Positional inconsistency between preprophase microtubule band and final cell plate arrangement during triangular subsidiary cell and atypical hair cell formation in two Triticum species

1984 ◽  
Vol 62 (2) ◽  
pp. 343-359 ◽  
Author(s):  
B. Galatis ◽  
P. Apostolakos ◽  
C. Katsaros
Keyword(s):  
Hair Cell ◽  
Mitotic Spindle ◽  
Cell Plate ◽  
Subsidiary Cell ◽  
Transverse Wall ◽  
Cortical Zone ◽  
Preprophase Microtubule Band ◽  
Mutual Disposition ◽  
Cell Plate Arrangement ◽  
Mother Cells

On the leaf epidermis of two Triticum species examined, an intervening cell of a stomatal or a hair row often flanks on one side two guard cell mother cells (GMC's) and usually functions twice as a subsidiary cell mother cell (SMC). In many of these cells and rarely in SMC's corresponding to one GMC, a triangular subsidiary cell (SC) instead of a lens-shaped one is formed. Some of these SC's in median paradermal sections appear triangular in form, while in internal and (or) external ones they exhibit a lenslike shape. In all SMC's investigated in which a triangular SC was expected to be formed, the preprophase microtubule band (PMB) occupied the usual position adjacent to the inducing GMC, except for instances in which the transverse wall of the SMC intersected the lateral wall of the GMC or was opposite its transverse wall. Therefore, during triangular SC formation a limited portion of the junction region of the cell plate with the parent walls is predicted by the PMB. In such cases the premitotic polarizing process in the SMC's and consequently the mutual disposition between the PMB and the mitotic spindle is disturbed. The PMB's of the hair cell mother cells (HMC's) are not so densely grouped as those of the SMC's, sometimes occupying an extensive portion along the walls. They were localized at the expected positions at the polar end of the cells. Only in few instances were atypical PMB's organized. However, the cell plate separating the hair cells (HC's) sometimes diverges and fuses with the parent walls at unpredictable positions far from the PMB cortical zone, except for a small part of it adjacent to one longitudinal anticlinal wall of the HMC. In addition, the preprophase–prophase nucleus often occupied an eccentric position in relation to the PMB or more rarely was situated outside it. Sometimes it exhibited a particular orientation. Moreover, mitotic spindles inclined in relation to the PMB plane were frequently observed. The above phenomena seem to be the result of the interference of a transverse polarizing stimulus with an axial one or of the establishment of an aberrant polarity in the HMC's for unknown reasons. The observations suggest that the spatial inconsistency between PMB and final cell plate arrangement in the cells investigated is an exception to the rule, caused by the disturbance of the mutual disposition and orientation between PMB cortical zone and mitotic spindle; these phenomena follow the disorder of the polarizing process of the cells. The PMB cortical zone seems to be effective only when the cell plate edges reach a critical distance from it.

Studies on the formation of ‘floating’ guard cell mother cells in Anemia

1986 ◽  
Vol 80 (1) ◽  
pp. 29-55
Author(s):  
B. Galatis ◽  
P. Apostolakos ◽  
D. Palafoutas
Keyword(s):  
Guard Cell ◽  
Intercellular Space ◽  
Cortical Microtubule ◽  
Cell Plate ◽  
Cell Polarization ◽  
Periclinal Wall ◽  
Wall Area ◽  
Cortical Zone ◽  
Neighbouring Region ◽  
Mother Cells

The protodermal cells producing the ‘floating’ guard cell mother cells (GMCs) in three Anemia species undergo an extraordinary polarization and an unexpected shaping. During interphase an intercellular space is initiated at the internal proximal end of the cell, while the polar region bulges outwards. At this stage a microtubule girdle traverses the cortical cytoplasm underneath the rims of the external periclinal wall curvature. In addition, another system of microtubules converges on a cortical site adjoining the wall delimiting the intercellular space and, or, the neighbouring region of the internal periclinal wall (internal polar cortical site, IPCS). Vacuoles are found in all regions of the cell except for that between the centrally located nucleus and the intercellular space. As the cell approaches mitosis, the growing vacuolar system retreats from the cytoplasmic region below the external periclinal wall curvature. In most cells the polarized cytoplasm forms an inclined truncated cone, the bases of which abut on the external periclinal wall curvature and the wall lining the IPCS. The organization of the cortical microtubule cytoskeleton does not change significantly during preprophase-prophase. A preprophase microtubule band (PMB) is localized in the cortex lining the rims of the external periclinal wall curvature, while some microtubules traverse the IPCS and the cytoplasm adjacent to the neighbouring wall regions. The mitotic spindle axis is diagonal, while the cell plate separating the GMCs exhibits an unusual mode of growth. It gradually encircles the proximal daughter nucleus, becoming funnel-shaped. One of its periclinal edges fuses with the external periclinal wall area lined by the PMB cortical zone and the other with the internal periclinal wall area adjoining the IPCS. The latter region seems to behave like the PMB cortical zone. The results show that the morphogenetic mechanism underlying the formation of the conical GMCs includes a series of highly integrated processes, initiated or carried out during cell polarization.

On the differential divisions and preprophase microtubule bands involved in the development of stomata of Vigna sinensis L

1979 ◽  
Vol 37 (1) ◽  
pp. 11-37
Author(s):  
B. Galatis ◽  
K. Mitrakos
Keyword(s):  
Cell Polarity ◽  
Cell Plate ◽  
Equatorial Position ◽  
Anticlinal Wall ◽  
Vigna Sinensis ◽  
Daughter Cells ◽  
Preprophase Microtubule Band ◽  
Dicotyledonous Plants ◽  
Mother Cells ◽  
Dictyosome Vesicles

The manifestation of premitotic cell polarity and the resultant structural asymmetry of the differential divisions participating in the development of stomata of Vigna sinensis vary considerably. However, two morphologically distinct types of differential division were distinguished: (a) ‘asymmetrical differential divisions’, in which the premitotic polarization of the cell, the eccentric position of the nucleus during division and the differences in size and organization of the daughter cells are obvious; and (b) differential divisions in which the above features are inconspicuous or almost absent. The former occur in the ordinary protodermal cells, the latter in some meristemoids. The organization of a sharply demarcated preprophase microtubule band (PMB) precedes, all differential and non-differential divisions. In the first type of differential division the PMB is formed eccentrically, while in the second it may display either an approximately symmetrical or a clearly asymmetrical disposition, always indicating with surprising accuracy the sites where the succeeding cell plate will join the parent walls. The PMB foreshadowing the highly curved cell plates in meristemoids I of the mesoperigenous process, as well as in meristemoids I and II of the mesogenous one, are apposed only on one anticlinal wall and therefore do not encircle the nucleus or traverse the cell. In the symmetrical divisions of guard cell mother cells (GMC), as well as in those of protodermal cells, the PMB runs right round the internal plasmalemma surface in an equatorial position, coinciding with that of the future cell plate. In the former cells the wall abutting the cortical cytoplasm traversed by the band becomes locally thickened. The variability in the pattern of the microtubules of the band along the walls of the GMC is directly mirrored in the pattern of the thickening. It seems that in GMC the PMB mediates a directed exocytosis of dictyosome vesicles. In contrast to what is now generally accepted in dicotyledonous plants, each meristemoid I of both the mesogenous and mesoperigenous stomata in Vigna sinensis leaves does not inhibit but induces the formation of other meristemoids close to it.

Microtubule Orientation During Stomatal Differentiation in Grasses

1989 ◽  
Vol 92 (4) ◽  
pp. 581-594
Author(s):  
SOON-OK CHO ◽  
SUSAN M. WICK
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Guard Cell ◽  
Mother Cell ◽  
Early Stage ◽  
Preprophase Band ◽  
Subsidiary Cell ◽  
Stomatal Complex ◽  
Face View ◽  
Mother Cells

The changing orientation of microtubules (MTs) during formation of the stomatal complex in grasses was observed by immunofluorescence microscopy, beginning with the asymmetrical division of the cell that gives rise to the guard cell mother cell, i.e. the guard cell grandmother cell. The asymmetrically placed preprophase band (PPB) of guard cell grandmother cells and hair cell mother cells is always laid down parallel to the distal end wall even when this wall is oblique to the long axis of the cell. The first step in formation of the PPB of a subsidiary cell mother cell appears to be establishment of an incomplete band of MTs. Whereas the mature PPB forms a curved line in a face view of a subsidiary cell mother cell, in this early stage MTs form fan-shaped arrays that focus on two points along the edge of the subsidiary cell mother cell. Replacement of the transversely oriented interphase microtubule band of the guard cell mother cell with the longitudinally oriented PPB involves several distinctive stages: (1) appearance of MTs directed toward the centre of the periclinal surface along the entire length of the lateral walls. (2) Appearance of another set of MTs along the entire width of both end walls, likewise focused toward the centre of the periclinal surface. Together these two groups of MTs form a cross with broadened tips in face view of the leaf. (3) Disappearance of the first set of MTs, and formation of an increasingly narrow band from the latter at the site of future cytokinesis. Although the anaphase spindles of guard cell grandmother cells, hair cell mother cells and guard cell mother cells are usually diagonally oriented relative to the site occupied previously by the PPB, the line connecting the centres of the spindle poles that are established at prophase is perpendicular to the persisting PPBs. Unlike the situation in certain other hair cells, MTs in leaf hair cells are transversely oriented even when the cells are highly elongated.

Comparative effects of phalloidin and cytochalasin B on motility and morphogenesis in Allium

1980 ◽  
Vol 58 (7) ◽  
pp. 773-785 ◽  
Author(s):  
Barry A. Palevitz
Keyword(s):  
Cytochalasin B ◽  
Cell Plate ◽  
Wall Thickening ◽  
Animal Cells ◽  
Host Fungus ◽  
Guard Mother Cells ◽  
Mother Cells ◽  
Chromosome Motion

Cytochalasin B (CB), thought to disaggregate F-actin in animal cells, and phalloidin (Phal), known to stabilize F-actin in vivo and in vitro, have nearly identical effects on cotyledon epidermal cells of Allium cepa. Both drugs rapidly induce cessation of streaming and both, by preventing normal telophase reorientation movement, lead to abnormal division planes in dividing guard mother cells. Neither, however, prevents normal microtubule deposition, wall thickening, and cellulose orientation during guard cell differentiation. Furthermore, both drugs have no effect on spindle formation and anaphase chromosome motion. Examination of Nitella and Chara cells, in which streaming had been stopped by either agent, shows that microfilament cables are still present. With both drugs, the minimum effective concentrations were routinely used (CB, 2 μM; Phal, 100–200 μM). Our results are discussed in terms of the mode of action of these drugs and their possible role in host-fungus interactions. Implications for the mechanisms underlying cell plate alignment, cellulose orientation, and cytoplasmic streaming are discussed.

scholarly journals A CENH3 mutation promotes meiotic exit and restores fertility in SMG7-deficient Arabidopsis

2021 ◽  
Author(s):  
Claudio Capitao ◽  
Sorin Tanasa ◽  
Jaroslav Fulnecek ◽  
Vivek Kumar Raxwal ◽  
Svetlana Akimcheva ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Growth And Development ◽  
Histone H3 ◽  
Wild Plants ◽  
Pollen Production ◽  
Plant Growth And Development ◽  
Apparent Effect ◽  
Viable Pollen ◽  
Mother Cells ◽  
Suppressor Screen

Meiosis in angiosperm plants is followed by mitotic divisions to form multicellular haploid gametophytes. Termination of meiosis and transition to gametophytic development is, in Arabidopsis, governed by a dedicated mechanism that involves SMG7 and TDM1 proteins. Mutants carrying the smg7-6 allele are semi-fertile due to reduced pollen production. We found that instead of forming tetrads, smg7-6 pollen mother cells undergo multiple rounds of chromosome condensation and spindle assembly at the end of meiosis, resembling aberrant attempts to undergo additional meiotic divisions. A suppressor screen uncovered a mutation in centromeric histone H3 (CENH3) that increased fertility and promoted meiotic exit in smg7-6 plants. The mutation led to inefficient splicing of the CENH3 mRNA and a substantial decrease of CENH3, resulting in smaller centromeres. The reduced level of CENH3 delayed formation of the mitotic spindle but did not have an apparent effect on plant growth and development. We suggest that impaired spindle re-assembly at the end of meiosis limits aberrant divisions in smg7-6 plants and promotes formation of tetrads and viable pollen. Furthermore, the reduced level of CENH3 did not induce haploid plants in crosses with wild plants, indicating that differences in centromere size is not the key determinant of centromere-mediate genome elimination.

Anther and Ovule Development in Tasmannia (Winteraceae)

1992 ◽  
Vol 40 (6) ◽  
pp. 877 ◽  
Author(s):  
N Prakash ◽  
AL Lim ◽  
FB Sampson
Keyword(s):  
Mother Cell ◽  
Female Gametophyte ◽  
Cell Plate ◽  
Basic Type ◽  
Ovule Development ◽  
Linear Tetrad ◽  
Polygonum Type ◽  
Secretory Type ◽  
Mother Cells ◽  
Female Gametophyte Development

Three species of Tasmannia R.Br. ex DC., T. glaucifolia, T. insipida and T. stipitata are studied. The anther is tetrasporangiate and its waU development conforms to the Basic type. The tapetum follows the secretory type of development. Cytokinesis in the microspore mother cells is simultaneous but an evanescent cell plate is present at telophase I and anaphase I1 during meiosis. Pollen tetrads are permanent and tetrahedral. The mature pollen is anaulcerate, reticulate and 2-celled. The ovule. is anatropous, bitegmic and crassinucellate. The micropyle in T. stipitata and T. Glaucifolia is formed by the inner integument only whereas in T. insipida it is formed by both the integuments and is zigzag in outline. Meiosis in the single megaspore mother cell produces a linear or T-shaped megaspore tetrad in T. stipitata and T. glaucifolia but only a linear tetrad in T. insipida. Female gametophyte development is of the monosporic Polygonum type. Fertilisation is porogamous; triple fusion and syngamy occur simultaneously.

scholarly journals Structural rearrangements of tubulin and actin during the cell cycle of the yeast Saccharomyces.

1984 ◽  
Vol 98 (3) ◽  
pp. 922-933 ◽  
Author(s):  
J V Kilmartin ◽  
A E Adams
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Neck Region ◽  
Wall Material ◽  
Double Labeling ◽  
Bud Emergence ◽  
Unusual Distribution ◽  
Significant Length ◽  
Cytoplasmic Microtubules ◽  
Mother Cells

The distribution of actin and tubulin during the cell cycle of the budding yeast Saccharomyces was mapped by immunofluorescence using fixed cells from which the walls had been removed by digestion. The intranuclear mitotic spindle was shown clearly by staining with a monoclonal antitubulin; the presence of extensive bundles of cytoplasmic microtubules is reported. In cells containing short spindles still entirely within the mother cells, one of the bundles of cytoplasmic microtubules nearly always extended to (or into) the bud. Two independent reagents (anti-yeast actin and fluorescent phalloidin) revealed an unusual distribution of actin: it was present as a set of cortical dots or patches and also as distinct fibers that were presumably bundles of actin filaments. Double labeling showed that at no stage in the cell cycle do the distributions of actin and tubulin coincide for any significant length, and, in particular, that the mitotic spindle did not stain detectably for actin. However, both microtubule and actin staining patterns change in a characteristic way during the cell cycle. In particular, the actin dots clustered in rings about the bases of very small buds and at the sites on unbudded cells at which bud emergence was apparently imminent. Later in the budding cycle, the actin dots were present largely in the buds and, in many strains, primarily at the tips of these buds. At about the time of cytokinesis the actin dots clustered in the neck region between the separating cells. These aspects of actin distribution suggest that it may have a role in the localized deposition of new cell wall material.

scholarly journals Organization of Microtubules and Endoplasmic Reticulum During Mitosis and Cytokinesis in Wheat Meristems

1966 ◽  
Vol 1 (1) ◽  
pp. 109-120
Author(s):  
J. D. PICKETT-HEAPS ◽  
D. H. NORTHCOTE
Keyword(s):  
Endoplasmic Reticulum ◽  
Mitotic Spindle ◽  
Structural Changes ◽  
Preprophase Band ◽  
Cell Plate ◽  
Late Prophase ◽  
Daughter Cells ◽  
Initial Stage ◽  
Spindle Microtubules ◽  
Mother Cell Wall

The fine-structural changes accompanying mitosis in meristematic cells of the roots and coleoptile tissue of wheat have been studied. A band of microtubules encircling the nucleus appeared in the cytoplasm before the cells entered prophase. These microtubules were oriented at right angles to the direction of the mitotic spindle and were located at the position on the mother cell wall where the future cell plate dividing the daughter cells would have joined it. During prophase the number of microtubules in this preprophase band decreased and eventually disappeared, while microtubules were found to be aligned along the spindle axis. These spindle microtubules appeared as a cone-shaped array of units radiating from the polar zones of the spindle and passing very close tangentially to the nucleus. At late prophase they penetrated the disintegrating nuclear envelope and were seen between the chromosomes. During metaphase and anaphase many microtubules were present running throughout the length of the spindle, and others were found to be attached to chromosomes. Paired sister chromosomes were found joined to microtubules from opposite poles of the spindle. The position and orientation of the lamellae of the endoplasmic reticulum which invaded the spindle from the two poles was closely related to the position and alignment of the microtubules. During the formation of the cell plate vesicles were seen to be collected between the microtubules. As the vesicles fused to form the plate the microtubules were found only at its growing edge, where the vesicles were still being aligned. At the initial stage of its formation the microtubules passed right through the plate, but as it extended they appeared to end at the plate region. The results of the investigation are discussed in relation to the descriptions of mitosis and cytokinesis based on optical microscopy of living cells.

Sign in / Sign up

Export Citation Format

Share Document