Genome size in natural and synthetic autopolyploids and in a natural segmental allopolyploid of several Triticeae species.

Nuclear DNA amount (1C) was determined by flow cytometry in the autotetraploid cytotype of Hordeum bulbosum, in the cytologically diploidized autotetraploid cytotypes of Elymus elongatus, Hordeum murinum subsp. murinum and Hordeum murinum subsp. leporinum, in Hordeum marinum subsp. gussoneanum, in their progenitor diploid cytotypes, and in a newly synthesized autotetraploid line of E. elongatus. Several lines collected from different regions of the distribution area of every taxon, each represented by a number of plants, were analyzed in each taxon. The intracytotype variation in nuclear DNA amount of every diploid and autotetraploid cytotype was very small, indicating that no significant changes have occurred in DNA amount either after speciation or after autopolyploid formation. The autotetraploid cytotypes of H. bulbosum and the cytologically diploidized H. marinum subsp. gussoneanum had the expected additive amount of their diploid cytotypes. On the other hand, the cytologically diploidized autotetraploid cytotypes of E. elongatus and H. murinum subsp. murinum and H. murinum subsp. leporinum had considerably less nuclear DNA (10%-23%) than the expected additive value. Also, the newly synthesized autotetraploid line of E. elongatus showed similar reduction in DNA as its natural counterpart, indicating that the reduction in genome size occurred in the natural cytotype during autopolyploidization. It is suggested that the diploid-like meiotic behavior of these cytologically dipolidized autotetraploids is caused by the instantaneous elimination of a large number of DNA sequences, different sequences from different homologous pairs, leading to differentiation of the constituent genomes. The eliminated sequences are likely to include those that participate in homologous recognition and initiation of meiotic pairing. A gene system determining exclusive bivalent pairing by utilizing the differentiation between the two groups of homologues has been presumably superimposed on the DNA reduction process.

[1]  I. Linde-Laursen,et al.  An ecogeographical study of the genus Hordeum , 1992 .

[2]  Xuefeng Ma,et al.  Timing and rate of genome variation in triticale following allopolyploidization. , 2006, Genome.

[3]  I. Leitch,et al.  Genome downsizing in polyploid plants , 2004 .

[4]  M. Feldman,et al.  The Impact of Polyploidy on Grass Genome Evolution , 2002, Plant Physiology.

[5]  Xuefeng Ma,et al.  Polyploidization-induced genome variation in triticale. , 2004, Genome.

[6]  J. W. Morrison,et al.  Chromosome behaviour in autotetraploid cereals and grasses , 2004, Chromosoma.

[7]  J. Dvorak GENOME RELATIONSHIPS AMONG ELYTRIGIA (=AGROPYRON) ELONGATA, E. STIPIFOLIA, "E. ELONGATA 4x," E. CAESPITOSA, E. INTERMEDIA, AND "E. ELONGATA 10x" , 1981 .

[8]  J. B. Smith,et al.  THE 4C NUCLEAR DNA CONTENT OF SEVERAL HORDEUM GENOTYPES , 1971 .

[9]  G. Segal,et al.  Rapid elimination of low-copy DNA sequences in polyploid wheat: a possible mechanism for differentiation of homoeologous chromosomes. , 1997, Genetics.

[10]  K. Vogel,et al.  Nuclear DNA Content of Perennial Grasses of the Triticeae , 1999 .

[11]  K. Jones Species differentiation inagrostis , 1956, Journal of Genetics.

[12]  R. Fritsch,et al.  Evolution of genome size inAllium (Alliaceae) , 1998, Plant Systematics and Evolution.

[13]  G. Ledyard Stebbins,et al.  Chromosomal evolution in higher plants , 1971 .

[14]  R. Bothmer,et al.  Supraspecific groups in the genus Hordeum , 2008 .

[15]  Jaroslav Dolezel,et al.  Plant DNA flow cytometry and estimation of nuclear genome size. , 2005, Annals of botany.

[16]  F. Blattner,et al.  Combined ecological niche modelling and molecular phylogeography revealed the evolutionary history of Hordeum marinum (Poaceae) — niche differentiation, loss of genetic diversity, and speciation in Mediterranean Quaternary refugia , 2007, Molecular ecology.

[17]  K. Arumuganathan,et al.  Nonadditive changes in genome size during allopolyploidization in the wheat (aegilops-triticum) group. , 2003, The Journal of heredity.

[18]  A. Meister,et al.  Lack of correlation between AT frequency and genome size in higher plants and the effect of nonrandomness of base sequences on dye binding. , 2002, Cytometry.

[19]  R. Bothmer,et al.  Meiosis in interspecific Hordeum hybrids. IV. Tetraploid (4x × 4x) hybrids , 1988 .

[20]  B. Murray When does intraspecific C-value variation become taxonomically significant? , 2005, Annals of botany.

[21]  F. Blattner Phylogenetic analysis of Hordeum (Poaceae) as inferred by nuclear rDNA ITS sequences. , 2004, Molecular phylogenetics and evolution.

[22]  K. Jones Species differentiation inAgrostis , 1956, Journal of Genetics.

[23]  Genetic control of meiotic chromosome pairing in polyploids in the genus Hordeum , 1985 .

[24]  J. Dvorak,et al.  Genome Symbols in the Triticeae (Poaceae) , 1994 .

[25]  H. Özkan,et al.  Alterations in subtelomeric tandem repeats during early stages of allopolyploidy in wheat. , 2004, Genome.

[26]  T. N. Khoshoo,et al.  Associated chromosomal DNA changes in polyploids. , 1994, Genome.

[27]  Christian Parisod,et al.  Evolutionary consequences of autopolyploidy. , 2010, The New phytologist.

[28]  K. H. Wolfe Yesterday's polyploids and the mystery of diploidization , 2001, Nature Reviews Genetics.

[29]  I. Linde-Laursen,et al.  Relationships in the genus Hordeum: Giemsa C-banded karyotypes , 2008 .

[30]  D. Galbraith,et al.  Rapid Flow Cytometric Analysis of the Cell Cycle in Intact Plant Tissues , 1983, Science.

[31]  R. Jørgensen,et al.  Systematic and Ecogeographic Studies on Crop Genepools, 7 2ND ED An ecogeographical study of the genus Hordeum , 1995 .

[32]  G. Petersen,et al.  Phylogenetic Analyses of the Diploid Species of Hordeum (Poaceae) and a Revised Classification of the Genus , 2009 .

[33]  R. Gregory The evolution of the genome , 2005 .

[34]  角田 重三郎,et al.  NUCLEAR VOLUME, NUCLEAR DNA CONTENT AND RADIOSENSITIVITY IN BRASSICA AND ALLIED GENERA , 1969 .

[35]  V. Jaaska Isoenzyme evidence on the systematics ofHordeum sectionMarina (Poaceae) , 1994, Plant Systematics and Evolution.

[36]  P. Holland,et al.  Polyploidy in vertebrate ancestry: Ohno and beyond , 2004 .

[37]  L Nardi,et al.  Plant Genome Size Estimation by Flow Cytometry: Inter-laboratory Comparison , 1998 .

[38]  F. Han,et al.  Rapid and Repeatable Elimination of a Parental Genome-Specific DNA Repeat (pGc1R-1a) in Newly Synthesized Wheat Allopolyploids , 2005, Genetics.

[39]  M. Feldman,et al.  Nuclear DNA amount and genome downsizing in natural and synthetic allopolyploids of the genera Aegilops and Triticum. , 2008, Genome.

[40]  J. Spring,et al.  Vertebrate evolution by interspecific hybridisation – are we polyploid? , 1997, FEBS letters.

[41]  M. Feldman,et al.  Sequence Elimination and Cytosine Methylation Are Rapid and Reproducible Responses of the Genome to Wide Hybridization and Allopolyploidy in Wheat , 2001, The Plant Cell Online.

[42]  A. Schulman,et al.  The genome sizes of Hordeum species show considerable variation. , 1996, Genome.

[43]  T. Ouellet,et al.  Rapid genomic changes in interspecific and intergeneric hybrids and allopolyploids of Triticeae. , 2003, Genome.

[44]  A. Schulman,et al.  Active retrotransposons are a common feature of grass genomes. , 2001, Plant physiology.

[45]  R. Bothmer,et al.  Meiosis in interspecific Hordeum hybrids , 2008 .

[46]  J. P. Gustafson,et al.  Genome evolution of allopolyploids: a process of cytological and genetic diploidization , 2005, Cytogenetic and Genome Research.

[47]  H. Giese,et al.  Physical localization of active and inactive rRNA gene loci in Hordeum marinum spp. gussoneanum (4x) by in situ hybridization , 1992 .

[48]  M. Feldman,et al.  Rapid genomic changes in newly synthesized amphiploids of Triticum and Aegilops. II. Changes in low-copy coding DNA sequences , 1998 .

[49]  R. Jørgensen Biosystematics of Hordeum bulbosum L. , 1982 .

[50]  Douglas E. Soltis,et al.  Advances in the study of polyploidy since Plant speciation , 2003 .

[51]  M. Feldman,et al.  Genome Size in Diploids, Allopolyploids, and Autopolyploids of Mediterranean Triticeae , 2010 .

[52]  David W. Galbraith,et al.  No DNA loss in autotetraploids of Arabidopsis thaliana , 2006 .

[53]  M. Feldman,et al.  Allopolyploidy-Induced Rapid Genome Evolution in the Wheat (Aegilops–Triticum) Group , 2001, The Plant Cell Online.

[54]  Avraham A. Levy,et al.  Genetic and epigenetic reprogramming of the wheat genome upon allopolyploidization , 2004 .

[55]  O. Sagi-Assif,et al.  Genome size and genome evolution in diploid Triticeae species. , 2007, Genome.

[56]  R. Jørgensen Relationships in the barley genus (Hordeum): an electrophoretic examination of proteins , 2008 .

[57]  I. Leitch,et al.  DNA Amounts in Two Samples of Angiosperm Weeds , 1998 .

[58]  J. W. Morrison,et al.  Frequency of Quadrivalents in Autotetraploid Plants , 1960, Nature.

[59]  J. W. Morrison,et al.  CYTOGENETIC STUDIES IN THE GENUS HORDEUM VI. THE MURINUM-COMPLEX , 1962 .

[60]  A. Seal,et al.  DNA variation in Festuca , 1983, Heredity.

[61]  H. Özkan,et al.  Rapid differentiation of homeologous chromosomes in newly-formed allopolyploid wheat , 2002 .

[62]  G. Segal,et al.  Rapid genomic changes in newly synthesized amphiploids of Triticum and Aegilops. II. Changes in low-copy coding DNA sequences. , 1998, Genome.

[63]  M. Feldman,et al.  Allopolyploidy – a shaping force in the evolution of wheat genomes , 2005, Cytogenetic and Genome Research.

[64]  C. N. Law,et al.  Genetic Variation in Chromosome Pairing , 1965 .

[65]  Jane Masterson,et al.  Stomatal Size in Fossil Plants: Evidence for Polyploidy in Majority of Angiosperms , 1994, Science.

[66]  A. Charpentier,et al.  Genetic control of meiotic chromosome pairing in tetraploid Agropyron elongatum. I. Pattern of pairing in natural and induced tetraploids and in F1 triploid hybrids , 1986 .

[67]  G. Ledyard Stebbins,et al.  Variation and Evolution in Plants , 1951 .

[68]  A. Sidow Gen(om)e duplications in the evolution of early vertebrates. , 1996, Current opinion in genetics & development.

[69]  L. Rieseberg,et al.  Plant Speciation , 2007, Science.

[70]  P. Šmarda,et al.  Genome size and GC content evolution of Festuca: ancestral expansion and subsequent reduction. , 2008, Annals of botany.

[71]  R. Jørgensen,et al.  Variation and differentiation in Hordeum marinum (Poaceae) , 1989 .

[72]  C. Dawson Tetrasomic inheritance inLotus corniculatus L. , 1941, Journal of Genetics.

[73]  H. Nordenskiöld A GENETICAL STUDY IN THE MODE OF SEGREGATION IN HEXAPLOID PHLEUM PRATENSE , 2010 .

[74]  N. Jouve,et al.  Physical mapping of repetitive DNA sequences and 5S and 18S–26S rDNA in five wild species of the genusHordeum , 1996, Chromosome Research.

[75]  A. Meister,et al.  The considerable genome size variation of Hordeum species (poaceae) is linked to phylogeny, life form, ecology, and speciation rates. , 2004, Molecular biology and evolution.

[76]  B. Gill,et al.  Variation in the distribution of a genome-specific DNA sequence on chromosomes reveals evolutionary relationships in the Triticum and Aegilops complex , 2002, Plant Systematics and Evolution.

[77]  T. Komatsuda,et al.  Molecular phylogeny of the genus Hordeum using three chloroplast DNA sequences. , 2002, Genome.

[78]  R. Knight,et al.  Vertebrate genome evolution: a slow shuffle or a big bang? , 1999, BioEssays : news and reviews in molecular, cellular and developmental biology.

[79]  Johann Greilhuber,et al.  Intraspecific variation in genome size in angiosperms: identifying its existence. , 2005, Annals of botany.