scholarly journals TUBULAR AND FIBRILLAR COMPONENTS OF MATURE AND DIFFERENTIATING SIEVE ELEMENTS

1967 ◽  
Vol 34 (3) ◽  
pp. 801-815 ◽  
Author(s):  
James Cronshaw ◽  
Katherine Esau
Keyword(s):  
Light And Electron Microscopy ◽  
Protein Body ◽  
Sieve Element ◽  
Protein Component ◽  
Sieve Plate ◽  
Sieve Elements ◽  
P Protein ◽  
Ontogenetic Study ◽  
P2 Protein ◽  
Fibrillar Component

An ontogenetic study of the sieve element protoplast of Nicotiana tabacum L. by light and electron microscopy has shown that the P-protein component (slime) arises as small groups of tubules in the cytoplasm. These subsequently enlarge to form comparatively large compact masses of 231 ± 2.5 (SE)A (n = 121) tubules, the P-protein bodies. During subsequent differentiation of the sieve element, the P-protein body disaggregates and the tubules become dispersed throughout the cell. This disaggregation occurs at about the same stage of differentiation of the sieve elements as the breakdown of the tonoplast and nucleus. Later, the tubules of P-protein are reorganized into smaller striated 149 ± 4.5 (SE)A (n = 43) fibrils which are characteristic of the mature sieve elements. The tubular P-protein component has been designated P1-protein and the striated fibrillar component P2-protein. In fixed material, the sieve-plate pores of mature sieve elements are filled with proteinaceous material which frays out into the cytoplasm as striated fibrils of P2-protein. Our observations are compatible with the view that the contents of contiguous mature sieve elements, including the P-protein, are continuous through the sieve-plate pores and that fixing solutions denature the proteins in the pores. They are converted into the electron-opaque material filling the pores.

Protein Component in Sieve Elements of Quercus Rubra L.

1976 ◽  
Vol 34 ◽  
pp. 40-41
Author(s):  
Lidija Murmanis
Keyword(s):  
Quercus Rubra ◽  
Sieve Element ◽  
Protein Component ◽  
Sieve Elements ◽  
P Protein ◽  
Intimate Association ◽  
Rough Er ◽  
Differentiation Stage ◽  
Oriented Parallel ◽  
Stage 1

At the earliest stage, P-protein in red oak sieve elements can be identified with the fine filaments embedded in the cytoplasm (Fig. 1), and they appear similar to the P-protein component in Cucurbita maxima at an early differentiation stage (1). At this time ribosomes (in a spiral configuration) and the rough ER are numerous and in intimate association with the filaments. As differentiation proceeds P-protein bodies are formed in which the filaments are randomly arranged (Fig. 2). Later the filaments become oriented parallel to one another (Fig. 1, at right) and are transformed structurally into tubules. Tubules aggregate into crystalline bodies (Figs. 3, 4) which resemble extruded nucleoli reported previously (2, 3). Individual tubules have a diameter of about 235A and a tripartite structure--60-70A thick electron-dense walls separated by an electron-transparent core. During the disintegration of sieve element protoplast the crystalline bodies disperse and tubules gradually change into fibrils.

Nuclear crystalloids in sieve elements of Boraginaceae: a protein digestion study

1983 ◽  
Vol 64 (1) ◽  
pp. 37-47
Author(s):  
J. Thorsch ◽  
K. Esau
Keyword(s):  
Proteolytic Enzymes ◽  
Differential Response ◽  
Sieve Element ◽  
Enzyme Digestion ◽  
The Other ◽  
Sieve Plate ◽  
Protein Digestion ◽  
Sieve Elements ◽  
P Protein ◽  
Parallel Arrangement

Nuclear crystalloids have been found in sieve elements of several Boraginaceae. Nuclei of differentiating sieve elements of Echium and other genera except Amsinckia contain one or more crystalloids composed of thin rods densely packed in parallel arrangement. After the nuclei disintegrate in the maturing sieve element the crystalloids are released into the cell lumen where they persist intact. In Amsinckia the crystalloid consists of two components: a dense component, similar to the crystalloid in the other genera and a loosely arranged paracrystalline component. The proteinaceous nature of the nuclear crystalloids and their possible similarity to P-protein was investigated by enzyme digestion techniques. Three proteolytic enzymes were employed in this study: protease, pepsin and trypsin. Successful digestion of the dense crystalloid in both Echium and Amsinckia was obtained with each enzyme tested. P-protein plugging the sieve plate pores was also digested. The loose component in Amsinckia and the aggregated and dispersed P-protein were not affected by the enzyme digestion procedures. These results seemed to indicate that the density or compactness of the proteinaceous inclusions may play a role in the differential response.

scholarly journals A crystalline inclusion in sieve element nuclei of Amsinckia. II. The inclusion in maturing cells

1979 ◽  
Vol 38 (1) ◽  
pp. 11-22
Author(s):  
K. Esau ◽  
A.C. Magyarosy
Keyword(s):  
Hydrostatic Pressure ◽  
Sieve Element ◽  
Crystalline Inclusion ◽  
Sieve Elements ◽  
P Protein ◽  
Sudden Release ◽  
Sieve Plates ◽  
Tubular Components

The compounds crystalloids formed in sieve element nuclei of Amsinckia douglasiana A. DC. (Boraginaceae) during differentiation of the cell become disaggregated during the nuclear breakdown characteristic of a maturing sieve element. The phenomenon occurs in both healthy and virus-infected plants. The crystalloid component termed cy, which is loosely aggregated, separates from the densely aggregated component termed cx and disperses. The cx component may become fragmented, or broken into large pieces, or remain intact after the cell matures. After their release from the nucleus both crystalloid components become spatially associated with the dispersed P-protein originating in the cytoplasm, but remain distinguishable from it. The component tubules of P-protein are hexagonal in transections and are somewhat wider than the 6-sided cy tubules. The cx tubules are much narrower than the P-protein or the cy tubules and have square transections. Both the P-protein and the products of disintegrated crystalloids accumulate at sieve plates in sieve elements subjected to sudden release of hydrostatic pressure by cutting the phloem. The question of categorizing the tubular components of the nuclear crystalloid of a sieve element with reference to the concept of P-protein is discussed.

Fine structure of the phloem of Pisum sativum. I. The sieve element ontogeny

1965 ◽  
Vol 13 (2) ◽  
pp. 171 ◽  
Author(s):  
MC Wark ◽  
TC Chambers
Keyword(s):  
Endoplasmic Reticulum ◽  
Pisum Sativum ◽  
Nuclear Material ◽  
Sieve Element ◽  
Secondary Phloem ◽  
Sieve Elements ◽  
Pisum Sativum L ◽  
Ontogenetic Study ◽  
Sieve Plates ◽  
Peripheral Cytoplasm

An ontogenetic study of secondary phloem sieve elements of Pisum sativum L., fixed on the intact plant for electron microscopy, indicates that the connecting strands across the sieve plates are continuities of the endoplasmic reticulum. Each connecting strand is surrounded by a callose cylinder. The peripheral cytoplasm of the nucleate "young" sieve elements contains longitudinally oriented tubules of endoplasmic reticulum. As the sieve elements develop, nuclear material is extruded into the cytoplasm by way of a fibrotubular body which is structurally distinct from the slime body. When the cells are fully expanded the slime bodies disperse. This process is followed by breakdown of a number of organelles including the nucleus and tonoplast. This apparently leaves the endoplasmic reticulum free in the cell lumen.

Nuclear Crystalloids in Sieve Elements of Species of Echium (Boraginaceae)

1982 ◽  
Vol 54 (1) ◽  
pp. 149-160
Author(s):  
KATHERINE ESAU ◽  
JENNIFER THORSCH
Keyword(s):  
Protein A ◽  
Sieve Element ◽  
Crystalline Form ◽  
Two Dimensional ◽  
Common Component ◽  
Dimensional Lattice ◽  
Sieve Elements ◽  
Ultrastructural Studies ◽  
P Protein ◽  
Systematic Character

Ultrastructural studies of differentiating phloem of the midvein in 15 species of Echium (Boraginaceae) have shown that in every species one or more crystalloids develop in sieve-element nuclei. These inclusions appear as soon as the cell begins to differentiate from a procambial derivative. Small at first, they enlarge later, particularly in length. The crystalloid may extend end-to-end in the correspondingly elongated nucleus. When the nucleus disintegrates in the maturing cell the crystalloid is released into the cell lumen where it remains intact or becomes fractured into large pieces. No dissociation into subunits was observed. The crystalloids are composed of tightly packed narrow rods (tubules) forming a two-dimensional lattice of squares in transections and a system of parallel striations in longitudinal sections. The similarities of these inclusions to the crystalline form of P-protein in Fabaceae raises the question of terminological delimitation of P-protein, a common component of angiospermous sieve-element protoplasts. The occurrence of nuclear crystalloids in another previously investigated genus in the Boraginaceae, Amsinckia, suggests that this inclusion should be explored in boraginaceous representatives for its possible value as a systematic character.

Development and Dispersal of P-Protein in the Phloem of Coleus Blumei Benth

1969 ◽  
Vol 4 (1) ◽  
pp. 155-169
Author(s):  
M. W. STEER ◽  
E. H. NEWCOMB
Keyword(s):  
Osmium Tetroxide ◽  
Close Association ◽  
Parenchyma Cell ◽  
Protein Body ◽  
Sieve Element ◽  
Phloem Parenchyma ◽  
Coleus Blumei ◽  
P Protein ◽  
Longitudinal View ◽  
Phloem Parenchyma Cell

The development of P-protein (slime) in the phloem of Coleus stem apices has been studied electron microscopically using material fixed in glutaraldehyde followed by osmium tetroxide. In phloem parenchyma cells the earliest-appearing groups of tubular P-protein commonly are seen as close association with clusters of ‘spiny’ vesicles similar to those reported in Phaseolus phloem (Newcomb, 1967). The vesicles break down as the P-protein masses enlarge, and are assumed to contribute to P-protein formation. Subsequently the groups of tubules are consolidated into a single spindle-shaped body aligned longitudinally in each phloem parenchyma cell or sieve element. The microtubules observed frequently in the vicinity of the young P-protein body may play a role in its consolidation or in the longitudinal alignment of its constituent tubules. Some P-protein bodies acquire a highly organized structure in which the tubules are arranged hexagonally around lightly staining centres. Disaggregation of the P-protein body occurs during disintegration of the cytoplasm and nucleus, and results initially in the presence of swirls of packed fibrils. During disaggregation, the tubules of the mature P-protein body, which are about 200 Å in diameter, are converted to fibrils about 70 Å in diameter in a process apparently with several intermediate stages. In longitudinal view the fibrils exhibit alternate electron transparent and dense bands that impart a striated appearance to the mass. During maturation of the sieve element the swirls of fibrillar masses separate into individual fibrils which become dispersed through the cell lumen.

Filamentous Component (Slime) in Coniferous Sieve Elements

1972 ◽  
Vol 30 ◽  
pp. 214-215
Author(s):  
Lidija Murmanis ◽  
Irving B. Sachs
Keyword(s):  
Electron Microscopy ◽  
Structural Component ◽  
Pinus Strobus ◽  
Sieve Element ◽  
Sieve Elements ◽  
Double Structure ◽  
Proteinaceous Material ◽  
Fibrillar Component ◽  
Filamentous Material

In the literature, it is agreed that in angiosperm sieve elements, a fibrillar, or filamentous, proteinaceous material is present, but the presence of this material in gymnosperms is not agreed upon. Some authors have reported filamentous material (slime) in Pinaceae by light and by electron microscopy. By contrast, some authors have found no structural component in conifers comparable to the sieve element fibrillar component in angiosperms.This report is an affirmation that filamentous material is present in Pinus strobus L. sieve elements. The finest filamentous unit, when measurable, appears to range from 40-60 A in diameter (Fig. 1, arrows). These filaments have a tendency to accumulate to various degrees. Generally, they aggregate in two; then the double structure measures 120-160 A in diameter (Fig. 1, double arrows), although the distance between two filaments is not constant.

scholarly journals Aspartate Residues in a Forisome-Forming SEO Protein Are Critical for Protein Body Assembly and Ca2+ Responsiveness

2020 ◽  
Vol 61 (10) ◽  
pp. 1699-1710
Author(s):  
Yan Liu ◽  
Winfried S Peters ◽  
Daniel R Froelich ◽  
Alexander H Howell ◽  
Sutton Mooney ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Protein Body ◽  
Phloem Transport ◽  
Sieve Element ◽  
Amino Acid Sequences ◽  
Yeast Saccharomyces Cerevisiae ◽  
Binding Motifs ◽  
Sieve Elements ◽  
Protein Protein Interaction ◽  
Transgenic Cells

Abstract Forisomes are protein bodies known exclusively from sieve elements of legumes. Forisomes contribute to the regulation of phloem transport due to their unique Ca2+-controlled, reversible swelling. The assembly of forisomes from sieve element occlusion (SEO) protein monomers in developing sieve elements and the mechanism(s) of Ca2+-dependent forisome contractility are poorly understood because the amino acid sequences of SEO proteins lack conventional protein–protein interaction and Ca2+-binding motifs. We selected amino acids potentially responsible for forisome-specific functions by analyzing SEO protein sequences in comparison to those of the widely distributed SEO-related (SEOR), or SEOR proteins. SEOR proteins resemble SEO proteins closely but lack any Ca2+ responsiveness. We exchanged identified candidate residues by directed mutagenesis of the Medicago truncatula SEO1 gene, expressed the mutated genes in yeast (Saccharomyces cerevisiae) and studied the structural and functional phenotypes of the forisome-like bodies that formed in the transgenic cells. We identified three aspartate residues critical for Ca2+ responsiveness and two more that were required for forisome-like bodies to assemble. The phenotypes observed further suggested that Ca2+-controlled and pH-inducible swelling effects in forisome-like bodies proceeded by different yet interacting mechanisms. Finally, we observed a previously unknown surface striation in native forisomes and in recombinant forisome-like bodies that could serve as an indicator of successful forisome assembly. To conclude, this study defines a promising path to the elucidation of the so-far elusive molecular mechanisms of forisome assembly and Ca2+-dependent contractility.

An Ultrastructural Study of the Phloem of Drimys (Winteraceae)

IAWA Journal ◽  
1985 ◽  
Vol 6 (3) ◽  
pp. 255-268 ◽  
Author(s):  
Jennifer Thorsch ◽  
Katherine Esau
Keyword(s):  
Endoplasmic Reticulum ◽  
Ultrastructural Study ◽  
Protein Body ◽  
Sieve Element ◽  
Companion Cell ◽  
Young Cell ◽  
P Protein ◽  
Companion Cells ◽  
Protein Granules ◽  
Sieve Plates

The ultrastructural features of mainly primary phloem of three species of Drimys (Winteraceae), D. winteri J. R. ' G. Forst., D. lanceolata (Poiret) Baill. and D. granadensis L. f. var. mexicana (DC.) A. C. Smith are similar to those usually observed in dicotyledons. The sieve element is early discernible by its association with a companion cell, the deposition of callose in nascent sieve areas, and the appearance in the cytoplasm of the nondispersing paracrystalline protein body. Plastids with starch (and in D. lanceolata also with paracrystalline protein granules), mitochondria, sparse endoplasmic reticulum cisternae (ER), dictyosomes, and ribosomes are present in the young cell. Stacking of ER was not conspicuous. The nucleus is moderately chromatic before its breakdown. P-protein occurs in more or less dense aggregates that usually become dispersed after the tonoplast disappears. The subunits of the P-pro tein have tubular structure before the dispersal. The plasmalemma is retained. The sieve areas are combined into sieve plates on long radial walls and on some transverse walls originating during secondary partitioning of sieve element precursors. The numerous lateral sieve areas intergrade with those of the sieve plates. The pores develop from plasmodesmatal connections and may involve the formation of median cavities. The connections between sieve elements alld companion cells consist of the usual combination of a pore embedded in callose and one plasmodesma or several branches of one on the companion cell side.

Fine structure of the differentiating sieve elements of Vicia faba

1969 ◽  
Vol 17 (3) ◽  
pp. 441 ◽  
Author(s):  
S Zee
Keyword(s):  
Fine Structure ◽  
Vicia Faba ◽  
Inclusion Bodies ◽  
Close Association ◽  
Membrane System ◽  
Sieve Element ◽  
Sieve Plate ◽  
Starch Granules ◽  
Sieve Elements ◽  
Early Stages

The fine structure of the sieve elements of the primary phloem of the epicotyl of Vicia faba is described. The cytoplasm of the young sieve element contains four distinct forms of "slime" body: amorphous, crystalline, tubular (each tubule measuring about 140 Å in diameter), and short fibrillar (each fibril measuring about 350 Å in diameter). At the very early stages of differentiation, polysome helices are prevalent often in close association with the amorphous but not the other forms of "slime" bodies. At the early stages of development of the sieve element the tubular form of "slime" is closely associated with the endoplasmic reticulum, which suggests their possible origin. The plastids of the sieve element lack a well-developed internal membrane system but contain two characteristic types of inclusion bodies, starch granules and crystalloids identical to those revorted for the secondarv vhloem of the root of Pisum sativum. Mitochondria - remain apparently unchanged throughout sieve element development. Microtubules are present during the early stages of sieve element development but become scarce at later stages. Dictyosomes, coated vesicles, ribosomes, polysomes, and nucleus disappear as the sieve element matures. The fine structure of the sieve plate pore initial is complex. It consists of an outer electron-dense ring ("desmotubule") which encloses a central dark core. The developmental pattern of the sieve plate pore has been traced from the very young to the mature stages.

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