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

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Chapter 1is only an equational segregation in which homologous chromatids segregated during meiosis,FDR gametes will be produced; and when there is only a reductional segregation, SDRgametes will arise. During SDR, homologous and homoeologous chromosomes paircompletely, and the chromatids in resultant products do not move to different poles but stay asone gamete without the simultaneous cytokinesis, and hence no formation of cell wall.However, in some of the interspecific hybrids of lily, bivalents disjoin reductionally andunivalents divide equally before telophase I. Since there is only one-time division followed bycytokinesis, the resultant products are also 2n gametes, and the mechanism is calledindeterminate meiotic restitution (IMR) (Lim et al. 2001a). For FDR-originated offspring,genetic loci that are proximal to the crossover point will be heterozygous, while for SDR, thesegments distal to the crossover point will be heterozygous (Fig. 1.1).The process of polyploidization using unreduced gametes is termed as sexualpolyploidization, which has progressed in some crops and contributed to plant breeding andcrop improvement dramatically. Superiority of vigor, growth, yield, which are of agronomicalimportance, has been found in some of the sexual polyploidized progenies in a range of crops,such as banana, sugarcane, potato, alfalfa, lily, which are all triploid or complex polyploids(reviewed by Ramanna and Jacobsen 2003).Table 1.1. Some mutants that produce high frequencies of unreduced gametes during malemeiosis in Arabidopsis thalianaMutant MutationType of unreducedgametesReferencesDyad An equational segregation(Agashe et al. 2002; MercierFDRduring meiosiset al. 2001)Cdka1;2/tam No meiosis II occurring SDR(Cromer et al. 2010; Wanget al. 2010)Osd1 Failing to enter the secondmeiosis divisionSDR (d’Erfurth et al. 2009)Atps1 Disruption of spindleorientation in Meiosis IIFDR (d'Erfurth et al. 2008)Tes/stud Failure of meiosis cytokinesis Tetraspores (Yang et al. 2003)Recently, Arabidopsis has become a well-studied species for unreduced gametes formation.A few genes have been proved to be involved in the production of unreduced gametes (Table1.1). In Arabidopsis, a FDR-relevant gene SWI1/DYAD has been characterized, in which thisdyad allele can result in an equational segregation without further division during female10
General Introductionmeiosis (Mercier et al. 2001; Agashe et al. 2002; Ravi et al. 2008). Interestingly, mutants oftwo proteins, CYCA1;2 (a member of the cyclin A family) (d’Erfurth et al. 2010; Wang et al.2010; ) and Ommision of Second Division 1 (OSD1) which both impede the entre of meiosisII and control the male and female meiosis (d’Erfurth et al. 2009), lead to the production ofSDR gametes. A mutant of Arabidopsis parallel spindle1 (Atps1) can also disrupt the spindleorientation, which will lead to a mix of dyads and triads (two haploid cells together with adiploid cell) as well as some tetrads during meiosis (d’Erfurth et al. 2008).The recent discoveries of the genetic mechanisms that unreduced gametes produced inArabidopsis and other species open an exciting avenue to put the knowledge into practice forplant breeding. Indeed, researchers are trying to develop new strategies to induce unreducedgametes by knockdown of specific proteins which have been mentioned before. With theavailable techniques of targeted gene manipulation, the generation of crops producingdesigned gametes is becoming realistic. Meanwhile, it will also enhance our understanding ofthe evolution and speciation of flowering plants.Meiotic abnormalities and bridges in interspecific hybridsInterspecific hybridization, which has been used for studying the relationship betweendifferent species and making new variation for further breeding, is quite a normal tool in plantbreeding. One of the most important features of these distant hybrids is the reduced fertility.The reason of the sterility has been well studied in a few species hybrids and the reasons hasbeen explained as due to the association failure and the abnormal segregation caused bychromosome structure differences at the first cell division during meiosis, which lead toaneuploidy and unviable gametes (Asano 1982; Barba-Gonzalez et al. 2005b; Gopinathan andBabu 1986; Jenkins and Scanlon 1987; Kopecký et al. 2008; Lee et al. 2011; Lim et al. 2001a;Pickering et al. 2004; Zhang et al. 1999; Zhou et al. 2008a).The main feature of interspecific hybrids during meiosis is the association failure in thefirst division. In interspecific hybrids, chromosomes from different species are normallypartly homologous (homoeologous). During meiosis, these homoeologous chromosomescannot recognize each other and hence, bivalents cannot be formed (Blanco et al. 1983;Jenkins and Scanlon 1987). As a consequence, univalents will randomly move to one of thecell poles and cause the imbalance of chromosome numbers between the subsequently formedtwo cells (Lim et al. 2001a; Poggio et al. 1999). Furthermore, it is also noticeable that in someof the distant hybrids, the meiosis is highly irregular due to the difference of basicchromosome number in the crossing parents. Even non-homologous chromosomessuccessfully paired together, interspecific hybrids could also suffer abnormal segregation atanaphase of the first division. During the process of speciation, genomes of related species are11
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 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 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
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Chapter 5AbstractSupernumerary (B)
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Chapter 5their origin, the structur
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Chapter 5Fig. 5.1. Discovery of B c
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Chapter 5In order to investigate th
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Chapter 5Centric breakage and fusio
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Chapter 5It has not, however, been
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Chapter 6The results presented in t
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Chapter 6model for molecular cytoge
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Chapter 6Fig. 6.2. The meiosis proc
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Chapter 6over events during FDR mei
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Chapter 6been detected with GISH an
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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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