Linear orientation of trivalents and quadrivalents in late metaphase I pollen mother cells of pearl millet

1984 ◽  
Vol 26 (5) ◽  
pp. 506-510 ◽  
Author(s):  
P. S. R. L. Narasinga Rao ◽  
J. Sybenga
Keyword(s):  
Pearl Millet ◽  
Random Order ◽  
Interval Length ◽  
Pollen Mother Cells ◽  
Mother Cells ◽  
Metaphase I

Robertsonian trivalents, trisomic trivalents, and tetrasomic ring quadrivalants showed linear or indifferent orientation frequencies at late metaphase I of 1/3. This fits a model assuming sequential centromere activation in the multivalent with random order of activation and sufficiently long interval to permit stable coorientation of any two early centromeres before the following centromere is activated. A late centromere trapped between two coorienting early ones is prevented from orientation. Reorientation in pearl millet, when it occurs, is late in these configurations. Chain quadrivalents have less linear but more indifferent orientations than the expected 1/6 and 1/3, respectively. Possible reasons for this are given. For rye the situation is very different: linear orientation of Robertsonian trivalents is practically absent, presumably owing to insufficiently long intervals between centromere activations, and to early reorientation. A reduction in interval length between centromere activations is assumed to accompany the stabilization of autotretraploids.Key words: pearl millet, trivalents, quadrivalents, centromere activation, chromosome orientation.

Chromosome numerical mosaicism in pearl millet (Pennisetum americanum (L.) Leeke)

1986 ◽  
Vol 28 (2) ◽  
pp. 203-206 ◽  
Author(s):  
Panuganti N. Rao ◽  
A. Nirmala
Keyword(s):  
Pearl Millet ◽  
Pennisetum Americanum ◽  
Pollen Mother Cells ◽  
Wide Range ◽  
Numerical Variation ◽  
Mother Cells

In pearl millet (Pennisetum americanum (L.) Leeke, 2n = 14), a wide range of intraplant chromosome numerical variation occurring in pollen mother cells at meiosis within the same anther, floret, or spike was found in eight plants. The types of mosaicism encountered were haploid–diploid, diploid–tetraploid, haploid–diploid–aneuploid, and diploid–tetraploid–aneuploid–teloaneuploid. Their probable mode of origin is discussed.Key words: Pennisetum, chromosomal numerical mosaicism.

The three-dimensional arrangement of chromosomes at meiotic metaphase I in normal and interchange heterozygotes of Briza humilis

1990 ◽  
Vol 97 (3) ◽  
pp. 565-570
Author(s):  
JANET M. MOSS ◽  
BRIAN G. MURRAY
Keyword(s):  
Mother Cell ◽  
Three Dimensional ◽  
Meiotic Metaphase ◽  
Central Position ◽  
Normal Plant ◽  
Serial Sections ◽  
Pollen Mother Cells ◽  
Sector Analysis ◽  
Mother Cells ◽  
Metaphase I

Pollen mother cells at metaphase I have been reconstructed from serial sections in normal and interchange heterozygotes of Briza humilis. The pollen mother cells have an irregular shape with a prominent projection from the tangential face into the anther loculus. The seven bivalents of the normal plant are usually arranged with one bivalent in a central position surrounded by a ring of the remaining six or as a ring of all seven bivalents. The central:peripheral distribution of quadrivalents is different in two different interchange plants; in a sector analysis, where cells are divided into four quarters relative to the tangential face of the pollen mother cell, the two plants also show differences in quadrivalent distribution, indicating that individual chromosomes occupy different positions in the cell. The relevance of these results to the positioning of quadrivalents in lateral squashes of meiotic metaphase I are discussed.

Meiosis in triploid Lolium. I. Synaptonemal complex formation and chromosome configurations at metaphase I in aneuploid autotriploid L. multiflorum

Genome ◽  
1994 ◽  
Vol 37 (2) ◽  
pp. 181-189 ◽  
Author(s):  
Huw M. Thomas ◽  
Barry J. Thomas
Keyword(s):  
Complex Formation ◽  
Synaptonemal Complex ◽  
Lolium Multiflorum ◽  
Synaptonemal Complexes ◽  
Pollen Mother Cells ◽  
Partner Exchange ◽  
Synaptonemal Complex Formation ◽  
Mother Cells ◽  
Axial Element ◽  
Metaphase I

A spreading technique for synaptonemal complexes (SCs) was applied to pollen mother cells of two aneuploid genotypes of autotriploid Lolium multiflorum (2n = 3x + 1 = 22). In the earliest nuclei analyzed the axial elements are in six groups of 3 and one group of 4. Most groups have formed multivalents with from one to five pairing partner exchanges, but there are also groups that have formed bivalents and univalents. Some axial elements have formed triple associations, in one case for the length of the trivalent. Unsynapsed axial elements remain aligned with their homologous SCs into pachytene, but this alignment is abolished as these axes pair heterologously among themselves until the entire axial element complement is synapsed. At metaphase I most chromosomes are associated as trivalents and quadrivalents.Key words: Lolium, triploid, pairing partner exchange, chiasma, multivalent.

Low glucosinolate Brassica juncea breeding line revealed to be nullisomic

Genome ◽  
2001 ◽  
Vol 44 (4) ◽  
pp. 738-741 ◽  
Author(s):  
B F Cheng ◽  
G Séguin-Swartz ◽  
D J Somers ◽  
G Rakow
Keyword(s):  
Brassica Juncea ◽  
Interspecific Cross ◽  
Meiotic Behaviour ◽  
Breeding Line ◽  
Pollen Mother Cells ◽  
Chromosomal Segregation ◽  
B Genome ◽  
Hybrid Plants ◽  
Mother Cells ◽  
Metaphase I

The low glucosinolate Brassica juncea breeding line 1058 was derived from a BC1F3 plant of an interspecific cross between high glucosinolate Indian B. juncea (genome AABB, 2n = 36) line 60143 and B. rapa (genome AA, 2n = 20) canola strain CZY. Line 60143 had 2n = 36 chromosomes (18 bivalents at metaphase I) and strain CZY had 2n = 20 chromosomes (10 bivalents). Line 1058 was nullisomic, with 2n - 2 = 34 chromosomes, with 17 bivalents formed at metaphase I and an even chromosomal segregation of 17:17 at anaphase I. In F1 hybrid plants of the cross 1058 × CZY, 98.3% of the pollen mother cells had 10 bivalents and seven univalents. This is evidence that plants of line 1058 are nullisomic, missing one pair of B-genome chromosomes.Key words: low glucosinolate mustard, meiotic behaviour, cytogenetics.

Chromosome pairing in triploid and tetraploid hybrids in Elytrigia (Triticeae; Poaceae)

1984 ◽  
Vol 26 (5) ◽  
pp. 519-522 ◽  
Author(s):  
Patrick E. McGuire
Keyword(s):  
Chromosome Pairing ◽  
Genome Analysis ◽  
Triploid Hybrid ◽  
Pollen Mother Cells ◽  
Tetraploid Hybrid ◽  
A Genome ◽  
Mother Cells ◽  
Metaphase I

Mean chromosome pairing of 5.14I + 1.28II (rod) + 3.86II (ring) + 1.47III + 0.11IV (open) + 0.11V was observed in pollen mother cells at metaphase I in the triploid hybrid Elytrigia scirpea (K. Presl) Holub, 2n = 4x = 28 × E. bessarabica (Savul. et Rayss) Dubrovik, 2n = 4x = 14. Mean chromosome pairing of 3.71I + 2.29II (rod) + 1.82II (ring) + 2.64III + 0.29IV (open) was observed in the triploid hybrid E. curvifolia (Lange) Holub, 2n = 4x = 28 × E. bessarabica. Mean chromosome pairing of 3.00I + 0.93II (rod) + 1.57II (ring) + 1.36III + 1.79IV (open) + 1.I4IV (closed) + 0.79V was observed in the tetraploid hybrid E. junceiformis Löve et Löve, 2n = 4x = 28 × E. curvifolia. The first hybrid provides the first evidence by genome analysis that E. bessarabica possesses a genome (designated Eb) which is closely related to the genomes of E. scirpea (ES and ESC) and hence to the E genome of E. elongata (Host) Nevski, 2n = 2x = 14. The second and third hybrids provide the first evidence that the two genomes of E. curvifolia (designated EC and ECU) are related to the Eb genome of E. bessarabica and thus to the E genome of E. elongata.Key words: Elytrigia, homoeology, Triticum, phylogeny, triploid, tetraploid.

scholarly journals The Culture and Correlative Electron Microscopy of Pollen Mother Cells in Meiosis: Development of Techniques and Some Observations on Selected Topics

2021 ◽  
Author(s):  
◽  
Kenneth George Ryan
Keyword(s):  
Electron Microscopy ◽  
Light And Electron Microscopy ◽  
Cell Formation ◽  
Cell Types ◽  
Future Research ◽  
Thin Sections ◽  
Pollen Mother Cells ◽  
Spindle Elongation ◽  
Mother Cells ◽  
Metaphase I

<p>Reliable techniques for the living cell culture and correlative light and electron microscopy (EM) of meiotic pollen mother cells (PMCs) of Iris spuria, Allium triquetrum and Tradescantia flumenensis are described in detail. Living PMCs were successfully cultured in a slide chamber on agar/sucrose medium. Cells were covered with an inert oil to prevent their dehydration, and some cells were cultured from metaphase I to tetrad cell formation over a 20 hour period. Other PMCs were fixed with glutaraldehyde and flat embedded using a modification of the agar sandwich technique of Mole-Bajer and Bajer (1968). This technique was developed to permit the preselection of PMCs at known meiotic stages, for subsequent EM examination. Serial thin sections were cut at known planes of section; and 3-D reconstructions of MT distribution, and MT counts from transverse sections were completed. It was also possible to examine sections of an Iris anaphase I PMC which had been previously studied in life. Anaphase I and II chromosome velocities were analysed in the three species. Mean velocities were approximately 0.5 mu m/min with some variation from cell to cell and between sister half-spindles. In Allium anaphase I there was also variation in chromosome velocity within the half-spindle; and this variation was found not to be related to chromosome position on the metaphase I plate. Spindle elongation was zero in Allium anaphase I and in Iris anaphase II, but was detectable in Allium anaphase II (40%) and in "Iris anaphase I (l5%). The extent of spindle elongation in Tradescantia could not be determined. The kinetochore region in the first meiotic division consisted of two closely appressed, but structurally (and functionally) distinct, sister kinetochores. At meiosis II, the two sister kinetochores were separate from each other and faced opposite poles. The kinetochore arrangement probably changes from side-by-side (meiosis I) to back-to-back (meiosis II) during chromosome recondensation at prophase II in these cells. Bundles of non-kinetochore microtubules (nkMTs) span the interzone between sister chromosome units at metaphase I and II and anaphase II. Bundles of kinetochore MTs (kMTs) do not increase in divergence at any stage of meiosis studied; there was little interaction between nkMTs and kMTs, and MT-MT cross bridges were rare. These observations are not consistent with models of chromosome movement based on MT sliding or zipping. No relationship was found between nkMT distribution and spindle elongation, and the several different nkMT distributions which have been reported for other cell types may be variations on a structural theme. Spindle endoplasmic reticulum (ER) in meiosis II was found to be derived largely from invaginations and evaginations of the nuclear envelope. Growth of existing spindle ER was proposed to account for the doubling in the amount of ER observed between interphase and prometaphase II. Randomly oriented elements of ER, in early prometaphase II spindles may become passively aligned along the interpolar axis and then actively transported polewards at later stages of prometaphase II and metaphase II. Suggestions for future research are offered.</p>

scholarly journals The Culture and Correlative Electron Microscopy of Pollen Mother Cells in Meiosis: Development of Techniques and Some Observations on Selected Topics

2021 ◽  
Author(s):  
◽  
Kenneth George Ryan
Keyword(s):  
Electron Microscopy ◽  
Light And Electron Microscopy ◽  
Cell Formation ◽  
Cell Types ◽  
Future Research ◽  
Thin Sections ◽  
Pollen Mother Cells ◽  
Spindle Elongation ◽  
Mother Cells ◽  
Metaphase I

<p>Reliable techniques for the living cell culture and correlative light and electron microscopy (EM) of meiotic pollen mother cells (PMCs) of Iris spuria, Allium triquetrum and Tradescantia flumenensis are described in detail. Living PMCs were successfully cultured in a slide chamber on agar/sucrose medium. Cells were covered with an inert oil to prevent their dehydration, and some cells were cultured from metaphase I to tetrad cell formation over a 20 hour period. Other PMCs were fixed with glutaraldehyde and flat embedded using a modification of the agar sandwich technique of Mole-Bajer and Bajer (1968). This technique was developed to permit the preselection of PMCs at known meiotic stages, for subsequent EM examination. Serial thin sections were cut at known planes of section; and 3-D reconstructions of MT distribution, and MT counts from transverse sections were completed. It was also possible to examine sections of an Iris anaphase I PMC which had been previously studied in life. Anaphase I and II chromosome velocities were analysed in the three species. Mean velocities were approximately 0.5 mu m/min with some variation from cell to cell and between sister half-spindles. In Allium anaphase I there was also variation in chromosome velocity within the half-spindle; and this variation was found not to be related to chromosome position on the metaphase I plate. Spindle elongation was zero in Allium anaphase I and in Iris anaphase II, but was detectable in Allium anaphase II (40%) and in "Iris anaphase I (l5%). The extent of spindle elongation in Tradescantia could not be determined. The kinetochore region in the first meiotic division consisted of two closely appressed, but structurally (and functionally) distinct, sister kinetochores. At meiosis II, the two sister kinetochores were separate from each other and faced opposite poles. The kinetochore arrangement probably changes from side-by-side (meiosis I) to back-to-back (meiosis II) during chromosome recondensation at prophase II in these cells. Bundles of non-kinetochore microtubules (nkMTs) span the interzone between sister chromosome units at metaphase I and II and anaphase II. Bundles of kinetochore MTs (kMTs) do not increase in divergence at any stage of meiosis studied; there was little interaction between nkMTs and kMTs, and MT-MT cross bridges were rare. These observations are not consistent with models of chromosome movement based on MT sliding or zipping. No relationship was found between nkMT distribution and spindle elongation, and the several different nkMT distributions which have been reported for other cell types may be variations on a structural theme. Spindle endoplasmic reticulum (ER) in meiosis II was found to be derived largely from invaginations and evaginations of the nuclear envelope. Growth of existing spindle ER was proposed to account for the doubling in the amount of ER observed between interphase and prometaphase II. Randomly oriented elements of ER, in early prometaphase II spindles may become passively aligned along the interpolar axis and then actively transported polewards at later stages of prometaphase II and metaphase II. Suggestions for future research are offered.</p>

The chromosomal location of a gene (msg) affecting megasporogenesis in durum wheat

Genome ◽  
1987 ◽  
Vol 29 (4) ◽  
pp. 578-581 ◽  
Author(s):  
L. R. Joppa ◽  
N. D. Williams ◽  
S. S. Maan
Keyword(s):  
Durum Wheat ◽  
Key Words ◽  
Chromosomal Location ◽  
Triticum Turgidum ◽  
Wheat Line ◽  
Pollen Mother Cells ◽  
Chromosome Arm ◽  
Pollen Nucleus ◽  
Mother Cells ◽  
Metaphase I

An aneuploid durum wheat line (Triticum turgidum L. var. durum) having 13 chromosome pairs and 2 unpaired chromosomes at metaphase I of meiosis in pollen mother cells (i.e., monosomic for chromosomes 7A and 7D) was observed to produce some progeny plants with 2n = 40 chromosomes. These aneuploid (triploid) plants were usually weak and sterile. Triploid plants also occurred in the progeny of durum plants monosomic for chromosome 7A, or in progeny of plants that were mono-telodisomic or ditelomonotelosomic for chromosome 7Aq (13 II + 1 t II or 13 II + t II + t I) but not in the progeny of plants ditelomonotelosomic for chromosome 7Ap (13 II + t II + t 1). Therefore, there is a gene(s) on chromosome arm 7Ap that prevents the production of diploid (2n) egg cells in wheat. In the absence of 7Ap, a portion of the egg cells have 26 chromosomes, which when fertilized with a pollen nucleus with 14 chromosomes, produces progeny plants with 2n = 40 chromosomes. The data also indicated that chromosome arm 7Dp probably contains a second gene that is capable of preventing the production of triploid plants. Key words: Triticum turgidum L. var. durum, polyploidy, aneuploid, triploid, monosomic.

scholarly journals Cytological Studies on Chironja

1969 ◽  
Vol 56 (4) ◽  
pp. 426-431
Author(s):  
Carlos G. Moscoso ◽  
K. G. Shambulingappa
Keyword(s):  
Puerto Rico ◽  
Citrus Fruit ◽  
Circumstantial Evidence ◽  
Meiotic Abnormalities ◽  
Pollen Mother Cells ◽  
Mother Cells ◽  
Metaphase I

Studies on somatic chromosomes in leaf-tips and meiosis in pollen mother cells were carried out in chironja, a new citrus fruit discovered in Puerto Rico. Meiotic abnormalities such as non-pairing regions at pachytene, occurrence of univalents and quadrivalents at diakinesis and metaphase I and presence of a well-marked heteromorphic bivalent at metaphase I were recorded. Based on the data gathered through meiotic studies, together with morphological and other circumstantial evidence, it appears that chironja may have arisen as a hybrid.

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