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PubMed1998

Homothallic life cycle in the diploid red yeast Xanthophyllomyces dendrorhous (Phaffia rhodozyma).

Sexual activity was induced in the basidiomyceteous Phaffia rhodozyma (Xanthophyllomyces dendrorhous) by depletion of nitrogen from the culture medium. This activity involved both mating between two yeast cells and the formation of basidiospores. Mating is possibly started by a G1 phase arrest of the cell cycle, as in other yeasts. The life cycle exhibited homothallic features. Crosses between genetically marked strains, and pulse-field gel electrophoresis of the chromosomal DNA of cells derived from individual spores revealed evidence of karyogamy, meiosis and even recombination. The segregation ratio in tetrads pointed to diploid vegetative cells, which formed tetraploid zygotes and the immediate meiosis then gave rise to diploid progenies again. Apart from the type strain Phaffia rhodozyma CBS 5905, all the examined strains were able to sporulate.

Basidiomycota↗

PubMed2002

Characterization of diploid, tetraploid and hexaploid Helianthus species by chromosome banding and FISH with 45S rDNA probe.

Comparative karyotype analyses of five diploid, two tetraploid, and three hexaploid species of Helianthus were performed using Feulgen staining, Giemsa C and CMA3 (C-CMA) staining, and FISH with 45S rDNA probe. The karyotypes are composed by a basic number of x = 17 with a predominance of meta- and submetacentric chromosome types. A polyploid series is associated with the basic number. Giemsa C- and C-CMA banding revealed terminal or interstitial heterochromatin according to the species, suggesting the existence of a mechanism that may be acting in the dispersion of heterochromatic segments in Helianthus. The nucleolar organizer regions were located at terminal chromosome positions by FISH with 45S rDNA probe. Diploid species presented four, six, and eight rDNA sites, tetraploid species showed eight sites and hexaploid species presented 12 rDNA sites. Karyomorphological differences include variation in number, size and chromosome morphology, suggesting that rearrangements involving small heterochromatic and rDNA segments played a major role in karyotype evolution.

Chromosome Banding↗

PubMed2002

Inheritance of dense spike in diploid wheat and Aegilops squarrosa.

The individuals of diploid wheat Triticum boeoticum, T. monococcum and T. sinskajae and goatgrass Aegilops squarrosa were picked out with screening the dense spike characteristics. The dense-spike accessions were discovered in diploid wheat (T. sinskajae) and Ae. squarrosa. Inheritance of the dense spike was studied. The trait was found to be controlled by a recessive gene in T. sinskajae and by an incomplete dominant gene in Ae. squarrosa. The dosage effect of dominant gene C was detected in interspecific pentaploid F1 hybrid plants T. compactum x T. palmovae (2n =35, A(u)A(b)BDD genome). The spike of pentaploid hybrid was not so dense as compared to hexaploid wheat T. compactum. This is the first report showing similarity of the expression of dominant gene C on D genome of the hexaploid wheat to that of dense spike gene in Ae. squarrosa. The existence of dense-spike accessions of Ae. squarrosa allows us to hypothesize that the origin of T. compactum is independent from that of common wheat.

Diploidy↗

PubMed1980

X-chromosome inactivation in extra-embryonic membranes of diploid parthenogenetic mouse embryos demonstrated by differential staining.

In somatic cells of female mammals one of the two X chromosomes is genetically inactive and heterochromatic, resulting in dosage compensation for X-linked genes. In marsupials the paternally derived X chromosome is preferentially inactivated. In eutherian mammals, although either X chromosome can be inactivated at random in somatic cells, preferential inactivation of the paternally derived X chromosome has been demonstrated cytologically in mouse and rat yolk sac and mouse chorion and biochemically in mouse yolk sac, chorionic ectoderm and trophoblast. In mouse yolk sac the non-random element has been shown both biochemically and cytologically to be confined to the endoderm layer in which there is almost total paternal X-chromosome activity in the separated yolk sac layers of diploid parthenogenetic mouse embryos in which both X chromosomes are maternally derived. Kaufman et al. have demonstrated X inactivation in somatic cells of diploid parthenogenetic embryos, and we have used a modification of Kanda's method, which renders the presumptive inactive X dark staining, to reveal an inactive X chromosome in both endoderm and mesoderm layers of separated yolk sacs from parthenogenones. Thus even in tissues in which there is normally total non-random paternal X inactivation, in the absence of a paternally derived X chromosome a maternally derived X can be inactivated.

Animals↗

PubMed2001

Yesterday's polyploids and the mystery of diploidization.

Thirty years after Susumu Ohno proposed that vertebrate genomes are degenerate polyploids, the extent to which genome duplication contributed to the evolution of the vertebrate genome, if at all, is still uncertain. Sequence-level studies on model organisms whose genomes show clearer evidence of ancient polyploidy are invaluable because they indicate what the evolutionary products of genome duplication can look like. The greatest mystery is the molecular basis of diploidization, the evolutionary process by which a polyploid genome turns into a diploid one.

Animals↗

PubMed2025

Expansion of satellite DNAs derived from transposable elements in beetles with reduced diploid numbers.

Repetitive DNA sequences are ubiquitous in eukaryotic genomes, significantly influencing their structure, function, and evolution. They can facilitate genomic rearrangements, contributing to chromosomal and genomic diversity. Chrysomelidae (Coleoptera) beetles are known for their highly diverse karyotypes and heterochromatin distribution. In this study, we advanced the understanding of the intricate relationship between satellite DNA-like sequences (named here solely as satDNA) and genome organization/reshuffling using three species of Eumolpinae chrysomelids. We investigated the satellitomes of three species with divergent karyotypes that had undergone independent chromosomal fusions: Colaspis laeta (2n = 22, Xyp), with a conserved karyotype; Endocephalus bigatus (2n = 10, neo-XY); and Iphimeis dives (2n = 14, neo-XY). Our comparative analysis revealed highly divergent patterns of satDNA origin, organization, and evolution. In species with reduced chromosome numbers and neo-sex chromosomes, we observed a high abundance of transposable element-related (TE-related) satDNAs. In Colaspis laeta, the sex chromosomes (Xyp) showed an advanced level of differentiation. However, in the species with a reduction in diploid number, such a level of differential enrichment of repetitive DNAs was not observed in the sex chromosomes, indicating an early stage of differentiation. Our findings support the hypothesis that chromosomal rearrangements and reorganization of repetitive DNA sequences are connected, with extensive reshuffling observed in species with reduced diploid numbers. Moreover, the data reinforce the involvement of TEs in satDNA origin, which could spread widely throughout the genome, including euchromatic areas. This study provides new insights into the evolutionary dynamics of repetitive DNAs in non-model species, emphasizing the impact of chromosomal rearrangements on genome architecture and evolution.

Animals↗

PubMed2025

The reference genome of the human diploid cell line RPE-1.

Recent technological advances have facilitated the assembly of telomere-to-telomere (T2T) genomes. The current T2T CHM13 showcases the complete architecture of the human genome, yet its use in functional experiments is limited by discrepancies with the actual genome of the specific biological system under study. Access to reference assemblies for experimentally relevant cell lines is therefore essential in advancing sequencing-based analyses and precise manipulation, particularly in highly variable regions such as centromeres. Here, we present RPE1v1.1, the near-complete diploid genome assembly of the hTERT RPE-1 cell line, a non-cancerous human retinal epithelial model with a stable karyotype. Using high-coverage Pacific Biosciences and Oxford Nanopore Technologies long-read sequencing, we generate a high-quality de novo assembly, validate it through multiple methods, and phase it by integrating high-throughput chromosome conformation capture (Hi-C) data. Our assembly includes chromosome-level scaffolds that span centromeres for all chromosomes. Comparing both haplotypes with the CHM13 genome, we detect haplotype-specific genomic variations, including the translocation between chromosome 10 and chromosome X t(X;10)(Xq28;10q21.2) characteristic of RPE-1 cells, and divergence peaking at centromeres. Altogether, the RPE1v1.1 genome provides a reference-quality diploid assembly of a widely used cell line, supporting high-precision genetic and epigenetic studies in this model system.

Humans↗

PubMed2004

Genetic relationships between diploid and allotetraploid cherry species (Prunus avium, Prunus x gondouinii and Prunus cerasus).

Prunus avium L. (diploid, AA, 2n=2x=16), Prunus cerasus L. (allotetraploid, AAFF, 2n=4x=32) species, and their hybrid Prunus x gondouinii Rehd., constitute the most widely cultivated cherry tree species. P. cerasus is supposed to be an hybrid species produced by the union of unreduced P. avium gametes and normal P. fruticosa gametes. A continuum of morphological traits between these three species makes their assignation difficult. The aim of this paper is to study the genetic relationships between tetraploid and diploid cherry species. In all, 114 genotypes belonging to these species were analyzed using 75 AFLP markers. The coordinates of these genotypes on the first axis of a correspondence analysis allowed us to clearly distinguish each species, to identify misclassifications and to assign unknown genotypes to one species. We showed that there are specific alleles in P. cerasus, which are not present in the A genome of P. avium and which probably come from the F genome of P. cerasus. The frequencies of each marker in the A and the F genomes were estimated in order to identify A and F specific markers. We discuss the utility of these specific markers for finding the origin of the A and F genomes in the allopolyploid species.

Diploidy↗

PubMed1977

Partial diploids of Escherichia coli carrying normal and mutant alleles affecting oxidative phosphorylation.

A plasmid was isolated which included the region of the Escherichia coli chromosome carrying the known genes concerned with oxidative phosphorylation (unc genes). This plasmid was used to prepare partial diploids carrying normal unc alleles on the episome and one of the three mutant alleles (unc A401, uncB402 or unc-405) on the chromosome. These strains were compared with segregants from which the plasmid had been lost. Dominance of either normal ormutant unc alleles was determined by growth on succinate, growth yields on glucose, Mg-ATPase (Mg2+-stimulated adenosine triphosphatase) activity, atebrin-fluorescence quenching, ATP-dependent transhydrogenase activity and oxidative phosphorylation. In all the above tests, dominance of the normal allele was observed. However, in membranes from the diploid strains which carried a normal allele and either of the mutant alleles affecting Mg-ATPase activity (uncA401 or unc-405), the energy-linked functions were only partially restored.

Adenosine Triphosphatases↗

PubMed2000

Mating systems of diploid and allotetraploid populations of Tragopogon (Asteraceae). II. Artificial populations.

Polyploidization has long been recognized as an important force in the diversification of plants. Theoretical models predict that polyploids may be expected to exhibit higher rates of self-fertilization than do closely related diploid species. Wild populations of the neopolyploid Tragopogon mirus (4n) exhibited slightly higher rates of outcrossing than did populations of one of its progenitors, T. dubius (2n). In the current study, outcrossing rates in populations of T. dubius and T. mirus were estimated using artificial arrays constructed to maximize the chances of detecting outcrossing events. The artificial diploid population is more highly outcrossing (t=0.727; family-level estimates range from 0.00 to 1. 32) than the tetraploid population (t=0.591; family-level estimates range from 0.00 to 1.14), although the difference between them is not statistically significant. The results of this study, combined with those of the previous work on wild populations, suggest that mating systems in these species vary more among populations than between ploidal levels. This could be because of the relatively recent origins of the tetraploid species; there may have been insufficient time since the formations of the tetraploids for shifts in mating systems to occur.

Alleles↗

PubMed2001

Physical locations of 5S and 18S-25S rDNA in Asian and American diploid Hordeum species with the I genome.

The physical locations of 5S and 18S-25S rDNA sequences in 15 diploid Hordeum species with the I genome were examined by double-target in situ hybridization with pTa71 (18S-25S rDNA) and pTa794 (5S rDNA) clones as probes. All the three Asian species had a species-specific rDNA pattern. In 12 American species studied, eight different rDNA types were found. The type reported previously in H. chilense (the 'chilense' type) was observed in eight American species. The chilense type had double 5S rDNA sites - two sites on one chromosome arm separated by a short distance - and two pairs of major 18S-25S rDNA sites on two pairs of satellite chromosomes. The other seven types found in American species were similar to the chilense type and could be derived from the chilense type through deletion, reduction or addition of a rDNA site. Intraspecific polymorphisms were observed in three American species. The overall similarity in rDNA patterns among American species indicates the close relationships between North and South American species and their derivation from a single ancestral source. The differences in the distribution patterns of 5S and 18S-25S rDNA between Asian and American species suggest differentiation between the I genomes of Asian and American species. The 5S and 18S-25S rDNA sites are useful chromosome markers for delimiting Asian species, but have limited value as a taxonomic character in American species. On the basis of rDNA patterns, karyotype evolution and phylogeny of the I-genome diploid species are discussed.

Americas↗

PubMed1986

Antibody response to preexposure human diploid-cell rabies vaccine given concurrently with chloroquine.

We conducted a randomized controlled trial to evaluate the antibody response of freshman veterinary students to intradermal human diploid-cell rabies vaccine administered concurrently with chloroquine, a drug frequently used for chemoprophylaxis against malaria. Fifty-one students who had not been vaccinated against rabies were enrolled: 26 received 300 mg of chloroquine base per week (the recommended dose for malaria prophylaxis); 25 did not receive chloroquine and served as controls. All subjects received 0.1 ml of rabies vaccine intradermally on days 0, 7, and 28. Chloroquine was administered weekly to the treatment group, beginning nine days before the first dose of vaccine and continuing until day 48. The mean rabies-neutralizing antibody titer for the chloroquine group was significantly lower than that for the control group on each day of testing--i.e., day 28 (P = 0.0094), day 49 (P = 0.0008), and day 105 (P = 0.0002)--although both groups had neutralizing antibody titers on days 49 and 105, according to the criteria of the Centers for Disease Control. The blood concentrations of chloroquine and desethylchloroquine (the major metabolite of chloroquine, which also has antimalarial properties) were negatively associated with log antibody titers. These results indicate that chloroquine taken in the dose recommended for malaria prophylaxis can reduce the antibody response to primary immunization with intradermal human diploid-cell rabies vaccine.

Adult↗

PubMed1995

Development of the gonads in the triploid (ZZW and ZZZ) fowl, Gallus domesticus, and comparison with normal diploid males (ZZ) and females (ZW).

Gonadal development in fowls aged from 1 day to more than 4.5 years was studied in 63 ZZW and 16 ZZZ triploid crossbreds and compared with normal diploid males (ZZ) and females (ZW). In the ZZW fowl, the right gonad developed into a testis (although this occurred earlier in the ZZ genotype), and a structurally-abnormal excurrent duct system containing some malformed spermatids and spermatozoa was associated with the gonad of young adults. The left gonad was an ovotestes at hatching and no excurrent ducts were associated with it. The ovarian component was much less developed than that in the ZW genotype-it started to degenerate by 1 week of age, and most of the oocytes had disappeared by about 3 weeks of age. The seminiferous tubules developed in the medullary region, but only abnormal spermatozoa were produced. Leukocytes infiltrated both gonads at about 9 months of age and the seminiferous epithelium had degenerated in most fowls over 1 year old. In ZZZ fowl, gonadal and excurrent duct development was normal, but occurred earlier than in the ZZ genotype. However, meiosis and spermiogenesis were abnormal and malformed spermatozoa were produced. The heads of spermatozoa from the ducts deferens were about 1.4-times longer in the ZZZ genotype than in the ZZ genotype, indicating that the former may be producing some diploid spermatozoa.

Animals↗

PubMed2003

Refractory nature of normal human diploid fibroblasts with respect to oncogene-mediated transformation.

Human cells are known to be more refractory than rodent cells against oncogenic transformation in vitro. To date, the molecular mechanisms underlying such resistance remain largely unknown. The combination of simian virus 40 early region and H-Ras V12 has been effective for transformation of rat embryo fibroblasts, but not for human cells. However, the additional ectopic expression of the telomerase catalytic subunit (hTERT) was reported to be capable of causing transformation of normal human cells. In this study, however, we demonstrate that the combined expression of the above-mentioned three genetic elements is not always sufficient to transform normal human diploid fibroblasts (HDF). Although the expression and function of these introduced genetic elements were essentially the same, among four HDF, TIG-1 and TIG-3 were resistant to transformation. The other two (BJ and IMR-90) showed transformed phenotypes, but they were much restricted compared with rat embryo fibroblasts in expressing simian virus 40 early region and H-Ras V12. In correlation with these phenotypes, TIG-1 and TIG-3 remained diploid after the introduction of these genetic elements, whereas BJ and IMR-90 became highly aneuploid. These results strongly suggest that the lack of telomerase is not the sole reason for the refractory nature of HDF against transformation and that normal human cells have still undefined intrinsic mechanisms rendering them resistant to oncogenic transformation.

Animals↗

PubMed1969

Evidence for intergenic complementation in hybrid cells derived from two human diploid strains each carrying an X-linked mutation.

Two male diploid fibroblast strains, each carrying deficiency mutations at different X-linked loci (glucose-6-phosphate dehydrogenase and hypoxanthine-guanine-phosphoribosyltransferase) have been successfully hybridized. The resulting mononucleated hybrid cells have been shown to synthesize both normal gene products, indicating that both X chromosomes are functionally active in the hybrid cells. We believe this is the first reported example of intergenic complementation in fused human diploid cells.

Autoradiography↗

PubMed1970

Interallelic complementation in hybrid cells derived from human diploid strains deficient in galactose-1-phosphate uridyl transferase activity.

Galactose-1-phosphate uridyl transferase activity has been demonstrated in hybrid cells formed from the fusion of human diploid fibroblasts obtained from different patients with galactosemia. The enzyme produced by the hybrid cells was similar to the normal enzyme in regard to K(m), pH optimum, and electrophoretic mobility on starch gel, but differed in specific activity, V(max) and thermal stability. This is the first reported example of interallelic complementation in fused human diploid cells.

Alleles↗

PubMed1972

Detection and quantitation of simian virus 40 genetic material in abortively transformed BALB-3T3 clones (mice-diploid cells-virus equivalents).

Infection with simian virus 40 is known to induce many cells to synthesize DNA and to divide in a medium lacking serum protein growth factor(s) that is essential for growth of uninfected cells (factor-free medium). Cells infected under these conditions then go through several rounds of division, since colonies containing more than 100 cells are formed. Many of these colonies are abortively transformed since, upon subsequent passage of the cells in standard medium, they can no longer grow in factor-free medium and show no other properties of viral transformation. We have examined these abortively transformed cells for the presence of simian virus 40 DNA sequences. Of the three clones tested, two were found to contain viral genetic material despite the fact that they were phenotypically normal. The number of simian virus 40 genome equivalents present was determined by measurement of DNA reassociation kinetics on hydroxyapatite. Two of the abortively transformed lines contained approximately five viral genome equivalents per diploid cell, while the DNA from a third abortive transformant was indistinguishable from that of uninfected BALB/3T3 cells. A standard simian virus 40 transformant, isolated under similar conditions, contained two copies of the viral genome per cell. The abortive transformants also appear to contain the entire viral genome rather than multiple partial copies. Subclones of one abortively transformed line containing five copies per cell had 2.7-10 copies of viral genetic material per diploid cell.

Animals↗

PubMed1974

An analysis of survival in haploid and diploid cell cultures after exposure to ICR acridine half-mustard compounds mutagenic for bacteria.

Population changes induced by acridine mustards in haploid and diploid cultured cell lines from Rana pipiens were compared to test the expectation that recessive mutations will be expressed in diploid cells with a frequency equal to the square of that in haploid cells, and to investigate the usefulness of such comparison for the screening of possible mutagens. The differences in survival frequency after treatment were much smaller than predicted on the basis of the expression of lethal (recessive) mutations alone. Survival was also affected by culture conditions, drug-resistance phenomena, and other cell properties. It is suggested that with the evolution of epigenetic processes for the production of stable phenotypes, the vertebrate cell also acquired more efficient means to prevent the expression of gene mutation and that the acridine compounds may affect both epigenetic and genetic changes.

Acridines↗