Synaptic mutants in hexaploid oats (Avena sativa L.)

Genome ◽  
1988 ◽  
Vol 30 (1) ◽  
pp. 1-7 ◽  
Author(s):  
H. W. Rines ◽  
S. S. Johnson
Keyword(s):  
Chromosome Pairing ◽  
Sodium Azide ◽  
Avena Sativa ◽  
Seed Set ◽  
Single Gene ◽  
Inheritance Pattern ◽  
Late Prophase ◽  
Homologous Chromosomes ◽  
Breeding Station ◽  
Meiotic Synapsis

Three meiotic synapsis-deficient mutants of oats (Avena sativa L.) were analyzed to determine their inheritance pattern, detailed chromosomal behavior, and location to chromosome. These highly sterile mutants, one in the cultivar 'Stout' and two in 'Noble', had been recovered from progeny of sodium azide mutagenized populations. Each segregated as a single gene recessive. The only synapsis-deficient variants previously described in hexaploid oats have been nullisomics or ditelosomics. Mutant 'Stout 1212' was classified as asynaptic due to deficiencies in chromosome pairing at all meiotic stages. Mutants 'Noble 1362' and 'Noble 1911' were classified as desynaptic since their homologous chromosomes were paired in early meiosis but they disassociated prematurely in late prophase I. Using a partial monosomic series from the Welsh Plant Breeding Station, mutant 1212 was mapped to monosome XII and is probably a mutation in Syn-5, a gene previously defined only by its nulli effect. Mutants 1362 and 1911 were mapped to monosome IV and are probably mutations in Syn-1, a gene also previously defined only by its nulli effect. Seed set on the synaptic mutant plants in the field was less than 0.2% of that on fertile sibs and likely resulted from pollination by surrounding fertile plants. This seed may serve as a source of unique aneuploid stocks in oats.Key words: meiotic mutants, gene mapping, monosomics, nullisomics, oat cytogenetics.

The initiation of meiotic chromosome pairing: the cytological view

Genome ◽  
1990 ◽  
Vol 33 (6) ◽  
pp. 759-778 ◽  
Author(s):  
Josef Loidl
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Meiotic Chromosome ◽  
Meiotic Pairing ◽  
Cytological Evidence ◽  
Homologous Chromosomes ◽  
Synaptonemal Complex Formation ◽  
Meiotic Synapsis ◽  
The One ◽  
First Contact

Opposing views are held with respect to the time when and the mechanisms whereby homologous chromosomes find each other for meiotic synapsis. On the one hand, some evidence has been presented for somatic homologous associations or some other kind of relationship between chromosomes in somatic cells as a preliminary to meiotic pairing. On the other hand, it is argued by many that homologous contacts are first established at meiotic prophase prior to, or in the course of, synaptonemal complex formation. The present paper reviews the controversial cytological evidence, hypotheses, and ideas on how the first contact between homologous chromosomes comes about.Key words: synapsis, meiosis, presynaptic alignment, homologous recognition, synaptonemal complex, chromosome pairing.

Inferences from genetical evidence on the course of meiotic chromosome pairing in plants

1977 ◽  
Vol 277 (955) ◽  
pp. 313-326 ◽  
Keyword(s):  
Chromosome Pairing ◽  
Developmental Stages ◽  
Meiotic Chromosome ◽  
Critical Assessment ◽  
Gene Control ◽  
Meiotic Pairing ◽  
Homologous Chromosomes ◽  
Meiotic Chromosome Pairing ◽  
Combined Use ◽  
Or Gene

Meiotic chromosome pairing is a process that is amenable to genetic and experimental analysis. The combined use of these two approaches allows for the process to be dissected into several finite periods of time in which the developmental stages of pairing can be precisely located. Evidence is now available, in particular in plants, that shows that the pairing of homologous chromosomes, as observed at metaphase I, is affected by events occurring as early as the last premeiotic mitosis; and that the maintenance of this early determined state is subsequently maintained by constituents (presumably proteins) that are sensitive to either colchicine, temperature or gene control. A critical assessment of this evidence in wheat and a comparison of the process of pairing in wheat with the course of meiotic pairing in other plants and animals is presented.

CHROMOSOME RELATIONSHIPS BETWEEN THE CULTIVATED OAT AVENA SATIVA (6x) AND A. VENTRICOSA (2x)

1970 ◽  
Vol 12 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Hugh Thomas
Keyword(s):  
Chromosome Pairing ◽  
Avena Sativa ◽  
Diploid Species ◽  
Meiotic Behaviour ◽  
Hexaploid Species ◽  
C Genome

Chromosome pairing in the F1 hybrid between the cultivated oat Avena sativa and a diploid species A. ventricosa, and in the derived amphiploid, shows that the diploid species is related to one of the genomes of the hexaploid species. The amount of chromosome pairing observed in complex interamphiploid hybrids demonstrates further that A. ventricosa is related to the C. genome of A. sativa. However, the chromosomes of the diploid species have become differentiated from that of the C genome of A. sativa and this is readily apparent in the meiotic behaviour of both the F1 hybrid and the amphiploid.

scholarly journals Synaptonemal complex antigen location and conservation.

1987 ◽  
Vol 105 (1) ◽  
pp. 93-103 ◽  
Author(s):  
P B Moens ◽  
C Heyting ◽  
A J Dietrich ◽  
W van Raamsdonk ◽  
Q Chen
Keyword(s):  
Chromosome Pairing ◽  
Meiotic Prophase ◽  
Structural Integrity ◽  
Genetic Recombination ◽  
Positive Control ◽  
Western Blots ◽  
Lateral Element ◽  
Homologous Chromosomes ◽  
Recombination Nodules ◽  
Grain Distribution

The axial cores of chromosomes in the meiotic prophase nuclei of most sexually reproducing organisms play a pivotal role in the arrangement of chromatin, in the synapsis of homologous chromosomes, in the process of genetic recombination, and in the disjunction of chromosomes. We report an immunogold analysis of the axial cores and the synaptonemal complexes (SC) using two mouse monoclonal antibodies raised against isolated rat SCs. In Western blots of purified SCs, antibody II52F10 recognizes a 30- and a 33-kD peptide (Heyting, C., P. B. Moens, W. van Raamsdonk, A. J. J. Dietrich, A. C. G. Vink, and E. J. W. Redeker, 1987, Eur. J. Cell Biol., 43: 148-154). In spreads of rat spermatocyte nuclei it produces gold grains over the cores of autosomal and sex chromosomes. The cores label lightly during the chromosome pairing stage (zygotene) of early meiotic prophase and they become more intensely labeled when they are parallel aligned as the lateral elements of the SC during pachytene (55 grains/micron SC). Statistical analysis of electronically recorded gold grain positions shows that the two means of the bimodal gold grain distribution coincide with the centers of the lateral elements. At diplotene, when the cores separate, the antigen is still detected along the length of the core and the enlarged ends are heavily labeled. Shadow-cast SC preparations show that recombination nodules are not labeled. The continued presence suggests that the antigens serve a continuing function in the cores, such as chromatin binding, and/or structural integrity. Antibody III15B8, which does not recognize the 30- and 33-kD peptides, produces gold grains predominantly between the lateral elements. The grain distribution is bimodal with the mean of each peak just inside the pairing face of the lateral element. The antigen is present where and while the cores of the homologous chromosomes are paired. From the location and the timing, it is assumed that the antigen recognized by III15B8 functions in chromosome pairing at meiotic prophase. The two anti-rat SC antibodies label rat and mouse SCs but not rabbit or dog SCs. A positive control using human CREST (calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasia) anti-centromere serum gives equivalent labeling of SC centromeres in the rat, mouse, rabbit, and dog. It is concluded that the SC antigens recognized by II52F10 and III15B8 are not widely conserved. The two antibodies do not bind to cellular or nuclear components of somatic cells.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Meiotic Chromosome Behavior and Capsule Setting in Doritaenopsis Hybrids

2008 ◽  
Vol 133 (1) ◽  
pp. 107-116 ◽  
Author(s):  
Pablo Bolaños-Villegas ◽  
Shih-Wen Chin ◽  
Fure-Chyi Chen
Keyword(s):  
Cell Division ◽  
Pollen Mother Cell ◽  
Chromosome Pairing ◽  
Chromosomal Aberrations ◽  
High Frequency ◽  
Mother Cell ◽  
Seed Set ◽  
Pollen Viability ◽  
High Pollen ◽  
Mother Cells

The development of new cultivars in Doritaenopsis Guillaum. & Lami orchids is often hindered by factors such as low seed count in hybrids. Cytological study may offer the ability to develop new hybrids by revealing cultivars with good chromosome pairing and high pollen viability, which are somewhat difficult to obtain under current breeding programs. Cross pollination, pollen viability, and chromosomal behavior during meiosis were analyzed to reveal the relation between seed fertility and capsule set in Doritaenopsis hybrids. The number of mature capsules harvested and their relative seed content were used as indices of crossing availability. The results of meiosis were evaluated according to pollen viability detected by fluorescein diacetate and quantification of sporad types by acid fuchsin staining. Chromosome number and pairing at meiosis were observed in root tips or in samples of pollen mother cells. A positive relation was found among high seed set, high frequency of viable tetrads, high degree of chromosome pairing, and low frequency of chromosomal aberrations such as inversions and translocations. On the basis of these factors, three types of hybrids could be distinguished. In type one hybrids, chromosomes paired as bivalents, pollen mother cells divided into tetrads, and capsule setting occurred after pollination of pollen acceptors. In type two hybrids, chromosomes remained mainly as univalents that developed into micromeiocytes, pollen mother cell division was disrupted, and seed recovery was low after pollination. Type three hybrids showed chromosomes paired mostly as multivalents, chromosome bridges, pollen mother cell division with massive failure, and little fertility. In Doritaenopsis orchids, high pollen viability and high fertility depends on a high frequency of normal tetrads, and low seed set in cross-pollination is predicted with micronuclei in the end products of meiosis. The occurrence of chromosomal aberrations may suggest a process of genome differentiation that could compromise breeding efforts if not taken into consideration.

THE MEIOTIC BEHAVIOR OF ANEUPOLYHAPLOIDS OF THE CULTIVATED OAT AVENA SATIVA (2n = 6x = 42)

1977 ◽  
Vol 19 (4) ◽  
pp. 651-656 ◽  
Author(s):  
J. M. Leggett
Keyword(s):  
Genetic Control ◽  
Chromosome Pairing ◽  
Avena Sativa ◽  
Meiotic Behavior ◽  
Homoeologous Chromosomes

Chromosome pairing and the frequency of secondary associations in two aneupolyhaploid plants of A. sativa are described. There was little evidence of pairing between homoeologous chromosomes in either plant. The results are discussed in relation to the genetic control of bivalent pairing in A. sativa and the possible divergence between the constituent genomes.

Root Absorption and Translocation of Picloram by Oats and Soybeans

Weed Science ◽  
1971 ◽  
Vol 19 (6) ◽  
pp. 727-731 ◽  
Author(s):  
A. R. Isensee ◽  
G. E. Jones ◽  
B. C. Turner
Keyword(s):  
Glycine Max ◽  
Plant Species ◽  
Sodium Azide ◽  
Avena Sativa ◽  
Sodium Arsenite ◽  
Solution Concentration ◽  
Metabolic Inhibitors ◽  
Root Absorption ◽  
Soybean Roots ◽  
Initial Uptake

The effects of time, concentration, pH, temperature, and metabolic inhibitors on 4-amino-3,5,6-trichloropicolinic acid (picloram) uptake from nutrient solution by oats (Avena sativaL. ‘Markton’) and soybeans (Glycine maxL. ‘Lee’) were studied. Oats and soybeans had similar absorption patterns of rapid initial uptake. However, total accumulation patterns markedly differed in that accumulation was concentration-dependent for oats but not for soybeans. Initial uptake by oats and soybean roots increased as solution concentration increased. Picloram was redistributed in oats and soybeans and some egress from roots to solution occurred. Picloram uptake by both plant species was markedly diminished with an increase in pH from 3.5 to 4.5, but pH had little effect from 4.5 to 9.5. Less picloram was taken up by oats and soybean roots from solution maintained at 4 C than at 26 C. Translocation to tops followed a similar trend. Increasing concentrations of three metabolic inhibitors, 2,4-dinitrophenol (DNP), sodium azide, and sodium arsenite, reduced root uptake of picloram in both species. All inhibitors (except DNP for oats) at 10−6to 10−5molar concentrations stimulated translocation of picloram to oats and soybean tops while higher concentrations depressed translocation.

Meiotic behaviour of induced autotetraploids in Triticum L.

Genome ◽  
1990 ◽  
Vol 33 (2) ◽  
pp. 302-307 ◽  
Author(s):  
Yang Yen ◽  
Gordon Kimber
Keyword(s):  
Chromosome Pairing ◽  
Seed Set ◽  
Chromosome Association ◽  
Meiotic Behaviour ◽  
Meiotic Analysis

Colchicine-induced autotetraploids of Triticum speltoides, T. longissimum, T. sharonense, T. bicorne, T. uniaristatum, T. monococcum, and T. tauschii were all morphologically similar to but larger than their diploid forms. Seed set was lower than in the diploids except for the autotetraploid T. speltoides. Meiotic analysis showed fewer quadrivalents and more bivalents than would be expected in all of these autotetraploids. Arm-pair switch, indicated by complex trivalents and quadrivalents, was found and involved 0.1% of total chromosomes in T. umbellulatum, 0.5% in T. longissimum, 0.7% in both T. sharonense and T. tauschii, 6.3% in T. bicorne, and 15.3% in T. uniaristatum.Key words: meiosis, chromosome association, arm-pair switch, chromosome pairing, bivalentization.

THE EFFECT OF COLCHICINE ON CHROMOSOME PAIRING

1977 ◽  
Vol 19 (2) ◽  
pp. 231-249 ◽  
Author(s):  
J. B. Thomas ◽  
P. J. Kaltsikes
Keyword(s):  
Aqueous Solution ◽  
Chromosome Pairing ◽  
Close Association ◽  
Tetraploid Wheat ◽  
Continuous Illumination ◽  
Hexaploid Triticale ◽  
Homologous Chromosomes ◽  
Wheat Hybrids ◽  
Bouquet Stage

Beginning at 120 hours prior to first metaphase of meiosis (MI) a 0.03% aqueous solution of colchicine was injected into the boot of pentaploid (hexaploid triticale × tetraploid wheat) hybrids developing at 20 °C ± 1° under continuous illumination. Colchicine applied 40 h or less prior to MI had no effect on chromosome pairing, while its application 40 h or more prior to MI induced a steady decline, culminating in a 40% reduction in chromosome pairing at about 80 h from MI. Between 48 and 35 h before MI (late premeiotic interphase to early zygotene) meiocytes underwent a period of active nucleolar fusion. The time, therefore, at which the colchicine sensitive aspects of chromosome pairing were completed coincided with the completion of nucleolar fusion. From comparison with other findings it was concluded that there is a colchicine sensitive bouquet stage which appears in leptotene and early zygotene; this bouquet is responsible for active nucleolar fusion and final close association between homologous chromosomes.

scholarly journals akirin is required for diakinesis bivalent structure and synaptonemal complex disassembly at meiotic prophase I

2013 ◽  
Vol 24 (7) ◽  
pp. 1053-1067 ◽  
Author(s):  
Amy M. Clemons ◽  
Heather M. Brockway ◽  
Yizhi Yin ◽  
Bhavatharini Kasinathan ◽  
Yaron S. Butterfield ◽  
...  
Keyword(s):  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Chromosome Condensation ◽  
Late Prophase ◽  
Homologous Chromosomes ◽  
Prophase I ◽  
Meiotic Prophase I ◽  
Evolutionarily Conserved ◽  
Key Events

During meiosis, evolutionarily conserved mechanisms regulate chromosome remodeling, leading to the formation of a tight bivalent structure. This bivalent, a linked pair of homologous chromosomes, is essential for proper chromosome segregation in meiosis. The formation of a tight bivalent involves chromosome condensation and restructuring around the crossover. The synaptonemal complex (SC), which mediates homologous chromosome association before crossover formation, disassembles concurrently with increased condensation during bivalent remodeling. Both chromosome condensation and SC disassembly are likely critical steps in acquiring functional bivalent structure. The mechanisms controlling SC disassembly, however, remain unclear. Here we identify akir-1 as a gene involved in key events of meiotic prophase I in Caenorhabditis elegans. AKIR-1 is a protein conserved among metazoans that lacks any previously known function in meiosis. We show that akir-1 mutants exhibit severe meiotic defects in late prophase I, including improper disassembly of the SC and aberrant chromosome condensation, independently of the condensin complexes. These late-prophase defects then lead to aberrant reconfiguring of the bivalent. The meiotic divisions are delayed in akir-1 mutants and are accompanied by lagging chromosomes. Our analysis therefore provides evidence for an important role of proper SC disassembly in configuring a functional bivalent structure.

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