Evidence of Genomic Exchanges between Homeologous Chromosomes in a Cross of Peanut with Newly Synthetized Allotetraploid Hybrids

We examined the inheritance of allelic variation at an isozyme locus, MDH-B, duplicated by ancestral polyploidy in salmonid fishes. We detected only disomic segregation in females. Segregation ratios in males were best explained by a mixture of disomic and tetrasomic inheritance. We propose a two-stage model of pairing in male meiosis in which, first, homologous chromosomes pair and recombine in the proximal region of the chromosome. Next, homeologous chromosomes pair and recombine distally. We suggest that this type of tetrasomic inheritance in which centromeres segregate disomically should be referred to as “secondary tetrasomy” to distinguish it from tetrasomy involving entire chromosomes (i.e., “primary tetrasomy”). Differences in segregation ratios between males indicate differences between individuals in the amount of recombination between homeologous chromosomes. We also consider the implication of these results for estimation of allele frequencies at duplicated loci in salmonid populations.

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Detection and Effects of a Homeologous Reciprocal Transposition in Brassica napus

Genetics ◽

10.1093/genetics/165.3.1569 ◽

2003 ◽

Vol 165 (3) ◽

pp. 1569-1577

Author(s):

Thomas C Osborn ◽

David V Butrulle ◽

Andrew G Sharpe ◽

Kathryn J Pickering ◽

Isobel A P Parkin ◽

...

Keyword(s):

Brassica Napus ◽

Genetic Mapping ◽

Doubled Haploid ◽

Selective Advantage ◽

F1 Hybrids ◽

Rflp Markers ◽

Cytological Analysis ◽

Linkage Groups ◽

Homeologous Chromosomes ◽

Seed Yields

Abstract A reciprocal chromosomal transposition was identified in several annual oilseed Brassica napus genotypes used as parents in crosses to biennial genotypes for genetic mapping studies. The transposition involved an exchange of interstitial homeologous regions on linkage groups N7 and N16, and its detection was made possible by the use of segregating populations of doubled haploid lines and codominant RFLP markers. RFLP probes detected pairs of homeologous loci on N7 and N16 for which the annual and biennial parents had identical alleles in regions expected to be homeologous. The existence of an interstitial reciprocal transposition was confirmed by cytological analysis of synaptonemal complexes of annual × biennial F1 hybrids. Although it included approximately one-third of the physical length of the N7 and N16 chromosomes, few recombination events within the region were recovered in the progenies of the hybrids. Significantly higher seed yields were associated with the parental configurations of the rearrangement in segregating progenies. These progenies contained complete complements of homeologous chromosomes from the diploid progenitors of B. napus, and thus their higher seed yields provide evidence for the selective advantage of allopolyploidy through the fixation of intergenomic heterozygosity.

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Resistance gene analogue markers are mapped to homeologous chromosomes in cultivated tetraploid cotton

Theoretical and Applied Genetics ◽

10.1007/s00122-005-1928-5 ◽

2005 ◽

Vol 110 (6) ◽

pp. 1074-1085 ◽

Cited By ~ 33

Author(s):

Doug J. Hinchliffe ◽

Yingzhi Lu ◽

Carol Potenza ◽

Champa Segupta-Gopalan ◽

Roy G. Cantrell ◽

...

Keyword(s):

Resistance Gene ◽

Tetraploid Cotton ◽

Resistance Gene Analogue ◽

Homeologous Chromosomes

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Meiotic crossing-over in the regions of homology between homeologous chromosomes V

Yeast ◽

10.1002/yea.759 ◽

2001 ◽

Vol 18 (12) ◽

pp. 1173-1183 ◽

Cited By ~ 3

Author(s):

Elena A. Shubochkina ◽

Trine L. Nielsen ◽

Torsten Nilsson-Tillgren

Keyword(s):

Crossing Over ◽

Homeologous Chromosomes

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JOINT SEGREGATION OF BIOCHEMICAL LOCI IN SALMONIDAE. II. LINKAGE ASSOCIATIONS FROM A HYBRIDIZED SALVELINUS GENOME (S. NAMAYCUSH x S. FONTINALIS)

Genetics ◽

10.1093/genetics/95.3.707 ◽

1980 ◽

Vol 95 (3) ◽

pp. 707-726

Author(s):

Bernie May ◽

Mark Stoneking ◽

James E Wright

Keyword(s):

Brook Trout ◽

Lake Trout ◽

Salvelinus Fontinalis ◽

De Novo ◽

Homeologous Chromosome ◽

Homeologous Chromosomes ◽

Joint Segregation ◽

Duplicate Loci ◽

Haploid Complement

ABSTRACT The results of more than 300 parwise examinations of biochemical loci for joint segregation in brook trout (Salvelinus fontinalis) and in the hybridized genome of lake trout (S. namaycush) × brook trout are summarized. Nineteen loci have been assigned to the following eight linkage groupings on the basis of nonrandom assortment, including cases of both classical linkage and pseudolinkage: ODH with PMI with PGI-3, PGI-2 with SDH, ADA-1 with AGP-2, AAT-(1,2) with AGP-1 with MDH-I, MDH-3 with MDH-4, LDH-3 with LDH-4, IDH-3 with ME-2 and GUS with CPK-I. Pseudolinkage (an excess of nonparental progeny types) was observed only for male testcross parents. The results suggest that this phenomenon involves homeologous chromosome arms as evidenced by the de novo association of presumed duplicate loci in each case. Classical linkage has not been found for the five pairs of duplicate loci examined in Salvelinus, suggesting that not all of the eight metacentrics in the haploid complement involve fusions of homeologous chromosomes. Females consistently showed a greater degree of recombination.

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Transfer of Downy Mildew Resistance from Wild Basil (Ocimum americanum) to Sweet Basil (O. basilicum)

Phytopathology ◽

10.1094/phyto-06-17-0207-r ◽

2018 ◽

Vol 108 (1) ◽

pp. 114-123 ◽

Cited By ~ 9

Author(s):

Yariv Ben-Naim ◽

Lidan Falach ◽

Yigal Cohen

Keyword(s):

Downy Mildew ◽

Dominant Gene ◽

Susceptible Parent ◽

Backcross Generation ◽

Sweet Basil ◽

Resistant Varieties ◽

Homeologous Chromosomes ◽

Tetraploid Parent ◽

Dominant Genes

Sweet basil (Ocimum basilicum) is susceptible to downy mildew caused by the oomycete foliar pathogen Peronospora belbahrii. No resistant varieties of sweet basil are commercially available. Here, we report on the transfer of resistance gene Pb1 from the highly resistant tetraploid wild basil O. americanum var. americanum (PI 500945, 2n = 4x = 48) to the tetraploid susceptible O. basilicum ‘Sweet basil’ (2n = 4x = 48). F1 progeny plants derived from the interspecific hybridization PI 500945 × Sweet basil were resistant, indicating that the gene controlling resistance (Pb1) is dominant, but sterile due to the genetic distance between the parents. Despite their sterility, F1 plants were pollinated with the susceptible parent and 115 first backcross generation to the susceptible parent (BCs1) embryos were rescued in vitro. The emerging BCs1 plants segregated, upon inoculation, 5:1 resistant/susceptible, suggesting that resistance in F1 was controlled by a pair of dominant genes (Pb1A and Pb1A’). Thirty-one partially fertile BCs1 plants were self-pollinated to obtain BCs1-F2 or were backcrossed to Sweet basil to obtain the second backcross generation to the susceptible parent (BCs2). In total, 1 BCs1-F2 and 22 BCs2 progenies were obtained. The BCs1-F2 progeny segregated 35:1 resistant/susceptible, as expected from a tetraploid parent with two dominant resistant genes. The 22 BCs2 progenies segregated 1:1 resistant/susceptible (for a BCs1 parent that carried one dominant gene for resistance) or 5:1 (for a BCs1 parent that carried two dominant genes for resistance) at a ratio of 4:1. The data suggest that a pair of dominant genes (Pb1A and Pb1A’) residing on a two homeologous chromosomes is responsible for resistance of PI 500945 against P. belbahrii.

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Rapid differentiation of homeologous chromosomes in newly-formed allopolyploid wheat

Israel Journal of Plant Sciences ◽

10.1560/e282-pv55-g4xt-drwj ◽

2002 ◽

Vol 50 (1) ◽

pp. 65-76 ◽

Cited By ~ 30

Author(s):

HAKAN OZKAN ◽

AVRAHAM A. LEVY ◽

MOSHE FELDMAN

Keyword(s):

Homeologous Chromosomes

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Evolution of duplicated growth hormone genes in autotetraploid salmonid fishes

Genome ◽

10.1139/g04-018 ◽

2004 ◽

Vol 47 (4) ◽

pp. 714-723 ◽

Cited By ~ 28

Author(s):

S J McKay ◽

J Trautner ◽

M J Smith ◽

B F Koop ◽

R H Devlin

Keyword(s):

Growth Hormone ◽

Evolutionary History ◽

Sequence Divergence ◽

Genome Doubling ◽

Disomic Inheritance ◽

A Genome ◽

Gh Gene ◽

Average Sequence Divergence ◽

History Of ◽

Homeologous Chromosomes

A defining character of the piscine family Salmonidae is autotetraploidy resulting from a genome-doubling event some 25–100 million years ago. Initially, duplicated genes may have undergone concerted evolution and tetrasomic inheritance. Homeologous chromosomes eventually diverged and the resulting reduction in recombination and gene conversion between paralogous genes allowed the re-establishment of disomic inheritance. Among extant salmonine fishes (e.g. salmon, trout, char) the growth hormone (GH) gene is generally represented by two functional paralogs, GH1 and GH2. Sequence analyses of salmonid GH genes from species of subfamilies Coregoninae (whitefish, ciscos) and Salmoninae were used to examine the evolutionary history of the duplicated GH genes. Two divergent GH gene paralogs were also identified in Coregoninae, but they were not assignable to the GH1 and GH2 categories. The average sequence divergence between the coregonine GH genes was more than twofold lower than the corresponding divergence between the salmonine GH1 and GH2. Phylogenetic analysis of the coregonine GH paralogs did not resolve their relationship to the salmonine paralogs. These findings suggest that disomic inheritance of two GH genes was established by different mechanisms in these two subfamilies.Key words: salmon, phylogeny, growth hormone, disomy, tetraploidy.

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The Colinearity of the Sh2/A1 Orthologous Region in Rice, Sorghum and Maize Is Interrupted and Accompanied by Genome Expansion in the Triticeae

Genetics ◽

10.1093/genetics/160.3.1153 ◽

2002 ◽

Vol 160 (3) ◽

pp. 1153-1162 ◽

Cited By ~ 6

Author(s):

Wanlong Li ◽

Bikram S Gill

Keyword(s):

Tandem Duplication ◽

Common Ancestor ◽

Barley Chromosome ◽

Orthologous Region ◽

Genome Species ◽

Large Genome ◽

Genome Expansion ◽

Triticeae Species ◽

Chromosome Gene ◽

Homeologous Chromosomes

Abstract The Sh2/A1 orthologous region of maize, rice, and sorghum contains five genes in the order Sh2, X1, X2, and two A1 homologs in tandem duplication. The Sh2 and A1 homologs are separated by ~20 kb in rice and sorghum and by ~140 kb in maize. We analyzed the fate of the Sh2/A1 region in large-genome species of the Triticeae (wheat, barley, and rye). In the Triticeae, synteny in the Sh2/A1 region was interrupted by a break between the X1 and X2 genes. The A1 and X2 genes remained colinear in homeologous chromosomes as in other grasses. The Sh2 and X1 orthologs also remained colinear but were translocated to a nonhomeologous chromosome. Gene X1 was duplicated on two nonhomeologous chromosomes, and surprisingly, a paralog shared homology much higher than that of the orthologous copy to the X1 gene of other grasses. No tandem duplication of A1 homologs was detected but duplication of A1 on a nonhomeologous barley chromosome 6H was observed. Intergenic distances expanded greatly in wheat compared to rice. Wheat and barley diverged from each other 12 million years ago and both show similar changes in the Sh2/A1 region, suggesting that the break in colinearity as well as X1 duplications and genome expansion occurred in a common ancestor of the Triticeae species.

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Recombination of Chromosomes 3Am and 5Am of Triticum monococcum With Homeologous Chromosomes 3A and 5A of Wheat: The Distribution of Recombination Across Chromosomes

Genetics ◽

10.1093/genetics/154.3.1301 ◽

2000 ◽

Vol 154 (3) ◽

pp. 1301-1308

Author(s):

Ming-Cheng Luo ◽

Zu-Li Yang ◽

Rama S Kota ◽

Jan Dvořák

Keyword(s):

Homologous Chromosome ◽

Triticum Monococcum ◽

Recombination Rates ◽

Crossover Interference ◽

Homeologous Chromosomes ◽

Multiple Crossovers

Abstract Recombination of chromosomes 3Am and 5Am of Triticum monococcum with closely homeologous chromosomes 3A and 5A of T. aestivum was compared with recombination across corresponding homologous chromosome pairs. Differentiation between the homeologues impacted recombination in the proximal regions of the long arms the most and in the distal regions of the long arms the least. It is concluded that this variation principally reflects allocation of multiple crossovers across an arm and positive crossover interference across chromosome arms. Recombination rates between homeologous chromosomes 5Am and 5A differed in the opposite sexes.

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