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PubMed1958

Genetics of somatic mammalian cells. II. Chromosomal constitution of cells in tissue culture.

A convenient, reliable method for chromosome delineation of animal cells grown as monolayers on glass has been applied to human, opossum, and Chinese hamster cells. Tissue cultured cells from 5 different, normal organs of 7 different human subjects uniformly displayed the expected chromosome number of 46 and showed no variations in morphology or number other than the expected sex differences and a small incidence of polyploidy. The chromosomes of normal cells from the American opossum were as uniform as those of human cells. Cells of the inbred Chinese hamster demonstrated appreciable karyotype variability, the cause of which is under investigation. The chromosome number and morphology of cells from normal human tissues have remained constant after more than 5 months of continuous, rapid growth in tissue culture involving scores of vessel transfers and a number of generations equivalent to many billions of progeny. By the use of routine recloning, even cells of malignant, aneuploid constitution have been maintained in active growth for 3 years and hundreds of generations, with stable chromosomal and metabolic characteristics. The cells of the American opossum and Chinese hamster which possess only 22 chromosomes have been established in vitro and are especially suitable for genetic studies. The readily recognizeable Y and X chromosomes of the male opossum are particularly favorable as cytological markers. Photomicrographs of the chromosomes of the various cells employed are presented.

Animals↗

PubMed2000

Comparative genomic hybridization in combination with flow cytometry improves results of cytogenetic analysis of spontaneous abortions.

More than 50% of spontaneous abortions (SAs) have abnormal chromosomes; the most common abnormalities are trisomy, sex chromosome monosomy, and polyploidy. Conventional cytogenetic analysis of SAs depends on tissue culturing and is associated with a significant tissue culture failure rate and contamination by maternally derived cells. Comparative genomic hybridization (CGH), in combination with flow cytometry (FCM), can detect numerical and unbalanced structural chromosomal abnormalities associated with SAs while avoiding the technical problems associated with tissue culture. Routine cytogenetic and CGH analysis was performed independently on tissue from 301 SAs. Samples shown to be chromosomally balanced by CGH were analyzed by FCM to determine ploidy. Of 253 samples successfully analyzed by both approaches, there was an absolute correlation of results in 235 (92.8%). Of the 18 cases with discrepancies between cytogenetic and CGH/FCM results, an explanation could be found in 17. Twelve samples produced a 46,XX karyotype by cytogenetics, whereas CGH/FCM demonstrated aneuploidy/polyploidy or a male genome, indicating maternal contamination of the tissue cultures. In two cases, where tetraploidy was demonstrated by cytogenetics and diploidy by FCM, tissue culture artifact is implied. In three cases, CGH demonstrated an aneuploidy, and cytogenetics demonstrated hypertriploidy. In one unexplainable case, aneuploidy demonstrated by CGH could not be detected by repeat CGH analysis, conventional cytogenetic, or FISH analysis. These results demonstrate that CGH supplemented with FCM can readily identify chromosomal abnormalities associated with SAs and, by avoiding maternal contamination and tissue culture artifacts, can do so with a lower failure rate and more accuracy than conventional cytogenetic analysis.

Abortion, Spontaneous↗

PubMed2005

Increased capacity for sustained locomotion at low temperature in parthenogenetic geckos of hybrid origin.

The evolution of parthenogenesis is typically associated with hybridization and polyploidy. These correlates of parthenogenesis may have important physiological consequences that need be taken into account in understanding the relative merits of sexual and parthenogenetic reproduction. We compared the thermal sensitivity of aerobically sustained locomotion in hybrid/triploid parthenogenetic races of the gecko Heteronotia binoei and their diploid sexual progenitors. Endurance times at low temperature (10 degrees , 12.5 degrees , and 15 degrees C, 0.05 km h(-1)) were significantly greater in parthenogenetic females than in sexual females. Comparison of oxygen consumption rates during sustained locomotion at increasing speeds (0.05, 0.10, 0.15, 0.20, 0.25, and 0.30 km h(-1), 25 degrees C) indicated that parthenogenetic lizards have higher maximum oxygen consumption rates and maximum aerobic speeds than do female sexual geckos. In addition, parthenogenetic geckos showed greater levels of voluntary activity at 15 degrees C than did sexual geckos, although this pattern appears strongest in comparison to male sexual forms. Parthenogenetic lineages of Heteronotia thus have an advantage over sexual lineages in being capable of greater aerobic activity. This result is opposite of that found in prior studies of parthenogenetic teiid lizards (genus Cnemidophorus) and highlights the idiosyncratic nature of phenotypic evolution in parthenogens of hybrid origin.

Analysis of Variance↗

PubMed2002

Flt3/Flk-2-ligand in synergy with thrombopoietin delays megakaryocyte development and increases the numbers of megakaryocyte progenitor cells in serum-free cultures initiated with CD34+ cells.

Megakaryocytopoiesis involves proliferation and maturation of committed precursors that increase their size by polyploidy, a process that is believed to be critical for the efficient production and release of platelets. Thrombopoietin has been shown to act on proliferation, maturation, and survival pathways in megakaryocytopoiesis. Less is known about the role of Flt3/Flk-2-ligand in this development. Apoptosis has an important role in hematopoiesis in general. It has been shown to have an effect on senescent megakaryocytes but not megakaryocyte progenitor cells. In this study, a serum-free culture model was developed, differentiating bone marrow CD34(+) hematopoietic stem cells into megakaryocytes, using thrombopoietin and Flt3/Flk-2-ligand. The model was used to study the effect of these growth factors on expansion of megakaryocyte progenitor cells, differentiation of megakaryocytes, and ploidy. Our results demonstrate that bone marrow CD34(+) cells cultured with thrombopoietin and Flt3/Flk-2-ligand show a lower developmental rate into MK cells compared to cells cultured with thrombopoietin alone. Cells cultured with thrombopoietin and Flt3/Flk-2-ligand expressed less CD41, the ploidy level was lower, and they appeared less mature. On the other hand, the cells showed up to 10-fold increase in cell numbers compared to five-fold increase when cultured with thrombopoietin alone. These results suggest that Flt3/Flk-2-ligand in synergy with thrombopoietin may slow down megakaryocyte development by causing increased proliferation of megakaryocyte progenitor cells.

Antigens, CD34↗

PubMed2003

Preferential ex vivo expansion of megakaryocytes from human cord blood CD34+-enriched cells in the presence of thrombopoietin and limiting amounts of stem cell factor and Flt-3 ligand.

The high proliferative potential of cord blood (CB) stem cells and the identification of the key factor of megakaryopoiesis, thrombopoietin (TPO), permit the ex vivo expansion of megakaryocytes (MKs) for possible use in early post-transplant support of patients and the production of functional platelets for transfusion. However, culture conditions for the generation of adequate MKs for this purpose are not yet optimized. Therefore, we sought to define the mixture of early-acting cytokines and TPO that would promote the expansion of MK progenitors over other lineages and result in overall better MK expansion and platelet yields. CB CD34(+)-enriched cells were cultured in serum-free medium for 17 days in presence of TPO alone or in various combinations with early-acting cytokines used at different concentrations and addition times. MK expansion and polyploidy and platelet production were monitored by flow cytometry analysis using specific surface markers (CD41 and CD42b) and propidium iodide labeling. Our results showed that the use of high concentrations of stem cell factor (SCF) and Flt-3 ligand (FL) in early CB TPO-supplemented cultures was more favorable to monocytic and granulocytic cell expansion. However, we observed that their presence in limiting amounts was required for the preferential expansion of MK progenitors. The addition of SCF, FL, TPO, and interleukin-6 (IL-6) at high concentrations in secondary cultures of these expanded MKs resulted in optimal MK proportion (approximately 25% of MKs) and expansion (>300 MK per seeded cell), highest proportions of polyploid MKs (22% of mature MKs > or = 8N), and best platelet yields. Our results indicate that TPO-induced MK progenitors are more sensitive to early-acting cytokines than non-MK cells. We propose that MKs generated in the optimized conditions, in combination with immature stem/progenitor cells, could prove useful for the short-term platelet recovery following CB transplantation.

Antigens, CD34↗

PubMed2002

Chromosomal abnormalities: a potential quality issue for cloned cattle embryos.

Nuclear transfer in cattle is associated with high levels of embryonic mortality and often with congenital malformation. Chromosomal abnormalities are a well-known cause of pregnancy failure and congenital malformation in humans, but their relative contribution to pregnancy failure and congenital malformation in cloned embryos and calves is largely unknown. This paper reviews existing literature on the chromosomal constitution of bovine embryos produced by fertilization in vivo and in vitro, parthenogenetic activation, and nuclear transfer. The published data suggest that chromosomally abnormal cells are common in embryos; however, the frequency reported varies with the method of embryo production. The most frequently observed deviation from the diploid karyotype was mixoploidy resulting from aberrant cell division causing polyploidy in a variable proportion of the embryo's cells.

Animals↗

PubMed1988

Flow cytometric analysis of DNA content in Hürthle cell adenomas and carcinomas of the thyroid.

Paraffin-embedded surgical biopsy material from 17 Hürthle cell tumors of the thyroid was examined for DNA content by flow cytometry to assess the diagnostic and prognostic utility of ploidy determinations in these rare tumors. Both adenomas (11 cases) and carcinomas (6 cases) were studied. As a control for methods, ten randomly selected normal autopsy thyroids were analyzed, all of which demonstrated normal diploid DNA content. Among the Hürthle cell tumors, however, aneuploid peaks were present in six adenomas (55%) and in four carcinomas (67%). Similarly, polyploid DNA peaks in the absence of other aneuploid peaks were present in two adenomas and two carcinomas (18% and 33%, respectively). These findings demonstrate the limited value of aneuploidy or polyploidy as diagnostic features for malignancy in Hürthle cell tumors of the thyroid. As for prognosis, there does not appear to be any unfavorable prognostic significance for abnormal DNA content in histologically benign Hürthle cell tumors treated by surgical excision because no metastases or recurrences occurred in this group at a mean disease-free follow-up of 50 +/- 19 months for six aneuploid lesions and 19 +/- 7 months for two polyploid adenomas. Preliminary data suggest that aneuploidy may, however, have an important prognostic value for histologically defined Hürthle cell carcinomas, because the only patient to die from the tumor in this series had an aneuploid Hürthle carcinoma. Thus, the authors' data indicate that the diagnostic utility of DNA content in Hürthle cell tumors is extremely limited and that there does not appear to be any negative prognostic significance for aneuploidy in histologically defined Hürthle cell adenomas.

Adenoma↗

PubMed2004

Analysis of the spatial expression pattern of seven Kip related proteins (KRPs) in the shoot apex of Arabidopsis thaliana.

BACKGROUND AND AIMS: Kip-related-proteins (KRPs), negative regulators of cell division, have recently been discovered in plants but their in planta function is as yet unclear. In this study the spatial expression of all seven KRP genes in shoot apices of Arabidopsis thaliana were compared. METHODS: In situ hybridization analyses were performed on longitudinal sections of shoot apices from 2-month-old Arabidopsis plants. KEY RESULTS: The study provides evidence for different expression pattern groups. KRP1 and KRP2 expression is restricted to the endoreduplicating tissues. In contrast, KRP4 and KRP5 expression is mainly restricted to mitotically dividing cells. KRP3, KRP6 and KRP7 can be found in both mitotically dividing and endoreduplicating cells. CONCLUSION: The results suggest differential roles for the distinct KRPs. KRP1 and KRP2 might specifically be involved in the establishment of polyploidy. In contrast, KRP4 and KRP5 might be involved in regulating the progression through the mitotic cell cycle. KRP3, KRP6 and KRP7 might have a function in both types of cell cycle.

Arabidopsis↗

PubMed2005

Nuclear DNA content estimates in multicellular green, red and brown algae: phylogenetic considerations.

BACKGROUND AND AIMS: Multicellular eukaryotic algae are phylogenetically disparate. Nuclear DNA content estimates have been published for fewer than 1 % of the described species of Chlorophyta, Phaeophyta and Rhodophyta. The present investigation aims to summarize the state of our knowledge and to add substantially to our database of C-values for theses algae. METHODS: The DNA-localizing fluorochrome DAPI (4', 6-diamidino-2-phenylindole) and RBC (chicken erythrocyte) standard were used to estimate 2C values with static microspectrophotometry. KEY RESULTS: 2C DNA contents for 85 species of Chlorophyta range from 0.2-6.1 pg, excluding the highly polyploidy Charales and Desmidiales with DNA contents of up to 39.2 and 20.7 pg, respectively. 2C DNA contents for 111 species of Rhodophyta range from 0.1-2.8 pg, and for 44 species of Phaeophyta range from 0.2-1.8 pg. CONCLUSIONS: New availability of consensus higher-level molecular phylogenies provides a framework for viewing C-value data in a phylogenetic context. Both DNA content ranges and mean values are greater in taxa considered to be basal. It is proposed that the basal, ancestral genome in each algal group was quite small. Both mechanistic and ecological processes are discussed that could have produced the observed C-value ranges.

Cell Nucleus↗

PubMed2005

The origin, evolution and proposed stabilization of the terms 'genome size' and 'C-value' to describe nuclear DNA contents.

BACKGROUND: Perusing the literature on nuclear 'genome size' shows that the term is not stabilized, but applied with different meanings. It is used for the DNA content of the complete chromosome complement (with chromosome number n), for which others use 'C-value', but also for the DNA content of the monoploid chromosome set only (with chromosome number x). Reconsideration of the terminology is required. AIM: Our purpose is to discuss the currently unstable usage of the terms 'genome size' and 'C-value', and to propose a new unified terminology which can describe nuclear DNA contents with ease and without ambiguity. PROPOSALS: We argue that there is a need to maintain the term genome size in a broad sense as a covering term, because it is widely understood, short and phonetically pleasing. Proposals are made for a unified and consensual terminology. In this, 'genome size' should mean the DNA content based on chromosome number x and n, and should be used mainly in a general sense. The necessary distinction of the kinds of genome sizes is made by the adjectives 'monoploid' and the neology 'holoploid'. 'Holoploid genome size' is a shortcut for the DNA content of the whole chromosome complement characteristic for the individual (and by generalization for the population, species, etc.) irrespective of the degree of generative polyploidy, aneuploidies, etc. This term was lacking in the terminology and is for reasons of linguistic consistency indispensable. The abbreviated terms for monoploid and holoploid genome size are, respectively, Cx-value and C-value. Quantitative data on genome size should always indicate the C-level by a numerical prefix, such as 1C, 1Cx, 2C, etc. The proposed conventions cover general fundamental aspects relating to genome size in plants and animals, but do not treat in detail cytogenetic particularities (e.g. haploids, hybrids, etc.) which will need minor extensions of the present scheme in a future paper.

Cell Nucleus↗

PubMed2006

Spore fitness components do not differ between diploid and allotetraploid species of Dryopteris (Dryopteridaceae).

BACKGROUND AND AIMS: Although allopolyploidy is a prevalent speciation mechanism in plants, its adaptive consequences are poorly understood. In addition, the effects of allopolyploidy per se (i.e. hybridization and chromosome doubling) can be confounded with those of subsequent evolutionary divergence between allopolyploids and related diploids. This report assesses whether fern species with the same ploidy level or the same altitudinal distribution have similar germination responses to temperature. The effects of polyploidy on spore abortion and spore size are also investigated, since both traits may have adaptive consequences. METHODS: Three allotetraploid (Dryopteris corleyi, D. filix-mas and D. guanchica) and three related diploid taxa (D. aemula, D. affinis ssp. affinis and D. oreades) were studied. Spores were collected from 24 populations in northern Spain. Four spore traits were determined: abortion percentage, size, germination time and germination percentage. Six incubation temperatures were tested: 8, 15, 20, 25 and 32 degrees C, and alternating 8/15 degrees C. KEY RESULTS: Allotetraploids had bigger spores than diploid progenitors, whereas spore abortion percentages were generally similar. Germination times decreased with increasing temperatures in a wide range of temperatures (8-25 degrees C), although final germination percentages were similar among species irrespective of their ploidy level. Only at low temperature (8 degrees C) did two allotetraploid species reach higher germination percentages than diploid parents. Allotetraploids showed faster germination rates, which would probably give them a competitive advantage over diploid parents. Germination behaviour was not correlated with altitudinal distribution of species. CONCLUSIONS: The results of this study suggest that (i) relative fitness of allopolyploids at sporogenesis does not differ from that of diploid parents and (ii) neither does allopolyploidization involve a change in the success of spore germination.

Dryopteris↗

PubMed2006

Karyotype variation, evolution and phylogeny in Borago (Boraginaceae), with emphasis on subgenus Buglossites in the Corso-Sardinian system.

BACKGROUND AND AIMS: Karyological variation in the Mediterranean genus Borago and cytogeography of subgenus Buglossites in Corsica, Sardinia and the Tuscan Archipelago were investigated in combination with a molecular phylogenetic analysis aimed at elucidating relationships between subgenera and taxa with different chromosome features. METHODS: Karyotype analysis was performed on population samples of B. pygmaea, B. morisiana, B. trabutii and B. officinalis. Phylogenetic analyses were based on ITS1 nrDNA and matK cpDNA sequences. KEY RESULTS: Four base numbers were found, x = 6, 8, 9 and 15, and three ploidy levels based on x = 8. In subgenus Buglossites the Sardinian endemic B. morisiana is diploid with 2n = 18, while B. pygmaea includes three allopatric cytotypes with 2n = 30 (Sardinia), 2n = 32 (southern Corsica) and 2n = 48 (central northern Corsica and Capraia). In subgenus Borago, the Moroccan endemic B. trabutii and the widespread B. officinalis have 2n = 12 and 2n = 16, respectively. Molecular data support the monophyly of Borago, while relationships in subgenus Borago remain unclear. Borago trabutii appears as the earliest divergent lineage and is sister to a clade with B. officinalis, B. morisiana and B. pygmaea. Subgenus Buglossites is also monophyletic, but no correspondence between ITS1 phylogeny and B. pygmaea cytotypes occurs. CONCLUSIONS: Chromosome variation in Borago is wider than previously known. Two base numbers may represent the ancestral condition in this small genus, x = 6 or x = 8. An increase in chromosome number and karyotype asymmetry, a decrease in chromosome size and heterochromatin content, and the appearance of polyploidy are the most significant karyological changes associated with the divergence of the Buglossites clade. High ITS1 variation in the tetra- and hypotetraploid races of B. pygmaea suggests a multiple origin, while the lower polymorphism of the hexaploid race and its allopatric distribution in the northernmost part of the range is better explained with a single origin via union of unreduced and reduced gametes.

Borago↗

PubMed1993

Ploidy and nuclearity of rat hepatocytes after compensatory regeneration or mitogen-induced liver growth.

The distribution pattern of rat liver parenchymal cells of different ploidy classes was investigated in Wistar rats following cell proliferation induced by surgical partial hepatectomy (compensatory regeneration) or primary mitogens (direct hyperplasia). Animals were killed at 1, 2, 3, 4 and 15 days after the proliferative stimulus, and ploidy and nuclearity were measured using a computer-assisted imaging system in hepatocytes isolated by collagenase perfusion. Analysis of hepatocytes from animals undergoing regeneration after partial hepatectomy revealed a large increase in tetraploid and octoploid mononucleate cells. The most striking feature was the almost complete disappearance of binucleate cells (from 20% to < 1%) at 3 days after partial hepatectomy. On the contrary, when hepatocytes were analyzed after treatment with the mitogen lead nitrate, a high number of binucleate cells (40%) was observed. The increase that was maximal at 3 days after treatment occurred mainly in 4 x 2c and in 8 x 2c compartments. This resulted in an overall increase in the ratio of binucleate/mononucleate cells as well as in the ratio (8c + 16c):(2c + 4c). The cytological changes induced by lead nitrate were not reversible 2 weeks after treatment. Because a massive elimination of excess liver cells occurred by apoptosis during this time period, it appears that polyploid cells are not preferentially eliminated. The hepatic content of DNA at the end of the regression phase was similar to control values. However, because of the higher ploidy state, the number of cells present in the liver 2 weeks after treatment appears to be lower than that of controls (approximately -16%). When liver growth was induced by a single treatment with another mitogen, the peroxisome proliferator nafenopin, a slight increase in the ploidy state of the liver was observed; because of the shift towards higher ploidy classes (8c), the increase in DNA content observed 3 days after a single treatment with nafenopin (+21%) appears to be almost entirely justified by polyploidy rather than by a hyperplastic event.

Animals↗

PubMed1998

AIM-1: a mammalian midbody-associated protein required for cytokinesis.

Mitosis is a highly coordinated process that assures the fidelity of chromosome segregation. Errors in this process result in aneuploidy which can lead to cell death or oncogenesis. In this paper we describe a putative mammalian protein kinase, AIM-1 (Aurora and Ipl1-like midbody-associated protein), related to Drosophila Aurora and Saccharomyces cerevisiae Ipl1, both of which are required for chromosome segregation. AIM-1 message and protein accumulate at G2/M phase. The protein localizes at the equator of central spindles during late anaphase and at the midbody during telophase and cytokinesis. Overexpression of kinase-inactive AIM-1 disrupts cleavage furrow formation without affecting nuclear division. Furthermore, cytokinesis frequently fails, resulting in cell polyploidy and subsequent cell death. These results strongly suggest that AIM-1 is required for proper progression of cytokinesis in mammalian cells.

Amino Acid Sequence↗

PubMed1988

Identification of the "A" genome of finger millet using chloroplast DNA.

Finger millet (Eleusine corocana subsp. coracana), an important cereal in East Africa and India, is a tetraploid species with unknown genomic components. A recent cytogenetic study confirmed the direct origin of this millet from the tetraploid E. coracana subsp. africana but questioned Eleusine indica as a genomic donor. Chloroplast (ct) DNA sequence analysis using restriction fragment pattern was used to examine the phylogenetic relationships between E. coracana subsp. coracana (domesticated finger millet), E. coracana subspecies africana (wild finger millet), and E. indica. Eleusine tristachya was included since it is the only other annual diploid species in the genus with a basic chromosome number of x = 9 like finger millet. Eight of the ten restriction endonucleases used had 16 to over 30 restriction sites per genome and were informative. E. coracana subsp. coracana and subsp. africana and E. indica were identical in all the restriction sites surveyed, while the ct genome of E, tristachya differed consistently by at least one mutational event for each restriction enzyme surveyed. This random survey of the ct genomes of these species points out E. indica as one of the genome donors (maternal genome donor) of domesticated finger millet contrary to a previous cytogenetic study. The data also substantiate E. coracana subsp. africana as the progenitor of domesticated finger millet. The disparity between the cytogenetic and the molecular approaches is discussed in light of the problems associated with chromosome pairing and polyploidy.

Chloroplasts↗

PubMed1992

Comparative genome mapping of Sorghum and maize.

Linkage relationships were determined among 85 maize low copy number nuclear DNA probes and seven isozyme loci in an F2 population derived from a cross of Sorghum bicolor ssp. bicolor x S. bicolor ssp. arundinaceum. Thirteen linkage groups were defined, three more than the 10 chromosomes of sorghum. Use of maize DNA probes to produce the sorghum linkage map allowed us to make several inferences concerning processes involved in the evolutionary divergence of the maize and sorghum genomes. The results show that many linkage groups are conserved between these two genomes and that the amount of recombination in these conserved linkage groups is roughly equivalent in maize and sorghum. Estimates of the proportions of duplicated loci suggest that a larger proportion of the loci are duplicated in the maize genome than in the sorghum genome. This result concurs with a prior estimate that the nuclear DNA content of maize is three to four times greater than that of sorghum. The pattern of conserved linkages between maize and sorghum is such that most sorghum linkage groups are composed of loci that map to two maize chromosomes. This pattern is consistent with the hypothesized ancient polyploid origin of maize and sorghum. There are nine cases in which locus order within shared linkage groups is inverted in sorghum relative to maize. These may have arisen from either inversions or intrachromosomal translocations. We found no evidence for large interchromosomal translocations. Overall, the data suggest that the primary processes involved in divergence of the maize and sorghum genomes were duplications (either by polyploidy or segmental duplication) and inversions or intrachromosomal translocations.

Chromosome Mapping↗

PubMed1995

Meiotic chromosome pairing in triploid and tetraploid Saccharomyces cerevisiae.

Meiotic chromosome pairing in isogenic triploid and tetraploid strains of yeast and the consequences of polyploidy on meiotic chromosome segregation are studied. Synaptonemal complex formation at pachytene was found to be different in the triploid and in the tetraploid. In the triploid, triple-synapsis, that is, the connection of three homologues at a given site, is common. It can even extend all the way along the chromosomes. In the tetraploid, homologous chromosomes mostly come in pairs of synapsed bivalents. Multiple synapsis, that is, synapsis of more than two homologues in one and the same region, was virtually absent in the tetraploid. About five quadrivalents per cell occurred due to the switching of pairing partners. From the frequency of pairing partner switches it can be deduced that in most chromosomes synapsis is initiated primarily at one end, occasionally at both ends and rarely at an additional intercalary position. In contrast to a considerably reduced spore viability (approximately 40%) in the triploid, spore viability is only mildly affected in the tetraploid. The good spore viability is presumably due to the low frequency of quadrivalents and to the highly regular 2:2 segregation of the few quadrivalents that do occur. Occasionally, however, quadrivalents appear to be subject to 3:1 nondisjunction that leads to spore death in the second generation.

Chromosomes, Fungal↗

PubMed2001

Transmission genetics of chromatin from a synthetic amphidiploid to cultivated peanut (Arachis hypogaea L.). broadening the gene pool of a monophyletic polyploid species.

Polyploidy creates severe genetic bottlenecks, contributing to the genetic vulnerability of leading crops. Cultivated peanut is thought to be of monophyletic origin, harboring relatively little genetic diversity. To introduce variability from diploid wild species into tetraploid cultivated Arachis hypogaea, a synthetic amphidiploid [[A. batizocoi K9484 x (A. cardenasii GKP10017 x A. diogoi GKP10602)](4x)] was used as donor parent to generate a backcross population of 78 progeny. Three hundred seventy RFLP loci were mapped onto 23 linkage groups, spanning 2210 cM. Chromatin derived from the two A-genome diploid ancestors (A. cardenasii and A. diogoi) comprised mosaic chromosomes, reflecting crossing over in the diploid A-genome interspecific F(1) hybrid. Recombination between chromosomes in the tetraploid progeny was similar to chromosome pairing reported for A. hypogaea, with recombination generally between chromosomes of the same subgenomic affinity. Segregation distortion was observed for 25% of the markers, distributed over 20 linkage groups. Unexpectedly, 68% of the markers deviating from expected segregation showed an excess of the synthetic parent allele. Genetic consequences, relationship to species origins, and significance for comparative genetics are discussed.

Arachis↗