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At least 19 recordsLinked to original sources
PubMed2026

Tetraploid Caenorhabditis elegans embryos exhibit enhanced tolerance to osmotic stress.

Polyploidy is a widespread phenomenon in development and evolution and is frequently associated with altered cellular physiology and developmental robustness. However, how genome doubling influences an embryonic robustness to environmental stress remains poorly understood. Here, we investigated developmental traits and osmotic responses in tetraploid Caenorhabditis elegans embryos. Tetraploid animals exhibited increased body and tissue sizes and produced larger embryos than diploids, accompanied by moderately delayed development and partial embryonic arrest. When exposed to a range of osmotic environments, both diploid and tetraploid embryos swelled or shrank in response to external osmolarity. Strikingly, tetraploid embryos at the early stage maintained normal cell division across a broader range of osmotic conditions than diploids. Quantitative analyses further revealed that tetraploid embryos exhibited reduced cytoplasmic mass density, primarily reflecting lower protein concentration, while lipid and RNA levels remain unaffected. These compositional differences likely buffer cellular size fluctuations and underlie the enhanced osmotic tolerance of tetraploid embryos. Together, our findings demonstrate that genome doubling reshapes embryonic cellular physiology in a non-proportional manner to ploidy, thereby enhancing robustness during early development.

Animals↗
PubMed1975

Embryonic development of tetraploid mice during the second half of gestation.

A small proportion (about 17%) of experimentally produced tetraploid blastocysts are capable of postimplantation development in the randomly bred Q strain of mice. Four newborn mice, three of which were confirmed as tetraploid, were produced but all were eaten by their mother within a few hours of birth. Studies on the embryonic development of tetraploid mice reveal a variety of developmental abnormalities, especially during the later stages of gestation. At 14 1/2 and 16 1/2 days, tetraploid embryos weigh significantly less than corresponding stage diploids, especially so if litter size is taken into account. Histologically, aberrations are found in many different tissues with a clear hierarchy of susceptibility shown among the organs. For instance, yolk-sac-derived blood, and gonads, are invariably affected and the anterior end of the neural tube also seems to be particularly at risk. Possible explanations for the aberrant development are discussed and it is concluded that strictly genetic reasons can be ruled out and that physiological difficulties imposed by the increased size of tetraploid cells and/or problems produced by lack of cell numbers are instrumental in causing abnormal development. Using weight as a guide it is estimated that tetraploid embryos at 14 1/2 and 16 1/2 days gestation contain about one-quarter as many cells as similar stage diploids.

Abnormalities, Multiple↗
PubMed1992

Comparison of chemically induced chromosome loss in a diploid, triploid, and tetraploid strain of Saccharomyces cerevisiae.

Triploid and tetraploid strains of Saccharomyces cerevisiae were constructed and the spontaneous loss during mitosis of one, two or three copies of chromosome VII was determined. In one strain, a triploid (VM2) in which expression of the recessive alleles can be observed only after loss of two copies of chromosome VII (3N-2), the spontaneous frequency of chromosome loss was lower than in the diploid D61.M. In another strain, a tetraploid (VM4) that also requires the loss of two copies of chromosome VII for observation (4N-2) of the recessive alleles, the spontaneous frequency was slightly higher than in the diploid D61.M. The spontaneous frequency of other genetic events (that is, mutation, recombination or chromosome breakage) were lower by 2-3 orders of magnitude than in the diploid strain D61.M. Induction of chromosome loss and other genetic events by nocodazole, ethyl acetate, hydroxyurea and ethyl methanesulfonate was determined in D61.M, VM2, and VM4, and the results were compared. Nocodazole and ethyl acetate induced chromosome loss in both the triploid and the tetraploid strains at lower concentrations than required in the diploid. These compounds also induced elevated frequencies of other genetic events in both the triploid and the tetraploid strains but not in the diploid. Hydroxyurea induced elevated frequencies of chromosome loss in the diploid and the tetraploid. Frequencies of chromosome loss in the triploid treated with hydroxyurea, although elevated, are based on observation of very few colonies of the correct phenotype. Ethyl methanesulfonate failed to induce chromosome loss in any of the three strains. Hydroxyurea and ethyl methanesulfonate did, however, induce very high frequencies of other genetic events.

Acetates↗
PubMed2026

DNA hypermethylation of abscisic-acid-related genes helps enhance the cold tolerance of tetraploid rice.

Polyploid plants exhibit enhanced stress resistance and superior adaptability to extreme environments, but the underlying molecular mechanisms remain incompletely understood. Here we confirm that tetraploid rice exhibits stronger cold tolerance than diploid rice. This improved tolerance is mediated by reduced malondialdehyde accumulation, elevated antioxidant enzyme activity, and epigenetic regulation of genes involved in abscisic acid (ABA) biosynthesis and signaling. Under cold stress, tetraploid rice induces stress-responsive genes (especially in the ABA pathway) more rapidly and to higher levels than diploid rice. This enhanced gene expression coincides with increased endogenous ABA accumulation. Furthermore, polyploidization and cold stress synergistically induce high methylation at CG, CHG, and CHH sites in genes and transposons (TEs). Notably, the methylation level of class II TEs in tetraploid rice is significantly higher than in diploid rice under low temperatures. To suppress TE activation in gene promoter regions under cold stress, tetraploid rice enhances the methylation level of ABA pathway-related gene promoters, thereby silencing TEs and maintaining genome stability. Collectively, these results enrich the theoretical understanding of the strong stress tolerance in polyploid plants and provide theoretical support for breeding cold-tolerant polyploid rice varieties.

ABA↗
PubMed1979

DNA reassociation kinetics in diploid and phylogenetically tetraploid cyprinidae.

Four diploid and three phylogenetically tetraploid Cyprinidae (Ostariophysi) have been characterized as for nuclear DNA content, modal chromosome number and DNA reassociation kinetics (hydroxyapatite chromatography). Among the diploid species nuclear DNA content (10(-12) g DNA/2C) was 1.62 for Tinca tinca, 1.87 for Scardinius erythrophthalmus, 2.53 for Leuciscus cephalus and 2.75 for Alburnus alburnus, while the phylogenetically tetraploid species Carassius auratus, Barbus barbus and Cyprinus carpio attained 3.40, 3.66 and 3.80 respectively. Modal chromosome number was 2n = 48-50 for diploid individuals and 2n = 100-104 for phylogenetically tetraploid ones. In all the species 5--8% of the genome is represented by highly repetitive and foldback DNA. In DNA reassociation kinetics of phylogenetically tetraploid Cyprinidae a distinct plateau separates an intermediate reassociating sequence fraction (about 22% of the genome; with average repetition frequencies between 1,000 and 1,400) from a slow reassociating one (unique DNA; about 72% of the genome). These two genome fractions are not clearly distinguishable from each other in Cot curves of the diploid Cyprinidae, where a similar plateau is not evident. Since simple ploidy changes are not expected to affect DNA reassociation kinetics we suggest a different evolution in the genome organization of the two ploidy groups. Some possible hypotheses are discussed.

Animals↗
PubMed1979

Non-repetitive DNA sequence divergence in phylogenetically diploid and tetraploid teleostean species of the family cyprinidae and the order isospondyli.

Non-repetitive DNA of anciently tetraploid teleostean species was analysed for the presence of duplicated sequences. Closely related diploid species were investigated in comparison. From the reassociation kinetics of total nuclear DNA, rate constants and fraction sizes of classes of repetitive and non-repetitive sequences were determined. DNA fractions enriched in the slowest renaturing sequence class were determined. DNA fractions enriched in the slowest renaturing sequence class were prepared and subjected to reassociation. The rate constants of these reactions were compared with the values expected for single-copy DNA from analytical genome size determinations. From reassociated DNA enriched in non-repetitive sequences also the melting temperatures were determined as a measure of internal base sequence heterogeneity. It has been shown that the two ancient tetraploids Cyprinus carpio and Thymallus thymallus are, with regard to the thermal stability of reassociated non-repetitive DNA, and with regard to the correspondence of reaction rates with the values expected for single copy DNA, indistinguishable from diploid controls (Rutilus rutilus, Clupea harengus and Sprattus sprattus). The tetraploid species Salmo irideus, Salvelinus fontinalis and Coregonus lavaretus appear as very recent tetraploids with regard to these criteria. The significance of the results for estimating the time of occurrence of polyploidisation events in these taxa is discussed.

Animals↗
PubMed1992

Alterations of DNA content in human endometrial stromal cells transfected with a temperature-sensitive SV40: tetraploidization and physiological consequences.

The normal genomic stability of human cells is reversed during neoplastic transformation. The SV40 large T antigen alters the DNA content in human endometrial stromal cells in a manner that relates to neoplastic progression. Human endometrial stromal cells were transfected with a plasmid containing the A209 temperature-sensitive mutant of SV40 (tsSV40), which is also defective in the viral origin of replication. Ninety-seven clonal transfectants from seven different primary cell strains were isolated. Initial analysis revealed that 20% of the clonal populations (19/97) had an apparent diploid DNA content, 35% (34/97) had an apparent tetraploid DNA content, and the remainder were mixed populations of diploid and tetraploid cells. No aneuploid populations were observed. Diploid tsSV40 transformed cells always give rise to a population of cells with a tetraploid DNA content when continuously cultured at the permissive temperature. The doubling of DNA content can be vastly accelerated by the sudden reintroduction of large T antigen activity following a shift from non-permissive to permissive temperature. Tetraploid tsSV40 transfected cells have a lower capacity for anchorage-independent growth and earlier entry into 'crisis' than diploid cells. These results indicate that during the pre-crisis, extended lifespan phase of growth, the SV40 large T antigen causes a doubling of DNA content. This apparent doubling of DNA content does not confer growth advantage during the extended lifespan that precedes 'crisis'.

Antigens, Polyomavirus Transforming↗
PubMed2025

Bistable Mutation-Selection Equilibria and Violations of Fisher's Theorem in Tetraploids: Insights from Nonlinear Dynamics.

Polyploidy and whole genome duplication (WGD) are widespread biological phenomena with substantial cellular, meiotic, and genetic effects. Despite their prevalence and significance across the tree of life, population genetics theory for polyploids is not well developed. The lack of theoretical models limits our understanding of polyploid evolution and restricts our ability to harness polyploidy for crop improvement amidst increasing environmental stress. To address this gap, we developed and analyzed deterministic models of mutation-selection balance for tetraploids under polysomic (autotetraploid) and disomic (allotetraploid) inheritance patterns and arbitrary dominance relationships. We also introduced a new mathematical framework based on ordinary differential equations and nonlinear dynamics for analyzing the models. We find that autotetraploids approach Hardy-Weinberg Equilibrium 33% faster than allotetraploids, but the different tetraploid inheritance models show little differences in mutation load and allele frequency at mutation-selection balance. Our model also reveals two bistable points of mutation-selection balance for dominant alleles with biased mutation rates over a wide range of selection coefficients in the tetraploid models compared to bistability in only a narrow range for diploids. Finally, using discrete time simulations, we explore the temporal dynamics of allele frequency and fitness change and compare these dynamics to the predictions of Fisher's Fundamental Theorem of Natural Selection. While Fisher's predictions generally hold, we show that the bistable dynamics for dominant mutations fundamentally alter the associated temporal dynamics. Overall, this work develops foundational theoretical models that will facilitate the development of population genetic models and methodologies to study evolution in empirical tetraploid populations.

Fisher’s Fundamental Theorem↗
PubMed1992

Direct induction of tetraploids or homozygous diploids in the industrial yeast Saccharomyces cerevisiae by hydrostatic pressure.

Hydrostatic pressure and a dye plate method were used to investigate the direct induction of tetraploids or homozygous diploids from the industrial diploid or haploid yeast Saccharomyces cerevisiae. Above 200 MPa, hydrostatic pressure greatly inactivated the strains HF399s1 (alpha haploid), P-540 (a/alpha diploid), and P-544 (a/alpha diploid). At the same time, when pressure-treated cells of these strains were spread on a dye plate, some of the visible colonies were stained red/blue or dark blue (variant colonies); the rest stained violet, similar to colonies originating from diploid cells or haploid cells that were not pressure-treated. In addition, above 100 MPa, the formation of variant colonies increased with increasing pressure, and maximized (1 x 10(-1)) at 200 and 250 MPa, respectively. The size of almost all variant cells from P-544, P-540, and HF399s1 was visibly increased compared with that of untreated cells and the measured cellular DNA content of P-540 and HF399s1 was double that of untreated cells. Furthermore, based on random spore analysis and mass-matings, induced variants in the diploid strains were found to be tetraploid with an a/a/alpha/alpha genotype at the mating-type locus or, in the haploid strains, homozygous diploid with an alpha/alpha genotype. From these results we conclude that pressure treatment in combination with a dye plate is a useful method for strain improvement by direct induction of tetraploids or homozygous diploids from industrial strains whether diploid or haploid.

Crosses, Genetic↗
PubMed1976

Gene action in fish of tetraploid origin. III. Ribosomal DNA amount in cyprinid fish.

Phylogenetically diploid and tetraploid cyprinid fish species have cells of very similar volumes and protein contents. This finding has prompted us to postulate a regulatory system established during the evolution of the tetraploids leading to a diploid state of genic expression. It was proposed that this might be accounted for by a selective loss of ribosomal genes. RNA-DNA hybridization experiments, however, reveal a clear-cut 1:2 relationship of ribosomal DNA amounts between the diploid and the tetraploid species.

Animals↗
PubMed1976

Gene action in fish of tetraploid origin. V. Cellular RNA and protein content and enzyme activities in cyprinid, clupeoid, and salmonoid species.

The ratio of cellular RNA and protein content is about 1:1 between phylogenetically diploid and tetraploid species of the teleost family Cyprinidae, but is roughly in proportion to ploidy in species of the teleost order Isospondyli. Enzyme activities do not unequivocally comply with this scheme. These findings are discussed in view of the hypothesis that a regulatory mechanism which reduces genic activity has evolved in the tetraploid cyprinids but not in the tetraploid species of the order Isopondyli.

Animals↗
PubMed1975

Gene action in fish of tetraploid origin. II. Cellular and biochemical parameters in clupeoid and salmonoid fish.

By use of cell size, protein and hemoglobin content, and enzyme activities as markers, it becomes apparent that in the course of evolution the gene expression of anciently tetraploid fish of the order Ostariophysi was diploidized, but no such regulatory mechanism has evolved in the phylogenetically tetraploid species of the order Isospondyli. This finding is discussed in terms of possible selective neutrality of tetraploid expression and the phylogenetic age of Isospondyli.

Animals↗
PubMed1975

Microphotometry of rat liver nucleoproteins during the cell cycle, and comparison of diploid nuclei in the G2 period with tetraploid nuclei.

The following facts were established with a microphotometric investigation of isolated nuclei from rat liver in different stages of the cell cycle. During the mitotic wave occurring in the liver of newborn animals after injection of casein it was found that the naphtol yellow S (NYS) protein content of the nuclei increases about 30% during the G1-period. A second increase of around 70% was established during the S-phase whereas no increase could be observed during the G2-phase. An indication for the existence of a "critical protein mass" of the nuclei before the onset of the S-phase could be observed. The protein content of diploid nuclei in the G1-phase of adult animals is about 50% higher than in newborns. This makes it probable that there is no significant difference in the NYS-protein content of diploid nuclei in the G2-period and tetraploid nuclei of adult rats. No differences were observed between diploid nuclei in the G2-period of newborn rats and tetraploid nuclei of adult rats in their Fastgreen histon, RNA and SH plus SS content. The only criterion to distinguish between G2 nuclei and tetraploid nuclei seems to be the number of nucleoli, but this is rather unreliable.

Aging↗
PubMed1979

Activation of phenotypic expression of human globin genes from nonerythroid cells by chromosome-dependent transfer to tetraploid mouse erythroleukemia cells.

Chromosome-dependent gene transfer mediated by cell fusion was used to show that it is possible to activate phenotypic expression of human alpha globin genes derived from nonerythroid cells. Hybrid cells containing the human alpha globin structural genes were derived by fusion of populations of adult human peripheral blood mononuclear cells (devoid of identifiable erythroid cells) with adenine phosphoribosyl-transferase-deficient mouse erythroleukemia cells that contained close to a tetraploid complement of mouse chromosomes. The hybrid cells retained a near tetraploid complement of mouse chromosomes but had lost 80% of the chromosomes of the human parent cell. All of these hybrid cells and their subclones, which contained human chromosome 16, exhibited synthesis of human alpha globin chains. Human alpha globin mRNA was also demonstrated to be present in one of these hybrid cells by RNA.cDNA molecular hybridization analysis. We conclude that the mechanism responsible for restricting expression of the human globin genes in nonerthroid cells is not irreversible, at least for those globin structural genes that are actively transcribed in erythroid cells during adult life. Moreover, some genetic factor or process in the tetraploid mouse erythroleukemia cell is, under the conditions of our experiments, capable of reactivating phenotypic expression (production of globin chains) of human globin genes derived from nonerythroid hematopoietic cells after chromosome-dependent gene transfer.

Animals↗
PubMed1977

Cell kinetics of mouse urinary bladder epithelium. IV. Changes in cell proliferation, nuclear DNA content, and number of diploid, tetraploid and octoploid cells after a single dose of dibutylnitrosamine.

The initial effect of a single subcutaneous injection of 0.01 ml of dibutylnitrosamine on the mouse (hr/hr strain) urinary bladder epithelium was a block in DNA synthesis in the diploid cells followed by a regenerative reaction. This did not, however, lead to a subsequent wave of increased DNA synthesis among the tetraploid cells. Later, a new wave of DNA synthesis occurred among the diploid cells, and again there was no subsequent wave of tetraploid DNA synthesis. The total cell number was not affected. These disturbances resulted in periods of reduced numbers of octoploid cells. This effect was unlike that obtained in previously published experiments using cyclophosphamide, which led to considerable hyperplasia, especially of octoploid cells, and no disturbance of tetraploid DNA synthesis. Thus the action of a single dose of dibutylnitrosamine on the epithelial cells in the mouse urinary bladder is very different from that of cyclophosphamide in a single dose, but it is not possible to say whether this has anything to do with the carcinogenicity of the nitrosamine.

Animals↗
PubMed2026

Integrated transcriptomic and metabolomic analysis reveals candidate regulatory networks associated with starch accumulation in tetraploid potato.

Potato (Solanum tuberosum L.) tuber starch is a major determinant of crop quality and industrial value, yet the regulatory mechanisms underlying starch accumulation in autotetraploid cultivars remain poorly resolved. Here, we performed integrated transcriptomic and metabolomic analyses using a segregating tetraploid population derived from parents with contrasting starch content. Extreme phenotypes were selected to systematically dissect the molecular basis of starch accumulation. Transcriptome profiling revealed extensive transcriptional reprogramming between high- and low-starch genotypes, with differentially expressed genes significantly enriched in carbohydrate metabolism, particularly the starch and sucrose metabolism pathway. Notably, multiple transcription factor families, including AP2/ERF, MYB, and bHLH, were prominently represented, suggesting coordinated regulatory control. Metabolomic analysis identified substantial metabolic divergence, with differentially accumulated metabolites predominantly enriched in starch and sucrose metabolism as well as secondary metabolic pathways. Most metabolites exhibited negative associations with starch content, indicating competitive carbon allocation between primary and secondary metabolism. Integrative multi-omics analysis further resolved a core regulatory module comprising key structural genes and transcription factors tightly associated with starch-related metabolites. In particular, genes involved in sucrose cleavage and ADP-glucose metabolism, together with trehalose-6-phosphate synthase (TPS) and UDP-glucose-associated pathways, emerged as critical nodes linking carbon flux to starch biosynthesis. Correlation network analysis suggested that AP2/ERF-, MYB-, and bHLH-type transcription factors modulate these pathways by coordinating structural gene expression and metabolic flux distribution. Collectively, our study establishes a transcriptional-metabolic framework for starch accumulation in tetraploid potato, highlighting the central role of carbon allocation and signaling intermediates in shaping starch content, and providing candidate targets for molecular breeding and genome editing.

Solanum tuberosum↗
PubMed1977

Duplicate gene expression in diploid and tetraploid loaches (Cypriniformes, Cobitidae).

Botia macracantha and B. modesta have been demonstrated to be tetraploid species on the basis of their karyotypes and on the basis of the expression of a number of isozymes encoded by duplicate loci. A rather low percentage of duplicate loci was detected by electrophoresis, compared to that for other tetraploid Cypriniformes. Several hypotheses have been advanced to account for the low levels of duplicate gene expression observed. Lastly, many of the duplicate loci have diverged to unique patterns of expressions in different tissues or different levels of activity within a single tissue.

Animals↗
PubMed1976

Gene action in fish of tetraploid origin. IV. Ribosomal DNA amount in clupeoid and salmonoid fish.

Phylogenetically tetraploid species of the fish order Isospondyli generally have twice the mean ribosomal gene content as closely related species on the phylogenetically diploid level. Considerable intraspecific variation of rDNA amount was observed. These findings are discussed in view of the hypothesis that selective loss of ribosomal genes may account for diminishing genic activity in phylogenetically tetraploid organisms.

Animals↗