Early Stages in the Development of Wheat Endosperm. II. Ultrastructural Observations on Cell Wall Formation

1977 ◽  
Vol 25 (6) ◽  
pp. 599 ◽  
Author(s):  
DJ Mares ◽  
BA Stone ◽  
C Jeffrey ◽  
K Norstog
Keyword(s):  
Cell Wall ◽  
Thin Layer ◽  
Embryo Sac ◽  
Central Cell ◽  
Wall Material ◽  
Cross Wall ◽  
Wheat Embryo ◽  
Wheat Endosperm ◽  
Early Stages ◽  
Cellular Endosperm

In the first 4-5 days after anthesis, the central cell of the wheat embryo sac undergoes transformation from a multinucleate syncytium to the cellular endosperm. This is accomplished initially by the centripetal growth of wall projections from the central cell wall and the formation of cylindrical, highly vacuolate alveoli. Growth is mediated through the production and planar aggregation of vesicles at the distal tip of the developing projections. The innermost ends of the alveoli are closed by a thin layer of cytoplasm which is bounded on the inner side by the vacuolar membrane of the central cell. Cell wall material is not found in this thin layer of cytoplasm and the alveoli therefore are not complete cells. Following the division of the alveolar nucleus a cross-wall is laid down between the daughter nuclei by a process which is similar to normal cytokinesis and a layer of endosperm cells is formed from the peripheral portions of the alveoli. This pattern of centripetal growth of alveoli and the formation of complete cells from the proximal portions continues until cellularization is completed by the confluence of alveoli originating from opposite sides of the central cell. Further growth of the cellular endosperm is accomplished by the meristematic activity of the peripheral layer of cells. The ultrastructure of the early stages of partitioning of the central cell is discussed in relation to current views on the ontogeny of wheat endosperm.

Ultrastructure of a marine psychrophilic Vibrio

1970 ◽  
Vol 16 (11) ◽  
pp. 1027-1031 ◽  
Author(s):  
S. F. Kennedy ◽  
R. R. Colwell ◽  
G. B. Chapman
Keyword(s):  
Electron Microscopy ◽  
Cell Wall ◽  
Plasma Membrane ◽  
Cell Division ◽  
Wall Material ◽  
Cross Wall ◽  
Growth Stages ◽  
Culture Age ◽  
Primary Mechanism ◽  
Age Studies

The structure of Vibrio marinus strain PS-207 was studied by both phase and electron microscopy. It was found to possess a trilaminar plasma membrane and cell wall. Membrane-bounded subunits containing DNA-like material were found dispersed throughout the cytoplasm. Giant round forms or "macrospheres" were observed in all growth stages. The size, shape, and construction of the "macrospheres" showed some variation, but could not be related to culture age. Studies of cell division in V. marinus strain PS-207 indicate the primary mechanism to be a synthesis and centripetal deposition of plasma membrane with a concomitant or subsequent synthesis and centripetal deposition of cross wall material.

Ultrastructure of the developing embryo sac of sunflower (Helianthus annuus) before and after fertilization

1991 ◽  
Vol 69 (1) ◽  
pp. 191-202 ◽  
Author(s):  
Hua Yan ◽  
Hong-Yuan Yang ◽  
William A. Jensen
Keyword(s):  
Plasma Membrane ◽  
Helianthus Annuus ◽  
Embryo Sac ◽  
Active Role ◽  
Central Cell ◽  
Wall Material ◽  
Young Embryo ◽  
Before And After ◽  
Membrane Contact ◽  
Female Germ Unit

The ultrastructure of the embryo sac of the sunflower (Helianthus annuus) was investigated before and after fertilization. In the young embryo sac, walls were observed that completely surrounded the egg, synergids, and the central cell. However, as maturation continued, the extent of the wall changed. By the time the embryo was mature, the chalazal portion of the walls of the egg and synergids had disappeared so these cells have a plasma membrane to plasma membrane contact. This is also true for the central cell, which has plasma membrane contact with the egg and synergids. However, the chalazal and lateral walls of the central cell become considerably thicker at this time. Before the entry of the pollen tube, the synergid that is located toward the placenta degenerates. After fertilization, a wall forms over the chalazal portion of the zygote and the persistent synergid. The endosperm appears to play an active role in this process, contributing substantial amounts of wall material. However, the wall covering the chalazal portion of the zygote is not complete by the time the zygote divides. In the proembryo, ribosome density increases and lipid bodies decrease in number. The suspensory cell has autophagic vacuoles that encircle some of the organelles. Our results support the concept that the egg, synergids, and central cell form a single functional unit, the female germ unit. Key words: sunflower, ultrastructure, embryo sac, female germ unit.

Fertilization in Plumbago zeylanica: entry and discharge of the pollen tube in the embryo sac

1982 ◽  
Vol 60 (11) ◽  
pp. 2219-2230 ◽  
Author(s):  
Scott D. Russell
Keyword(s):  
Cell Wall ◽  
Pollen Tube ◽  
Female Gametophyte ◽  
Embryo Sac ◽  
Central Cell ◽  
Vegetative Nucleus ◽  
Egg Cell ◽  
Ultrastructural Organization ◽  
Plumbago Zeylanica ◽  
Male Gametes

The ultrastructural organization of the megagametophyte of Plumbago zeylanica, which lacks synergids, was examined in chemically and physically fixed ovules after entry of the pollen tube. Similar to angiosperms with conventionally organized megagametophytes, the pollen tube enters the ovule through a micropyle, formed by the inner integument, and approaches the female gametophyte by growing between nucellar cells. Unlike other described female gametophytes, however, continued pollen tube growth results in direct penetration of the base of the egg through cell wall projections forming a filiform apparatus and is completed between the egg and central cell without disrupting either of these cells' plasma membranes. A terminal pollen tube aperture forms when the pollen tube reaches an area of strong curvature near the summit of the egg; this results in the release of two sperm cells, the vegetative nucleus, and a limited amount of pollen cytoplasm. The formerly continuous chalazal egg cell wall is locally disrupted near the tip of the pollen tube and apparently is thus modified for reception of male gametes. Discharged pollen cytoplasm rapidly degenerates between the egg and central cell, but unlike pollen tube discharge in conventionally organized megagametophytes, it is unassociated with the degeneraton of any receptor cell within the female gametophyte. Sperm nuclei are transmitted, one to the egg and the other to the central cell, to effect double fertilization by nuclear fusion with their respective female reproductive nuclei. The vegetative nucleus and discharged pollen cytoplasm degenerate between the developing embryo and endosperm during early embryogenesis. The emerging concept that the egg of Plumbago possesses combined egg and synergid functions is supported by the present study and suggests that the megagametophyte of this plant displays a highly specialized egg apparatus composed exclusively of a single, modified egg cell.

Early Stages in the Development of Wheat Endosperm. I. The Change From Free Nuclear to Cellular Endosperm

1975 ◽  
Vol 23 (2) ◽  
pp. 311 ◽  
Author(s):  
DJ Mares ◽  
K Norstog ◽  
BA Stone
Keyword(s):  
Mitotic Spindle ◽  
Endosperm Development ◽  
Wall Material ◽  
Ventral Region ◽  
Wheat Endosperm ◽  
Cellular Endosperm ◽  
Dorsal Area ◽  
Cytological Features ◽  
Ventral Area ◽  
Days After Anthesis

The cytological features of the cellularization of the free nuclear endosperm of wheat are described. Following the initial proliferation of nuclei the endosperm is divided into a small ventral area and a larger dorsal area which then develop separately. Cell wall formation in both regions is independent of a mitotic spindle and appears to be mediated by freely growing walls. Wall material is laid down along lines already marked out by ingrowth from the plasma membrane into the central cell cyto- plasm. By the time that cellularization is complete the smaller ventral region has been transformed into a layer of small, thick-walled cells whilst the larger dorsal area contains large, highly vacuolate endosperm cells. A model is proposed which endeavours to link the morphological features observed in embryo sacs, collected from wheat ovules 2-6 days after anthesis, into an ontogenetic sequence. This model is compared with previously published descriptions of wheat endosperm development.

CELL WALL REPLICATION: II. CELL WALL GROWTH AND CROSS WALL FORMATION OF ESCHERICHIA COLI AND STREPTOCOCCUS FAECALIS

1964 ◽  
Vol 10 (3) ◽  
pp. 473-482 ◽  
Author(s):  
K. L. Chung ◽  
R. Z. Hawirko ◽  
P. K. Isaac
Keyword(s):  
Cell Wall ◽  
Cell Division ◽  
Initial Step ◽  
Wall Material ◽  
Cross Wall ◽  
Cell Wall Growth ◽  
E Coli ◽  
Rapid Enlargement ◽  
Wall Growth ◽  
Polar Type

Cell wall replication in E. coli and S. faecalis was studied by differential labelling of living cells with fluorescent and non-fluorescent antibody.In E. coli the initial step in cell division was the formation of a cross wall at the cell equator, followed by the appearance of new cell wall on either side of the cross wall. The process was repeated in sequence at subsequent sites in the polar, the subcentral, and the subpolar areas. Constriction occurred at random so that the divided parent cells were composed of several daughter cells.A polar type of unidirectional cell wall growth and elongation was also observed in E. coli. It was initiated by the synthesis of a ring of new cell wall material around the polar tip. A second ring was then formed at the subpolar area during the rapid enlargement of the first ring in a single direction.Evidence shows that cell wall synthesis is independent of cell division and that in E. coli, it is initiated at multiple but specific sites within the cell and not by diffuse intercalation of old and new walls.Contrary to the synthesis of cell wall at multiple sites in E. coli, S. faecalis replicated new cell wall at only one site per coccus. The new wall segment was initiated and enlarged at the coccal equator, and was followed by the formation of a cross wall, centripetal growth and constriction to separate the daughter cells.

Silica Incorporation in the Cell Wall of the Singing Cell of Urtica dioica

1975 ◽  
Vol 33 ◽  
pp. 584-585
Author(s):  
A. E. Sowers ◽  
E. L. Thurston
Keyword(s):  
Cell Wall ◽  
Unique Feature ◽  
Urtica Dioica ◽  
Wall Material ◽  
Pain Response ◽  
Apical Portion ◽  
Ultrastructural Investigation ◽  
Plant Families ◽  
Bulbous Tip

Plant stinging emergences exhibit functional similarities in that they all elicit a pain response upon contact. A stinging emergence consists of an elongated stinging cell and a multicellular pedestal (Fig. 1). A recent ultrastructural investigation of these structures has revealed the ontogeny and morphology of the stinging cells differs in representative genera in the four plant families which possess such structures. A unique feature of the stinging cell of Urtica dioica is the presence of a siliceous cell wall in the apical portion of the cell. This rigid region of the cell wall is responsible for producing the needle-like apparatus which penetrates the skin. The stinging cell differentiates the apical bulbous tip early in development and the cell continues growth by intercalary addition of non-silicified wall material until maturity.The uppermost region of the stinging cell wall is entirely composed of silica (Fig. 2, 3) and upon etching with a 3% solution of HF (5 seconds), the silica is partially removed revealing the wall consisting of individualized silica bodies (Fig. 4, 5).

scholarly journals New methods for confocal imaging of infection threads in crop and model legumes

Plant Methods ◽  
2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Angus E. Rae ◽  
Vivien Rolland ◽  
Rosemary G. White ◽  
Ulrike Mathesius
Keyword(s):  
Cell Wall ◽  
Root Hair ◽  
Periodic Acid ◽  
Confocal Imaging ◽  
Wall Material ◽  
Future Research ◽  
Thin Sections ◽  
New Methods ◽  
Infection Threads ◽  
Imaging Of Infection

Abstract Background The formation of infection threads in the symbiotic infection of rhizobacteria in legumes is a unique, fascinating, and poorly understood process. Infection threads are tubes of cell wall material that transport rhizobacteria from root hair cells to developing nodules in host roots. They form in a type of reverse tip-growth from an inversion of the root hair cell wall, but the mechanism driving this growth is unknown, and the composition of the thread wall remains unclear. High resolution, 3-dimensional imaging of infection threads, and cell wall component specific labelling, would greatly aid in our understanding of the nature and development of these structures. To date, such imaging has not been done, with infection threads typically imaged by GFP-tagged rhizobia within them, or histochemically in thin sections. Results We have developed new methods of imaging infection threads using novel and traditional cell wall fluorescent labels, and laser confocal scanning microscopy. We applied a new Periodic Acid Schiff (PAS) stain using rhodamine-123 to the labelling of whole cleared infected roots of Medicago truncatula; which allowed for imaging of infection threads in greater 3D detail than had previously been achieved. By the combination of the above method and a calcofluor-white counter-stain, we also succeeded in labelling infection threads and plant cell walls separately, and have potentially discovered a way in which the infection thread matrix can be visualized. Conclusions Our methods have made the imaging and study of infection threads more effective and informative, and present exciting new opportunities for future research in the area.

Synchrotron infrared microspectroscopy reveals the response of Sphagnum cell wall material to its aqueous chemical environment

2018 ◽  
Vol 15 (8) ◽  
pp. 513
Author(s):  
Ewen Silvester ◽  
Annaleise R. Klein ◽  
Kerry L. Whitworth ◽  
Ljiljana Puskar ◽  
Mark J. Tobin
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Chemical Environment ◽  
Wall Material ◽  
Organic Soils ◽  
Cell Wall Material ◽  
Acid Base ◽  
Widespread Species ◽  
Flowing Liquid ◽  
Infrared Microspectroscopy

Environmental contextSphagnum moss is a widespread species in peatlands globally and responsible for a large fraction of carbon storage in these systems. We used synchrotron infrared microspectroscopy to characterise the acid-base properties of Sphagnum moss and the conditions under which calcium uptake can occur (essential for plant tissue integrity). The work allows a chemical model for Sphagnum distribution in the landscape to be proposed. AbstractSphagnum is one the major moss types responsible for the deposition of organic soils in peatland systems. The cell walls of this moss have a high proportion of carboxylated polysaccharides (polygalacturonic acids), which act as ion exchangers and are likely to be important for the structural integrity of the cell walls. We used synchrotron light source infrared microspectroscopy to characterise the acid-base and calcium complexation properties of the cell walls of Sphagnum cristatum stems, using freshly sectioned tissue confined in a flowing liquid cell with both normal water and D2O media. The Fourier transform infrared spectra of acid and base forms are consistent with those expected for protonated and deprotonated aliphatic carboxylic acids (such as uronic acids). Spectral deconvolution shows that the dominant aliphatic carboxylic groups in this material behave as a monoprotic acid (pKa=4.97–6.04). The cell wall material shows a high affinity for calcium, with a binding constant (K) in the range 103.9–104.7 (1:1 complex). The chemical complexation model developed here allows for the prediction of the chemical environment (e.g. pH, ionic content) under which Ca2+ uptake can occur, and provides an improved understanding for the observed distribution of Sphagnum in the landscape.

scholarly journals Characterization of Glycoside Hydrolase Family 5 Proteins in Schizosaccharomyces pombe

2010 ◽  
Vol 9 (11) ◽  
pp. 1650-1660 ◽  
Author(s):  
Encarnación Dueñas-Santero ◽  
Ana Belén Martín-Cuadrado ◽  
Thierry Fontaine ◽  
Jean-Paul Latgé ◽  
Francisco del Rey ◽  
...  
Keyword(s):  
Cell Wall ◽  
Schizosaccharomyces Pombe ◽  
Protein Characterization ◽  
Wall Material ◽  
Glycoside Hydrolase Family ◽  
Content Type ◽  
Hydrolysis Of ◽  
Controlled Hydrolysis ◽  
Hydrolase Family

ABSTRACT In yeast, enzymes with β-glucanase activity are thought to be necessary in morphogenetic events that require controlled hydrolysis of the cell wall. Comparison of the sequence of the Saccharomyces cerevisiae exo-β(1,3)-glucanase Exg1 with the Schizosaccharomyces pombe genome allowed the identification of three genes that were named exg1 + (locus SPBC1105.05), exg2 + (SPAC12B10.11), and exg3 + (SPBC2D10.05). The three proteins have different localizations: Exg1 is secreted to the periplasmic space, Exg2 is a membrane protein, and Exg3 is a cytoplasmic protein. Characterization of the biochemical activity of the proteins indicated that Exg1 and Exg3 are active only against β(1,6)-glucans while no activity was detected for Exg2. Interestingly, Exg1 cleaves the glucans with an endohydrolytic mode of action. exg1 + showed periodic expression during the cell cycle, with a maximum coinciding with the septation process, and its expression was dependent on the transcription factor Sep1. The Exg1 protein localizes to the septum region in a pattern that was different from that of the endo-β(1,3)-glucanase Eng1. Overexpression of Exg2 resulted in an increase in cell wall material at the poles and in the septum, but the putative catalytic activity of the protein was not required for this effect.

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