy is successful only if the new polyploids are able to complete with their parents. Success depends on availability of suitable habitals, as well as the ability to produce successful offspring. 9. The most successful polyploids combine the diploid genomes of cytogenetically allied, but differently adapted taxa. 10. Fertility is restored in polyploids through cytological diploidization of the genomes or through gametophytic apomixis. 11. Reversible tetaploidy is part of polyploid evolution.

Biological Evolution↗

PubMed1978

Cytogenetic diagnosis of cancer: abnormalities of chromosomes and polyploid levels in the bone marrow of patients with small cell anaplastic carcinoma of the lung.

The chromosomes of metastatic cells and polyploid levels in the bone marrow of 26 patients with small cell anaplastic carcinoma were studied by direct bone marrow preparation and trypsin-Giemsa banding. Eighteen of these patients had received no tumor therapy and 8 had had chemotherapy and/or radiation therapy; 18 patients, including 5 who had received therapy, had karyotypic abnormalities with or without elevation of the polyploid level. Modal numbers and chromosome abnormalities were highly variable in treated and untreated patients. Modes ranged from hypodiploid to polyploid, but polyploid modes were the most frequently observed abnormal modes. Polyploid modes were not seen, however, in post-therapy patients with the exception of one who had received radiation therapy to the mediastinum for only 4 days prior to withdrawal of the specimen for chromosome analysis. Ten patients had elevated polyploid levels that ranged from 4.24 to 44.8% and always occurred in conjunction with karyotypic abnormalities. Both aneusomy (abnormal number) of normal chromosomes and structural aberrations (markers) occurred frequently. Some markers were consistent within an individual, but other variable aberrations were also typically present. Very few markers were common to 2 or more patients. The no. 1 chromosome participated in marker formation in 14 of the 18 patients with karyotypic abnormalities. Of the 26 patients, 5 were negative for metastasis to the marrow by pathologic examination but positive by cytogenetic diagnosis, whereas none were positive by pathologic examination and negative by cytogenetic diagnosis; this demonstrated that cytogenetics may be used as a rapid adjunct diagnostic procedure for the detection of metastasis in the marrow.

Bone Marrow↗

PubMed1979

Polyploidy and domestication: the origin and survival of polyploids in cytotype mixtures.

The origin and survival of a polyploid in a mixture of this polyploid and its parent(s) is reviewed. With several examples a picture is drawn of the interference of cytotypes in a mixture of cytotypes. Some natural polyploids, both wild and domesticated, are very successful. They, like bread wheat and banana, largely replaced their parents. The same is true for some artificial polyploids like autotriploid hybride sugar beet in Europe and autotetraploid perennial ryegrass. But when grown together with their parents for several generations they will disappear from this misture. Although in South America under primitive conditions, diploid, triploid, and tetraploid potatoes are grown, elsewhere only the tetraploids have survived. Various causes are presented to explain why the diploids and triploids succumbed. Autotetraploids of maize, rye, barley, and rice cannot maintain themselves in diploid/tetraploid mixtures. The maintenance of diploid or tetraploid rye varieties is less difficult as both are "self-cleaning" with respect to the other. Only two haploid cultivars exist but they can only maintain themselves with the help of man. It is concluded that the survival chances of a polyploid after its origination is low. Firstly, under conditions of random sampling a rare type has a very small chance of occurring in the next generation. Furthermore, seedset of triploids and tetraploids is often low which limits their survival. In addition, in mixtures of cross-fertilizing diploid and autotetraploids the n gamete has an advantage over the 2n gamete. This limits the survival of the autotetraploids again. It is concluded that our knowledge of the the mutual interference of cytotypes in a cytotype mixture is quite limited. Much more research is needed and some proposals concerning this research are made.

Agriculture↗

PubMed2024

Interspecific transfer of genetic information through polyploid bridges.

Hybridization blurs species boundaries and leads to intertwined lineages resulting in reticulate evolution. Polyploidy, the outcome of whole genome duplication (WGD), has more recently been implicated in promoting and facilitating hybridization between polyploid species, potentially leading to adaptive introgression. However, because polyploid lineages are usually ephemeral states in the evolutionary history of life it is unclear whether WGD-potentiated hybridization has any appreciable effect on their diploid counterparts. Here, we develop a model of cytotype dynamics within mixed-ploidy populations to demonstrate that polyploidy can in fact serve as a bridge for gene flow between diploid lineages, where introgression is fully or partially hampered by the species barrier. Polyploid bridges emerge in the presence of triploid organisms, which despite critically low levels of fitness, can still allow the transfer of alleles between diploid states of independently evolving mixed-ploidy species. Notably, while marked genetic divergence prevents polyploid-mediated interspecific gene flow, we show that increased recombination rates can offset these evolutionary constraints, allowing a more efficient sorting of alleles at higher-ploidy levels before introgression into diploid gene pools. Additionally, we derive an analytical approximation for the rate of gene flow at the tetraploid level necessary to supersede introgression between diploids with nonzero introgression rates, which is especially relevant for plant species complexes, where interspecific gene flow is ubiquitous. Altogether, our results illustrate the potential impact of polyploid bridges on the (re)distribution of genetic material across ecological communities during evolution, representing a potential force behind reticulation.

Polyploidy↗

PubMedDate not supplied

[Biomass accumulation by polyploid forms of Candida guilliermondii yeasts].

Under the action of a mitotic poison (acenaphthene), the haploid culture of Candida guilliermondii assimilating n-alkanes yielded a polyploid form whose cells were four times larger, on the average, than in the haploid culture. When the pure culture was grown under stationary conditions in media with glucose, the economical coefficient, i. e. the ratio between the assimilated glucose and the accumulated biomass, was by 16, 47 and 157% higher in the polyploid culture than in the haploid one after 24, 48 and 72 hours, respectively. The amount of biomass and the content of protein in it were the same in the haploid and diploid cultures grown in liquid nutrient media with n-alkanes. Cells of the polyploid culture were always larger in media containing n-alkanes, which facilitated separation; no cells were found after it in the cultural fluid. Not all cells of the haploid culture could be separated; therefore, the polyploid culture had the advantage over it. The polyploid cultures of C. guilliermondii were very stable when stored in the lyophilized state. Their morphological and physiological properties did not change within two years.

Alkanes↗

PubMed1976

The ultrastructure of polyploid B-cells in the islets of normal mice.

Light and electron microscopic studies of diploid, tetraploid and octaploid B-cells in the islets of normal C57BL/KsJ mice revealed that polyploid cells were characterized by a wider range of granulated states than diploid B-cells. The maximum granule densities were similar for polyploid and diploid cells; however, some polyploid cells were almost devoid of granules, while the least granulated diploid cells contained intermediate granule densities. The tetraploid cell also appeared to be characterized by an increased mitochondrial stage which suggests compensation for the greater degree of degranulation. These observations were confirmed by morphometric analysis. Two interpretations of the apparent polyploidy are discussed; that polyploid B-cells may be more responsive to insulin releasing stimuli than diploid B-cells and that tetraploid cells may only be diploid cells in the G2 phase of the mitotic cycle.

Animals↗

PubMed2025

Genomic resequencing unravels species differentiation and polyploid origins in the aquatic plant genus Trapa.

Trapa L. is a non-cereal aquatic crop with significant economic and ecological value. However, debates over its classification have caused uncertainties in species differentiation and the mechanisms of polyploid speciation. This study employed whole-genome resequencing together with the fruit morphology of 229 Trapa accessions (153 Asian and 76 North American samples) to elucidate species differentiation and polyploidization events in Trapa. For the species with AA genome and large fruits, clear genetic differentiation was found between two clades with different geographic origins, that is, from the Yangtze River and Amur River basins. The invasive AA species in North America (T. natans) was identified as originating from the Amur River based on genetic and morphological similarities, while all the cultivated accessions were AA species originating from the Yangtze River with severe genetic impoverishment. The separation of the two BB species with small seeds, that is, T. incisa and T. maximowiczii, was strongly supported by both morphological and genetic evidence. For the tetraploids, Asian and North American tetraploids were revealed to have distinct evolutionary origins. Asian allotetraploids (AABB) originated through hybridization between AA diploids from the Yangtze River Basin and BB diploids T. maximowiczii, supported by nuclear and chloroplast evidence. In contrast, the invasive North American tetraploids (T. bispinosa var. iinumai) exhibited an AACC-like genome, suggesting an independent polyploidization involving an unknown "CC" diploid. These findings provide critical insights into Trapa's complex evolutionary history, polyploidizations, and invasive origins, offering a genomic foundation for the conservation and sustainable utilization of the underutilized aquatic crop amid global environmental challenges.

Polyploidy↗

PubMed2025

Distinct evolutionary trajectories of subgenomic centromeres in polyploid wheat.

BACKGROUND: Centromeres are crucial for precise chromosome segregation and maintaining genome stability during cell division. However, their evolutionary dynamics, particularly in polyploid organisms with complex genomic architectures, remain largely enigmatic. Allopolyploid wheat, with its well-defined hierarchical ploidy series and recent polyploidization history, serves as an excellent model to explore centromere evolution. RESULTS: In this study, we perform a systematic comparative analysis of centromeres in common wheat and its corresponding ancestral species, utilizing the latest comprehensive reference genome assembly available. Our findings reveal that wheat centromeres predominantly consist of five types of centromeric-specific retrotransposon elements (CRWs), with CRW1 and CRW2 being the most prevalent. We identify distinct evolutionary trajectories in the functional centromeres of each subgenome, characterized by variations in copy number, insertion age, and CRW composition. By utilizing CENH3-ChIP data across various ploidy levels, we uncover a series of CRW invasion events that have shaped the evolution of AA subgenome centromeres. Conversely, the evolutionary process of the DD subgenome centromeres involves their expansion from diploid to hexaploid wheat, facilitating adaptation to a larger genomic context. Integration of complete einkorn centromere assemblies and Aegilops tauschii pan-genomes further revealed subgenome-specific centromere evolutionary trajectories. By inclusion of synthetic hexaploid from S2-S3 generations, alongside 2x/6 × natural accessions, we demonstrate that DD subgenome centromere expansion represents a gradual evolutionary process rather than an immediate response to polyploidization. CONCLUSIONS: Our study provides a comprehensive landscape of centromere adaptation, evolution, and maturation, along with insights into how retrotransposon invasions drive centromere evolution in polyploid wheat.

Centromere↗

PubMed1979

[Polyploidizing mitoses and the biological meaning of polyploidy in liver cells].

The ontogenetic polyploidization of hepatocytes is regarded, within which normal mitoses are changed to polyploidizing mitoses, and diploid hepatocytes transform into polyploid mono- and binuclear cells. A new hypothesis is put forward of the biological significance of the liver cell polyploidy. The hypothesis takes into account a high level of spontaneous chromosomal aberrations in mitotic hepatocytes. The chromosome structural changes interfere with mitosis resulting in the chromosomal imbalance. Polyploidy bestows for hepatocytes a tolerance towards a chromosomal imbalance. Some implications of the hypothesis are discussed: unbalanced genome of hepatocytes after the treatment with mutagens and mitotic stimulators; the reasons of liver cell polyploidy differences in mammalian species; mechanisms of radioresistance of hepatocytes. Chromosomal imbalance of polyploid hepatocytes is assumed to be the basis for wome chronic liver diseases in man.

Animals↗

PubMed2026

RHAMM drives formation of polyploid cancer cells and confers resistance to ER-targeted therapy in breast cancer.

Endocrine resistance in ER+ breast cancer remains a major clinical challenge. Here, we identify RHAMM as a key driver of resistance by orchestrating polyploid cancer cell (PCC) formation. Single-cell transcriptomics uncovered a G2/M-enriched, RHAMM+ subpopulation in endocrine-resistant tumors. Mechanistically, RHAMM binds Septin9/10 to promote aberrant cytoskeleton polymerization, activating YAP independent of Hippo signaling, which induces cytokinesis failure and facilitates PCC generation. Concurrently, RHAMM destabilizes p21 mRNA, enabling cell cycle progression despite genomic instability. The RHAMM-p21 axis serves as a bypass mechanism supporting polyploidization. Upon endocrine treatment, RHAMM is transcriptionally up-regulated by Slug. Clinically, RHAMMhigh signatures are enriched in metastatic and recurrent ER+ tumors and correlate with poor prognosis, highlighting its therapeutic relevance. Importantly, targeting RHAMM or YAP abrogates PCC formation and restores fulvestrant sensitivity. These findings reveal RHAMM-mediated polyploidization as an adaptive mechanism underlying endocrine resistance, suggesting the therapeutic potential of targeting the RHAMM-YAP axis.

Humans↗

PubMed1979

Physiology of polyploids.

Polyploidy, a multiplication of the whole chromosomal complement, is a very widespread phenomenon in higher plants. Natural polyploids have been suggested to be more successful than their diploid progenitors under certain conditions. This success may be due to "balance hybridity," i.e., the combination of the advantage of hybridity together with the balancing of excessive segregation and sterility by chromosome doubling, and possibly also to the effect of genome multiplication per se. The latter effect can be studied independently of the effect of other genetic changes only in autopolyploid newly derived from single ancestral strains. The existing knowledge on the effect of genome multiplication on the physiology of the plant is fragmentary and based on too narrow a representation of plant types; much of the information available on the effect of genome multiplication pertains to the tomato. Various aspects of polyploidy are discussed according to levels of function and organization: gene action, cell characteristics, growth substance, water balance, ion balance, stability of phenotypic expression and the response of polyploid plants to stress. Future work on the physiology of autopolyploid plants should be directed towards: (1) the investigation of more representative experimental systems that should include genetically homogeneous and heterogeneous species of both wild and cultivated plants; and (2) diploid-polyploid comparisons on the level of isolated tissues and cells, in addition to the whole plant.

Cell Cycle↗

PubMed1979

Evolution of the differential regulation of duplicate genes after polyploidization.

In the 50 million years since the polyploidization event that gave rise to the catostomid family of fishes the duplicate genes encoding isozymes have undergone different fates. Ample opportunity has been available for regulatory evolution of these duplicate genes. Approximately half the duplicate genes have lost their expressions during this time. Of the duplicate genes remaining, the majority have diverged to different extents in their expression within and among adult tissues. The pattern of divergence of duplicate gene expression is consistent with the accumulation of mutations at regulatory genes. The absence of a correlation of extent of divergence of gene expression with the level of genetic variability for isozymes at these loci is consistent with the view that the rates of regulatory gene and structural gene evolution are uncoupled. The magnitude of divergence of duplicate gene expressions varies among tissues, enzymes, and species. Little correlation was found with the extent of divergence of duplicate gene expression within a species and its degree of morphological "conservatism", although species pairs which are increasingly taxonomically distant are less likely to share specific patterns of differential gene expression. Probable phylogenetic times of origin of several patterns of differential gene expression have been proposed. Some patterns of differential gene expression have evolved in recent evolutionary times and are specific to one or a few species, whereas at least one pattern of differential gene expression is present in nearly all species and probably arose soon after the polyploidization event. Multilocus isozymes, formed by polyploidization, provide a useful model system for studying the forces responsible for the maintenance of duplicate genes and the evolution of these once identical genes to new spatially and temporally specific patterns of regulation.

Animals↗

PubMed2025

Unraveling evolutionary pathways: allopolyploidization and introgression in polyploid Prunus (Rosaceae).

Allopolyploidization, resulting from hybridization and subsequent whole-genome duplication (WGD), is a fundamental mechanism driving evolutionary diversification across various lineages within the Tree of Life. The polyploid Prunus (Rosaceae), significant for its economic and agricultural value, provides an ideal model for investigating the evolutionary dynamics associated with allopolyploidy. In this study, we utilized deep genome skimming (DGS) data to demonstrate a comprehensive analytical framework for elucidating the underlying allopolyploidy that includes a newly adapted tool (DGS-Tree2GD) tailored explicitly for accurately detecting WGD events. Additionally, we introduced two methods to evaluate the contribution of incomplete lineage sorting (ILS) to lineage diversification. Phylogenomic discordance analyses revealed that allopolyploidization, rather than ILS, played a dominant role in the origin and dynamics of polyploid Prunus. Moreover, we inferred that the uplift of the Himalayas from the Middle to Late Miocene was a key driver in the rapid diversification of the Maddenia clade, an endemic group in East Asia. This geological event facilitated extensive hybridization and allopolyploidization, particularly the introgression between the Himalayas-Hengduan and Central-Eastern China clades. This case study demonstrates the robustness and efficacy of our analytical approach in precisely identifying WGD events and elucidating the evolutionary mechanisms underlying allopolyploidization in polyploid Prunus.

Polyploidy↗

PubMed2026

Deciphering the mosaic genome of sugarcane cultivars through polyploid admixture inference with AdmixPoly.

BACKGROUND: Characterizing population structure and admixture events between ancestral groups plays a key role in understanding the evolutionary history of species and crops. Most tools for inferring admixture have been developed for diploids and are not suitable for polyploids, in particular those with high and mixed ploidy such as Saccharum. RESULTS: Here we present AdmixPoly, an R-package designed to infer admixture in polyploid species both at the genome-wide scale and locally along chromosomes. We compare AdmixPoly with state-of-the-art methods using simulations, demonstrating its precision and computational efficiency. Notably, local admixture inference in complex scenarios, such as high ploidy levels, large numbers of ancestral groups and alleles per marker is enabled through efficient approximations of emission and transition probabilities within a hidden Markov model framework. We apply this approach to characterize the contributions of wild Saccharum species to the complex polyploid genome of modern sugarcane cultivars. A panel of wild and cultivated Saccharum accessions is genotyped for 80K genomic regions, each revealing approximately 50 read-scale haplotypes. CONCLUSIONS: The results reveal that most of the approximately 12 copies of each basic chromosome in modern cultivars are derived from the domesticated species Saccharum officinarum, with one to four copies typically contributed by distinct subgroups of the wild species Saccharum spontaneum. In addition, contributions from an unknown wild Saccharum group originating from the Pacific were identified in most cultivars. The conserved pattern of these introgressions suggests that they can be traced back to the early stages of sugarcane breeding approximately a century ago.

Saccharum↗

PubMed1976

[A study of the polyploid nuclei of the giant trophoblast cells of several species of rodents using phase contrast microscopy].

Patterns of chromosome morphology in high polyploid trophoblast nuclei of placenta were compared in the rat, rabbit and Microtus arvalis. In the rat and rabbit placenta two types of nuclei were recognized. Some nuclei have ribbon-like chromosomes, while others display thin oligotene fibrils with paired chromomers evenly distributed throughout all karyoplasm. In the latter case, the polytenic structure of chromosomes is seen preserved only near the nucleoli. In the rat and rabbit trophoblast nuclei, the ribbon-like polytene chromosomes could be distinguished only with phase contrast microscopy. In the trophoblast nuclei of Microtus arvalis polytene chromosomes were found only at early stages of embryonic development (9 day old embryo). On later stages of cell differentiation, the chromosomes or chromosome rosetts are seen. Similarities in mechanisms of polyploidization in the high polyploid nuclei of Diptera and in trophoblast nuclei of rodents are discussed.

Animals↗

PubMed1977

Variability of polyploid strains of Candida scottii in accumulation of riboflavin in the medium.

Polyploid strains of Candida scottii show a higher spontaneous and UV-induced variability in accumulation of riboflavin in the medium than the original haploid strain. UV irradiation affects the formation of variants and induces those which accumulate more riboflavin than any of the most productive variants resulting from spontaneous variability. In the polyploid strains the frequency of plus-variants increases. Therefore, polyploid strains of C. scottii are advantageous for selection processes.

Candida↗

PubMed2025

Genomic analyses of three Acanthus L. species provide insight into polyploidization-driven speciation and evolution.

Allopolyploidy fundamentally influences plant evolution, yet the genomic dynamics of allotetraploidization remain incompletely understood. We investigated Acanthus tetraploideus (2n = 4x = 96), an ecologically significant allotetraploid true mangrove from Indo-West Pacific intertidal zones. Our prior integrative investigations indicate that A. tetraploideus originated through hybridization of the diploid species A. ilicifolius and A. ebracteatus with subsequent chromosome doubling. Here, we present complete chromosome-scale genome assemblies for all three species, representing the first genomic resources for true mangrove polyploid research. Our analysis reveals that the three species have experienced at least four rounds of polyploidization events, with the most recent, approximately 53 mya, possibly an Acanthus-specific event. The allotetraploid A. tetraploideus, which emerged between 1.5 and 2.2 mya, has A. ebracteatus as its maternal progenitor and A. ilicifolius as its paternal one. Through a comprehensive genomic comparison and analysis of homoeologous gene expression, we propose a gradual evolutionary trajectory for allotetraploidy in A. tetraploideus. Despite the allotetraploidization event dating back to around 2 mya, A. tetraploideus retains a high degree of colinearity with its ancestral genomes, with the majority (76.2%) of duplicated genes retained and no significant sub-genome bias in gene expression. Furthermore, we have identified positive selection in specific genes that may facilitate the adaptation of Acanthus mangrove species to their intertidal habitats. These findings establish A. tetraploideus as a model for studying allopolyploid evolution while providing new insights into mangrove speciation processes.

Genome, Plant↗

PubMed1979

Normal human endometrium in cell culture. II. A microspectrophotometric study of polyploid nuclei in short-term primary epithelial cultures.

The growth of short-term primary cultures of endometrial epithelium has been studied using Feulgen microspectrophotometry. A gradual increase in the number of polyploid nuclei up to 64C has been observed and is associated with a decline in the growth capacity of the cultures. The specific mechanism(s) of this polyploidization is not known.

Cell Nucleus↗