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Letteratura scientifica selezionata sul tema "Tetraploid"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 20 febbraio 2023

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Articoli di riviste sul tema "Tetraploid"

Jan, C. C., J. M. Chandler e S. A. Wagner. "Induced tetraploidy and trisomic production of Helianthus annuus L." Genome 30, n. 5 (1 ottobre 1988): 647–51. http://dx.doi.org/10.1139/g88-109.

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Seedlings of the Helianthus annuus inbred lines P21 and HA89 were treated with colchicine to study chromosome doubling. Frequency of tetraploids, meiotic chromosome pairing, pollen stainability, and fertility were examined. Five-hour colchicines treatments at 0.15%, pH 5.4, with 2% dimethyl sulfoxide resulted in tetraploid sectors on 42% of P21 and 11% of HA89 plants. Tetraploids had larger disk florets and larger pollen grains. Otherwise, tetraploid plants were morphologically similar to their diploid progenitors. Tetraploidy in P21 was not stable, with plants having 2n = 4x = 65 to 70 chromosomes. Tetraploid plants of HA89 had reduced vigor and did not produce seed. At diakinesis, tetraploid P21 plants had an average of 0.85 univalents, 21.12 open bivalents, 6.66 closed bivalents, 0.21 trivalents, and 2.74 quadrivalents per cell. The number of chiasma per chromosome pair in P21 was reduced from 1.50 for diploid to 1.32 for tetraploid plants. Pollen stainability in tetraploid P21 was less than 50% and the plants produced an average of eight seeds per sibbed head, about 1% of normal seed set. Reciprocal crosses of diploid and tetraploid P21 produced four triploid plants. Backcrossing triploids to P21 produced 137 plants with 2n = 34 to 47 + t. Thirty-one of these plants were trisomies having 2n = 35.Key words: Helianthus annuus, tetraploids, triploids, trisomies.

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Weber, Gregory M., Mark A. Hostuttler, Kenneth J. Semmens e Brian A. Beers. "Induction and viability of tetraploids in brook trout (Salvelinus fontinalis)". Canadian Journal of Fisheries and Aquatic Sciences 72, n. 10 (ottobre 2015): 1443–49. http://dx.doi.org/10.1139/cjfas-2014-0536.

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Brook trout (Salvelinus fontinalis) populations are threatened by introduction of invasive species, habitat loss, and habitat degradation in their native range and are a problem invasive species in western Unites States and Canada and in Europe. Stocking sterile triploids has been promoted as an approach to reduce negative effects of stocking of brook trout for recreational fishing on native fish populations. Crossing a tetraploid with a diploid is a method of triploid production that may help hatcheries meet demand. We induced tetraploidy in brook trout by application of 633 kg·cm−2 of hydrostatic pressure for 8 min at 70%–72.5% of the first cleavage interval. Yields of above 50% tetraploid progeny at hatching were readily achieved, although few animals reached 1 year of age. We crossed a male tetraploid with female diploid fish and produced interploid-triploids with eyeing rates in excess of 50%, demonstrating male tetraploids are fertile and capable of siring triploid progeny. Female tetraploid fish were reared to 16 months posthatching and possessed follicles in secondary vitellogenesis, suggesting tetraploid females are also fertile. Tetraploid induction rates in excess of 96% were achieved applying the same hydrostatic pressure treatment to zygotes of tetraploid × diploid crosses at 30 min postfertilization.

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Panopoulos, Andreas, Cristina Pacios-Bras, Justin Choi, Mythili Yenjerla, Mark A. Sussman, Rati Fotedar e Robert L. Margolis. "Failure of cell cleavage induces senescence in tetraploid primary cells". Molecular Biology of the Cell 25, n. 20 (15 ottobre 2014): 3105–18. http://dx.doi.org/10.1091/mbc.e14-03-0844.

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Tetraploidy can arise from various mitotic or cleavage defects in mammalian cells, and inheritance of multiple centrosomes induces aneuploidy when tetraploid cells continue to cycle. Arrest of the tetraploid cell cycle is therefore potentially a critical cellular control. We report here that primary rat embryo fibroblasts (REF52) and human foreskin fibroblasts become senescent in tetraploid G1 after drug- or small interfering RNA (siRNA)-induced failure of cell cleavage. In contrast, T-antigen–transformed REF52 and p53+/+ HCT116 tumor cells rapidly become aneuploid by continuing to cycle after cleavage failure. Tetraploid primary cells quickly become quiescent, as determined by loss of the Ki-67 proliferation marker and of the fluorescent ubiquitination-based cell cycle indicator/late cell cycle marker geminin. Arrest is not due to DNA damage, as the γ-H2AX DNA damage marker remains at control levels after tetraploidy induction. Arrested tetraploid cells finally become senescent, as determined by SA-β-galactosidase activity. Tetraploid arrest is dependent on p16INK4a expression, as siRNA suppression of p16INK4a bypasses tetraploid arrest, permitting primary cells to become aneuploid. We conclude that tetraploid primary cells can become senescent without DNA damage and that induction of senescence is critical to tetraploidy arrest.

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Bothmer, Roland von, Jan Flink e Tomas Landström. "Meiosis in interspecific Hordeum hybrids. IV. Tetraploid (4x × 4x) hybrids". Genome 30, n. 4 (1 agosto 1988): 479–85. http://dx.doi.org/10.1139/g88-080.

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The meiotic pairing behaviour of 31 interspecific combinations of tetraploid Hordeum species are reported. The autoploid H. bulbosum with the II genomic constitution has no homology to the other species. The constitution of tetraploid H. murinum is not clear, but it is not homologous to other tetraploids. Hordeum marinum is a probable autoploid (XX) but with a very strong genetic regulation of pairing. The X genome is possibly found in H. secalinum and H. capense, both of which also possess the H genome in several diploids. Hordeum fuegianum, H. tetraploidum, H. jubatum, H. brachyantherum, and H. roshevitzii are segmental alloploids all with the same two partly homoeologous genomes. Hordeum depressum is probably a segmental alloploid with the H genome and with a very strong pairing regulation. Hordeum brevisubulatum is a pure autoploid with two homologous H genomes.Key words: Hordeum, interspecific hybrids, meiosis, tetraploids.

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Compton, Michael E., D. J. Gray e G. W. Elmstrom. "150 THE IDENTIFICATION OF TETRAPLOID REGENERANTS FROM COTYLEDONS OF DIPLOID WATERMELON AND THEIR USE IN BREEDING TRIPLOID HYBRIDS". HortScience 29, n. 5 (maggio 1994): 450c—450. http://dx.doi.org/10.21273/hortsci.29.5.450c.

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Tetraploid individuals were identified among plants regenerated from cotyledons of diploid watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] cultured in vitro. Tetraploid and diploid plants were distinguished by counting the number of chloroplast per guard cell pair. The mean number of chloroplasts was 19 and 11 for tetraploid and diploid plants, respectively. Self-fertile tetraploids were obtained from the diploid cultivars Mickylee, Jubilee II and Royal Sweet. `Dixielee' and `Minilee' tetraploids failed to set fruit. Progeny obtained from self-fertile tetraploids were crossed with diploid pollinators to produce triploid hybrid seed. All triploid plants produced seedless fruit that was superior or equal to fruit produced by currently available triploid hybrids. This demonstrates that tissue culture can be used to produce high quality tetraploid plants for use in triploid hybrid seed production.

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SMITH, K. F., R. J. SIMPSON, R. A. CULVENOR, M. O. HUMPHREYS, M. P. PRUD'HOMME e R. N. ORAM. "The effects of ploidy and a phenotype conferring a high water-soluble carbohydrate concentration on carbohydrate accumulation, nutritive value and morphology of perennial ryegrass (Lolium perenne L.)". Journal of Agricultural Science 136, n. 1 (febbraio 2001): 65–74. http://dx.doi.org/10.1017/s0021859600008480.

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Tetraploidy or the use of diploid genotypes with genes conferring high water-soluble carbohydrate concentrations are two mechanisms to increase the nutritive value of perennial ryegrass. This experiment compared the morphology, nutritive value and diurnal variation in water-soluble carbohydrate (WSC) concentrations of 56-day-old plants from six perennial ryegrass cultivars grown under controlled environment conditions. Three of these cultivars were diploid (Melle, Aurora and Cariad) and three were tetraploids (Meltra, Prospero and AberOnyx) which had been derived from the respective diploid cultivars. Two of the diploid cultivars (Cariad and Aurora) had previously been selected for high concentrations of water-soluble carbohydrates. The tetraploid cultivars had fewer (mean 59), larger tillers than the diploids (mean 83). However, with the exception of Melle and Meltra the dry matter yield of the diploid cultivars was not significantly different from their tetraploid derivatives. The effect of tetraploidy on WSC concentrations was dependent on the genetic background of the cultivars. Melle, which had not been previously selected for increased WSC, had a significantly lower WSC concentration than its tetraploid derivative, Meltra. However, tetraploidy did not further increase the WSC concentration in those cultivars previously selected for high WSC concentrations. WSC concentrations in the leaf of both Aurora and Melle rose by 65–70 g/kg throughout the photoperiod, suggesting that differences in the total WSC concentration of these cultivars were not due to any increase in the amount of carbon fixed by Aurora but rather due to differences in the allocation of carbon during growth and development. This experiment demonstrated that tetraploidy was not beneficial in improving the WSC concentration of perennial ryegrass when imposed on two diploid cultivars which had the genetic potential for increased WSC accumulation. However, tetraploidy significantly increased the WSC concentration and by implication the nutritive value of a cultivar derived from a perennial ryegrass cultivar with standard WSC concentrations.

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Hassan, Jahidul, Ikuo Miyajima, Yukio Ozaki, Yuki Mizunoe, Kaori Sakai e Wasimullah Zaland. "Tetraploid Induction by Colchicine Treatment and Crossing with a Diploid Reveals Less-Seeded Fruit Production in Pointed Gourd (Trichosanthes dioica Roxb.)". Plants 9, n. 3 (17 marzo 2020): 370. http://dx.doi.org/10.3390/plants9030370.

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Pointed gourd (Trichosanthes dioica Roxb.) (2n = 2x = 22) is a dioecious cucurbit vegetable and green fruit that is edible after cooking. Consumers prefer to consume seedless or less-seeded fruit because seeds are unpalatable due to their hard coats. Therefore, the cross compatibility between the diploid and induced tetraploid will be helpful for seedless or less-seeded fruit production. Thus, the present study was conducted using mature seeds that were immersed in 0.05%, 0.1%, and 0.5% colchicine for 24, 48, and 72 h to induce tetraploids. These tetraploids were used as parents (male or female) in the inter-ploidy and intra-ploidy crosses. A flow cytometric analysis confirmed the induction of three tetraploids at 0.5% colchicine for 48 and 72 h soaking periods. Among these, two (2) females and one (1) male were differentiated after flower initiation. Crossing between the tetraploid’s maternal and diploid paternal parent (4x × 2x), which were revealed to be compatible, resulted in a similar fruit set rate and shape as those of the diploid. In addition, a seed number of 4x × 2x produced fruits that were drastically reduced to 1.8 seeds per fruit, whereas the natural diploid fruits had 26.4 seeds per fruit. These findings suggest that colchicine-induced tetraploid females are important genetic resources for less-seeded fruit production. The genetic stability of tetraploid clones can easily and effectively be maintained by vine cutting for advanced uses.

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Mahony, MJ, SC Donnellan e JD Roberts. "An Electrophoretic Investigation of Relationships of Diploid and Tetraploid Species of Australian Desert Frogs Neobatrachus (Anura: Myobatrachidae)". Australian Journal of Zoology 44, n. 6 (1996): 639. http://dx.doi.org/10.1071/zo9960639.

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Allozyme electrophoresis of 27 loci was used to characterise genetic variation among 29 populations of six diploid species of the myobatrachid frog genus Neobatrachus. All six species are well differentiated genetically with the percentage of fixed differences between species ranging from 11 to 59%. The genetic data are in agreement with the currently accepted species boundaries. The four tetraploid species were examined for 25 of the 27 loci assayed in the diploid species. In contrast to the diploid species, the tetraploid species shared electromorphs with each other at all the loci examined. The tetraploid species were examined for the presence of electromorphs specific to individual diploid species. The majority of these electromorphs were observed in the tetraploid species. For cases in which the range of a tetraploid species contacts that of a diploid species and the diploid population can be characterised by unique electromorphs, then evidence of current gene flow was found in the direction of the tetraploid populations. The data are compatible with single or multiple discrete or hybrid origins of the tetraploids overlain by gene flow among the tetraploids and between the tetraploids and some and perhaps all of the diploids by means of geographically limited but ongoing episodes of introgressive hybridisation.

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de Sousa, Joana Teixeira, Standish K. Allen, Brittany M. Wolfe e Jessica Moss Small. "Mitotic instability in triploid and tetraploid one-year-old eastern oyster, Crassostrea virginica, assessed by cytogenetic and flow cytometry techniques". Genome 61, n. 2 (febbraio 2018): 79–89. http://dx.doi.org/10.1139/gen-2017-0173.

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For commercial oyster aquaculture, triploidy has significant advantages. To produce triploids, the principal technology uses diploid × tetraploid crosses. The development of tetraploid brood stock for this purpose has been successful, but as more is understood about tetraploids, it seems clear that chromosome instability is a principal feature in oysters. This paper is a continuation of work to investigate chromosome instability in polyploid Crassostrea virginica. We established families between tetraploids—apparently stable (non-mosaic) and unstable (mosaic)—and normal reference diploids, creating triploid groups, as well as tetraploids between mosaic and non-mosaic tetraploids. Chromosome loss was about the same for triploid juveniles produced from either mosaic or non-mosaic tetraploids or from either male or female tetraploids. However, there was a statistically significant difference in chromosome loss in tetraploid juveniles produced from mosaic versus non-mosaic parents, with mosaics producing more unstable progeny. These results confirm that chromosome instability, as manifested in mosaic tetraploids, is of little concern for producing triploids, but it is clearly problematic for tetraploid breeding. Concordance between the results from cytogenetics and flow cytometry was also tested for the first time in oysters, by assessing the ploidy of individuals using both techniques. Results between the two were non-concordant.

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Muthoni, Jane, Hussein Shimelis e Rob Melis. "Production of hybrid potatoes: Are heterozygosity and ploidy levels important?" Australian Journal of Crop Science, n. 13(05) 2019 (20 maggio 2019): 687–94. http://dx.doi.org/10.21475/ajcs.19.13.05.p1280.

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It has been proposed that maximizing heterosis for yield in potato may be achieved by maximizing heterozygosity and associated intra and interlocus interactions. Tetraploids offer more opportunities to create such interactions than diploids hence the general observations that tetraploids are higher yielding than diploids. Consequently, efforts have been made to increase heterozygosity in tetraploids by introgressing allelic diversity from other Solanum species into cultivated potato. However, conventional potato breeding is difficult because the cultivated potato is an autotetraploid with tetrasomic inheritance and it comprises highly heterozygous individuals which suffer inbreeding depression upon selfing; breeding at the tetraploid level is slow and less efficient than at diploid level. At the diploid level, it is possible to breed for and fix traits under recessive genetic control; it is nearly impossible to do so at the tetraploid level. There is also rapid response to selection due to greater variation in diploids than tetraploids. Consequently, there have been efforts to convert potato from an asexually propagated tetraploid crop into an inbred seed-propagated diploid; this is by production of inbred lines through selfing of the tetraploids to assemble desirable combinations of genes in the inbreds. These efforts are at the experimental stages and a lot of research needs to be done before they are confirmed. Because currently there is little experimental evidence to support superiority of the inbred seed-propagated diploid strategy, it appears the theory that heterosis for yield in potato may be achieved by maximizing heterozygosity and associated intra and interlocus interactions remain unchallenged; these interactions are more in tetraplods than in diploids. This paper therefore looks at genetic basis of yield heterosis in cultivated potato and the role of heterozygosity and ploidy level in production of hybrid potatoes.

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Più fonti

Tesi sul tema "Tetraploid"

Crockford, Andrew. "Deciphering tetraploid tolerance". Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1475158/.

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Chromosomal instability and aneuploidy are common features of human malignancies, which fuel genetic heterogeneity and can lead to inaccurate diagnosis and treatment failure. Tetraploidy has been shown as an intermediate of aneuploidy and, thus, understanding the molecular mechanisms governing tetraploid tolerance is of great importance. A frequent tolerance mechanism observed in experimental systems and human tumours is loss of TP53, highlighting its central role in the tetraploidy checkpoint. However, despite this association, more than half of genome-doubled tumours are TP53 wild-type. The aim of this project was to understand how tetraploid cells could tolerate the polyploidy phenotype with a functional p53/p21 axis. Firstly, tetraploidy tolerance was investigated in an isogenic HCT-116 diploid and tetraploid system. The HCT-116 tetraploids showed functional p53, in response to DNA damage and segregation error induction, while also displayed elevated basal level of both proteins. Despite this, the tetraploid clones could proliferate and showed no evidence of cell cycle arrest, suggesting the p53/p21 tetraploidy checkpoint response had been overridden. Quantitative proteomics revealed cyclin D1 overexpression in the tetraploid clones. As cyclin D1 can sequester p21, their relationship was investigated and validated in the HCT-116 system. To further test if elevated cyclin D1 could affect tolerance, cytokinesis failure was pharmacologically induced in RPE cells, where cyclin D1 overexpression promoted tetraploidy tolerance across multiple assays. In addition, bioinformatics analysis revealed that D-type cyclins were overexpressed in TP53, CDKN1A and RB1 wild-type, genome-doubled testicular germ cell tumours (TGCT). These findings indicate that D-type cyclin overexpression can provide tetraploidy tolerance in vitro and may be implicated in TGCT genome-doubling and pathogenesis.

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Muramoto, H. "Tetraploid Caducous Bract Cotton". College of Agriculture, University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/203924.

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Tavakkol, Afshari Reza. "Variation in seed dormancy of tetraploid wheat". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ37916.pdf.

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Kuffer, Christian. "Proliferation and arrest of human tetraploid cells". Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-182558.

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Durch Fehler entstandene tetraploide Zellen sind chromosomal instabil und können zu Zelltransformation führen. Die Beweise verdichten sich, dass die Propagation von tetraploiden Säugetierzellen durch einen p53-vermittelten Arrest eingeschränkt wird; jedoch ist weiterhin unklar, was die Ursache dieses p53-vermittelten Arrests ist. Um die Ursache des p53-vermittelten Arrests zu identifizieren, wurden individuelle Zellen mittels zeitraffender Mikroskopie in Echtzeit verfolgt. Neu entstandene tetraploide Zellen können einen Zellzyklus vollenden, aber die Mehrzahl der Zellen starb oder verharrte in einem Arrest in der folgenden G1-Phase, abhängig davon ob die vorangegangene Mitose fehlerfrei verlief oder nicht. Tochterzellen, denen eine fehlerhafte Mitose voranging, akkumulierten p53 im Zellkern, was zum Zelltod oder einem irreversiblen Zellzyklusarrest führte. Es zeigte sich durch den Anstieg von 8-OHdG, einem Indikator für oxidative DNA Schädigung, dass tetraploide Zellen durch die vermehrten fehlerhaften Mitosen höheren Konzentrationen von reaktiven oxidativen Spezien (ROS) ausgesetzt sind. Der Anstieg von 8-OHdG korrelierte mit der p53-Akkumulation im Zellkern. Da keine vermehrte Phosphorylierung des Histons H2AX (γ-H2AX), ein Marker für DNA-Strangbrüche, detektiert wurde, lässt sich schlussfolgern, dass ROS entscheidend für den p53 vermittelten Arrest verantwortlich sind. Mehrere p53-aktivierende Kinasen wurden mittels RNA Interferenz (RNAi) und chemischer Genetik untersucht, ob sie einen Einfluss auf den Zellzyklusarrest von tetraploiden Zellen haben. Von den getesteten Kinasen hatte nur ATM einen Einfluss auf die Aktivierung von p53 nach fehlerhaften tetraploiden Mitosen. Zwar wird ATM in der Regel durch DNA-Schäden aktiviert, jedoch wurde bereits zuvor gezeigt, dass ATM auch durch erhöhte ROS Konzentrationen aktiviert werden kann. Um die Zusammenhänge des Zellzyklusarrests weiter aufzuklären, wurde ein genomübergreifender esiRNA Screen etabliert, der die Zellproliferation nach induzierter Tetraploidisierung analysiert. Durch Kombination der Zellzyklusanalyse an Hand des DNA-Gehalts zusammen mit den FUCCI-Zellzyklusindikatoren, konnten tetraploide und diploide Zellen nebeneinander mikroskopisch analysiert werden, ohne zuvor tetraploide und diploide Zellen isolieren zu müssen. Dieser neue experimentelle Ansatz ermöglichte die Identifikation von Genen, die spezifisch die Proliferation von tetraploiden Zellen verstärken oder einschränken Im Primärscreen wurden 1159 Gene identifiziert, deren Inhibition die Proliferation einschränken. Weiter wurden 431 Gene identifiziert, deren Inhibition die Proliferation der tetraploiden Zellen verstärken. Von den 431 Genen, deren Inhibition die Proliferation verstärken, wurden 371 Gene einem Konfirmationsscreen unterzogen, in dem 158 der identifizierten 371 Gene bestätigt wurden. Die bioinformatische Analyse der 158 Gene zeigte eine signifikante Anhäufung von Genen, die mit DNA-Replikation, dem kanonischen Wnt-Signalweg oder mit Tumorsignalwegen assoziiert sind. Unter letzteren ist CCDC6 sehr interessant, da dessen Genprodukt durch ATM phosphoryliert wird und nachgeschaltet den Tumorsuppressor 14-3-3σ reguliert. Des weiteren wurden mittels einer Meta Analyse der Ergebnisse des Primärscreens, zusammen mit den Daten aus dem “Project Achilles”, welches genomweit den Effekt von shRNA-vermittelter Geninhibition auf die Proliferation von 108 Krebszelllinien untersuchte, 18 Gene identifiziert, deren Inhibition sowohl die Proliferation von tetraploiden Zellen einschränkt, als auch die Proliferation von Zelllinien hemmt, welche von Krebsarten stammen, die zu meist chromosomale Instabilitäten (CIN) aufweisen. Damit bilden die präsentierten Daten nicht nur eine gute Basis zur Aufklärung des Zellzyklusarrests tetraploider Zellen, sondern auch für die Identifikation neuer potentieller Zielmoleküle, welche benutzt werden können um Tumorerkrankungen mit chromosomaler Instabilität zu behandeln, welche häufig resistent gegen die bislang verfügbaren Behandlungen sind.
Erroneously arising tetraploid mammalian cells are chromosomally unstable and may facilitate cell transformation. An increasing body of evidence suggests that the propagation of mammalian tetraploid cells is limited by a p53-dependent arrest, however, the triggers of this arrest have thus far not been identified. To elucidate the timing and causes of this arrest, time-lapse live cell imaging was performed to track the fate of individual cells immediately after tetraploidization. Newly formed tetraploid cells can progress through one cell cycle, but the majority of cells arrest or die in the subsequent G1 stage, with the fate of these tetraploid cells determined by the preceding mitosis. Daughter cells arising from defective mitosis accumulated p53 in the nucleus, which led to irreversible cell cycle arrest or death. Furthermore this p53 accumulation coincides and correlates with an increase of the oxidative DNA damage marker 8-OHdG, suggesting an increase in reactive oxygen species (ROS), but does not coincide with the phosphorylation of H2AX (γ-H2AX), a marker for canonical DNA damage. Using RNA interference and chemical genetics, several p53 activating kinases were tested for their contribution to the cell cycle arrest of tetraploid cells. Of the tested kinases, only ATM was shown to play a role in the activation of p53 after defects in mitosis. ATM kinase is a DNA damage-responsive kinase, however, it has been shown that increased ROS levels activate ATM in a non-canonical way. To gain further insights into arrest of tetraploid cells, an unbiased genome-wide esiRNA screen was performed to analyze cell proliferation after induced tetraploidization. Using FUCCI cell cycle probes, combined with DNA content cell cycle profiling, allowed an image-based assay to examine tetraploid and diploid cells side-by-side. This novel approach enabled us to screen for genes that specifically restricts or enhances cell proliferation after tetraploidization, if inhibited by esiRNA mediated knockdown. From the primary screen we identified 1159 genes that decreased and 431 genes that increased the cell proliferation after tetraploidization, if knocked down by esiRNA. From the 431 genes that increased proliferation upon knockdown, 374 were selected and subjected to a re-screen. Of these 374 genes, we were able to confirm the results for 158 of the genes. A bioinformatics analysis of the 158 genes for which the phenotype were confirmed by the re-screen revealed a significant enrichment of genes involved in DNA replication, the canonical Wnt signaling pathway and in pathways linked to cancer. Among the latter, CCDC6 is particularly interesting, because its gene product is a target of the ATM kinase and an upstream regulator of the tumor suppressor 14-3-3σ. Moreover, by comparing the results of the primary screen with the data of the “Project Archilles”, which measured the proliferation in genome wide pooled-shRNA screens for 108 cancer cell lines, 18 genes were identified that are essential for the proliferation of cells after tetraploidization, as well as for the proliferation of cancer cell lines that derive from cancer types with a high incidence for chromosomal instability (CIN). Taken together, the presented data builds an excellent resource not only for elucidating how the arrest after tetraploidization is mediated, but also to identify novel potential therapeutic targets against tumors with CIN, which are frequently resistant to many of today’s anti-cancer therapies.

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Khan, Javed Ahmad. "Salinity effects on 4D recombinant tetraploid wheat genotypes". Thesis, Bangor University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321525.

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Diffoot, Nanette. "Corydoras aeneus: a diploid-tetraploid fish species complex". Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/101468.

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Corydoras aeneus is an armoured catfish found in the upper amazon regions of South America. It is a member of the family Callichthyidae. Studies done with this species of fish showed that C. aeneus is a tetraploid with a chromosome number of 132 (Scheel et al. , 1972). Dunham et al. (1980) reported 120 chromosomes. The C. aeneus used in this study were bought from direct importers. We had four samples of fishes supposedly coming from Brazil (Belem), Guyana, Peru and Trinidad. During our initial studies in an attempt to karyotype aeneus we came across individuals with a highly reduced chromosome number. A diploid form of C. aeneus was discovered. Only those fishes from our Belem sample were diploid. A comparison of the diploid and tetraploid forms was done. Both forms were karyotyped, the tetraploid form of C. aeneus has 134 chromosomes and the diploid has 56. Physically both forms looked exactly the same. Morphometric as well as meristic data was collected from 131 fishes and analyzed by multivariate, discriminant and contingency chi- square analyses. The results obtained do not suggest any absolute morphological differences between the diploid and the tetraploid forms anymore than between tetraploids.
M.S.

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Morgan, Christopher Henry. "Coordination of meiotic recombination in diploid and tetraploid arabidopsis". Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/7092/.

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Homologous recombination is an integral part of meiosis and is essential for generating crossovers that ensure balanced segregation of homologous chromosomes and establish genetic variation within offspring. It is therefore exceedingly important that meiotic cells employ stringent control mechanisms to safeguard crossover formation. Work in yeast has indicated that the meiotic axis, a proteinaceous structure that tethers meiotic chromosomes into looped arrays, plays a crucial role in many aspects of homologous recombination, from double strand break formation to crossover interference. It has also been suggested that increased crossover interference helps to establish meiotic stability by inhibiting multivalent formation during autopolyploid meiosis. Using immunocytochemistry coupled with super-resolution microscopy, we have further investigated the role played by the meiotic axis protein ASY1 in stabilising meiosis in the established autotetraploid Arabidopsis arenosa. We have also used Arabidopsis arenosa as a model for studying how meiotic interference might operate within an autopolyploid context. Alongside this, experiments using transgenic lines of the model plant Arabidopsis thaliana have helped to shed light on how crossover formation and synapsis are affected by reduced expression of ASY1 and ASY3 and to determine what effect limiting meiotic crossover numbers might have on neopolyploid meiotic stabilisation.

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Schuck, Susan M., e Steven P. McLaughlin. "Flowering Phenology and Outcrossing in Tetraploid Grindelia camporum Green". University of Arizona (Tucson, AZ), 1988. http://hdl.handle.net/10150/609102.

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Several reproductive processes of tetraploid Grindelia camporum were investigated. This plant is a potential resin crop for the southwestern United States. Field observations of 100 flower heads from unopened buds through 100% achene dispersal were made. It was found that individual flower heads are available for pollination for approximately 5 days but all disc florets are open for only 1 day. On average, achenes mature in 22 days and are dispersed 53 days after flowering. Fourteen-hundred hand-pollinations were also made on plants from 6 wild populations of G. camporum grown in a greenhouse and shade house. Estimates of fertility and crossability of populations were made based on achene number and achene weight data from these crosses. All populations studied were interfertile and no evidence of outbreeding depression in between -population crosses was found. It is shown that tetraploid G. camporum is self-incompatible and requires manipulation for achene set.

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Stone, Harriet. "Evolution and conservation of tetraploid Euphrasia L. in Britain". Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7740.

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In the UK, nearly half of the plants short listed for high conservation priority in the UK Biodiversity Action Plan are found in taxonomically complex groups. It is thought that a shift from species- to process-based conservation strategies, aimed at conserving the processes that generate diversity as opposed to simply the end product of these dynamic interactions, may benefit these groups. One group for which this strategy has been proposed is tetraploid Euphrasia. The underlying taxonomic complexity in this group is hypothesised to arise via breeding systems, hybridisation and local ecotypic adaptation. The goal of this thesis is to use morphological, ecological and molecular marker data to examine taxon limits and evolutionary processes in order to further understand the mechanisms involved in maintaining species boundaries and generating taxonomic complexity in tetraploid Euphrasia. This will not only make conservation in this group more effective, but will also provide a broader insight into some of the processes involved in plant speciation. A detailed study of two widespread, small flowered, tetraploid taxa, E. micrantha and E. scottica, showed that offspring are almost exclusively the result of self-fertilization. These taxa maintain distinctive morphologies, habitat preferences and chloroplast DNA variation throughout their range, suggesting that they represent coherent lineages within Scotland. As in other widespread inbreeding species, there are high levels of microsatellite differentiation among different populations of the same species. In northwest Scotland three complex populations of tetraploid Euphrasia were identified which comprised an array of many different morphs (recognised species, and putative hybrids). Analysis of chloroplast and microsatellite markers suggests that these different morphs represent distinct genetic groups. Within each site there is evidence both for habitat heterogeneity, and for association of morphs with this habitat variation. Intermediate morphs were not simple F1 hybrids, but are likely to have originated via hybridisation and subsequent selfing, surviving as independent recombinant lines, perhaps specialised for habitat types different from that of their progenitor parents. These stable morphs of hybrid origin could represent groups with adaptive potential that may result in the origin of a novel Euphrasia species. It will be important to further examine the processes involved in generating novel diversity in Euphrasia. For the time being, these complex populations must be recognised as sites requiring special protection within the context of a process-based conservation strategy.

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Acuna, Carlos A. "Bahiagrass germplasm reproductive characterization and breeding at the tetraploid level". [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0014399.

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Più fonti

Libri sul tema "Tetraploid"

Bauernfeind, Marion. Zur Entwicklungsfähigkeit tetraploider Zellen in diploid/tetraploid-Chimären der Maus. Konstanz: Hartung-Gorre, 1989.

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Canada. Dept. of Fisheries and Oceans. Biological Sciences Branch. A bibliography of tetraploidy in fish (1964-1991). Vancouver, B.C: Dept. of Fisheries and Oceans, 1992.

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Kosina, Romuald. Tetraploids of the genus Triticum in the light of caryopsis structure. Wrocław: Wydawnictwo Uniwersytetu Wrocławskiego, 1995.

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Adiwilaga, Kartika Dorothea. Introgression of tetraploid Mexican wild species germplasm into cultivated potato gene pool. 1989.

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KHATEFOV, E. B., V. I. KHOREVA, B. R. SHOMAKHOV, R. S. KUSHKHOVA, Z. T. KHASHIROVA, R. A. KUDAEV e A. KH GYAURGIEV. REDIPLOID MAIZE LINES: (RESYNTHESIZED FROM A TETRAPLOID POPULATION FOR BREEDING HYBRID MAIZE). N.I. Vavilov All-Russian Institute of Plant Genetic Resources, 2021. http://dx.doi.org/10.30901/978-5-907145-75-7.

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The catalogue was compiled based on the results of studying the breeding value of 200 accessions of rediploid lines isolated from tetraploid maize populations with a description of 37 morphological traits, which have economic and breeding importance. The catalogue is addressed to geneticists, breeders and agronomists to be used as a starting material for breeding hybrid forage and food maize in the Russian Federation.

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DeNoma, Jeanine Streeter. The feasibility of using diploid by tetraploid crosses to obtain triploid hops (Humulus lupulus L.). 1994.

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Romano, Patrick Robert. Restriction endonuclease mapping of rRNA genes and the origin of the tetraploid tree frog Hyla versicolor. 1985.

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Liao, Shaoyi Alexander. Restriction mapping and molecular cloning of ribosomal RNA genes from the diploid/tetraploid frog species pair Hyla chrysoscelis/Hyla versicolor. 1988.

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Melzheimer, Volker, e Elvira Hörandl. Die Ranunculaceae der Flora von Zentraleuropa: Ranunculus sect. Auricomus. Universitätsbibliothek Johann Christian Senckenberg, 2022. http://dx.doi.org/10.21248/gups.68734.

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Ranunculus sect. Auricomus umfasst außer den heimischen Vertretern der R. auricomus-Gruppe und R. pygmaeus eine Reihe weiterer, temperat bis arktisch verbreiteter Arten in Nordamerika und in den Zentralasiatischen Gebirgen. R. sect. Auricomus ist daher nicht mit der/dem vorwiegend apomiktischen R. auricomus-Gruppe / -Komplex (R. auricomus agg.) gleichzusetzen, sondern hat einen größeren taxonomischen Umfang. Die Ranunculus auricomus-Gruppe umfasst im Gebiet der Flora von Zentraleuropa zwei der insgesamt fünf sexuellen Arten des Komplexes sowie eine Reihe von apomiktischen, hybridogenen Taxa. Diese beiden diploiden bis tetraploiden Arten (R. cassubicifolius und R. notabilis) repräsentieren zwei unterschiedliche Morphotypen, die früher als Artengruppen (R. cassubicus L. s.l. und R. auricomus L. s.l.) unterschieden und von manchen Autoren als Subsektionen innerhalb Ranunculus sect. Auricomus klassifiziert oder auch als informelle Artengruppen (Großgruppen, Sammelgruppen, Aggregate, Komplexe) behandelt wurden. Jedoch haben neuere genetische Untersuchungen gezeigt, dass diese morphologisch definierten Gruppen keine Abstammungsgemeinschaften darstellen. Sie werden daher hier nicht aufrechterhalten. Die in manchen Publikationen auch als gleichwertig eingestuften und unterschiedenen Artengruppen des R. fallax und des R. monophyllus werden hier ebenfalls nicht berücksichtigt. Umfassende phylogenomische Untersuchungen zeigen, dass in Europa drei große, unscharf getrennte genetische Cluster vorliegen, die eine West-Ost-Differenzierung zeigen.

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Capitoli di libri sul tema "Tetraploid"

Taylor, N. L., e K. H. Quesenberry. "Tetraploid Red Clover". In Red Clover Science, 161–69. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-015-8692-4_13.

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Gertsenstein, Marina. "Tetraploid Complementation Assay". In Springer Protocols Handbooks, 357–75. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-662-45763-4_16.

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Akinroluyo, O., G. Statkevičiūtė e V. Kemešytė. "Tetraploid Induction in Lolium multiflorum". In Breeding Grasses and Protein Crops in the Era of Genomics, 73–77. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-89578-9_13.

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Joppa, L. R. "Aneuploid Analysis in Tetraploid Wheat". In Agronomy Monographs, 255–67. Madison, WI, USA: American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, 2015. http://dx.doi.org/10.2134/agronmonogr13.2ed.c11.

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Lapinski, Boguslaw, Barbara Apolinarska, Grzegorz Budzianowski, Malgorzata Cyran e Maria Rakowska. "An Attempt at Tetraploid Triticale Improvement". In Triticale: Today and Tomorrow, 627–34. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-0329-6_81.

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Shenk, Elizabeth M., e Neil J. Ganem. "Generation and Purification of Tetraploid Cells". In Methods in Molecular Biology, 393–401. New York, NY: Springer New York, 2016. http://dx.doi.org/10.1007/978-1-4939-3542-0_24.

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Apolinarska, Barbara. "Different Chromosome Combinations on Tetra- and Hexaploid Level from Hybrids of Tetraploid Rye × Tetraploid Triticale". In Triticale: Today and Tomorrow, 189–94. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-0329-6_23.

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Münnich, C., M. Klaas, V. Bartels e C. Gebhardt. "Creation of Novel Tetraploid Miscanthus sinensis Genotypes". In Perennial Biomass Crops for a Resource-Constrained World, 119–26. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-44530-4_11.

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Pfeiffer, Martin J., Martin Stehling, Anna Jauch e Michele Boiani. "ES Cell Lines from Tetraploid Mouse Blastocysts". In Advances in Stem Cell Research, 1–16. Totowa, NJ: Humana Press, 2012. http://dx.doi.org/10.1007/978-1-61779-940-2_1.

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Zwierzykowski, Z., W. Jokś e B. Naganowska. "Potential of Tetraploid × Festulolium (Festuca Pratensis × Lolium Multiflorum)". In Developments in Plant Breeding, 299–300. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-0966-6_51.

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Atti di convegni sul tema "Tetraploid"

Gravendeel, Lonneke A., Nanne K. Kloosterhof, Linda B. Bralten, Johan M. Kros, Clemens M. Dirven, Peter A. Sillevis Smitt, Martin J. van den Bent e Pim J. French. "Abstract 3932: Tetraploid gliomas share molecular features with pilocytic astrocytomas". In Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL. American Association for Cancer Research, 2011. http://dx.doi.org/10.1158/1538-7445.am2011-3932.

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Rekashus, Eduard, e Anna Makaeva. "Choosing parental pairs for development initial material of alsike clover". In Multifunctional adaptive feed production 27 (75). ru: Federal Williams Research Center of Forage Production and Agroecology, 2022. http://dx.doi.org/10.33814/mak-2022-27-75-16-22.

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The article presents the results of a study in 2021 of 13 tetraploid selective varieties of alsike clover (Trifolium hybridum L.) from Norway, Germany, Sweden, Denmark, Canada, Latvia, Belarus and Russia in terms of the productivity of air-dry matter of the standing crop and seed yield. The observations were carried out in a greenhouse experiment set up in the greenhouse complex of the Federal Williams Research Center of Forage Production & Agroecology. The purpose of the research is to choose for crossing and further breeding work the most productive tetraploid clover genotypes from different geographical regions in terms of standing crop and seed yield. The criterion for selecting promising selective numbers for crossing was the deviation of the standing crop yield and (or) seed yield by more than 3 standard deviations (σ) from the corresponding arithmetic mean in the experiment. For experimental data on the yield of air-dry matter of the standing crop, a normal distribution was characteristic, and for seed yield, an exponential distribution. This made it possible to use the critical value of 3σ in making breeding decisions. The average productivity of air-dry matter of the standing crop is 47 g/vessel, σ=16 g/vessel. The average seed productivity is 1.1 g/vessel, and σ=0.9 g/vessel. According to the value of air-dry matter of the standing crop of 102 g/vessel, selective number 56 (cv. Tetraploid from the Republic of Belarus) was identified, and according to seed yield of 4.2 g/vessel, selective number 42 (cv. Alpo from Norway). They belonged to the productivity of Novator variety 213% and 233%, respectively. Selective numbers 56 and 42 are promising for crossing and studying the ability of offspring to combine high fodder and seed productivity.

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Pecciarini, Lorenza, Valeria De Pascali, Ilaria Francaviglia, Anna Talarico, Chiara Iacona, Massimo Freschi, Maria Giulia Cangi e Claudio Doglioni. "Abstract 756: Molecular characterization of triploid and tetraploid urine FISH samples". In Proceedings: AACR Annual Meeting 2017; April 1-5, 2017; Washington, DC. American Association for Cancer Research, 2017. http://dx.doi.org/10.1158/1538-7445.am2017-756.

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Ganem, Neil J., Kevin P. O'Rourke e David Pellman. "Abstract 2941: Defining novel pathways that arrest genetically unstable tetraploid cells". In Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL. American Association for Cancer Research, 2011. http://dx.doi.org/10.1158/1538-7445.am2011-2941.

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Кутузова, Анэля, Anel Kutuzova, Елена Проворная, Elena Provornaya, Надежда Цыбенко e Nadezhda Tsybenko. "EFFICIENCY OF ANTHROPOGENIC ENERGY EXPENDITURES IN CREATION AND USE OF LEGUME-CEREAL GRASS OF CULTURAL PASTURE". In Multifunctional adaptive feed production. ru: Federal Williams Research Center of Forage Production and Agroecology, 2019. http://dx.doi.org/10.33814/mak-2019-21-69-62-69.

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On legume-grass pasture grasslands with the participation of creeping clover (varieties VIC 70 and Lugovik), meadow clover (Tetraploid VIC and Veteran), alfalfa changeable (Pasture 88 and Agnia), the total cost of anthropogenic energy for the creation, care, use and production of feed in the exchange energy in a single SI system (GJ/ha) is determined. The high rates of return given the cost of collecting metabolizable energy per 1 GJ of metabolizable energy.

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Van Spijk, Ab C., Steve Barnes e Jan Pertus. "Monitoring the nematode resistance gene in tetraploid pollinators by using genetic markers". In 33rd Biennial Meeting of American Society of Sugarbeet Technologist. ASSBT, 2005. http://dx.doi.org/10.5274/assbt.2005.29.

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Yuan xiangyue e Chen Zhongjia. "Experimental research on cutting force and cutting parameters of Tetraploid Black Locust". In 2011 International Conference on New Technology of Agricultural Engineering (ICAE). IEEE, 2011. http://dx.doi.org/10.1109/icae.2011.5943770.

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Kuroda, Taruho S., Regina K. Dagher e David Pellman. "Abstract A79: Genome‐wide RNAi screen for tetraploid‐specific lethality in cancer cells". In Abstracts: First AACR International Conference on Frontiers in Basic Cancer Research--Oct 8–11, 2009; Boston MA. American Association for Cancer Research, 2009. http://dx.doi.org/10.1158/0008-5472.fbcr09-a79.

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Novoselov, Mikhail, Lyubov Drobysheva e Ol'ga Starshinova. "Results of competitive variety testing of red clover of tetraploid and diploid types". In Multifunctional adaptive feed production 27 (75). ru: Federal Williams Research Center of Forage Production and Agroecology, 2022. http://dx.doi.org/10.33814/mak-2022-27-75-9-15.

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The article presents the results of competitive variety testing of red clover in one test cycle. Promising cultivars have been identified for further research and the formation of adapted and ecologically differentiated varieties that combine high feed productivity with winter hardiness and longevity.

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Sorina, Popescu. "THE KNOX GENES INVOLVEMENT IN THE DEVELOPMENT OF MULTILEAFLED TRAIT ON TETRAPLOID MEDICAGO SATIVA". In 14th SGEM GeoConference on NANO, BIO AND GREEN � TECHNOLOGIES FOR A SUSTAINABLE FUTURE. Stef92 Technology, 2014. http://dx.doi.org/10.5593/sgem2014/b61/s25.075.

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Rapporti di organizzazioni sul tema "Tetraploid"

Ladizinsky, Gideon, e Frederic Kolb. Transformation of the Wild Tetraploid Oats into Domesticated Forms. United States Department of Agriculture, novembre 1994. http://dx.doi.org/10.32747/1994.7604296.bard.

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Dubcovsky, Jorge, Tzion Fahima e Ann Blechl. Positional cloning of a gene responsible for high grain protein content in tetraploid wheat. United States Department of Agriculture, settembre 2003. http://dx.doi.org/10.32747/2003.7695875.bard.

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High Grain Protein Content (GPC) is a desirable trait in breadmaking and pasta wheat varieties because of its positive effects on quality and nutritional value. However, selection for GPC is limited by our poor understanding of the genes involved in the accumulation of protein in the grain. The long-term goal of this project is to provide a better understanding of the genes controlling GPC in wheat. The specific objectives of this project were: a) to develop a high-density genetic map of the GPC gene in tetraploid wheat, b) to construct a T. turgidum Bacterial Artificial Chromosome (BAC) library, c) to construct a physical map of the GPC gene and identify a candidate for the GPC gene. A gene with a large effect on GPC was detected in Triticum turgidum var. dicoccoides and was previously mapped in the short arm of chromosome 6B. To define better the position of the Gpc-B1 locus we developed homozygous recombinant lines with recombination events within the QTL region. Except for the 30-cM region of the QTL these RSLs were isogenic for the rest of the genome minimizing the genetic variability. To minimize the environmental variability the RSLs were characterized using 10 replications in field experiments organized in a Randomized Complete Block Design, which were repeated three times. Using this strategy, we were able to map this QTL as a single Mendelian locus (Gpc-B1) on a 2.6-cM region flanked by RFLP markers Xcdo365 and Xucw67. All three experiments showed that the lines carrying the DIC allele had an average absolute increase in GPC of 14 g/kg. Using the RFLP flanking markers, we established the microcolinearity between a 2.l-cM region including the Gpc-B1 gene in wheat chromosome 6BS and a 350-kb region on rice chromosome 2. Rice genes from this region were used to screen the Triticeae EST collection, and these ESTs were used to saturate the Gpc-B1 region with molecular markers. With these new markers we were able to map the Gpc-B1 locus within a 0.3-cM region flanked by PCR markers Xucw83 and Xucw71. These flanking markers defined a 36-kb colinear region with rice, including one gene that is a potential candidate for the Gpc-B1 gene. To develop a physical map of the Gpc-B1 region in wheat we first constructed a BAC library of tetraploid wheat, from RSL#65 including the high Gpc-B1 allele. We generated half- million clones with an average size of l3l-kb (5.1 X genome equivalents for each of the two genomes). This coverage provides a 99.4% probability of recovering any gene from durum wheat. We used the Gpc-BI flanking markers to screen this BAC library and then completed the physical map by chromosome walking. The physical map included two overlapping BACs covering a region of approximately 250-kb, including two flanking markers and the Gpc-B1 gene. Efforts are underway to sequence these two BACs to determine if additional wheat genes are present in this region. Weare also developing new RSLs to further dissect this region. We developed PCR markers for flanking loci Xucw79andXucw71 to facilitate the introgression of this gene in commercial varieties by marker assisted selection (httQ://maswheat.ucdavis.edu/ orotocols/HGPC/index.hlm). Using these markers we introgressed the Gpc-B1 gene in numerous pasta and common wheat breeding lines.

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Devos, Katrien, Jeff Bennetzen, Ali Missaoui e Paul Schliekelman. Unraveling the Genetics of Two Key Biomass Traits that Differentiate Upland and Lowland Tetraploid Switchgrass Ecotypes, Colonization by Mycorrhizal Fungi and Frost Tolerance. Office of Scientific and Technical Information (OSTI), dicembre 2020. http://dx.doi.org/10.2172/1735505.

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Adelberg, Jeff, Halina Skorupska, Bill Rhodes, Yigal Cohen e Rafael Perl-Treves. Interploid Hybridization of Cucumis melo and C. metuliferus. United States Department of Agriculture, dicembre 1999. http://dx.doi.org/10.32747/1999.7580673.bard.

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The long-term motivation for this research is to transfer useful traits from a broad based gene pool of wild species into the narrow base of a cultivated crop in Cucumis. Our primary focus was to use polyploid prior to fertilization as a tool to overcome fertility barriers in the cross between C. melo and C. metuliferus. In conducting this research, we explored all combinations of tetraploid and diploid parents, in reciprocal combinations. Pollinations were made in both the field and greenhouse, using emasculated flowers, moneocious females, and open pollination by insect vectors, with morphological selection criteria. After observations of thousands of ovaries, we still have no definitive proof that this hybridization yielded viable embryos. The most promising results came from using tetraploid C. metuliferus, as the maternal parent in the interspecific hybridization, that set fruit were seeds contained small embryos that did not germinate. To obtain fruit set, it was important to rear plants in a cooler sunny greenhouse, as would be found in late winter/early spring. A second interspecific hybrid between wild and cultivated Cucumis, C. hystrix x C. sativus, yielded fertile progeny for the first time, while concomitantly working toward our primary goal. Two distinct treatments were necessary; 1) special plant husbandry was necessary to have the wild species produce fruit in cultivation, and 2) embryo rescue followed by chromosome doubling in vitro was required for fertility restoration. Backcrosses to crop species and resistance to nematodes are compelling areas for further work.

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Veilleux, Richard E., Jossi Hillel, A. Raymond Miller e David Levy. Molecular Analysis by SSR of Genes Associated with Alkaloid Synthesis in a Segregating Monoploid Potato Family. United States Department of Agriculture, maggio 1994. http://dx.doi.org/10.32747/1994.7570550.bard.

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More than 15,000 anthers of an interspecific hybrid (CP2) between two diploid (2n=2x=24) potato species, Solanum chacoense (weedy) and S. phureja (cultivated), were cultured to generate a family of monoploid (haploid, 2n-1x=12) plants. Of 260 regenerated plants, 34 were monoploid, 210 diploid and 16 tetraploid. SSR analysis revealed that six monoploids were genetically identical and 14 diploids were homozygous, thus limiting the population to 42 (28 monoploids and 14 homozygous diploids). New microsatellite loci were developed for potato from database sequences (15), a conventional genomic library (6), an enriched library (18) and tomato (11). Of these, 13 were polymorphic in the CP2 family and 11 were used to study genetic segregatin. Four of 11 exhibited skewed segregation in the monoploid family. Seven of 18 microsatellite markers were polymorphic and informative on a set of 12 tetraploid potato cultivars. Acetylleptinidine (ALD) is the aglycone of leptines, a natural defense against insects, especially the highly destructuve Colorado potato beetle. ALD is absend in S. phureja but highly expressed in the S. chacoense parent of CP2. A backcross population between CP2 and tis S. phureja parent was used to examine segregation for ALD. Bulks of 10 backcross individuals that expressed ALD and 10 that did not were used to identify putative RAPD markers associatd with the trait. Of 80 primers tested, one putative marker amplified by OPQ02 was present in eight of ten individuals comprising the high bulk and absent in all 10 individuals comprising the low bulk. This is a putative marker for ALD expression in potato.

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Tel-Zur, Neomi, e Jeffrey J. Doyle. Role of Polyploidy in Vine Cacti Speciation and Crop Domestication. United States Department of Agriculture, gennaio 2012. http://dx.doi.org/10.32747/2012.7697110.bard.

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1. Abstract: Over the past 25 years, vine cacti of the genera Hylocereus and Selenicereus have been introduced into Israel and southern California as new exotic fruit crops. The importance of these crops lies in their high water use efficiency and horticultural potential as exotic fruit crops. Our collaboration focused on the cytological, molecular and evolutionary aspects of vine cacti polyploidization to confront the agricultural challenge of genetic improvement, ultimately to improve success of vine cacti as commercial fruit crop plants. More specifically, we worked on the: 1- Identification of the putative ancestor(s) of the tetraploid H. megalanthus; 2- Determination of the number of origins of H. megalanthus (single vs. multiple origins of polyploidy); 3- Cytogenetic analysis of BC1 and F1 hybrids; 4- Determination of important agricultural traits and the selection of superior hybrids for cultivation. The plant material used in this study comprised interspecific Hylocereus F1 and first backcross (BC1) hybrids, nine Hylocereus species (58 genotypes), nine Selenicereus species (14 genotypes), and four Epiphyllum genotypes. Two BC1 hexaploids (BC-023 and BC-031) were obtained, a high ploidy level that can be explained only by a fertilization event between one unreduced female gamete from the triploid hybrid and a balanced gamete from the pollen donor, the diploid H. monacanthus. These findings are scientific evidence that support the possibility that “hybridization followed by chromosome doubling” could also occur in nature. Cytomixis, the migration of chromatin between adjacent cells through connecting cytoplasmatic channels, was observed in vine cacti hybrids and may thus imply selective DNA elimination in response to the allopolyploidization process. Evidence from plastid and nrDNA internal transcribed spacers (ITS) sequences support the placement of H. megalanthus within a monophyletic Hylocereus group. Furthermore, both plastid and ITS datasets are most consistent with a conclusion that this tetraploid species is an autopolyploid, despite observations that the species appears to be morphologically intermediate between Hylocereus and Selenicereus. Although the possibility of very narrow allopolyploidly (i.e., derivation from parents that are barely diverged from each other such as closely related species in the same genus) cannot be ruled out entirely based on our data (in part due to the unavailability of Hylocereus species considered to be morphologically the closest relatives of H. megalanthus), the possibility of H. megalanthus representing an intergeneric cross (i.e., Hylocereus × Selenicereus) seems extremely unlikely. Interestingly, the process of homogenization of ITS sequences (concerted evolution) is either incomplete or lacking in both Hylocereus and Selenicereus, and the inclusion of several artificial hybrids in the molecular study revealed the potential for biparental plastid inheritance in Hylocereus. The most important agricultural implication of this research project was the information collected for F1 and BC1 hybrids. Specifically, this project concluded with the selection of four superior hybrids in terms of fruit quality and potential yields under extreme high temperatures. These selected hybrids are self-compatible, avoiding the need for hand cross pollination to set fruits, thus reducing manpower costs. We recently offered these hybrids to growers in Israel for prioritized rapid evaluation and characterization.

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Dubcovsky, Jorge, Tzion Fahima, Ann Blechl e Phillip San Miguel. Validation of a candidate gene for increased grain protein content in wheat. United States Department of Agriculture, gennaio 2007. http://dx.doi.org/10.32747/2007.7695857.bard.

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High Grain Protein Content (GPC) of wheat is important for improved nutritional value and industrial quality. However, selection for this trait is limited by our poor understanding of the genes involved in the accumulation of protein in the grain. A gene with a large effect on GPC was detected on the short arm of chromosome 6B in a Triticum turgidum ssp. dicoccoides accession from Israel (DIC, hereafter). During the previous BARD project we constructed a half-million clones Bacterial Artificial Chromosome (BAC) library of tetraploid wheat including the high GPC allele from DIC and mapped the GPC-B1 locus within a 0.3-cM interval. Our long-term goal is to provide a better understanding of the genes controlling grain protein content in wheat. The specific objectives of the current project were to: (1) complete the positional cloning of the GPC-B1 candidate gene; (2) characterize the allelic variation and (3) expression profile of the candidate gene; and (4) validate this gene by using a transgenic RNAi approach to reduce the GPC transcript levels. To achieve these goals we constructed a 245-kb physical map of the GPC-B1 region. Tetraploid and hexaploid wheat lines carrying this 245-kb DIC segment showed delayed senescence and increased GPC and grain micronutrients. The complete sequencing of this region revealed five genes. A high-resolution genetic map, based on approximately 9,000 gametes and new molecular markers enabled us to delimit the GPC-B1 locus to a 7.4-kb region. Complete linkage of the 7.4-kb region with earlier senescence and increase in GPC, Zn, and Fe concentrations in the grain suggested that GPC-B1 is a single gene with multiple pleiotropic effects. The annotation of this 7.4-kb region identified a single gene, encoding a NAC transcription factor, designated as NAM-B1. Allelic variation studies demonstrated that the ancestral wild wheat allele encodes a functional NAC transcription factor whereas modern wheat varieties carry a non-functional NAM-B1 allele. Quantitative PCR showed that transcript levels for the multiple NAMhomologues were low in flag leaves prior to anthesis, after which their levels increased significantly towards grain maturity. Reduction in RNA levels of the multiple NAMhomologues by RNA interference delayed senescence by over three weeks and reduced wheat grain protein, Zn, and Fe content by over 30%. In the transgenic RNAi plants, residual N, Zn and Fe in the dry leaves was significantly higher than in the control plants, confirming a more efficient nutrient remobilization in the presence of higher levels of GPC. The multiple pleiotropic effects of NAM genes suggest a central role for these genes as transcriptional regulators of multiple processes during leaf senescence, including nutrient remobilization to the developing grain. The cloning of GPC-B1 provides a direct link between the regulation of senescence and nutrient remobilization and an entry point to characterize the genes regulating these two processes. This may contribute to their more efficient manipulation in crops and translate into food with enhanced nutritional value. The characterization of the GPC-B1 gene will have a significant impact on wheat production in many regions of the world and will open the door for the identification of additional genes involved in the accumulation of protein in the grain.

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Feldman, Moshe, Eitan Millet, Calvin O. Qualset e Patrick E. McGuire. Mapping and Tagging by DNA Markers of Wild Emmer Alleles that Improve Quantitative Traits in Common Wheat. United States Department of Agriculture, febbraio 2001. http://dx.doi.org/10.32747/2001.7573081.bard.

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The general goal was to identify, map, and tag, with DNA markers, segments of chromosomes of a wild species (wild emmer wheat, the progenitor of cultivated wheat) determining the number, chromosomal locations, interactions, and effects of genes that control quantitative traits when transferred to a cultivated plant (bread wheat). Slight modifications were introduced and not all objectives could be completed within the human and financial resources available, as noted with the specific objectives listed below: 1. To identify the genetic contribution of each of the available wild emmer chromosome-arm substitution lines (CASLs) in the bread wheat cultivar Bethlehem for quantitative traits, including grain yield and its components and grain protein concentration and yield, and the effect of major loci affecting the quality of end-use products. [The quality of end-use products was not analyzed.] 2. To determine the extent and nature of genetic interactions (epistatic effects) between and within homoeologous groups 1 and 7 for the chromosome arms carrying "wild" and "cultivated" alleles as expressed in grain and protein yields and other quantitative traits. [Two experiments were successful, grain protein concentration could not be measured; data are partially analyzed.] 3. To derive recombinant substitution lines (RSLs) for the chromosome arms of homoeologous groups 1 and 7 that were found previously to promote grain and protein yields of cultivated wheat. [The selection of groups 1 and 7 tons based on grain yield in pot experiments. After project began, it was decided also to derive RSLs for the available arms of homoeologous group 4 (4AS and 4BL), based on the apparent importance of chromosome group 4, based on early field trials of the CASLs.] 4. To characterize the RSLs for quantitative traits as in objective 1 and map and tag chromosome segments producing significant effects (quantitative trait loci, QTLs by RFLP markers. [Producing a large population of RSLs for each chromosome arm and mapping them proved more difficult than anticipated, low numbers of RSLs were obtained for two of the chromosome arms.] 5. To construct recombination genetic maps of chromosomes of homoeologous groups 1 and 7 and to compare them to existing maps of wheat and other cereals [Genetic maps are not complete for homoeologous groups 4 and 7.] The rationale for this project is that wild species have characteristics that would be valuable if transferred to a crop plant. We demonstrated the sequence of chromosome manipulations and genetic tests needed to confirm this potential value and enhance transfer. This research has shown that a wild tetraploid species harbors genetic variability for quantitative traits that is interactive and not simply additive when introduced into a common genetic background. Chromosomal segments from several chromosome arms improve yield and protein in wheat but their effect is presumably enhanced when combination of genes from several segments are integrated into a single genotype in order to achieve the benefits of genes from the wild species. The interaction between these genes and those in the recipient species must be accounted for. The results of this study provide a scientific basis for some of the disappointing results that have historically obtained when using wild species as donors for crop improvement and provide a strategy for further successes.

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Gray, Dennis, e Victor Gaba. Genotype, Explant and Growth Regulator Effects in the Determination of Adventitious Regeneratin in Curcurbits, in Aid of Genetic Transformation. United States Department of Agriculture, giugno 1992. http://dx.doi.org/10.32747/1992.7561060.bard.

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The objective of this study was to gain an understanding of the in vitro regeneration process in watermelon and melon to enable the development of genetic transformation systems. The objectives were met and additional progress, unplanned during the original proposal, was made. Organogenic regeneration in vitro was studied in both melon and watermelon. Genotype played a significant role in regeneration. In melon, epidermal cells were responsible for most regeneration. Methods to obtain in vitro-derived watermelon tetraploids, needed for seedless varieties, were developed. The culture systems were refined so that they could be routinely used for transformation. Particle guns were constructed and Agrobacterium strains were obtained to study the effect of transformation procedures on culture system performance, allowing refinement of transformation protocols. The culture systems were shown to enable the stable transformation of both crops, allowing their future use for insertion of agriculturally-important genes. In addition, we showed that shoot apical meristems might be suitable target tissue for transformation and allow a wider range of genotypes to be used, which is needed for crops as diverse as cucurbits.

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