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PubMed1994

Sex determination in polyploids of Caenorhabditis elegans.

In Caenorhabditis elegans triploid animals with two X chromosomes (symbolized 3A;2X) are males. However, these triploid males can be feminized by making them mutant for recessive dosage compensation mutations, by adding X chromosome duplications or by microinjecting particular DNA sequences termed feminizing elements. None of these treatments affects diploid males. This study explores several aspects of these treatments in polyploids. The dosage compensation mutants exhibit a strong maternal effect, such that reduction of any of the dosage compensation gene functions in the mother leads to sex reversal of 3A;2X animals. Likewise, all X chromosome duplications tested cause both sex reversal and intersexual development of many 3A;2X animals. Microinjected feminizing element DNA does not cause extensive sex reversal, but does result in intersexual development in 3A;2X animals. Neither X chromosome duplications nor microinjected feminizing elements show that extreme maternal effect of the dosage compensation mutants, although there is indirect evidence for a maternal effect of the feminizing elements. In particular, very little feminizing element DNA needs to be microinjected in order to feminize triploid males, far less than what is needed for stable inheritance, implying that feminizing elements can work within the mother's gonad. However, even very high concentrations of microinjected feminizing elements do not affect sex determination in diploid males, suggesting that they are not part of the numerator of the X/A ratio. In addition, no pair of X chromosome duplications feminizes diploid males, suggesting that none of these duplications contains a numerator of the X/A ratio. Instead, I infer that an X-linked locus, as yet undefined, must be present in two copies for hermaphrodite development to ensue or that the two X chromosomes might interact.

Animals↗

PubMed1994

Sex determination and polyploid gigantism in the dwarf surfclam (Mulinia lateralis Say).

Mulinia lateralis, the dwarf surfclam, is a suitable model for bivalve genetics because it is hardy and has a short generation time. In this study, gynogenetic and triploid M. lateralis were successfully induced. For gynogenesis, eggs were fertilized with sperm irradiated with ultraviolet light and subsequently treated with cytochalasin B to block the release of the second polar body (PB2). Triploidy was induced by blocking PB2 in normally fertilized eggs. The survival of gynogenetic diploids was very low, only 0.7% to 8 days post-fertilization (PF), compared with 15.2% in the triploid groups and 27.5% in the normal diploid control. Larvae in all groups metamorphosed at 8-10 days PF, and there was no significant post-larval mortality. At sexual maturation (2-3 months PF), all gynogenetic diploids were female, and there was no significant difference (P > 0.05) in sex ratio between diploids and triploids. These results suggested that the dwarf surfclam may have an XX-female, XY-male sex determination with Y-domination. Compared with diploids, triploids had a relative fecundity of 59% for females and 80% for males. Eggs produced by triploid females were 53% larger (P < 0.001) in volume than those from diploid females. In both length and weight measurements at three months PF, the gynogenetic diploids were not significantly (P > 0.33) different from normal diploid females, suggesting that inbreeding depression was minimal in meiosis II gynogens. Triploid clams were significantly larger (P < 0.001) than normal diploids. We hypothesize that the increased body-size in triploids was caused by a polyploid gigantism due to the increased cell volume and a lack of cell-number compensation.

Animals↗

PubMed1996

RFLP mapping in cultivated sugarcane (Saccharum spp.): genome organization in a highly polyploid and aneuploid interspecific hybrid.

Sugarcane cultivars are polyploid, aneuploid, interspecific hybrids between the domesticated species Saccharum officinarum and the wild relative S. spontaneum. Cultivar chromosome numbers range from 100 to 130 with approximately 10% contributed by S. spontaneum. We have undertaken a mapping study on the progeny of a selfed cultivar, R570, to analyze this complex genome structure. A set of 128 restriction fragment length polymorphism probes and one isozyme was used. Four hundred and eight markers were placed onto 96 cosegregation groups, based on linkages in coupling only. These groups could tentatively be assembled into 10 basic linkage groups on the basis of common probes. Origin of markers was investigated for 61 probes and the isozyme, leading to the identification of 80 S. officinarum and 66 S. spontaneum derived markers, respectively. Their distribution in cosegregation groups showed better map coverage for the S. spontaneum than for the S. officinarum genome fraction and occasional recombination between the two genomes. The study of repulsions between markers suggested the prevalence of random pairing between chromosomes, typical of autopolyploids. However, cases of preferential pairing between S. spontaneum chromosomes were also detected. A tentative Saccharum map was constructed by pooling linkage information for each linkage group.

Aneuploidy↗

PubMed1998

D-subgenome bias of Xcm resistance genes in tetraploid Gossypium (cotton) suggests that polyploid formation has created novel avenues for evolution.

A detailed RFLP map was used to determine the chromosomal locations and subgenomic distributions of cotton (Gossypium) genes/QTLs that confer resistance to the bacterial blight pathogen, Xanthomonas campestris pv. malvacearum (Xcm). Genetic mapping generally corroborated classic predictions regarding the number and dosage effects of genes conferring Xcm resistance. One recessive allele (b6) was a noteworthy exception to the genetic dominance of most plant resistance alleles. This recessive allele appeared to uncover additional QTLs from both resistant and ostensibly susceptible genotypes, some of which corresponded in location to resistance (R)-genes effective against other Xcm races. One putatively "defeated" resistance allele (B3) reduced severity of Xcm damage by "virulent" races. Among the six resistance genes derived from tetraploid cottons, five (83%) mapped to D-subgenome chromosomes-if each subgenome were equally likely to evolve new R-gene alleles, this level of bias would occur in only about 1.6% of cases. Possible explanations of this bias include biogeographic factors, differences in evolutionary rates between subgenomes, gene conversion or other intergenomic exchanges that escaped detection by genetic mapping, or other factors. A significant D-subgenome bias of Xcm resistance genes may suggest that polyploid formation has offered novel avenues for phenotypic response to selection.

Biological Evolution↗

PubMed1998

Detailed alignment of saccharum and sorghum chromosomes: comparative organization of closely related diploid and polyploid genomes.

The complex polyploid genomes of three Saccharum species have been aligned with the compact diploid genome of Sorghum (2n = 2x = 20). A set of 428 DNA probes from different Poaceae (grasses) detected 2460 loci in F1 progeny of the crosses Saccharum officinarum Green German x S. spontaneum IND 81-146, and S. spontaneum PIN 84-1 x S. officinarum Muntok Java. Thirty-one DNA probes detected 226 loci in S. officinarum LA Purple x S. robustum Molokai 5829. Genetic maps of the six Saccharum genotypes, including up to 72 linkage groups, were assembled into "homologous groups" based on parallel arrangements of duplicated loci. About 84% of the loci mapped by 242 common probes were homologous between Saccharum and Sorghum. Only one interchromosomal and two intrachromosomal rearrangements differentiated both S. officinarum and S. spontaneum from Sorghum, but 11 additional cases of chromosome structural polymorphism were found within Saccharum. Diploidization was advanced in S. robustum, incipient in S. officinarum, and absent in S. spontaneum, consistent with biogeographic data suggesting that S. robustum is the ancestor of S. officinarum, but raising new questions about the antiquity of S. spontaneum. The densely mapped Sorghum genome will be a valuable tool in ongoing molecular analysis of the complex Saccharum genome.

DNA, Plant↗

PubMed1975

Genetic polymorphism and evolution in parthenogenetic animals. II. Diploid and polyploid Solenobia triquetrella (Lepidoptera: Psychidae).

Genic polymorphism at sixteen enzyme loci of four different chromosomal races of Solenobia triquetrella (bisexual, two diploid parthenogenetic races and tetraploid parthenogentiic) has been studied by starch gel electrophoresis. Isolated small diploid bisexual populations have rather uniform allele frequencies at all loci which we have studied. Diploid and tetraploid parthenogenetic individuals of this species are in general as heterozygous as bisexual ones. All parthenogenetic local populations are different from each other in the Alps. These parthenogenetic genotypes cannot be derived from a common ancestor through single mutations but rather bear evidence for a polyphyletic origin of parthenogenesis in Solenobia triquetrella. In the marginal distribution areas of the species in northern Europe single genotypes are spread over far larger areas than in the mountain regions of central Europe. This may be due to the old origin of parthenogenesis and polyploidy in northern Europe. No new parthenogenetic and polyploid strains have lately arisen in the regions outside of the Alps.

Alcohol Oxidoreductases↗

PubMed1995

Statistical methods for polyploid radiation hybrid mapping.

Radiation hybrid mapping is a somatic cell technique for ordering genetic loci along a chromosome and estimating physical distances between adjacent loci. This paper presents a model of fragment generation and retention for data involving two or more copies of the chromosome of interest per clone. Such polyploid data can be generated by initially irradiating normal diploid cells or by pooling haploid or diploid clones. The current model assumes that fragments are generated in the ancestral cell of a clone according to an independent Poisson breakage process along each chromosome. Once generated, fragments are independently retained in the clone with a common retention probability. On the basis of this and less restrictive retention models, statistical criteria such as minimum obligate breaks, maximum likelihood ratios, and Bayesian posterior probabilities can be used to decide locus order. Distances can be estimated by maximum likelihood. Likelihood computation is particularly challenging, and computing techniques from the theory of hidden Markov chains prove crucial. Within this context it is possible to incorporate typing errors. The statistical tools discussed here are applied to 14 loci on the short arm of human chromosome 4.

Chromosome Mapping↗

PubMed1999

Posttranscriptional gene silencing in transgenic sugarcane. Dissection Of homology-dependent virus resistance in a monocot that has a complex polyploid genome

RNA-mediated, posttranscriptional gene silencing has been determined as the molecular mechanism underlying transgenic virus resistance in many plant virus-dicot host plant systems. In this paper we show that transgenic virus resistance in sugarcane (Saccharum spp. hybrid) is based on posttranscriptional gene silencing. The resistance is derived from an untranslatable form of the sorghum mosaic potyvirus strain SCH coat protein (CP) gene. Transgenic sugarcane plants challenged with sorghum mosaic potyvirus strain SCH had phenotypes that ranged from fully susceptible to completely resistant, and a recovery phenotype was also observed. Clones derived from the same transformation event or obtained after vegetative propagation could display different levels of virus resistance, suggesting the involvement of a quantitative component in the resistance response. Most resistant plants displayed low or undetectable steady-state CP transgene mRNA levels, although nuclear transcription rates were high. Increased DNA methylation was observed in the transcribed region of the CP transgenes in most of these plants. Collectively, these characteristics indicate that an RNA-mediated, homology-dependent mechanism is at the base of the virus resistance. This work extends posttranscriptional gene silencing and homology-dependent virus resistance, so far observed only in dicots, to an agronomically important, polyploid monocot.

Journal Article↗

PubMed1993

Binucleation and polyploidization patterns in developmental and regenerative rat liver growth.

The hepatocellular binucleation rate, measured as the percentage of binuclear cells amongst newly formed bromodeoxyuridine-labelled and immunostained collagenase-isolated rat hepatocytes, decreased from 12% to 4% between days 30 and 40 after birth, rose to 20% between days 50 and 60, and then declined again to the adult rate of about 10% at day 80. During regenerative growth following a two-thirds partial hepatectomy, the rate of binucleation declined to about 3%, causing the fraction of binuclear cells to fall from 27% (before hepactectomy) to 5% (at 45 h after hepactectomy) as pre-existing binuclear cells replicated and formed mononuclear daughter cells. Essentially all (97%) hepatocytes replicated at least once, starting their DNA synthesis at around 13 h and reaching a peak at 30 h, irrespective of ploidy and nuclearity. At later time points, the diploid hepatocytes had a higher labelling index than the polyploid cells, suggesting a greater tendency to go through several cell cycles.

Animals↗

PubMed1978

Indirect immunofluorescence microscopy of microtubular structures in male germ cells of wildtype and l(3)pl (lethal-polyploid) Drosophila hydei.

Tubulin-containing structures of the male germ cells of Drosophila hydei crossreact in indirect immunofluorescence microscopy with antibody directed against homogeneous porcine brain tubulin. There is no detectable difference in reactivity between germ cells of wildtype flies and the mutant l(3)pl (lethal-polyploid) which is characterized by microtubular abnormalities. However, the technique of indirect immunofluorescence microscopy allows the direct visualization of several abnormalities in the arrangement of the microtubular system of the mutant, particularly in the axonemal complex.

Animals↗

PubMed1966

Hylid frogs: polyploid classes of DNA in liver nuclei.

Microspectrophotometric DNA determinations on liver nuclei of hylid frogs have revealed the presence of several polyploid classes of DNA in several specimens belonging to five species. All such specimens were breeding.

Animals↗

PubMed1976

Polyploid amphibians: three more diploid-tetraploid cryptic species of frogs.

The nominal African species Pyxicephalus delalandii and Dicroglossus occipitalis have diploid and tetraploid populations. There are also cryptic tetraploid and diploid species similar to Bufo kerinyagae. These represent the first bisexual polyploid "species" so far encountered in the major frog families Ranidae and Bufonidae. The contention that polyploidy is a widespread and important evolutionary phenomenon in anuran amphibians is supported.

Africa↗

PubMed1982

Dengue virus replication in a polyploid mosquito cell culture grown in serum-free medium.

A subline of a polyploid cell line (TRA-284) derived from a nonbiting mosquito, Toxorhynchites amboinensis, was adapted to a serum-free medium. The sensitivity of the subline (TRA-284-SF) to all serotypes of adapted dengue viruses was generally comparable to that of Aedes albopictus (C6/36), and DEN 3 viruses replicated to higher titers in TRA-28F-SF cells than in C6/36 cells. The subline was found to be useful for isolation of dengue viruses from human serum, since isolation rates were higher in TRA-284-SF cells than in C6/36 cells. The advantages of using a serum-free medium and mosquito cells for virus isolation are discussed.

Animals↗

PubMed1977

Origin of human trisomics and polyploids.

A mathematical theory is derived for the distribution of heteromorphisms in trisomics and polyploids. Applied to the sparse literature, it appears that most trisomy 21 is due to first division maternal nondisjunction, although there are case reports of second division nondisjunction, both paternal and maternal. Most triploids appear to be due to dispermy or failure of the first meiotic division in the oocyte. The need for larger systematic samples is stressed. This maximum likelihood analysis gives great resolution to epidemiological studies, permitting discrimination of etiological factors acting on fathers and mothers, at different meiotic stages, and on dispermy.

Chromosomes, Human, 21-22 and Y↗

PubMed1997

Polyploid-specific repetitive DNA sequences from triploid ginbuna (Japanese silver crucian carp, Carassius auratus langsdorfi).

Repetitive DNA sequences (Cal3nDr) in the genome of a triploid ginbuna (Carassius auratus langsdorfi) were isolated from the DraI digests of the genomic DNA. This AT-rich (61%) Cal3nDr monomer was 137 bp in length. The nucleotide similarity among the monomers from the same individual was considerably high (above 97%). Hybridization analyses revealed that the Cal3nDr sequences were organized into tandem arrays. These DNA sequences were present only in triploid and tetraploid ginbunas and were absent from diploid ginbuna, gengorobuna, goldfish, and other cyprinid fishes, and therefore appeared to be specific to polyploid ginbunas. In situ hybridization data showed their localization on one to four out of a total of 150 to 156 chromosomes, depending on the individuals or clonal lines, of the triploid ginbuna. The origin of the Cal3nDr sequences is also discussed on the basis of observation of the artificial triploid ginbuna produced by crossing a diploid female with a tetraploid male.

Animals↗

PubMed1975

The recognition and incidence of haploid and polyploid spermatozoa in man, rabbit and mouse.

The existence of polyploid mammalian spermatozoa has been inferred from studies of Feulgen-DNA absorption. Rabbit spermatozoa fell into two discrete groups with mean absorptions close to a 1:2 ratio (inferred to be haploids and diploids respectively); simple visual appraisal of the size of the head or nucleus gave an identical classification. The incidences of ploidy classes were 98-94% haploid, 1-06% diploid, 0-00% higher than diploid (N = 3010; from DNA measurements and visual appraisal of the size in a rabbit chosen to have a high incidence of diploids) and, correspondingly, 99-691%, 0-308%, 0-001% (N = 138001; from sixty-nine unselected rabbits, scored by visual appraisal of the size of the sperm head). In man also, virtually discrete groups with absorptions close to a 1:2 ratio existed and were inferred to be haploids and diploids respectively. A few human spermatozoa were found with absorptions corresponding to a ploidy of three and/or four. Visual appraisal of the size of the human sperm nucleus as Small, Medium or Large was only a partial guide to ploidy. All Small human spermatozoa measured for DNA absorption were found to be haploid. About two-thirds of Medium human spermatozoa were found, however, to be haploid, and some Large spermatozoa were haploid or diploid. The incidences of ploidy classes in the human were 99-37% haploid, 0-56% diploid, 0-07% higher than diploid (N = 5554; with consistency between duplicate slides and between two subjects; from DNA measurements and visual appraisal of nuclear size). The estimated incidence of diploid human spermatozoa is consistent with the known incidence oftriploid fetuses. In a mouse with a putatively high incidence of diploids, all 1000 DNA measurements were nevertheless within the haploid range, with one diploid encountered outside the main sampling.

Animals↗

PubMed1975

[Basic factors in the polyploidization of cerebellar Purkinfe cells in chick embryogenesis. III. Kinetics of RNA and DNA in Purkinje cell nuclei].

The content and concentration of RNA and DNA in the nuclei of the Purkinje cells of cerebellum of chick embryos (10-21 day-old) were determined by cytospectrophotometry. The RNA concentration shows a dayly rhythm, its content significantly increasing. The periods of the increase of RNA synthesis coincide with the periodicity of protein synthesis, the morphogenesis of the Purkinje cells and with the embryo's development as a whole. The DNA concentration remaining constant, its content increases sharply with the onset of the specific functional activity of cells and of the intensive growth of axons and dendrites. The variability of the mean values of this growth increases which is conditioned by the appearance of cells with hyperdiploid, tetraploid and hypertetraploid DNA contents in their nuclei. The Purkinje cells do not divide, their increased DNA content may be regarded as the expression of polyploidization or polytenization (which are functionaly equivalent) of a part of the nuclei. It is not excluded that in this case a differential gene amplification may take place. The increase of DNA content is associated with the onset of morphofunctional maturity of cells and may be due to a continuously increasing intensity of protein synthesis secured by the matrix material.

Animals↗

PubMedDate not supplied

[Changes in the content of different nuclear proteins and DNA from diploid and polyploid hepatocytes in regenerating liver of mice].

The content of 4 fractions of nuclear proteins (histones, acid chromatin protein, globulins and chromatin-free acid protein) in diploid and polyploid hepatocytes from intact and regenerating liver of mice is studied. These types of nuclei are found to differ in the protein content and in the protein/DNA ratio. Synthesis of all classes of nuclear proteins was intensified at the G1-stage, and synthesis of DNP non-histone proteins at the end of S- and G2-stage. Possible role of different nuclear proteins in the regulation of cell multiplication is discussed.

Animals↗