Developmental Features of Cell Wall Formation in Sieve Elements of the Grass Aegilops comosa var. thessalica

In differentiating sieve elements of Aegilops comosa var. thessalicadictyosomes are abundant and they produce numerous smooth vesicles.Coated vesicles seem to bud from smooth ones. Since both kindsof vesicles appear both in the cytoplasm and in associationwith the plasmalemma, it is proposed that they move to and fusewith the plasmalemma transferring products for cell wall synthesis.During differentiation sub-plasmalemmal microtubules are initiallyscarce and randomly oriented but soon afterwards they becomenumerous and transversely oriented to the long axis. Cellulosemicrofibrils in the cell wall appear to run parallel to themicrotubules and the latter may regulate microfibril orientation. Root protophloem sieve elements develop wave-like wall thickenings,which are, during development, overlaid by microtubules perpendicularto the long axis. Just after maturation these thickenings progressivelybecome smooth and finally the walls appear uniform in thickness.The wave-like wall thickenings may function as stored wall material,utilized in later stages of development when wall material willbe needed and its synthesis will be impossible because of theabsence of a synthesizing mechanism in the highly degraded protoplastsof mature sieve elements. It is suggested that in this way thethickenings may enable root protophloem sieve elements to growand keep pace with the active clongation of the surroundingcells. Aegilops comosa var. thessalica, sieve elements. cell wall, microtubules, dictyosomes, coated vesicles, wave-like thickenings     

Invaginations in plant cell protoplasts containing mycoplasma-like bodies (MLO)

MLO containing invaginations were found in protoplasts of phloem parenchyma cells in symptomless young leaves ofRibes houghtonianum Jancz. infected with a yellows disease. The invaginations originate between the cell wall and plasmalemma, usually at plasmodesmata, and change apparently into superficial vesicles in the protoplast; they are entirely or partially limited by host plasmalemma. The formations mentioned occur in parenchyma cells which contain normal organelles. Sometimes they are divided by a smooth membrane system enclosing MLO. Besides MLO the invaginations contain in some cases slimy fibrils resembling the P-protein in sieve tubes. The MLO bodies seen in invaginations have usually a diameter of 50–250 nm and their plasmalemma (unit membrane) is identical with the plasmalemma of MLO bodies occurring in sieve tubes. However, only few MLO bodies in invaginations are electron dense, so that they resemble naturally degenerated forms of MLO. Similar MLO containing invaginations were formerly described from some leafhoppers transmitting MLO.     

ULTRASTRUCTURE OF DEVELOPING SIEVE ELEMENTS IN THLASPI ARVENSE L. I. THE IMMATURE STATE

Immature sieve elements of pennycress (Thlaspi arvense, Brassicaceae) were studied with the electron microscope in connection with studies on virus-infected plants. Immature sieve elements contained cytoplasm rich in organelles and other components: endoplasmic reticulum, dictyosomes and associated smooth and coated vesicles, mitochondria, plastids, ribosomes, microtubules, microfilaments, vacuoles, and nuclei that were sometimes lobed. Tubular P-protein (phloem protein) and one to three granular P-protein bodies also were present in the cytoplasm. Coated vesicles may be involved in formation of the granular P-protein body and in some aspect of cell wall development, for in the latter case, they were often seen united with the plasmalemma. The association of coated vesicles with the P-protein body is discussed with reference to proposed concepts of the origin and function of these vesicles.     

Involvement of smooth and coated vesicles in the function of the contractile vacuole complex of some cryptophycean flagellates

The contractile vacuole complex of cryptophycean flagellates comprises the contractile vacuole, a pore and a vesicular spongiome. A minority of spongiome vesicles bear a 15-nm coat on the cytoplasmic surface of the membrane. The coat superficially resembles a clathrin coat. The majority of vesicles are smooth surfaced. Both types of vesicles are found at the same time. Smooth vesicles can be seen in profile suggesting vesicle-vesicle and vesicle-vacuole fusion. It is suggested that smooth vesicles are involved in the segregation of fluid from the cytoplasm and in filling the vacuole. Coated elements exist only as independent vesicles and as coated pits in the contractile vacuole membrane. There is no evidence of fusion of coated vesicles. It is suggested that coated vesicles function to retrieve specific membrane components from the contractile vacuole.     

Cotton fibre differentiation: Occurrence and distribution of coated and smooth vesicles during primary and secondary wall formation

Summary Coated vesicles occur in differentiating cotton fibres during primary and secondary wall formation. The coated vesicles are often associated with the plasmalemma, or with membranes at the secreting face of dictyosomes, corresponding positionally to GERL. During secondary wall formation the number of dictyosome-associated coated vesicles seems to be smaller than during primary wall formation. When sections are stained for periodateoxidizable polysaccharides (Thiéry reaction) the membrane of plasmalemma-associated coated vesicles is intensely stained. The membrane of dictyosome-associated coated vesicles is only weakly stained. On the basis of the present evidence it is not possible to clearly decide, whether the staining in plasmalemma-associated coated vesicles is due to obliquely cut membrane or to vesicle contents. The vesicle coat material is not stained. Possible functions of coated vesicles in differentiating cotton fibres are discussed.Vesicles with contents positively stained with the Thiéry reaction are observed only during primary wall formation. The membrane of these vesicles is smooth and seems to bud from the same cisternae, probably GERL, as do the coated vesicles. During secondary wall formation no vesicles containing periodate-oxidizable polysaccharides could be detected, even under conditions that result in a strong, specific reaction in the cellulosic secondary wall. In some instances polysaccharidic material, resembling secondary wall material, has been seen to adhere to the outside of the plasmalemma. These results are consistent with the hypothesis that, in higher plants, at least part of primary wall material may already be synthesized in dictyosome vesicles, whereas cellulose biosynthesis occurs at the cell surface.     

Developmental and comparative ultrastructure of glandular hairs in the two Urticaceae. I. Urtica dioica

Secretion produced by glandular hairs is deposited mainly in the periplasmic space of the head cells. It stains intensely for both proteins and polysaccharides. The ultrastructure of meristematic, differentiating, mature and senescent head cells as well as the stalk and basal cells has been described in comparison to that in other cell types of the leaf. The specific features of the head cells are the proliferation of the granular endoplasmic reticulum as well as the multiplication of the dictyosomes and mitochondria during transition to the secretion stage. However, the frequency of dictyosomes varies among secreting hairs. The ER produces neither secretory nor transition vesicles and does not anastomose with the plasmalemma. In the absence of transition vesicles, the transport of secretory proteins and enzymes of polysaccharide synthesis from the ER to dictyosomes apparently includes the cytosolic step. Dictyosomes, though not appearing hypersecretory, produce two types of smooth secretory vesicles generated by the trans Golgi reticulum. The vectorial transfer of prosecretion and membranes across the dictyosome stack proceeds via the transport (shuttle) vesicles. It is, therefore, concluded that exocytosis of smooth secretory Golgi vesicles is the sole mechanism of release of both proteins and polysaccharides. Coated vesicles occasionally seen near the plasmalemma are likely to be involved in the endocytotic membrane retrieval. The secretion product disappears during senescence of the hairs and the secretory cells undergo vacuolation by means of local autophagy.     

Differences in patterns of cell death between ray parenchyma cells and ray tracheids in the conifers <Emphasis Type="Italic">Pinus densiflora</Emphasis> and <Emphasis Type="Italic">Pinus rigida</Emphasis>

Differences in patterns of cell death between ray parenchyma cells and ray tracheids in the conifers Pinus densiflora and Pinus rigida were clarified. Differentiation and cell death of ray tracheids occurred successively and both were related to the distance from the cambium. In this respect, they resembled those of longitudinal tracheids. Thus, the cell death of short-lived ray tracheids could be characterized as time-dependent programmed cell death. In contrast, ray parenchyma cells survived for several years or more, and no successive cell death occurred, even within a single radial line of cells in a ray. Thus, the features of death of the ray parenchyma cells were different from those of ray tracheids. Cell death occurred early in ray parenchyma cells that were in contact with ray tracheids. The initiation of secondary wall thickening occurred earlier in ray parenchyma cells that were in contact with ray tracheids in Pinus densiflora than in others. In addition, localized thickening of secondary walls occurred only in ray parenchyma cells that were in contact with ray tracheids in Pinus rigida. Moreover, no polyphenols were evident in such cells in either species. Therefore, ray parenchyma cells that were in contact with ray tracheids appeared not to play a role in the formation of heartwood extractives. Our observations indicate that short-lived ray tracheids might affect the pattern of differentiation and, thus, the functions of neighboring long-lived ray parenchyma cells in conifers.     

The Influence of Volatile Substances from Incubated Litter of Pinus radiata on Seed Germination

Vapour from incubated Pinus radiata D. Don litter caused a depressionin the germination of Lolium perenne L. seeds and responsesvarying from stimulation to depression in germination of Trifoliumrepens L. seeds. These effects could be attributed to ethyleneand carbon dioxide. Experiments using ethylene and carbon dioxidesupported this conclusion. Pinus radiata, litter, Lolium perenne, Trifolium repens, seed germination, ethylene, carbon dioxide     

Fine Structure of Parenchymatous and Differentiated Pinus radiata Callus

The fine structure of Pinus radiata D. Don callus before andafter differentiation into stem-like tissues has been examinedwith the electron microscope. In callus prior to differentiation(here called parenchymatous callus) the cells accumulate tanninsas they age and are quite distinct from the cells of differentiatedcallus. In the latter, cambium, phloem and xylem cells may beidentified by their general morphology and by their ultrastructuralfeatures. Differentiation into a true stem-like structure is,however, incomplete in that the tissues are not uniformly oriented,and parenchyma cells of the rays and phloem contain chloroplasts.The tracheids also show unusual differentiation in that borderedpits form over their entire surface and may be of two types.The reasons for these variations are discussed.     

Ultrastructure of Papillar Cells in Brassica campestris Revealed by Liquid Helium Rapid-Freezing and Substitution-Fixation Method

The ultrastructure of papillar cells of Brassica campestrison the day of anthesis was studied by the liquid helium rapid-freezingand a substitution-fixation method, abbreviated as the RFS method.Application of the RFS method to the analysis of papillar cellsenabled us to examine clear images of these cells which havenot been observed previously. The well-developed rough and smoothendoplasmic reticulum, numerous Golgi bodies and mitochondria,various small vesicles and clathrin-coated vesicles, were presentin the cells. The numbers of Golgi bodies, as well as the numbersof cisternae of each Golgi body, increased as compared to thatin the other cells of style. Lattice-like fenestrated and flattenedcisternae were seen adjacent to the narrowest trans cisternaof the Golgi body, which had a partially coated region at itsperiphery. Many coated vesicles were observed in the vicinityof this structure and the plasma membrane. Coated areas on theplasma membrane were also observed. The ultrastructure of papillarcells on the day of anthesis indicated that they are very activesecretory cells. By using an antibody against S₈-protein andsections prepared by the RFS method, we demonstrated the distributionof S₈-protein in the cell wall of papillar cells of homozygousplants of Brassica campestris S_gS₈. (Received June 26, 1990; Accepted September 29, 1990)     

FUNCTIONS OF COATED VESICLES DURING PROTEIN ABSORPTION IN THE RAT VAS DEFERENS

The role of coated vesicles during the absorption of horseradish peroxidase was investigated in the epithelium of the rat vas deferens by electron microscopy and cytochemistry. Peroxidase was introduced into the vas lumen in vivo. Tissue was excised at selected intervals, fixed in formaldehyde-glutaraldehyde, sectioned without freezing, incubated in Karnovsky's medium, postfixed in OsO₄, and processed for electron microscopy. Some controls and peroxidase-perfused specimens were incubated with TPP,¹ GP, and CMP. Attention was focused on the Golgi complex, apical multivesicular bodies, and two populations of coated vesicles; large (> 1000 A) ones concentrated in the apical cytoplasm and small (<750 A) ones found primarily in the Golgi region. 10 min after peroxidase injection, the tracer is found adhering to the surface plasmalemma, concentrated in bristle-coated invaginations, and within large coated vesicles. After 20–45 min, it is present in large smooth vesicles, apical multivesicular bodies, and dense bodies. Peroxidase is not seen in small coated vesicles at any interval. Counts of small coated vesicles reveal that during peroxidase absorption they first increase in number in the Golgi region and later, in the apical cytoplasm. In both control and peroxidase-perfused specimens incubated with TPP, reaction product is seen in several Golgi cisternae and in small coated vesicles in the Golgi region. With GP, reaction product is seen in one to two Golgi cisternae, multivesicular bodies, dense bodies, and small coated vesicles present in the Golgi region or near multivesicular bodies. The results demonstrate that (a) this epithelium functions in the absorption of protein from the duct lumen, (b) large coated vesicles serve as heterophagosomes to transport absorbed protein to lysosomes, and (c) some small coated vesicles serve as primary lysosomes to transport hydrolytic enzymes from the Golgi complex to multivesicular bodies.     

Characean charasome-complex and plasmalemma vesicle development

Summary We report on an unusual phenomenon which occurs in some characean algae as a normal plasma membrane activity and also in association with charasome formation. The phenomenon of formation of coated invaginations of the plasma membrane was observed in twoChara and 6Nitella species. These invaginations are coated on their cytoplasmic surface, are 50–60 nm in diameter and rarely exceed 60 nm in length. They are abundant in the young cells ofChara andNitella and also occur in mature cells, but at a lower frequency.N. translucent is an exception in that coated invaginations were few in the young cells and absent in mature cells. Coated vesicles (50–60 nm diameter) were closely associated with these invaginations. Our observations suggest the vesicles may be derived from the invaginations by endocytosis.A close relationship was noted between the development of charasomes (plasmalemma modifications) and coated invaginations. Numerous coated invaginations are seen along the membranes of young charasomes; these invaginations appear to be associated with growth of the charasomes. Coated vesicles were not associated with the coated invaginations of the charasome membrane. The tubular network of cytoplasm and wall space seen in the mature charasome may be formed by fusion of coated invaginations of the developing charasomes, leaving cytoplasmic strands between the fused portions. Coated invaginations were not present along charasomes of the mature cells.     

Endothelial plasmalemmal vesicles have a characteristic striped bipolar surface structure

Capillary endothelial cells have a large population of small (65-80 nm diameter in transmission electron microscopy) vesicles of which a large fraction is associated with the plasmalemma of the luminal and abluminal side. We studied the fine structure and distribution of these plasmalemmal vesicles by high resolution scanning electron microscopy in cultured endothelial cells obtained from bovine adrenal cortical capillaries. Cell monolayers were covered with polylysine-coated silicon chips, split in high potassium buffer, fixed in aldehyde mixtures, and then treated with OsO4 and thiocarbohydrazide. After critical point drying, the specimens were coated with a thin (less than 2 nm) continuous film of chromium. On the cytoplasmic aspect of the dorsal plasmalemmal fragments seen in such specimens, plasmalemmal vesicles appear as uniform vesicular protrusions approximately 70-90 nm in diameter, preferentially concentrated in distinct large fields in which they occur primarily as single units. Individual plasmalemmal vesicles exhibit a striped surface fine structure which consists of ridges approximately 10 nm in diameter, separated by furrows and oriented as meridians, often ending at two poles on opposite sides of the vesicles in a plane parallel to the plasmalemma. This striped surface structure is clearly distinct from the cage structure of coated pits found, at low surface density, on the same specimens. The cytoplasmic aspect of the plasmalemma proper is covered by a fibrillar infrastructure which does not extend over plasmalemmal vesicles but on which the latter appear to be anchored by fine filaments.     

Morphological changes induced by sodium bromide in murine neuroblastoma cells in vitro

Summary Sodium bromide was applied in vitro to mouse neuroblastoma cells of different ages for short and long periods (2h to 10 days). The changes observed light-and-electron microscopically were similar to those described earlier after GABA treatment. Coated vesicles proliferated and originated by pinching off from the Golgi complex and from the rough endoplasmic reticulum. Numerous coated vesicles were continuous with the plasma membrane, especially near zones in which electron-dense material aggregated at the inner aspect of the plasmalemma. Small invaginations, similar in ultrastructure to coated vesicles, were also formed. It is unclear whether the coated vesicles or the dense plasmalemma invaginations contribute to the undercoating by fusing with the adjacent electron-dense plasma membrane. There was a distinct increase in the number and area of specialized contacts (intermediate junctions and zonulae adhaerentes) between cells and their processes. A floccular or filamentous electron-dense substance varying in amount and appearance was occasionally seen between the contacting membranes. Varicosities of terminal swellings of cell processes contained vesicles of variable size, shape and density, and also profiles of the smooth endoplasmic reticulum. Under the influence of sodium bromide, similar to the effect of GABA, mitochondria appeared within the varicosities, and primitive contacts (intermediate junctions) were formed between the terminal swellings and potential postsynaptic elements, which were absent in controls.Additionally, dense-core vesicles proliferated and aggregated at the cell periphery. They were often arranged linearly below the plasma membranes of perikarya and processes, and surrounded by a highly electron-dense substance. The similarity of the present findings to those obtained after GABA treatment and their relation to synaptogenesis are discussed.     

A Comparison of the Seasonal Rates of Dry Matter Production of Three Coniferous Species with Contrasting Patterns of Growth

Seasonal rates of growth and dry-matter production were examinedin second-year seedlings of Larix leptolepis, Pinus contorta,and Pinus radiata grown in an unheated glasshouse. The deciduousLarix had a higher rate of production of dry matter than eitherof the two species of Pinus until the time of leaf fall, andthis was accompanied by a greater height and diameter increment.However, between the time of leaf fall in Larix and the endof the growing season, the species of Pinus increased in dryweight by more than 25 per cent, and in consequence Larix, becauseof its deciduous habit, lost much of the advantage of its fastgrowth-rate. Comparison of the two pine species showed thatP. radiata, while making nearly 3.5 times as much height incrementas P. contorta, had only a 45 per cent higher dry weight thanthat species at the end of the experiment. The dry-weight differenceswere due to differences in relative growth-rate (RGR). The RGR differences between the two pine species resulted fromdifferences in net assimilation rate (NAR) rather than differencesin the ratio of photosynthetic to non-photosynthetic tissue,and P. radiata gained most of its dry-weight advantage duringthe two months of October and November. It seems possible thatthe higher NAR of P. radiata at this time was a reflection ofthe difference in growth habit between the two pine species,and possible mechanisms by which growth may have affected NARin this experiment are briefly considered.     

Immunocytochemical localization of coated vesicle protein in rodent nervous system

Immunocytochemistry has been used to study the distribution of the major 180,000-mol wt protein of coated vesicles in rodent cerebellum. An antibody to the coat protein was prepared in rabbits and characterized by immunodiffusion and immunofixation of polyacrylamide gels. At the light microscope level the protein was primarily localized in punctate profiles surrounding Purkinje cells and within the cerebellar glomeruli. At the electron microscope level the punctate distribution was confined to presynaptic terminals of basket and Golgi II neurons as well as mossy fiber terminals of the glomeruli. This label was heaviest on the lattice coat of coated vesicles but, in addition, label was found within the presynaptic axoplasm and along the cytoplasmic surface of the plasmalemma. Coated vesicles in cell somata were labeled as well as the cytosol around groupings of these vesicles. These data suggest that there may be two forms (or more) of coated vesicle protein in neurons, a lattice form associated with coated vesicles and a soluble form associated with the cytoplasmic matrix.     

Intracellular Transport and Elimination of Resin from Epithelial Duct-cells of Pinus halepensis

The ultrastructure of the resin secreting cells of root ductsof young Pinus halepensis seedlings was studied. It is suggestedthat the endoplasmic reticulum (ER) in addition to taking partin resin synthesis also plays a role in transporting the resinfrom the plastids, mitochondria and nuclear envelope to theplasmalemma. By fusing with the plasmalemma the ER releasesthe resin to the outside of the protoplast. The resin producedin the ground cytoplasm and by the Golgi apparatus seems tobe eliminated by plasmalemma invaginations. Pinus halepensis, resin secretion, root ducts, endoplasmic reticulum     

Isolation and characterization of a Pinus radiata lignin biosynthesis-related O-methyltransferase promoter

A putative promoter fragment of a Pinus radiata gene encoding a multi-functional O-methyltransferase (AEOMT) was isolated from genomic DNA. Sequence analysis revealed a number of putative cis elements, including AC-rich motifs common in promoters of genes related to the phenylpropanoid pathway. The isolated promoter was fused to the GUS reporter gene and its expression profile analyzed in transgenic tobacco and in transient transformation experiments with P. radiata embryogenic and xylogenic tissue. The promoter conferred weak expression in embryogenic tissue but caused strong GUS activity in both ray parenchyma cells and developing tracheary elements of xylem strips. Histochemical analysis in transgenic tobacco plants revealed that the AEOMT promoter induced GUS expression in cell types associated with lignification, such as developing vessels, phloem and wood fibers and xylem parenchyma as well as in non-lignifying phloem parenchyma. The isolated promoter was activated by challenge of the tissue with a fungal pathogen. Our results also indicate that the control of lignin-related gene expression is conserved and can be compared in evolutionarily distant species such as tobacco and pine.     

在被小泡参与突触前后膜特化增厚的形态学研究

Our object was to characterize the morphological changes of coated vesicles and synaptic membranes during synaptogenesis. Neurons from spinal cords of fetal mice were established as isolated cells in primary culture. After a few days in vitro, the neurons extended their neurites and started their interaction. At timed intervals thereafter, cultures were fixed for electron microscopic observation. Coated vesicles were prominent in the neuronal cytoplasm at the time of synaptogenesis (about 7-10 days in vitro). Similar vesicles were seen in continuity with some cisternae in the Golgi regions and there was an increase in number during the synaptogenic period. Indeed it is not established whether the coated vesicles were exocytotic or pinocytotic in nature, but the cisternae which were in continuity with coated vesicles could be labelled by glucose-6-phosphatase (G6Pase) but not by thiamine pyrophosphatase (TPPase). Such vesicles were also seen in continuity with the neuronal plasmalemma near the closest contact site and contributed their undercoating to pre- and postsynaptic densities. The formation of bilateral membrane specialization was described as being structurally similar to synaptic active zones and appeared to be the first definitive sign of synapseformation. It has been suggested that the synaptic dense material may derive wholly or in part from the exocytic coated vesicles which apparently budding off from endoplasmic reticulum cisternae. This incorporation could provide the mechanism for confining specific characteristics of neuronal membrane to the synaptic region.     

Ultrastructural Changes Associated with Spore Formation in Sporangia and Sporangiola of Thamnidium elegans Link

Fully formed pre-cleavage sporangia and sporangiola of Thamnidiumelegans Link were bounded by a primary wall plus a thick, internalsecondary wall layer. In sporangia in late pre-cleavage, Golgi-likecisternae were associated with groups of cytoplasmic vesiclesof characteristic size and appearance which were not found insporangia containing large cleavage vesicles. In both sporangia and sporangiola, protoplast cleavage was effectedby enlargement of endogenous cleavage vesicles each containinga lining layer of variable appearance, mutual fusion of cleavagevesicle membranes and fusion of cleavage vesicle membranes withthe plasmalemma. Golgi-like cisternae and small vesicular profileswere present in sporangium protoplasts at all stages of cleavagevesicle enlargement. In sporangia, the columella zone was delimitedby cleavage vesicles and separated from the sporogenous zoneby a fibrillar wall. A similar wall, which sometimes protrudedto form a small columella, was formed in sporangiola. Recently delimited spore protoplasts were bounded by plasmalemmamembrane derived from cleavage vesicle bounding membrane andsporangium or sporangiolum plasmalemma and surrounded by aninvesting layer derived from cleavage vesicle lining material.The investing layer at first appeared single, but later twoelectron opaque profiles were discernible. The spore wall wasformed between the investing layer and the plasmalemma. Wallsof sporangia and sporangiola which contained fully formed sporesconsisted of the primary layers only.