Evidence Of Polyploidy Research Articles

Abstract 4343: Revealing ovarian cancer copy number variation in single cells

Abstract The mortality rate associated with ovarian cancer (OvCa) is disproportionately high in comparison to its incidence rate. This is partly due to the heterogeneous nature of the disease, which reduces treatment efficacy and contributes to high rates of relapse and chemotherapy resistance. Most OvCa are epithelial in origin and can be classified into four main subtypes: serous, mucinous, endometrioid, and clear cell. Of these, high grade serous ovarian cancer (HGSOC) is the deadliest. Epithelial ovarian carcinomas (EOC) typically exhibit widespread chromosomal and arm-level copy number abnormalities across most of the genome; in HGSOC, focal amplifications and microdeletions are especially prevalent and indicative of high genomic instability. To understand the heterogeneity of aneuploidy in EOC and HGSOC, we performed shallow single-cell whole genome sequencing on four EOC samples: two HGSOC, one clear cell, and one mixed clear cell and endometrioid. All samples were late stage and treatment naïve, and one sample had a known BRCA2 mutation. Sequencing data was processed by two complementary methods to call copy number alterations. First, we used the Cell Ranger DNA pipeline (10x Genomics) to align cell-identified sequencing reads to human reference genome GRCh38 for coverage-based copy number estimation. Resulting copy number calls were cleaned up for mappability, quality, and noisiness. Each sample was then subject to clustering and subclustering analysis using maximum likelihood genetic clustering algorithms. All samples exhibited a high level of aneuploidy, including characteristic alterations known to be associated with EOC. Two tumors contained readily distinguishable clonal populations, and all samples contained main tumor clones that could be further divided by unique subclonal characteristics. Evidence of polyploidy was also seen in all four specimens, with some tumor clusters exhibiting triploid and tetraploid baselines. In parallel, sequencing data was analyzed by the Copy-number Haplotype Inference in Single-cell by Evolutionary Links (CHISEL) algorithm. CHISEL utilizes both binned read depth ratio and B-allele frequency data to determine allele- and haplotype-specific copy numbers in single cells. Results from CHISEL confirmed the copy number calls from Cell Ranger DNA, and revealed widespread loss of heterozygosity in all samples. These findings were corroborated with allele-specific copy number data derived from matched tumor-normal whole exome sequencing. Furthermore, CHISEL detected polyploidy in one-third of the tumor cells with no preference for the A or B alleles. Overall, our findings highlight that the known heterogeneity of ovarian cancer extends to the level of aneuploidy and CNAs, shedding light on factors which pose significant barriers to effective personalized medicine implementation. Citation Format: Yuxin Jin, Rania Bassiouni, Lee D. Gibbs, Jing Qian, Solomon Rotimi, Michelle G. Webb, Seeta Rajpara, David W. Craig, Lynda D. Roman, John D. Carpten. Revealing ovarian cancer copy number variation in single cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4343.

Genetic data support reproductively isolated species in the endemic Cladophoraceae (Chlorophyta) of Lake Baikal, Russia

ABSTRACT Ancient lakes are centres of biological diversification that hold many examples of adaptive radiation and species flocks. The recently discovered species flock of Cladophoraceae in Lake Baikal is a group of green algae that exhibit low genetic divergence in ribosomal markers (LSU, SSU, and ITS), but wide morphological differentiation. Microsatellite markers showed evidence of polyploidy in this group, requiring alternate data scoring methodologies. In this study, we use two clustering methods (STRUCTURE and Gaussian Clustering) to delineate species within 15 distinct morphotaxa of the cladophoralean Baikal clade. The two cluster analyses produced comparable results, although subtle differences in the assignment of individuals were observed. Our results indicate that many morphologically distinguishable species are discrete genetic clusters supporting reproductive isolation. This is the case for Chaetomorpha (= Ch.) baicalensis, the attached form of Ch. curta, Ch. moniliformis, Cladophora (= Cl.) compacta, and Cl. kursanovii. The unattached form of Ch. curta and a species of Rhizoclonium are recovered as growth forms of Ch. moniliformis and the attached form of Ch. curta, respectively. The remaining morphotaxa were not clearly delimited. While we have evidence for polyploidy within this species flock, it was not possible to determine the ploidy level of each individual with accuracy as no correlation in the number of alleles was observed between loci. A more detailed study including other sources of data, such as nuclear DNA content or chromosome counts, is required to demonstrate the ploidy changes and their role in speciation in these species.

A natural hybrid, an autopolyploid, or a new species? An integrative case study of a distinctive Costus species (Costaceae) from the Atlantic Forest of Brazil

Sixteen species of Costus s.s. are cited to Brazil, all of which can be found in the Brazilian Amazon, while only three also grow in the Atlantic Forest: C. arabicus, C. scaber, and C. spiralis. Studies of the genus from the Brazilian Atlantic Forest evidenced a distinctive fourth taxon, similar overall to C. spiralis, which is an ornithophilous species, however the flower morphology of this new taxon indicates it to be melittophilous. Hybridization and polyploidy (allopolyploidy or autopolyploidy) may play a role as an important source for evolutionary events, especially in recent speciose lineages such as Neotropical Costus. Here we investigated the evolutionary origin of this interesting Costus species using an integrative approach. This approach comprised a morphological analysis, cytogenetic analyses (chromosome counts, CMA/DAPI staining, and fluorescent in situ hybridization), genome size estimations, and a molecular phylogenetic reconstruction (using the plastid regions rps16 and trnL-F, and the nuclear ITS and ETS), aiming to answer the following questions: is it a hybrid?; is it an autopolyploid of C. spiralis?; or, if it is a different species, is it even phylogenetically related to C. spiralis or C. arabicus? The studies performed did not indicate any evidence of polyploidy, however, a chromosomal polymorphism was observed between the populations of the taxon studied. The phylogenetic position of this peculiar taxon with C. erythrophyllus, C. spiralis, and C. varzearum also excludes the putative partial heritage of C. arabicus which had been previously hypothesized. Our results confirm that it is a new, undescribed species, which is confirmed by our morphological observations of floral features. A complete taxonomic treatment of the new species is provided, including a key for the species of the genus in the Atlantic Forest.

DNA as genetic material and as a nutrient in halophilic Archaea.

DNA as genetic material and as a nutrient in halophilic Archaea.

Mitotically Active Proliferative Nodule Arising in a Giant Congenital Melanocytic Nevus

Proliferative (cellular) nodules (PN) which mimic malignant melanoma clinically and histologically are described in congenital melanocytic nevi (CMN) and may pose significant diagnostic challenges. We report the case of a 10-day-old male with a giant congenital nevus involving the neck, upper chest, back, and left shoulder containing several nodular lesions, some crusted. Biopsy of a nodule revealed densely packed nevus cells with hyperchromatic round to oval and occasionally irregularly shaped nuclei. There was no necrosis or pushing border, and the nodule blended with the adjacent nevus; however, the lesion demonstrated a significant number of mitoses (27 per mm2) and a 60% labeling index with Ki-67. Further analysis by fluorescence in situ hybridization (FISH) with a 4-color probe set targeting 6p25, 6q23, 11q13, and centromere 6 revealed increased chromosomal copy numbers of all 4 probes, which was interpreted as evidence of polyploidy. In addition, analysis of DNA copy number changes using a single nucleotide polymorphism microarray (Affymetrix, Santa Clara, CA) showed no chromosomal aberrations. The diagnosis of PN in a giant congenital nevus was eventually rendered. At 13-month follow-up, the nodules showed no evidence of growth. Our case illustrates that PNs in the neonatal period might demonstrate extreme mitotic activity. This feature is worrisome when encountered in melanocytic lesions; however, it should not trigger by itself a diagnosis of melanoma in the absence of other histologic criteria of malignancy. In addition, we document polyploidy by FISH in PN, which can potentially be misinterpreted as a FISH-positive result.

Extending the Activities of Human Nucleus Pulposus Cells with Recombinant Adeno-Associated Virus Vector-Mediated Human Telomerase Reverse Transcriptase Gene Transfer

Even though human nucleus pulposus (HNP) cells have a limited replicative lifespan in vitro culture, the lifespan of ovine nucleus pulposus cells transferred by lipofectamine with human telomerase reverse transcriptase (hTERT) gene could be prolonged. However, the lipofectamine is a transient expression system with an expressed duration of hTERT for less than 73 days. Here we present a viral vector system to investigate whether recombinant adenoassociated virus vector-mediated hTERT gene (rAAV-hTERT) could safely prolong the activities of HNP cells. Our hypothesis was that the activities of HNP cells could be extended with rAAV-hTERT gene transfer. Therefore, we designed an in vitro and in vivo evaluation of a HNP cells gene transfectant. Second-generation HNP cells were transfected with rAAV-hTERT and the expression of hTERT determined by reverse transcription-polymerase chain reaction (RT-PCR) and western blot. Cumulative population doubling, senescence assay, real-time RT-PCR, and enzyme-linked immunosorbent assay were used to determine cellular activities. Genetic phenotype was validated by karyotypic analysis and ontogenicity by nude mice injected in vivo. The continuing expression of hTERT gene and production of extra cellular matrix for 120 days were found in the transfected HNP cells, and karyotypic instability was detected, but there was no evidence of polyploidy or oncogenicity in nude mouse. The results showed that this transfection model might provide a resource cells necessary for the biological treatment of degenerative disc disease.

Evidence of polyploidy in fluted pumpkin (Telfairia occidentalis Hook F.)

Mitotic studies were carried out on fluted pumpkin (Telfairia occidentalis Hook. F.) lines collected from South East, South West, South South and North Central geopolitical zones of Nigeria where the crop is mainly cultivated. The results obtained revealed diploids (2n = 22), aneuploids (2n = 22 + 1), triploid (3n = 3x = 33) and tetraploid (4n = 4x = 44) chromosome numbers among the cells investigated. About 4% of the 123 cells investigated were anueploids (2n = 22 + 1), 1.2% were triploid (3n = 33), 1.2%, tetraploid (4n = 44). About 84% of the total cells investigated had 2n = 22. The implications of these polyploidized conditions on the evolutionary trend of the Nigerian fluted pumpkin lines were discussed. Key words: Aneuploid, chromosomes, evolutionary trend, landraces, tetraploid, triploid.

First evidence of polyploidy in Psylloidea (Homoptera, Sternorrhyncha): a parthenogenetic population of Cacopsylla myrtilli (W. Wagner, 1947) from northeast Finland is apomictic and triploid

This paper reports results of the first cytogenetic study of parthenogenetic psyllids, carried out on an asexual population of the holarctic species Cacopsylla myrtilli W. Wagner from northeast Finland. Preparations of mature eggs extracted from females revealed 39 univalent chromosomes in prophase and metaphase cells. Hence, female meiosis is of apomictic type and replaced by a modified mitosis. The karyotype consists of 3n = 39 (36 + XXX). Clearly, the population is triploid, the haploid number being n = 12 + X as characteristic of the genus Cacopsylla as a whole. As typical for Psylloidea, the chromosomes are holokinetic, only slightly varying in size and without any visible markers, rendering impossible the precise identification of triplets of homologous chromosomes in the triploid complement. The distribution of bisexual and parthenogenetic populations of C. myrtilli throughout the world is briefly given, and a possible origin of the triploid parthenogenetic population is discussed.

New chromosome counts and evidence of polyploidy in Haageocereus and related genera in tribe Trichocereeae and other tribes of Cactaceae

Chromosome numbers for a total of 54 individuals representing 13 genera and 40 species of Cactaceae, mostly in tribe Trichocereeae, are reported. Five additional taxa examined belong to subfamily Opuntioideae and other tribes of Cactoideae (Browningieae, Pachycereeae, Notocacteae, and Cereeae). Among Trichocereeae, counts for 35 taxa in eight genera are reported, with half of these (17 species) for the genus Haageocereus. These are the first chromosome numbers reported for 36 of the 40 taxa examined, as well as the first counts for the genus Haageocereus. Both diploid and polyploid counts were obtained. Twenty nine species were diploid with 2n=2x=22. Polyploid counts were obtained from the genera Espostoa, Cleistocactus, Haageocereus, and Weberbauerocereus; we detected one triploid (2n=3x=33), nine tetraploids (2n=4x=44), one hexaploid (2n=6x=66), and three octoploids (2n=8x=88). In two cases, different counts were recorded for different individuals of the same species (Espostoa lanata, with 2n=22, 44, and 66; and Weberbauerocereus rauhii, with 2n=44 and 88). These are the first reported polyploid counts for Haageocereus, Cleistocactus, and Espostoa. Our counts support the hypothesis that polyploidy and hybridization have played prominent roles in the evolution of Haageocereus, Weberbauerocereus, and other Trichocereeae.

Cytogenetic and DNA cytophotometric image analysis of some promising sugarcane varieties

Cytogenetic and DNA cytophotometric image analyses were conducted for the identification and labelling of nine (9) genotypes of commercial hybrids of sugarcane,Saccharum officinarum, include GT 54-9, Bo 10, A 63-20, NCo 310, Co 413, G 75-393, G 88-68, G 67-55 and Co 301. These genotypes were locally available in Sabahia Sugar Crops Research Station, Alexandria, Egypt. Squash of root-tips, of 10–14 days-old sprouts, fixed in Carnoy’s solution was stained with Feulgen reagent and the cell image was determined using ComputerizedImage Analysis in Scientific Application (CIASA) system. The study showed that DNA content ranged from 200–2000 Arbitrary Units, detecting over six ploidy level (>6C) in three genotypes namely, A 63-20, NCo 310 and Co 413. The genotypes GT 54-9, Bo 10, and Co 301 contained up to 5C, and the remaining four genotypes contained only up to 4C. Cytogenetic examination revealed different numbers ofnucleoli per nucleus of the root-tip squash; three to four nucleoli in genotypes Bo 10 and Co 301, two in genotypes G 75-393 and G 67-55, and six to more than eight in genotypes GT 54-9, NCo 310 and Co 413. This indicates that these genotypes were obtained from hybridization and or translocation of ribosomal DNA cistrons. Genotypes NCo 310 and Co 413 displayed eight nucleoli.Mitotic indices ranged from 2.1 (G 88-68) to 4.6 (Co 413). A high degree of heterochromatin at interphase was observed in A 63-20 and G 67-55; reflecting low transcriptional activity. The mitotic index is an accurate differential measure of cell proliferation, suggesting different kinetic levels of the investigated genotypes, which can be ranked descending in the order Co 413, BO 10, GT 54-9,G 67-55,NCo 310,Co 301, A 63-20,G 75-393 and G 88-68.Cytological examination revealed several aberrations in the Pollen Mother Cells (PMCs) in various stages of meiosis. The genotypes NCo 310 and Co 413 showed abnormal behaviour of chromosomes, giving evidence of polyploidy. The results of this study show that the genetic and cytogenetics features of the nine investigated genotypes reflect genotype-specific characteristics including DNA content (ploidy level), estimated volume of nucleoli per cell (No. x Size), mitotic index and transcriptional activity (heterochromatin) that may offer means of sugarcane clonal genotypes or varietal verification and avoidance of mislabelling for use as parental lines in breeding programmes and sugarcane improvement.

Cytogenice Studies on Bambara groundnut (<i>Vigna subterranea </i> (L..) verdc)

The study reports the result of analysis of chromosomes of Vigna subterranea performed in the mitotic prometaphase and metaphase stages using conventional techniques. The somatic chromosome study was done using the shoot meristem as the root tips persistently showed very low mitotic indices. The result revealed somatic chromosome number of 2n = 22. There was no evidence of polyploidy in any of the accessions. The chromosome morphology was described on the basis of the centromere position. From the F% value, it was evident that the different accessions showed wide range of variation in their karyoptypes. The minimum F% range of 33.33 to 50.00 was recorded for Ac-01, Ac-02 and Ac-03. They had metacentric and submetacentric chromosomes. Ac-04 had F% range of 25.00 to 50.00. With the exception of the 9th chromosome pair that was telocentric, the chromosomes were mostly metacentric and submetacentric. Because the accessions were diploid, the uniformity in chromosome number of the four accessions investigated is a clear indication that they may have evolved from a common ancestor, forming a homogeneous assemblage. Keywords: Cytogenetics, chromosome, Bambara groundnut, Vigna subterraneaAgro-Science Vol. 3 (2) 2006: pp. 13-20

Widespread genome duplications throughout the history of flowering plants

Genomic comparisons provide evidence for ancient genome-wide duplications in a diverse array of animals and plants. We developed a birth-death model to identify evidence for genome duplication in EST data, and applied a mixture model to estimate the age distribution of paralogous pairs identified in EST sets for species representing the basal-most extant flowering plant lineages. We found evidence for episodes of ancient genome-wide duplications in the basal angiosperm lineages including Nuphar advena (yellow water lily: Nymphaeaceae) and the magnoliids Persea americana (avocado: Lauraceae), Liriodendron tulipifera (tulip poplar: Magnoliaceae), and Saruma henryi (Aristolochiaceae). In addition, we detected independent genome duplications in the basal eudicot Eschscholzia californica (California poppy: Papaveraceae) and the basal monocot Acorus americanus (Acoraceae), both of which were distinct from duplications documented for ancestral grass (Poaceae) and core eudicot lineages. Among gymnosperms, we found equivocal evidence for ancient polyploidy in Welwitschia mirabilis (Gnetales) and no evidence for polyploidy in pine, although gymnosperms generally have much larger genomes than the angiosperms investigated. Cross-species sequence divergence estimates suggest that synonymous substitution rates in the basal angiosperms are less than half those previously reported for core eudicots and members of Poaceae. These lower substitution rates permit inference of older duplication events. We hypothesize that evidence of an ancient duplication observed in the Nuphar data may represent a genome duplication in the common ancestor of all or most extant angiosperms, except Amborella.

Inhibition of clonogenic tumor growth: a novel function of Smac contributing to its antitumor activity

While second mitochondria derived activator of caspase (Smac) has been described to sensitize for apoptosis, its effect on cell viability in the absence of apoptotic stimuli has remained unclear. Here, we report that Smac inhibits clonogenic tumor growth by blocking random migration and proliferation and by enhancing apoptosis in a cell density and cell type dependent manner in SH-EP neuroblastoma cells. Inhibition of clonogenic survival by overexpression of full-length or processed Smac strictly depended on low cell density, and was reversible by replatement at high density. We discovered that Smac inhibits cell motility and random migration at low cell density. In addition, Smac enhanced apoptosis and inhibited protein, but not mRNA expression of XIAP, survivin and other short-lived proteins (FLIP, p21), indicating that Smac may globally inhibit protein expression. Also, Smac inhibited proliferation and increased polynucleation with no evidence for polyploidy, cell cycle arrest or senescence indicating that Smac impaired cell division. Interestingly, inhibition of clonogenic capacity by Smac occurred independent of its apoptosis promoting activity. By demonstrating that Smac restrains clonogenic tumor growth, our findings may have important implications for control of tumor growth and/or its metastatic spread. Thus, Smac agonists may be useful in cancer therapy, for example, for tumor control in minimal residual disease. Oncogene (2005) 24, 7190-7202. doi:10.1038/sj.onc.1208876; published online 8 August 2005.

RbcL sequences reveal multiple cryptic introductions of the Japanese red alga Polysiphonia harveyi.

In Europe, the last 20 years have seen a spectacular increase in accidental introductions of marine species, but it has recently been suggested that both the actual number of invaders and their impacts have been seriously underestimated because of the prevalence of sibling species in marine habitats. The red alga Polysiphonia harveyi is regarded as an alien in the British Isles and Atlantic Europe, having appeared in various locations there during the past 170 years. Similar or conspecific populations are known from Atlantic North America and Japan. To choose between three competing hypotheses concerning the origin of P. harveyi in Europe, we employed rbcL sequence analysis in conjunction with karyological and interbreeding data for samples and isolates of P. harveyi and various congeners from the Pacific and North Atlantic Oceans. All cultured isolates of P. harveyi were completely interfertile, and there was no evidence of polyploidy or aneuploidy. Thus, this biological species is both morphologically and genetically variable: intraspecific rbcL divergences of up to 2.1% are high even for red algae. Seven rbcL haplotypes were identified. The four most divergent haplotypes were observed in Japanese samples from Hokkaido and south-central Honshu, which are linked by hypothetical 'missing' haplotypes that may be located in northern Honshu. These data are consistent with Japan being the centre of diversity and origin for P. harveyi. Two non-Japanese lineages were linked to Hokkaido and Honshu, respectively. A single haplotype was found in all North Atlantic and Mediterranean accessions, except for North Carolina, where the haplotype found was the same as that invading in New Zealand and California. The introduction of P. harveyi into New Zealand has gone unnoticed because P. strictissima is a morphologically indistinguishable native sibling species. The sequence divergence between them is 4-5%, greater than between some morphologically distinct red algal species. Two different types of cryptic invasions of P. harveyi have therefore occurred. In addition to its introduction as a cryptic sibling species in New Zealand, P. harveyi has been introduced at least twice into the North Atlantic from presumed different source populations. These two introductions are genetically and probably also physiologically divergent but completely interfertile.

Multiple soluble malate dehydrogenase of Geophagus brasiliensis (Cichlidae, Perciformes)

A recent locus duplication hypothesis for sMDH-B* was proposed to explain the complex electrophoretic pattern of six bands detected for the soluble form of malate dehydrogenase (MDH, EC 1.1.1.37) in 84% of the Geophagus brasiliensis (Cichlidae, Perciformes) analyzed (AB1B2 individuals). Klebe's serial dilutions were carried out in skeletal muscle extracts. B1 and B2 subunits had the same visual end-points, reflecting a nondivergent pattern for these B-duplicated genes. Since there is no evidence of polyploidy in the Cichlidae family, MDH-B* loci must have evolved from regional gene duplication. Tissue specificities, thermostability and kinetic tests resulted in similar responses from both B-isoforms, in both sMDH phenotypes, suggesting that these more recently duplicated loci underwent the same regulatory gene action. Similar results obtained with the two sMDH phenotypes did not show any indication of a six-banded specimen adaptive advantage in subtropical regions.

High frequency plant regeneration from Eucalyptus globulus Labill. hypocotyls: Ontogenesis and ploidy level of the regenerants

Up to 70% regenerating hypocotyls provided with 5 to 20 buds were obtained on MS medium containing 0.01 or 1m g l 1 NAA and 0.2 mg l 1 BA or 0.2 mg l 1 BA and 0.2 mg l 1 TDZ. The ability to regenerate buds was correlated with the presence of oil glands at a stage in germination when oil secretion was not yet occurring. The regenerationofshootmeristemstookplacefromthecellsinvolvedinthedifferentiationoftheseglands.Suchglands could also appear during callus redifferentiation, giving rise to indirect regeneration. Rooting of the regenerants was efficient using a two-step procedure of induction under darkness in the presence of 3 mg l 1 IBA, followed by root development on medium devoid of growth regulators under a 16-h photoperiod, the medium being solidified with Gelrite. Regeneratedplantsshowednophenotypicalterations. Nuclear DNAcontentsin mother-plantmaterial and regenerants were analysed using flow cytometry. There was no evidence of polyploidy in any of the samples, indicating the absence ofpolyploidisationduring cell differentiationand underin vitro conditions. No regeneration was obtained from leaf or stem explants from micropropagated plantlets. Abbreviations: BA ‐ benzyladenine; CH ‐ casein hydrolysate; IBA ‐ indole butyric acid; MS ‐ Murashige and Skoog; NAA ‐ -naphthalene acetic acid; TDZ ‐ thidiazuron; WPM ‐ Woody Plant Medium

Parthenogenesis in the Tribe Naupactini (Coleoptera: Curculionidae)

Twenty-eight species of Naupactini have at least some populations that appear to reproduce parthenogenetically. For most of these species, parthenogenesis is inferred from the absence of males; in 3 species it has been corroborated by evidence of polyploidy, and in 2 others it has been confirmed by rearing experiments. Several independent lineages of Naupactini have lost their metathoracic wings, and it is only within these lineages that parthenogenesis has arisen. Several clades within the tribe consist largely of parthenogenetic species but some of them also include sexual populations. Although Naupactini range throughout most of the New World with their highest species diversity in the tropics, all the parthenogenetic lineages are native to the subtropical and temperate areas of southern South America with their highest diversity and abundance in the Pampas.

Investigations into the mechanisms of carcinogen-induced nuclear enlargement in HeLa S3 cells in vitro

Carcinogen-induced nuclear enlargement has been reported both in vitro and in vivo, but the mechanism, and whether it is causally related to carcinogenesis, has not yet been established. This study was designed to investigate the role of increased DNA content, such as might occur in polyploidy, in induction of nuclear enlargement. The effects of two genotoxic carcinogens, N-methyl- N-nitrosourea and adriamycin, were compared with the effects induced by diethylstilboestrol, which is arguably a non-genotoxic carcinogen but is known to induce polyploidy. HeLa S3 cells were used as the model system for comparison with previous studies. N-methyl- N-nitrosourea and adriamycin both induced a concentration-related increase in nuclear size 24 to 72 hr after a 30 min pulse-treatment. This was accompanied by an increase in the proportions of cells in the G 2 + M stage of the cell cycle, possibly due to a G 2 block. There was some evidence of polyploidy with adriamycin but not with N-methyl- N-nitrosourea. The distributions of nuclear areas indicated that increases in ploidy contributed to, but did not totally account for, the nuclear enlargement. In contrast, diethylstilboestrol increased the range of nuclear areas and DNA content, to both less than and greater than that of control cells, but only after a prolonged exposure period of 48 hr. These data were consistent with diethylstilboestrol inducing spindle damage. These results demonstrate that carcinogen-induced nuclear enlargement is only partially explained by increased nuclear DNA content, and that certain classes of non-genotoxic carcinogen may produce a completely different pattern to that from genotoxic carcinogens.

Chromosome numbers in the Arthropodium–Dichopogon complex (Asparagales: Anthericaceae)

SummaryWestphalen, G. & Conran, J. G.: Chromosome numbers in the Arthropodium–Dichopogon complex (Asparagales: Anthericaceae). – Taxon 43: 377‐381.1994. – ISSN 0040‐0262.The genera Arthropodium and Dichopogon (Asparagales: Anthericaceae) are considered to be closely related, if at all distinct. Limited evidence from previous cytological studies suggested a polyploid series within the complex where Arthropodium taxa have 2n = 22 chromosomes, intermediate species, 2n = 44, and Dichopogon taxa, 2n = 66. Examination of chromosomes in two thirds of the species in the Arthropodium–Dichopogon complex did not support that suggestion, as most of the species in both genera have a chromosome complement of 2n = 22. Evidence of polyploidy was found in D. strictus (2n = 22, 66), A. curvipes and D. preissii (2n = 44). The chromosomes are too small to provide useful information on chromosome morphology and C‐band patterns. The lack of morphological features to delimit the two genera unequivocally, combined with the prevailing 2n = 22 karyotype across both, supports merging them under the name Arthropodium.

Nuclear DNA content of commercially important Eucalyptus species and hybrids

This paper reports the nuclear DNA content estimates obtained by flow cytometry for a group of twelve Eucalyptus species and five fast-growing hybrids that includes those most widely planted throughout the world. Estimates of nuclear (2C) DNA content for the species surveyed ranged from 0.77 pg/2C for Eucalyptuscitriodora Hook. (subgenus Corymbia) to 1.47 pg/2C for Eucalyptussaligna Smith (subgenus Symphyomyrtus). This range corresponds to a haploid genome size range of 370–700 megabase pairs. The average physical equivalent of a 1 cM distance could be as low as 200 kilobase pairs in Eucalyptus, an attractive feature for positional cloning efforts in woody plants. The closer the species were in phylogenetic relationship the more similar were their nuclear DNA content values. All the interspecific hybrids surveyed displayed a nuclear DNA content in the expected intermediate range between the respective parental species, with the exception of one originating from Rio Claro, Brazil, whose exact parentage is unknown. No evidence of polyploidy was observed in any of the hybrids. The flow cytometry procedure employed in this study is an efficient method for investigating ploidy levels of high yielding hybrids of Eucalyptus.