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

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Chapter 6Fig. 6.2. The meiosis process of chromosomes with a reciprocal translocation and their relevance to genetic mapping. Gametes from adjacent segregation of aquadrivalent from a reciprocal translocation are generally unviable, while gametes from alternate segregation are balanced and viable if crossovers happenedin the translocated chromosome segments, as well as the other chromosome arms. Any single crossover between non-sister chromatids in the interstitial areawill lead to the production of duplication-deficiency gametes. Note: “+” stands for gametes that are viable, “-” stands for gametes that are unviable.76
General DiscussionTwo translocated chromosomes usually form ‘pseudolinkage’ (Albrecht and Chetelat 2009;Farré et al. 2010; Kamphuis et al. 2007). Meanwhile, since normal and translocated segmentslead to reduced crossover interference, distance between markers on normal and translocatedchromosome fragments will be wrongly estimated, marker order is ambiguous along themerged linkage groups and higher stringencies (increase the LODs) do not result in a divisioninto two balanced chromosomes (Albrecht and Chetelat 2009). Third, the existence ofduplication leads to erroneous location of markers in the linkage group associated with thechromosome with duplication (Fig. 6.1). Furthermore, chromosomes with two or more typesof structure variation make the genetic maps even more complicated. In conclusion,chromosome rearrangements not only cause reduced fertility, but also lead to errors whenestimating genetic distances between markers.Sexual polyploidization and its significance in polyploidy mappingWhen interspecific crosses are made between distantly related species, the resulting hybridsare generally sterile. This hybrid sterility is explained to be due to the failure of chromosomeassociation and the forthcoming error-disjoining during meiosis because of the parentaldivergence (Asano 1982). However, there is still a wide genetic variation, with someindividuals possessing a low fertility. These outstanding genotypes normally produceunreduced (2n) gametes, as well as fewer n gametes (Ramanna and Jacobsen 2003). Theprocess of restoring fertility through unreduced gametes is termed as sexual (meiotic)polyploidization, as a comparison with asexual (mitotic) polyploidization. The production ofunreduced gametes has been reported in many interspecific hybrids, such as Lilium (Van Tuylet al. 1989), Alstroemeria (Kamstra et al. 1999), Allium (Khrustaleva and Kik 1998) andothers. One of the main advantages of sexual polyploidization, compared with its counterpart,is the occurrence of intergenomic recombination during the production of unreduced gametes,which will lead to segregation and diversity in the next generation (Ramanna and Jacobsen2003). The segregation in the resulting population provides a possibility for genetic mapping.When detecting intergenomic alteration in sexual polyploidized allopolyploids, molecularcytogenetic techniques (GISH and FISH) are more powerful compared with molecularmarkers. The detecting efficiency of the two methods with respect to unreduced (2n) gametesis compared in Fig. 6.3. GISH can simultaneously detect intergenomic recombination,characterize the crossing over events and trace the origin of non-sister chromatid exchangeswhen combined with meiosis observation. However, molecular markers with multi-locusanalysis in crossing progenies cannot detect reciprocal crossing over, and quantification ofallele number by the intensity of bands is not always accurate (Gaeta and Pires 2010; Nicolaset al. 2007). For example, in four types of segregated products between homoeologouschromosomes with a single or two strand double crossover during FDR meiosis (Fig. 6.3),GISH can detect all the intergenomic recombinations, whereas molecular markers can onlydetect two types of them. In the recombinant chromosomes derived from different crossing77
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A molecular cytogenetic analysis of
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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
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Chapter 1is only an equational segr
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Chapter 1quite divergent with vario
Page 21 and 22:
Chapter 2An assessment of chromosom
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Chromosome rearrangements in Lilium
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Page 27 and 28:
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Page 31 and 32: Chromosome rearrangements in Lilium
Page 37 and 38: Chapter 3Elucidation of intergenomi
Page 39 and 40: 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 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
Page 91 and 92: ReferencesAbe, H.A., Nakano, M.N.,
Page 93 and 94: ReferencesChen, Q., and Armstrong,
Page 95 and 96: ReferencesHartlerode, A.J., and Scu
Page 97 and 98: ReferencesLarson, S.R., Kishii, M.,
Page 99 and 100: ReferencesMcClintock, B. 1931. Cyto
Page 101 and 102: ReferencesRai, R., Zheng, H., He, H
Page 103 and 104: ReferencesStewart, R.N. 1947. The m
Page 105: ReferencesZhang, L., Pickering, R.,
Page 108 and 109: Summarychromosome rearrangements. T
Page 111 and 112: SamenvattingLelie (Lilium) is in de
Page 113 and 114: Samenvattingaantal 35 met daarnaast
Page 115 and 116: 摘要百合系百合科百
Page 117 and 118: Acknowledgements淡看世事去
Page 119: Curriculum VitaeSonglin Xie was bor
Page 123: Education Statement of the Graduate
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