Establishment of division plane and mitosis in monoplastidic guard mother cells ofSelaginella

1992 ◽  
Vol 23 (2) ◽  
pp. 89-101 ◽  
Author(s):  
Ann L. Cleary ◽  
Roy C. Brown ◽  
Betty E. Lemmon
Keyword(s):  
Division Plane ◽  
Guard Mother Cells ◽  
Mother Cells

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 The MAP She1 coordinates directional spindle positioning by spatially restricting dynein activity

2021 ◽  
Author(s):  
Kari H. Ecklund ◽  
Megan E. Bailey ◽  
Carsten K. Dietvorst ◽  
Charles L. Asbury ◽  
Steven M. Markus
Keyword(s):  
Daughter Cell ◽  
Cell Types ◽  
Division Plane ◽  
Spindle Positioning ◽  
Daughter Cells ◽  
Anaphase Onset ◽  
Microtubule Binding Domain ◽  
Mother And Daughter ◽  
Mother Cells ◽  
Cell Division Plane

ABSTRACTDynein motors move the mitotic spindle to the cell division plane in many cell types, including in budding yeast, in which dynein is assisted by numerous factors including the microtubule-associated protein (MAP) She1. Evidence suggests that She1 plays a role in polarizing dynein-mediated spindle movements toward the daughter cell; however, how She1 performs this function is unknown. We find that She1 assists dynein in maintaining the spindle close to the bud neck, such that at anaphase onset the chromosomes are segregated to mother and daughter cells. She1 does so by attenuating the initiation of dynein-mediated spindle movements specifically within the mother cell, ensuring such movements are polarized toward the daughter cell. Our data indicate that this activity relies on She1 binding to the microtubule-bound conformation of the dynein microtubule-binding domain, and to astral microtubules within mother cells. Our findings reveal how an asymmetrically localized MAP directionally tunes dynein activity by attenuating motor activity in a spatially confined manner.

Blue light-induced, intrinsic vacuolar fluorescence in onion guard cells

1979 ◽  
Vol 37 (1) ◽  
pp. 1-10
Author(s):  
E. Zeiger ◽  
P.K. Hepler
Keyword(s):  
Blue Light ◽  
Single Cells ◽  
Broad Band ◽  
Guard Cells ◽  
Emission Peak ◽  
Blue Light Receptor ◽  
Guard Cell Protoplasts ◽  
Guard Mother Cells ◽  
Mother Cells ◽  
Eleven Species

Guard cells of onion irradiated with broad-band blue light display a green intrinsic fluorescence. The fluorescence has been found in eleven species of Allium, but it has not been observed in any other monocot or dicot examined. The fluorescence occurs only in guard cells and is absent in neighbouring epidermal cells. During development it is first apparent in guard mother cells soon after the asymmetric division. Microscopic observation reveals that the fluorescence is associated with the vacuole and examination of vacuoles isolated from guard cell protoplasts suggests that it may be localized on the tonoplast. Microspectrophotometric analysis of single cells reveals an emission peak at around 520 nm. Our results are consistent with the view that this blue light receptor is a flavin or flavoprotein and that it might be related to the blue light-enhanced stomatal opening observed in onion.

The subcellular organization of stomatal initials in sugarcane leaves: the guard and subsidiary mother cells

1977 ◽  
Vol 55 (22) ◽  
pp. 2801-2809 ◽  
Author(s):  
A. P. Singh
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Close Association ◽  
Preprophase Band ◽  
Central Position ◽  
Guard Mother Cell ◽  
Subcellular Organization ◽  
Guard Mother Cells ◽  
Mother Cells ◽  
Preprophase Bands

The subcellular organization of guard and subsidiary mother cells in sugarcane leaves was examined by electron microscopy. Guard and subsidiary mother cells assume a characteristic shape before mitosis and contain variable numbers of mitochondria, proplastids, dictyosomes, and cisternae of rough endoplasmic reticulum. In guard mother cells, the nucleus occupies a central position, whereas in subsidiary mother cells, the nucleus is located toward one end of the cell, near the guard mother cell. Microtubules are found in both guard and subsidiary mother cells and are either closely grouped to form defined preprophase bands or randomly dispersed between the nucleus and the preprophase bands. Many of the dispersed microtubules occur in close association with the nucleus in both guard and subsidiary mother cells. Possible functions for these preprophase microtubules are discussed in relation to their organization in the preprophase band, their orientation, and their distribution within guard and subsidiary mother cells.

scholarly journals Arabidopsis EGY1 Is Critical for Chloroplast Development in Leaf Epidermal Guard Cells

Plants ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1254
Author(s):  
Alvin Sanjaya ◽  
Ryohsuke Muramatsu ◽  
Shiho Sato ◽  
Mao Suzuki ◽  
Shun Sasaki ◽  
...  
Keyword(s):  
Chloroplast Development ◽  
Fluorescent Proteins ◽  
Guard Cells ◽  
Cell Types ◽  
Mesophyll Cells ◽  
Pavement Cells ◽  
Normal Number ◽  
Chloroplast Formation ◽  
Guard Mother Cells ◽  
Mother Cells

In Arabidopsis thaliana, the Ethylene-dependent Gravitropism-deficient and Yellow-green 1 (EGY1) gene encodes a thylakoid membrane-localized protease involved in chloroplast development in leaf mesophyll cells. Recently, EGY1 was also found to be crucial for the maintenance of grana in mesophyll chloroplasts. To further explore the function of EGY1 in leaf tissues, we examined the phenotype of chloroplasts in the leaf epidermal guard cells and pavement cells of two 40Ar17+ irradiation-derived mutants, Ar50-33-pg1 and egy1-4. Fluorescence microscopy revealed that fully expanded leaves of both egy1 mutants showed severe chlorophyll deficiency in both epidermal cell types. Guard cells in the egy1 mutant exhibited permanent defects in chloroplast formation during leaf expansion. Labeling of plastids with CaMV35S or Protodermal Factor1 (PDF1) promoter-driven stroma-targeted fluorescent proteins revealed that egy1 guard cells contained the normal number of plastids, but with moderately reduced size, compared with wild-type guard cells. Transmission electron microscopy further revealed that the development of thylakoids was impaired in the plastids of egy1 mutant guard mother cells, guard cells, and pavement cells. Collectively, these observations demonstrate that EGY1 is involved in chloroplast formation in the leaf epidermis and is particularly critical for chloroplast differentiation in guard cells.

scholarly journals The MAP She1 coordinates directional spindle positioning by spatially restricting dynein activity

2021 ◽  
Author(s):  
Kari H. Ecklund ◽  
Megan E. Bailey ◽  
Kelly A. Kossen ◽  
Carsten K. Dietvorst ◽  
Charles L. Asbury ◽  
...  
Keyword(s):  
Daughter Cell ◽  
Cell Types ◽  
Division Plane ◽  
Spindle Positioning ◽  
Daughter Cells ◽  
Anaphase Onset ◽  
Microtubule Binding Domain ◽  
Close Proximity ◽  
Mother And Daughter ◽  
Mother Cells

Dynein motors move the mitotic spindle to the cell division plane in many cell types, including in budding yeast, in which dynein is assisted by numerous factors including the microtubule-associated protein (MAP) She1. Evidence suggests that She1 plays a role in polarizing dynein-mediated spindle movements toward the daughter cell; however, how She1 performs this function is unknown. We find that She1 assists dynein in maintaining the spindle in close proximity to the bud neck, such that at anaphase onset the chromosomes are segregated to mother and daughter cells. She1 does so by attenuating the initiation of dynein-mediated spindle movements within the mother cell, thus ensuring such movements are polarized toward the daughter cell. Our data indicate that this activity relies on She1 binding to the microtubule-bound conformation of the dynein microtubule-binding domain, and to astral microtubules within mother cells. Our findings reveal how an asymmetrically localized MAP directionally tunes dynein activity by attenuating motor activity in a spatially confined manner.

scholarly journals Occurrence and cytological mechanism of numerically unreduced pollen in diploid Populus euphratica

2013 ◽  
Vol 62 (1-6) ◽  
pp. 285-291 ◽  
Author(s):  
Pingdong Zhang ◽  
Xiangyang Kang
Keyword(s):  
Indirect Immunofluorescence ◽  
Populus Euphratica ◽  
Unreduced Gametes ◽  
2N Pollen ◽  
Tetrad Stage ◽  
Division Plane ◽  
Parallel Spindles ◽  
Chromosome Staining ◽  
Mother Cells ◽  
Cytological Mechanism

AbstractUnreduced gametes are the driving force for the polyploidizaiton of plants in nature, and are also an important tool for breeding of triploid individuals. The final heterozygosity of a 2n pollen grain depends on the cytological mechanism behind 2n pollen formation. In this study, meiotic abnormalities were analysed using fluorescent chromosome staining and indirect immunofluorescence during the microsporogenesis of 18 genotypes of diploid P. euphratica Oliv. (2n = 2x = 38). Among the 18 genotypes, 16 genotypes produce 2n pollen and two genotypes produce only normal n pollen. In all 2n pollen producers, we found that the first meiotic division was normal but that the second division was characterized by frequent abnormal spindle orientation (parallel, tripolar, and fused spindles) and premature cytokinesis. The parallel, fused spindles and premature cytokinesis were considered to be leading dyad formation, and tripolar spindles seemed to be causing triad formation at the tetrad stage. There was a higher frequency of parallel spindles than other spindle forms, but no significant correlations between parallel spindles and dyads were observed. However, a significant association (r = 0.68, P < 0.05) between the tripolar spindles and dyads was found. In some Microspore mother cells (MMCs), an indirect immunofluorescence examination of meiosis II revealed that the parallel spindles led to the gathering of one or two non-sister groups of chromosomes, causing an incorporation of RMSs from two daughter nuclei. Therefore, the incorporated RMSs established two nuclear cytoplasmic domains for the control of division plane, resulting in either triad or dyad formation.

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