A molecular cytogenetic analysis of chromosome behavior in Lilium ...

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Chapter 3AbstractWith the aim of tracing the origin of intergenomic exchanges in lily backcross progenies anddistinguish differences, if any, between intergenomic recombination and translocation, 13genotypes of an interspecific hybrids, which were previously used as parents to generatesexual polyploids, were selected for a detailed meiosis analysis. In all genotypes variablenumbers of bivalents (0-12) resulting from homoeologous pairing and univalents wereobserved. But in two genotypes (006001-6 and 006001-13), a multivalent which was either aquadri- or a trivalent, as well as a bivalent involving two Asiatic chromosomes, was observed.An interesting feature of the multivalent in the case of 006001-6 was that two of the Asiaticchromosomes were always found to be associated either in the quadrivalent or the trivalentconfigurations. This indicated that there was a duplication common to two non-homologouschromosomes within the Asiatic parent. Such a duplication might have resulted from thesegregation of a chromosomal translocation between two non-homologous chromosomes inthe Asiatic parent ‘Connecticut King’ which was transmitted to the progeny (006001-6). Withthe exception of two genotypes, in 11 genotypes that formed variable frequencies of bivalents,the homoeologous chromosome pairing and chiasma formation were similar to that betweenhomologous chromosomes. Especially from the analysis of anaphase I stages it was evidentthat the expected types of chiasma formation involving non-sister chromatids gave rise to twostrand single, two strand double, three strand double , four strand double and multipleexchanges. Whereas these events resulted from locus specific homoeologous exchanges, thetranslocations resulted from an aberrant form of non-homologous chromosomal exchange ofsegments. Elucidation of such differences is only possible through the analysis of meiosisusing GISH.Keywords: Recombination; crossing-over; translocation; Lily; meiosis; interspecific hybrids;genomic in situ hybridization (GISH)32
Intergenomic recombination and chromosome translocation in Lilium hybridsIntroductionIntergenomic recombination and chromosome translocation are totally different phenomena,although exchanges of chromosome segments occur in both cases. Whereas recombination isthe result of crossing-over between homo- or homoeologous chromosomes during meiosis (anatural event), chromosome translocations occur due to chromosome aberrations or mutations(Rieger et al. 1976). Among many other differences, recombinations are locus specific events,whereas translocations are random events – implying that any chromosome segment may betransferred to another location in the genome through breakage and reunion. Despite thesedifferences, in recent years the terms recombination and translocation have been used assynonyms in the cytogenetic literature because little is known about the origin of such geneticchanges (Heslop-Harrison 2000; Nicolas et al. 2007; Osborn et al. 2003; Szadkowski et al.2011; Udall et al. 2005). Especially in the case of newly induced polyploids (neo-polyploids)of species such as Brassica napus, intergenomic recombinations have been considered astranslocations that lead to extensive chromosomal structural alterations (Gaeta et al. 2007).Lily (Lilium, 2n=2x=24) species have been used for investigating chromosome structuralalteration by traditional cytogeneticists during the past century. Together with a few otherplant species, especially maize (Zea mays), barley (Hordeum vulgare), wheat (Triticumaestivum) and other crops (Burnham 1962; Lewis and John 1963), chromosomerearrangements such as translocations, inversions, duplications and deletions, have beenextensively investigated. These studies were not only confined to spontaneous events thatoccurred in nature but also included aberrations induced by radiations as well as chemicalagents. In addition to gaining insights into various aspects of chromosome functions andbehaviour, chromosome aberrations were also helpful to establish the relationship betweenchiasma formation and crossing-over (chiasmatype hypothesis). For this purpose, the plantspecies with large chromosomes such as those of lilies are especially helpful because they arefavourable for critical cytological studies. Some of the examples are: inversion heterozygotesin Lilium martagon var. album and L. hansonii in which spontaneous paracentric inversionswere used to test chiasmatype hypothesis (Richardson 1936); x-ray induced terminal deletionand paracentric inversion in L. formosanum were used to establish the relationship betweenchiasma and crossing-over (Brown and Zohary 1955); using a reciprocal translocation in L.maximowiczii, chiasmatype hypothesis was confirmed (Noda 1960); by analysing a pair ofheteromorphic chromosomes resulting from reciprocal translocations in Disporum sessile,chiasmatype hypothesis was also confirmed (Kayano 1960). A favourable feature ofreciprocal translocations in the case of L. maximowiczii and Disporum sessile was thepossibility to quantify the frequencies of chiasmata in the interstitial segments (chromosomesegments that lie between the centromere and the translocated segment) by estimatingequational and reductional separation at anaphase I stages (see later). In all the above casesanalyses of meiotic stages in pollen mother cells have been successfully used.33
Page 3 and 4: A molecular cytogenetic analysis of
Page 5: Table of ContentsChapter 1General I
Page 8 and 9: Chapter 1LilyLilies belong to genus
Page 10 and 11: Chapter 1counterparts (Finnegan 200
Page 12 and 13: Chapter 1renewed interest in detect
Page 14 and 15: Chapter 1recombination, mechanisms
Page 16 and 17: Chapter 1is only an equational segr
Page 18 and 19: Chapter 1quite divergent with vario
Page 21 and 22: Chapter 2An assessment of chromosom
Page 23 and 24: Chromosome rearrangements in Lilium
Page 37: Chapter 3Elucidation of intergenomi
Page 41 and 42: Intergenomic recombination and chro
Page 49: Intergenomic recombination and chro
Page 52 and 53: Chapter 4AbstractMeiotic abnormalit
Page 54 and 55: Chapter 4There are some criteria to
Page 56 and 57: Chapter 4FISH experiments were perf
Page 58 and 59: Chapter 4was apparently shorter, wi
Page 60 and 61: Chapter 4bridges is explained as U-
Page 62 and 63: Chapter 4of the sexual polyploidize
Page 64 and 65: Chapter 4fragment have the same len
Page 66 and 67: Chapter 5AbstractSupernumerary (B)
Page 68 and 69: Chapter 5their origin, the structur
Page 70 and 71: Chapter 5Fig. 5.1. Discovery of B c
Page 72 and 73: Chapter 5In order to investigate th
Page 74 and 75: Chapter 5Centric breakage and fusio
Page 76 and 77: Chapter 5It has not, however, been
Page 78 and 79: Chapter 6The results presented in t
Page 80 and 81: Chapter 6model for molecular cytoge
Page 82 and 83: Chapter 6Fig. 6.2. The meiosis proc
Page 84 and 85: Chapter 6over events during FDR mei
Page 86 and 87: Chapter 6been detected with GISH an
Page 88 and 89:
Chapter 6Another feature caused by
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ReferencesAbe, H.A., Nakano, M.N.,
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ReferencesChen, Q., and Armstrong,
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ReferencesHartlerode, A.J., and Scu
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ReferencesLarson, S.R., Kishii, M.,
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ReferencesMcClintock, B. 1931. Cyto
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ReferencesRai, R., Zheng, H., He, H
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ReferencesStewart, R.N. 1947. The m
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ReferencesZhang, L., Pickering, R.,
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Summarychromosome rearrangements. T
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SamenvattingLelie (Lilium) is in de
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Samenvattingaantal 35 met daarnaast
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摘要百合系百合科百
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Acknowledgements淡看世事去
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Curriculum VitaeSonglin Xie was bor
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Education Statement of the Graduate
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