Cytological evidence for assortment mitosis leading to loss of heterozygosity in rice

Genome ◽  
2006 ◽  
Vol 49 (5) ◽  
pp. 556-557 ◽  
Author(s):  
Richard R.-C Wang ◽  
Xiaomei Li ◽  
N Jerry Chatterton
Keyword(s):  
Loss Of Heterozygosity ◽  
Homologous Chromosome ◽  
Root Meristem ◽  
Mitotic Metaphase ◽  
Equatorial Plate ◽  
Cytological Evidence ◽  
Rice Line ◽  
Daughter Cells ◽  
Normal Mitosis

In the root meristem cells of the rice line AMR, which causes loss of heterozygosity in its hybrids, both normal and assortment mitoses were observed. During normal mitosis, chromosomes did not form homologous pairs at metaphase; all chromosomes lined up at the equatorial plate and 2 chromatids of each chromosome disjoined at the centromere and moved toward opposite poles. During assortment mitosis, varying numbers of paired homologues were observed at mitotic metaphase. Two groups of 12 chromosomes separated and moved towards the opposite poles of daughter cells with few chromosomes having their chromatids separated at anaphase. These observations support the proposed mechanism that is responsible for early genotype fixation in rice hybrids involving AMR.Key words: mitosis, homologous chromosome, genotype fixation, loss of heterozygosity, rice.

Cell shape, chromosome orientation and the position of the plane of division in Vicia faba root cortex cells

1992 ◽  
Vol 103 (3) ◽  
pp. 847-855 ◽  
Author(s):  
J.L. Oud ◽  
N. Nanninga
Keyword(s):  
Vicia Faba ◽  
Cell Shape ◽  
Root Meristem ◽  
Three Dimensional ◽  
Progressive Increase ◽  
Root Cortex ◽  
Division Plane ◽  
Daughter Cells ◽  
Spindle Axis ◽  
Original Cell

Three-dimensional chromosome orientation was studied in thick sections of Vicia faba root meristem, using confocal microscopy and digital image analysis techniques. In the proliferative part of the root meristem, where the cells are organized in longitudinal files, it was expected to find dividing cells with a spindle axis parallel to the file axis and, occasionally, perpendicular to the file axis (resulting in a local file bifurcation). However, we observed a large number of oblique spindle axes. From metaphase to telophase there was a progressive increase in the rotation of the spindle axis. A 90° turn of the metaphase equator plane was never observed. Three-dimensional measurements of both the space occupied by the ana- and telophase chromosome configurations, and the size of the corresponding cortex cells, showed that most cells were too flat for an orientation of the spindle parallel to the file axis. Apparently, cell size limitations forced the spindle to rotate during mitosis. Consequently, the nuclei in the daughter cells were positioned diagonally in opposite directions, instead of on top of each other. In the majority of these cells, a transverse plane of division would intersect the nuclei. Therefore, the new cell wall was sigmoid shaped or oblique. Most daughter cells remained within the original cell file but, occasionally, in extremely flat cells the position of the daughter nuclei forced the cell to set a plane of division parallel to the file axis. This resulted in file bifurcation. It has been concluded that cell shape, the extent of spindle rotation and the position of the division plane are related.

Loss of heterozygosity and accelerated genotype fixation in rice hybrids

Genome ◽  
1999 ◽  
Vol 42 (5) ◽  
pp. 789-796 ◽  
Author(s):  
RR -C Wang ◽  
X -M Li ◽  
N J Chatterton
Keyword(s):  
Loss Of Heterozygosity ◽  
Random Amplified Polymorphic Dna ◽  
Somatic Cells ◽  
Rice Cultivar ◽  
Molecular Data ◽  
Breeding Cycle ◽  
Chromosome 2 ◽  
Somatic Variation ◽  
Daughter Cells

Loss of heterozygosity is reported in rice hybrids of a particular heritage. Hybrids derived from a plant selected from the Chinese rice cultivar 'Zhongxin No. 1' exhibited somatic variations as evidenced by having both segregating and uniform panicle rows in F2 progenies. F3 plants from uniform F2 rows were found to be homozygous for all 14 RAPD (random amplified polymorphic DNA) markers, of which two co-dominant markers were located on chromosome 2 and five other markers were on five different chromosomes. RAPD markers unique to either parent were present or absent in all F2 plants within some panicle rows, yet segregated in a Mendelian manner in other panicle rows. The molecular data suggest that somatic cells in these hybrids do not always contain both parental homologues of some chromosomes. These findings support the hypothesis that somatic chromosome pairing and recombination lead to loss of heterozygosity and non-identical daughter cells following mitosis. Sequential mitotic assortment of chromosome homologues of a plant's genome can lead to homozygous or nearly homozygous somatic cells that eventually develop into reproductive cells. As a result of this unique mechanism in rice hybrids derived from Zhongxin No. 1, uniform or less-segregating progenies can be identified from F2 or F3 panicle rows at a much higher frequency than normally expected. This phenomenon can be utilized to shorten the breeding cycle of rice, or other crops when plants containing gene(s) for mitotic pairing are identified, or when the genes are isolated from rice and effectively transferred into other crops.Key words: LOH, in vivo somatic variation, homozygous F2, RAPD, apomixis.

Chromosome behavior in living cells and the electron microscopy of chromosome attachment to the spindle

1983 ◽  
Vol 41 ◽  
pp. 548-551
Author(s):  
D. F. Kubai ◽  
R. B. Nicklas
Keyword(s):  
Homologous Chromosome ◽  
Meiotic Chromosome ◽  
Spindle Pole ◽  
Chromosome Movement ◽  
Chromosome Behavior ◽  
Daughter Cells ◽  
Chromosome Distribution ◽  
Chromosome Attachment

During mitosis and meiosis, chromosomes are distributed to daughter cells in controlled fashion, with patterns of chromosome distribution determined by specific interactions between chromosomes and the microtubules composing the spindle. In meiosis, for example, homologous chromosome pairs (bivalents) attach to the spindle so that the kinetochore of one chromosome of the pair is associated with kinetochore microtubules extending toward one spindle pole while the kinetochore-associated microtubules of the partner chromosome extend toward the opposite pole. This arrangement assures that partner chromosomes proceed in opposite directions during anaphase chromosome movement and results in the delivery of only one member of the homologous chromosome pair to each daughter cell. This sort of descriptive/mechanical account of mitotic and meiotic chromosome behavior is now well-established. However, total understanding of the role of the spindle in precise chromosome distribution demands a much more detailed analysis of spindle organization than is yet available. For instance, determination of where and how the innumerable microtubules of the spindle are mechanically linked should help to clarify exactly where forces for chromosome movement are applied.

Homologous chromosome pairing

1977 ◽  
Vol 277 (955) ◽  
pp. 245-258 ◽  
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Homologous Chromosome ◽  
Crossing Over ◽  
Supporting Evidence ◽  
Mitotic Metaphase ◽  
Sister Chromatids ◽  
Homologous Chromosome Pairing ◽  
Attachment Sites ◽  
Crossover Site

Commonly accepted precepts are challenged : (1) that homologous chromosome pairing is normally mediated by nuclear envelope attachment sites; (2) that crossover site establishment awaits synaptic completion; and (3) that it is the function of the synaptonemal complex to hold homologues in register so that equal crossing over can occur, and perhaps to provide machinery for the crossover process. Although these views may eventually be shown to be true, it is felt that currently available evidence does not warrant their full acceptance, and that alternatives should be considered. As examples of alternatives the following ideas, with some supporting evidence, are suggested: (1) homologous chromsome pairing (in non-haplont organisms) may be accomplished by chance meeting of homologue segments (followed by establishment of invisible, elastic connectors) at congression for a mitotic metaphase (in many cases perhaps the premeiotic mitosis); (2) crossover sites may be established before, during, or immediately following initiation of synapsis; and (3) the synaptonemal complex may somehow function in the crossover process at the inception of its formation, but its complete deployment throughout each normal bivalent may serve some other role, such as mediation of the binding of sister chromatids apparently required for chiasma maintenance until anaphase I.

scholarly journals ARGONAUTE10 is required for cell fate specification and the control of formative cell divisions in the Arabidopsis root meristem

2021 ◽  
Author(s):  
Nabila El Arbi ◽  
Ann-Kathrin Schürholz ◽  
Alexei Schiffner ◽  
Inés Hidalgo Prados ◽  
Friedrich Böhme ◽  
...  
Keyword(s):  
Cell Fate ◽  
Root Meristem ◽  
Control Cell ◽  
Plant Biology ◽  
Cell Fate Specification ◽  
Cell Type ◽  
Arabidopsis Root ◽  
Daughter Cells ◽  
Cell Divisions ◽  
Xylem Elements

SummaryA key question in plant biology is how oriented cell divisions are integrated with patterning mechanisms to generate organs with adequate cell type allocation. In the root vasculature, a miRNA gradient controls the abundance of HD-ZIP III transcription factors, which in turn control cell fate and spatially restrict vascular cell proliferation to specific cells. Here, we show that a functional miRNA gradient requires an opposing gradient of ARGONAUTE10, which sequesters miRNAs to protect HD-ZIP III transcripts from degradation. In the absence of ARGONAUTE10, xylem precursor cells undergo periclinal divisions that lead to continuous strands of differentiated xylem elements at ectopic positions. Notably, periclinal daughter cells maintain xylem identity even when they are located outside of the xylem axis, resulting in disrupted tissue boundaries. We further demonstrate that ARGONAUTE10 and HD-ZIP IIIs buffer cytokinin signalling to control formative cell divisions, providing a framework for integration of phytohormone and miRNA-mediated patterning.

scholarly journals INTERGROUP PHYLOGENIES IN DROSOPHILA AS DETERMINED BY COMPARISONS OF SALIVARY BANDING PATTERNS

Genetics ◽  
1972 ◽  
Vol 70 (3) ◽  
pp. 457-474
Author(s):  
Harrison D Stalker
Keyword(s):  
Homologous Chromosome ◽  
New World ◽  
Central Position ◽  
Cytological Evidence ◽  
Banding Patterns ◽  
Chromosome Maps ◽  
Species Groups ◽  
Relationship Of ◽  
The Relationship ◽  
Phylogenetic Scheme

ABSTRACT A salivary gland chromosome phylogeny is presented which summarizes the evolutionary relationships of twenty-two species belonging to the sub-genus Drosophila, and members of the twelve species groups: D. melanica, D. repleta, D. carbonaria, D. polychaeta, D. annulimana, D. robusta, D. carsoni, D. virilis, D. funebris and the "picture-wing," D. mimica and D. crassifemur groups (of Hawaii).—Photographic salivary chromosome maps were prepared for all twenty-two species studied. While the chromosomes of different species belonging to the same group can usually be homologized almost completely, so that construction of intragroup phylogenies is easy, chromosomes of members of different groups are so modified structurally that in most cases only short sections can be fully homologized, and these in only one or two chromosome elements.—Broadly homologous chromosome elements were compared for three species at a time, and on the basis of overlapping homologous sections, or overlapping inversions included within homologous sections, the trio of chromosomes, and the species to which they belonged can often be arranged in a two-step phylogenetic series. Detection of many such ordered trios permits construction of a single phylogenetic scheme encompassing all species.—D. nigromelanica, of the D. melanica group is found to be chromosomally intermediate between the rest of its group and the species belonging to other groups, suggesting that it is the most nearly ancestral member of its group. When trios of species including D. nigromelanica and members of two other species groups are compared, it is found that in twelve of fourteen such comparisons the chromosomes of D. nigromelanica are structurally intermediate between those of the members of the other two species groups, indicating the central position of D. nigromelanica in the phylogeny as a whole.—Available cytological evidence indicates that among the nine continental groups studied, it is the D. robusta group which is chromosomally closest to the Hawaiian "picture-wing" groups. Among the members of the Hawaiian groups it is D. primaeva and D. attigua which are found to be closest to the continental species. This finding tends to confirm the earlier conclusion of Carson and Stalker, based on different evidence, that the above two species were in an ancestral position in the Hawaiian phylogeny.—The relationship of the D. robusta and D. melanica groups demonstrated in this paper, the phylogenies within each of these two groups earlier worked out by Narayanan and by Stalker, and the present geographical distributions of the species within them, require that at least three Asiatic–New World migrations must have occurred during the evolution of the two groups.

Stimulated Virus Production in Vinblastine and Cytochalasin-Induced Multinucleate Cells

1970 ◽  
Vol 28 ◽  
pp. 186-187
Author(s):  
Krishan Awtar
Keyword(s):  
Cell Division ◽  
Normal Cell ◽  
Virus Production ◽  
Multinucleate Cells ◽  
Daughter Cells ◽  
Cell Divisions ◽  
Nuclear Membranes ◽  
Division 2 ◽  
Vinblastine Sulfate

Exposure of cells to low sublethal but mitosis-arresting doses of vinblastine sulfate (Velban) results in the initial arrest of cells in mitosis followed by their subsequent return to an “interphase“-like stage. A large number of these cells reform their nuclear membranes and form large multimicronucleated cells, some containing as many as 25 or more micronuclei (1). Formation of large multinucleate cells is also caused by cytochalasin, by causing the fusion of daughter cells at the end of an otherwise .normal cell division (2). By the repetition of this process through subsequent cell divisions, large cells with 6 or more nuclei are formed.

Some Conditions Necessary for Pinocytosis

1968 ◽  
Vol 26 ◽  
pp. 142-143
Author(s):  
M. W. Brightman
Keyword(s):  
Smooth Muscle ◽  
Cell Membrane ◽  
Toxic Effects ◽  
Cytological Evidence ◽  
Cell Processes

The cytological evidence for pinocytosis is the focal infolding of the cell membrane to form surface pits that eventually pinch off and move into the cytoplasm. This activity, which can be inhibited by oxidative and glycolytic poisons, is performed only by cell processes that are at least 300A wide. However, the interpretation of such toxic effects becomes equivocal if the membrane invaginations do not normally lead to the formation of migratory vesicles, as in some endothelia and in smooth muscle. The present study is an attempt to set forth some conditions under which pinocytosis, as distinct from the mere inclusion of material in surface invaginations, can take place.

Fine Structure of Cytochalasin Induced Polyploid Cells

1968 ◽  
Vol 26 ◽  
pp. 122-123
Author(s):  
Awtar Krishan ◽  
Nestor Bohonos
Keyword(s):  
Fine Structure ◽  
Cytochalasin B ◽  
Present Report ◽  
Cell Monolayer ◽  
Polyploid Cell ◽  
Specific Cell ◽  
Nuclear Surface ◽  
Unsuccessful Attempt ◽  
Daughter Cells ◽  
Polyploid Cells

Cytochalasin B, a mould metabolite from Helminthosporium dermatioideum has been shown to interfere with specific cell activities such as cytoplasmic cleavage and cell movement. Cells undergoing nuclear division in the presence of cytochalasin B are unable to complete the separation of the resulting daughter cells. In time-lapse studies, the daughter cells coalesce after an initial unsuccessful attempt at separation and form large multinucleate polyploid cells. The present report describes the fine structure of the large polyploid cells induced in Earle's L-cell monolayer cultures by exposure to cytochalasin B (lγ/ml) for 92 hours.In the present material we have seen as many as 7 nuclei in these polyploid cells. Treatment with cytochalasin B for longer periods of time (6 to 7 days, with one medium change on the 3rd day) did not increase the number of nuclei beyond the 7 nuclei stage. Figure 1 shows a large polyploid cell with four nuclei. These nuclei are indistinguishable in their fine structure from those of the cells from control cultures but often show unusually large numbers of cytoplasmic invaginations and extensions of the nuclear surface (Figure 2).

Ultrastructural Changes in the Root Meristem Cells of Rubus Chamaemorus L. (Cloudberry)

1975 ◽  
Vol 33 ◽  
pp. 562-563
Author(s):  
Arya K. Bal
Keyword(s):  
Root Meristem ◽  
Uranyl Acetate ◽  
Particulate Material ◽  
Ultrastructural Changes ◽  
Cell Organelles ◽  
Cytoplasmic Matrix ◽  
Golgi Membranes ◽  
Rubus Chamaemorus ◽  
Dense Substance ◽  
Ultrathin Sections

In the course of studies in the root meristem tissue of Rubus chamaemorus L. some important changes in the ultrastructural morphology were observed during the initiation of senescence at the end of the growing season.Root meristems were collected from naturally growing healthy populations of Cloudberry plants, and fixed in Karnovsky's mixture or in 2.5% glutaraldehyde in phosphate buffer. The samples were osmicated, dehydrated following usual methods and embedded in Epon. Ultrathin sections were stained in uranyl acetate and lead citrate.Figure 1 shows part of a dense cell in the meristem. The electron density of these cells is due to large amounts of a particulate material in the cytoplasmic matrix. The smallest particle seen in electron micrographs is about 40 A, although larger aggregates are also found, which remain randomly distributed in association with various cell organelles. Dense substance has been found associated with golgi membranes, proplastids, vacuoles and microtubules (Fig. 2).

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