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PubMed2000

Chromosomal rearrangement in autotetraploid plants of Arabidopsis thaliana.

Recent development of cytogenetic techniques has facilitated significant progress in Arabidopsis thaliana karyotype studies. Double-target FISH with rRNA genes provides makers that allow individual chromosome in the genome to be distinguished. Those studies have revealed that the number and position of rDNA loci is ecotype-specific. Arabidopsis is believed to be a true diploid (x = 5) with numerous ecotypes (accessions) and only a very few natural polyploid populations reported. Few studies were undertaken to induce polyploidy in Arabidopsis, however none of those gave the cytogenetic characteristics of polyploid plants. Our analysis of chromosome pairing of colchicine-induced autotetraploid Arabidopsis (Wilna ecotype) revealed preferential bivalent pairing in PMCs (pollen mother cells). In order to attempt to explain this phenomenon, first of all more detailed cytogenetic studies of autopolyploid plants have been undertaken. The localization of 45S and 5S rDNA loci in the diploid and autotetraploid plants revealed that Wilna ecotypes belongs to the group of Arabidopsis accessions with only two 5S rDNA loci present in a genome. Furthermore, the rearrangement of 45S rDNA locus in autopolyploid, when compared to the diploid plants of the same ecotype, was revealed. These results are interesting also in the context of the recently emphasised role of polyploidy in plant evolution and speciation. Arabidopsis, despite having small chromosomes, is a good system to study chromosome behaviour in relation to diploidization of autopolyploids and to evaluate the degree of chromosomal rearrangements during this process.

Arabidopsis↗
PubMed2004

Genetic relationships among Aster species by multivariate analysis and AFLP markers.

Fourteen species of Aster were characterized for morphological traits of commercial interest, chromosome number and genetic diversity by AFLP markers to exploit this material not only for breeding purposes but also as source of pharmaceuticals. The variation observed among the Aster species for five morphological traits was summarized by means of discriminant analysis. Three significant canonical variables, accounting for about 96% of total variance, were mainly correlated with capitulum diameter, number of ligulae and leaf length. The morphological variation appeared related to ploidy level of the species. A diploid chromosome number ranging from 10 to 18 was evident in seven species whereas the other species are polyploids with variable chromosome numbers up to 52. The pollen production and stainability were quite variable among Aster species. Furthermore, seven species produced big pollen grains besides normally-sized ones, at a frequency ranging from 1 to 12%, possibly due to 2n pollen production. The possibility that evolution of Aster genus could be driven by 2n gametes and sexual polyploidization is discussed. Implications of 2n gametes for Aster breeding are also mentioned. AFLP analysis of the fourteen Aster species based on six primer combinations revealed a total number of 421 polymorphic amplified DNA fragments. The genetic similarities estimated between the Aster species, based on both shared and unique amplification products ranged from 0.335 to 0.604 across all species and revealed a geographically based clustering within the genus. The highest similarity was detected between A. alpinus and A. amellus with Eurasian origin.

Aster Plant↗
PubMed1975

Karyometry of liver biopsies in virus hepatitis.

Liver biopsies from ten patients with clinically mild or moderate acute virus hepatitis, taken in the acute phase of the disease and in the recovery phase or later, were assessed for the size of liver cell nuclei and the number of binuclear nuclei. A parametric model of the distributions of the nuclear radii was used to estimate the mean nuclear radius of diploid nuclei and the frequencies of di-, tetra- and octaploid nuclei. During the acute phase of virus hepatitis the liver cell nuclei were often larger, with greater variation in size, than in the recovery phase. This pleomorphism was not only due to pyknotic and necrotic nuclei as these were not measured. It is assumed that the enlargment of the nuclei was due to increased metabolic activity of the nuclei. The frequencies of polyploid nuclei and binuclear liver cells were higher in the first biopsies, probably reflecting regenerative activity. No correlation was found between the severity of the disease as judged by liver histology or routine liver tests and the degree of nuclear changes with respect to size and frequency of polyploid or binuclear liver cells.

Acute Disease↗
PubMed1999

Spermatocytic seminoma as compared to classical seminoma: an immunohistochemical and DNA flow cytometric study.

UNLABELLED: Based on immunohistochemistry (IHC) and DNA ploidy, different paths of carcinogenesis have been suggested for spermatocytic seminoma (SS) and classical seminoma (CS). The present study extends current knowledge on the above parameters. METHOD: Seventeen SSs and twenty-two CSs were assessed by IHC for placental-like alkaline phosphatase (PLAP), c-kit, cytokeratin and adhesion carbohydrate molecyles. All SSs and 11 CSs were also analysed for DNA ploidy. RESULTS: All CSs, but none of the SSs, were positive for PLAP. C-kit positivity was found in 7 of 17 SSs and in all CSs. The other IHC parameters were similarly distributed among the evaluated SSs and CSs. Fourteen SSs were diploid or polyploid, and three were aneuploid. All CSs were aneuploid. CONCLUSION: The new observation of c-kit positivity in about 40% of SSs suggests that at least some of the SSs originate from primordial cells. The predominantly diploid or polyploid DNA pattern indicates that SSs follow a pathogenetic pathway which is most probably different from that of CSs.

Adult↗
PubMed2026

A robust biotechnology induces artificial genomic duplication via transient RNAi-mediated suppression of OSD1 in rice.

Ploidy manipulation is a crucial strategy for generating germplasm in crop breeding. However, artificial genomic duplication, often induced by colchicine treatment, is associated with toxicity and unpredictability. Although mutations in OSD1 have shown promise for inducing genomic duplication, the instability of ploidy across generations limits their practical application. In this study, we developed a Plant Polyploidization via Gene Interference (PPGI) system that utilizes transient RNAi-mediated suppression of OSD1 to efficiently induce artificial genomic duplication, demonstrating obvious potential for producing autotetraploids. We first validated this system by successfully generating PPGI-induced autotetraploid plants from the Taichung65 cultivar. These PPGI-induced plants exhibited notable differences from Taichung65 but resembled the existing Taichung65-4x line obtained through colchicine treatment. Haplotype analysis indicated that the OSD1 RNAi fragment is conserved across 2,908 rice cultivars. Consequently, we employed the same PPGI vector to develop autotetraploid lines from various germplasms, including another japonica cultivar, seven indica cultivars, and one Oryza rufipogon line. The probability of genomic duplication achieved by our PPGI method was higher than that obtained by colchicine treatment. Typically, autotetraploid lines exhibit severe sterility in the first generation following polyploidization. Leveraging fertile neo-tetraploid rice and the PPGI system, we designed and verified two strategies to directly induce fertile autotetraploid germplasms in the first generation, thereby substantially shortening the breeding cycle. Our method provides a universal, efficient, and non-toxic approach for inducing autotetraploid rice germplasms and contributes to enriching fertile autotetraploid rice germplasm resources.

OSD1↗
PubMed2025

Restoring cytonuclear harmony: Distinct strategies in Arabidopsis auto- and allopolyploids.

Plants rely on tight coordination between nuclear, mitochondrial, and chloroplast genomes to form essential multi-enzyme cytonuclear complexes. Whole-genome duplication (WGD) doubles the nuclear genome, potentially disrupting cytonuclear stoichiometry unless organellar genomes respond accordingly. Targeted analyses of chloroplasts and mitochondria enabled us to dissect the extent and mechanisms of adjustments in both organelles immediately after WGD and across generations in Arabidopsis auto- and allopolyploids. We observed a substantial overcompensation of organellar genome copies in both organelles in early-generation autotetraploids primarily through multiplication of DNA copies within organelles rather than increasing the number of organelles. Despite higher DNA content, mitochondria maintained their volume, and chloroplasts were even smaller. In successive generations, chloroplast DNA copy numbers continued to rise, whereas mitochondrial DNA copies declined. Gene expression patterns also differed between chloroplasts and mitochondria and between auto- and allopolyploids. In autopolyploids, immediate transcriptional changes were minimal, but by the fourth generation after WGD, nuclear genes involved in mitochondria-nuclear complexes were downregulated. In allopolyploids, transcriptional changes appeared immediately in the first generation (chloroplast genes were upregulated and mitochondrial genes were downregulated). Our findings demonstrate that cytonuclear balance is restored through dynamic, organelle-specific, and polyploid-type-specific mechanisms. These insights advance our understanding of the evolution of polyploid genomes.

Arabidopsis↗
PubMed2026

A spatiotemporal resolution to genetic redundancy: MIR164 diversification coordinates development and metabolism in Brassica.

Whole-genome duplication (WGD) events create genetic redundancy, posing the evolutionary challenge of how paralogs escape functional overlap to drive innovation. Here, we demonstrate that the MIR164 family in Brassica oleracea resolves this redundancy through spatiotemporal niche partitioning. Following WGD, the family expanded to eight members, which subsequently underwent divergent selection-some preserved under purifying selection, while others showed signals of positive selection. This led to expression divergence, with Bol-MIR164a1 emerging as a key universally expressed paralog. CRISPR-Cas9 mutagenesis of Bol-MIR164a1 revealed its essential role in coordinating two pivotal traits: leaf serration and leaf coloration. Mutants exhibited enhanced leaf serration due to spatial deregulation of CUC2 at organ boundaries, concurrently with yellow-green leaves and elevated flavonoid accumulation. We mechanistically linked the metabolic phenotype to direct transactivation of the anthocyanidin reductase (ANR) promoter by NAC100, alongside its upregulation of chlorophyll catabolism genes. Our findings establish a paradigm in which spatial segregation of target gene expression domains enables a single, widely expressed miRNA paralog to resolve genetic redundancy by independently orchestrating distinct regulatory programs. This provides a fundamental framework for understanding complex trait evolution in polyploids. This allows a single miRNA locus to independently orchestrate both morphological patterning and metabolic programming, providing a fundamental framework for understanding complex trait evolution in polyploid crops.

MicroRNAs↗
PubMed1985

Phenotypic expression of Kluyveromyces lactis killer toxin against Saccharomyces spp.

The secretion of killer toxins by some strains of yeasts is a phenomenon of significant industrial importance. The activity of a recently discovered Kluyveromyces lactis killer strain against a sensitive Saccharomyces cerevisiae strain was determined on peptone-yeast extract-nutrient agar plates containing as the carbon source glucose, fructose, galactose, maltose, or glycerol at pH 4.5 or 6.5. Enhanced activity (50 to 90% increase) was found at pH 6.5, particularly on the plates containing galactose, maltose, or glycerol, although production of the toxin in liquid medium was not significantly different with either glucose or galactose as the carbon source. Results indicated that the action of the K. lactis toxin was not mediated by catabolite repression in the sensitive strain. Sensitivities of different haploid and polyploid Saccharomyces yeasts to the two different killer yeasts S. cerevisiae (RNA-plasmid-coded toxin) and K. lactis (DNA-plasmid-coded toxin) were tested. Three industrial polyploid yeasts sensitive to the S. cerevisiae killer yeast were resistant to the K. lactis killer yeast. The S. cerevisiae killer strain itself, however, was sensitive to the K. lactis killer yeast.

Fructose↗
PubMed1996

Alleviation of glucose repression of maltose metabolism by MIG1 disruption in Saccharomyces cerevisiae.

The MIG1 gene was disrupted in a haploid laboratory strain (B224) and in an industrial polyploid strain (DGI 342) of Saccharomyces cerevisiae. The alleviation of glucose repression of the expression of MAL genes and alleviation of glucose control of maltose metabolism were investigated in batch cultivations on glucose-maltose mixtures. In the MIG1-disrupted haploid strain, glucose repression was partly alleviated; i.e., maltose metabolism was initiated at higher glucose concentrations than in the corresponding wild-type strain. In contrast, the polyploid delta mig1 strain exhibited an even more stringent glucose control of maltose metabolism than the corresponding wild-type strain, which could be explained by a more rigid catabolite inactivation of maltose permease, affecting the uptake of maltose. Growth on the glucose-sucrose mixture showed that the polypoid delta mig1 strain was relieved of glucose repression of the SUC genes. The disruption of MIG1 was shown to bring about pleiotropic effects, manifested in changes in the pattern of secreted metabolites and in the specific growth rate.

DNA-Binding Proteins↗
PubMed2001

Trichinella spiralis-infected muscle cells: abundant RNA polymerase II in nuclear speckle domains colocalizes with nuclear antigens.

Infection of mammalian skeletal muscle cells by Trichinella spiralis causes host nuclei to become polyploid (ca. 4N) and abnormally enlarged. It has been postulated that this enlargement reflects an infection-induced elevation of host transcription. Anthelmintic treatment of T. spiralis-infected rodents with mebendazole (MBZ) causes a reduction in the size of infected cell nuclei and a significant reduction in the total RNA content of individual infected muscle cells. A monoclonal antibody to the large subunit of RNA polymerase II (Pol II) was used here to assess the effects of infection on Pol II levels in isolated infected cell nuclei. Pol II was localized to speckle domains in isolated infected cell nuclei. Similar domains have been previously localized to sites of RNA synthesis or processing. When compared to the levels in nuclei from other, uninfected host cells, speckle-localized Pol II (SL-Pol II) levels were significantly elevated in infected cell nuclei by a mean of 3.9- to 6.8-fold. Nuclear antigens (NA) recognized by antibodies against T. spiralis localized to infected cell nuclei. By use of confocal microscopy, a subpopulation of NA was found colocalized with most speckle domains defined by Pol II. MBZ treatment of chronically infected mice, which depletes NA from infected cell nuclei, caused a significant depletion of SL-Pol II from infected cell nuclei. Control nuclei had a mean of 70% more SL-Pol II than MBZ-treated nuclei. The mean residual level of Pol II in these polyploid nuclei remained elevated by 120% over the level in 2N control nuclei. These observations may indicate two distinct effects of infection on Pol II levels in host cells.

Animals↗
PubMed1994

Correlation between polyploidy and auxotrophic segregation in the imperfect yeast Candida albicans.

In order to clarify the relationship between polyploidization and the capability of phenotypic switching in the imperfect yeast Candida albicans, two types of variants were isolated as segregants from a fusant, which produced a proportion of the cell population with a higher ploidy than the rest, either in a temperature-dependent or -independent manner, when incubated at low (28 degrees C) and high (37 degrees C) temperatures. In the case of the temperature-dependent type of variants, high-ploidy cells appeared at 37 degrees C but rarely at 28 degrees C. This phenotype was named Pldts (temperature-sensitive polyploidization), and the temperature-independent phenotype was called Pld-. The appearance of high-ploidy cells in the culture of the Pldts strain at 37 degrees C was accompanied by a significant increase in the frequency of auxotrophic variants; these variants probably occur as a result of segregation of auxotrophic markers from the heterozygous to the homozygous state. Both Pldts and Pld- phenotypes were recessive in a fusion with a Pld+ parent. An adenine auxotrophic marker (ade1) was introduced into a Pldts strain in a heterozygous state, and the individual high-ploidy cells of this strain, grown at 37 degrees C, were micromanipulated to form colonies, which consisted of red and white sectors appearing at high frequency on a pink background. When the ade1 auxotrophy was introduced into Pld- strains, frequently sectored colonies were produced. These results suggested an increased level of chromosome missegregation in both types of Pld mutants. Analyses by pulsed-field gel electrophoresis of Ade-segregants, derived from a micromanipulated high-ploidy cell of a Pld(ts) strain, suggested the occurrence of nonreciprocal recombination, some of which includes chromosome loss.

Adenine↗
PubMed1996

Essential and nonessential histone H2A variants in Tetrahymena thermophila.

Although variants have been identified for every class of histone, their functions remain unknown. We have been studying the histone H2A variant hv1 in the ciliated protozoan Tetrahymena thermophila. Sequence analysis indicates that hv1 belongs to the H2A.F/Z type of histone variants. On the basis of the high degree of evolutionary conservation of this class of histones, they are proposed to have one or more distinct and essential functions that cannot be performed by their major H2A counterparts. Considerable evidence supports the hypothesis that the hv1 protein in T. thermophila and hv1-like proteins in other eukaryotes are associated with active chromatin. In T. thermophila, simple mass transformation and gene replacement techniques have recently become available. In this report, we demonstrate that either the HTA1 gene or the HTA2 gene, encoding the major H2As, can be completely replaced by disrupted genes in the polyploid, transcriptionally active macronucleus, indicating that neither of the two genes is essential. However, only some of the HTA3 genes encoding hv1 can be replaced by disrupted genes, indicating that the H2A.F/Z type variants have an essential function that cannot be performed by the major H2A genes. Thus, an essential gene in T. thermophila can be defined by the fact that it can be partially, but not completely, eliminated from the polyploid macronucleus. To our knowledge, this study represents the first use of gene disruption technology to study core histone gene function in any organism other than yeast and the first demonstration of an essential gene in T. thermophila using these methods. When a rescuing plasmid carrying a wild-type HTA3 gene was introduced into the T. thermophila cells, the endogenous chromosomal HTA3 could be completely replaced, defining a gene replacement strategy that can be used to analyze the function of essential genes.

Animals↗
PubMed2005

Changes to hepatocyte ploidy and binuclearity profiles during human chronic viral hepatitis.

BACKGROUND AND AIMS: The importance of the hepatocyte ploidisation pattern to the control of cell proliferation and differentiation has been well established. However, there are no data that have characterised hepatocyte ploidy at various stages of chronic liver inflammation and fibrosis in vivo. METHODS: We therefore investigated hepatocyte ploidy/binuclearity patterns in 57 patients with chronic hepatitis, using a recently developed methodology which allows simultaneous hepatocyte ploidy and binuclearity analyses on the same liver section. RESULTS: The percentage of mononuclear diploid hepatocytes was significantly reduced in patients with high hepatitis activity and marked fibrosis (low activity: 75.1 (18.8)% v high activity: 61.8 (21.6)%, p=0.0111, and low fibrosis: 77.3 (13.8)% v high fibrosis: 57.4 (23.3)%, p=0.0002). Accordingly, the percentage of mononuclear polyploid hepatocytes increased in patients with high hepatitis activity and marked fibrosis (low activity: 11.9 (15.5)% v high activity: 22.2 (20.1)%, p=0.0166, and low fibrosis: 9.4 (10.7)% v high fibrosis: 26.4 (21.6)%, p=0.0001). In addition, the fraction of binuclear hepatocytes was significantly higher in patients with hepatitis B virus (HBV) than in those with hepatitis C virus (HCV) infections (HBV: 18.2 (7.6)% v HCV: 12.0 (4.8)%; p=0.0020). Under multivariate analysis, HBV infection was an independent factor accounting for the larger binuclear hepatocyte fraction (p=0.0294). CONCLUSION: Our results revealed an increase in the polyploid hepatocyte fraction which correlates with the severity of chronic hepatitis; moreover, we demonstrated that HBV and HCV related chronic hepatitis exhibited distinctive hepatocyte ploidy patterns, thus allowing the suggestion that these two viral infections may modulate liver ploidy through different mechanisms.

Adult↗
PubMed1976

Chromosomal characterisation of five lepidopteran cell lines of Malacosoma disstria (Lasiocampidae) and Christoneura fumiferana (Tortricidae).

Chromosome number and morphology have been examined in four established cell lines (Md63, Md66, Md108, and Md109) of the forest tent caterpillar, Malacosoma disstria Hübner, and one (Cf124) of the spruce budworm, Choristoneura fumiferana (Clemens). Chromosome number distributions of Md63 (mode = 112) Md108 (mode = 103), Md109 (mode= 103), and Cf124 (mode = 110) overlap sufficiently to prevent identification of individual lines by number alone. However, Md66 is exceptional in possessing a modal number of 157. One large chromosome occurs in cells of all lines. The presence of this chromosome, the lack of any distinct polyploid series among chromosome numbers encountered, and the general inverse relationship between number and size of chromosomes, suggest that the high level of heteroploidy characteristic of these and other lepidopteran cell lines reflects not only a possible polyploid origin but also extensive chromosomal rearrangement and fragmentation. Tolerance for such change is attributed to the holokinetic organisation of lepidopteran chromosomes. A distinct heteropycnotic body is present in about 10% of Cf124 cell nuclei, and can be used as a marker for this line. This body may represent the sex chromatin normally encountered in somatic cells of female C. fumiferana.

Cell Line↗
PubMed1980

Comparative karyology of the freshwater snails Bulinus tropicus and B. natalensis.

Species of the subgenus Bulinus s.s. occur in a polyploid series which is of interest because of the rarity of polyploidy in animal species and because there appears to be a relation between ploidy level and ability to transmit Schistosoma haematobium, a parasite of major public health importance. We describe a technique for the preparation of standard karyotypes using cell suspensions from colchicine-treated embryos. The results for two diploid species, B. tropicus (Krauss) and B. natalensis (Küster), are presented. Both karyotypes consist of 15 metacentric and 3 submetacentric chromosomes. However, differences in centromere position are found in four pairs of chromosomes, and in the appearance of a secondary constriction. Because B. natalensis may represent a relict taxon involved in the origin of the polyploids, the results of significance for future work on the phylogeny of this group.

Animals↗
PubMed1992

Influence of chronic nadolol treatment on blood pressure and vascular changes in spontaneously hypertensive rats.

Chronic treatment of spontaneously hypertensive rats (SHR) and Kyoto-Wistar normotensive rats (WKY) with nadolol was carried out from gestation until 28 weeks of age. Nadolol treatment caused some lowering of blood pressure but did not prevent the development of hypertension or cardiac hypertrophy in the SHR, in spite of significant beta-blockade. The lumen of large mesenteric arteries from control SHR was smaller than from WKY, and nadolol treatment increased the lumen size in the SHR. An increased number of smooth muscle cell layers present in the control SHR as compared with WKY was reduced slightly by nadolol treatment. However, the changes produced by nadolol did not reach the levels of control and treated WKY. In the aorta, the incidence of polyploid smooth muscle cells was higher in the SHR than the WKY in the control group. Nadolol treatment reduced the percentage of polyploid cells in both SHR and WKY, so that the difference between these two groups of animals was eliminated in the treated groups. The tissue level of norepinephrine in the plasma, heart, mesenteric arteries, and adrenal glands in the SHR and WKY was not affected by the treatment. We suggest that the ineffectiveness of nadolol in preventing hypertension development may be due to its lack of effect in preventing primary changes in the resistance arteries, and that the development of polyploidy of smooth muscle cells may be mediated by beta-receptors.

Adrenal Glands↗
PubMed1999

Partial hepatectomy-induced polyploidy attenuates hepatocyte replication and activates cell aging events.

In understanding mechanisms of liver repopulation with transplanted hepatocytes, we studied the consequences of hepatic polyploidization in the two-thirds partial hepatectomy model of liver regeneration. Liver repopulation studies using genetically marked rodent hepatocytes showed that the number of previously transplanted hepatocytes did not increase in the liver with subsequential partial hepatectomy. In contrast, recipients undergoing partial hepatectomy before cells were transplanted showed proliferation in transplanted hepatocytes, with kinetics of DNA synthesis differing in transplanted and host hepatocytes. Also, partial hepatectomy caused multiple changes in the rat liver, including accumulation of polyploid hepatocytes along with prolonged depletion of diploid hepatocytes, as well as increased senescence-associated beta-galactosidase and p21 expression. Remnant hepatocytes in the partially hepatectomized liver showed increased autofluorescence and cytoplasmic complexity on flow cytometry, which are associated with lipofuscin accumulation during cell aging, and underwent apoptosis more frequently. Moreover, hepatocytes from the partially hepatectomized liver showed attenuated proliferative capacity in cell culture. These findings were compatible with decreased proliferative potential of hepatocytes experiencing partial hepatectomy compared with hepatocytes from the unperturbed liver. Attenuation of proliferative capacity and other changes in hepatocytes experiencing partial hepatectomy offer novel perspectives concerning liver regeneration in the context of cell ploidy.

Animals↗
PubMed1998

Evolution by polyploidy in Amphibia: new insights.

Polyploidy is an important mechanism of evolution in lower vertebrates, resulting in gene duplication and loci duplication evolving to diploidization. In polyploid anurans DNA is increased, but RNA and protein synthesis is kept at the same levels as in their diploid counterparts. Recent cytogenetic findings in Odontophrynus americanus show: (1) amphiplasty and asynchrony of the cell division cycle in 4n and (2) intra- and interindividual alterations of chromosome 4 morphology in 4n and 2n through breaks at secondary constrictions and at/or around the centromeres, followed by the appearance of changes of centromeres position, dicentrics, bisatellited chromosomes, precocious sister-chromatid segregation, and loss or unequal segregation of the chromosomes. This genome instability suggests the presence of chromosomal aberrations with chromodomain alterations at the centromeres affecting the mechanisms ensuring normal segregation of the chromatids in anaphase of mitosis and meiosis. Cell division asynchrony and chromosome abnormalities, novel findings in polyploids, are discussed respectively in function of gene activity and putative translocations producing polymorphisms in nucleolus organizers and secondary constrictions.

Amphibians↗