Mung Bean Hypocotyl Homogalacturonan: Localization, Organization and Origin

Specific antibodies were used to localize both pectic structuresand pectinmethylesterases (PME) along the mung bean hypocotyl.Calcium ions were also detected and estimated in both young,plastic and mature, stiffened cell walls. Highly methylesterifiedpectins were present in all cell walls but decreased from thehypocotyl hook downwards. Expanded cell walls were characterizedby a high content of calcium ions and acidic pectins, althoughthe latter's cross-reactivity to JIM 5 antibodies was partlylost. Co-localization of acidic homogalacturonan and calciumions suggests the presence of egg-box structures that mightparticipate in the cell wall stiffening process which developsalong the hypocotyl. Acidic polymers could originate from theactivity of the pectinmethylesterases present in precise wallareas but direct export of acidic polygalacturonan through Golgivesicles was also observed. Copyright 1999 Annals of BotanyCompany Cell walls, immunolocalization, hypocotyl, mung bean, pectin organization, Vigna radiata.     

Calcium levels increase in the lily stylar transmitting tract after pollination

Pollen tube growth in vitro requires calcium for most species but the in vivo source or reservoir of this calcium is not known. Using methods to localize calcium in situ, we confirm that low levels of calcium are detected in the transmitting tract extracellular matrix (ECM) in unpollinated lily styles. Pollination in lily induces an increase in the detectable levels of calcium in the transmitting tract ECM binding to the stylar cell and pollen tube walls. This calcium is detected in the cytoplasm and vesicles near the pollen tube tip.An erratum to this article can be found at     

Lysis of Staphylococcus aureus Cell Walls by a Soluble Staphylococcal Enzyme

Enzyme preparations of Staphylococcus aureus were examined for their ability to solubilize (32)P-labeled cell walls of the parent organism. Enzymatic activity was observed in the growth medium, in soluble fractions, and associated with native cell walls. Enzyme associated with isolated cell walls could be inactivated with formaldehyde without reducing the susceptibility of the walls to the action of added enzyme. When cells are frozen and thawed, 50 to 75% of the intracellular enzyme is released along with 2% of the intracellular protein. This freeze-thaw extracted enzyme has little, if any, activity on intact S. aureus cells. It appears that the enzyme resides near the cell wall and acts on the cell-wall inner surface.     

Cortical development in roots of the aquatic plant Pontederia cordata (Pontederiaceae)

Adventitious roots of marsh-grown Pontederia cordata were examined to determine cortical development and structure. The innermost layer of the ground meristem forms the endodermis and aerenchymatous cortex. The outermost layer of the early ground meristem undergoes a precise pattern of oblique and periclinal cell divisions to produce a single or double layer of prohypodermis with an anchor cell for each radial file of aerenchyma cells. At maturity, endodermal cell walls are modified only by narrow Casparian bands. The central regions of the ground meristem become proaerenchyma and exhibit asymmetric cell division and expansion. They produce an aerenchymatous zone with barrel-shaped large cells and irregularly shaped small cells traversing the aerenchyma horizontally along radii; some crystalliferous cells with raphides are present in the aerenchyma. The walls of the hypodermis are modified early by polyphenols. The outermost layer of the hypodermis later matures into an exodermis with Casparian bands that are impermeable to berberine, an apoplastic tracer dye. The nonexodermal layer(s) of the hypodermis has suberin-modified walls. Radial files of aerenchyma are usually connected by narrow protuberances near their midpoints, the aerenchyma lacunae having been produced by expansion of cells along walls lining intercellular spaces. We are terming this type of aerenchyma development, which is neither schizogenous nor lysigenous, "differential expansion."     

Cellular and subcellular localization of calcium in gravistimulated oat coleoptiles and its possible significance in the establishment of tropic curvature

Light—and electron-microscopic studies of the distribution of calcium in gravitropically responding oat (Avena sativa L. cv. “Garry”) coleoptiles are described. A modification of the antimonate precipitation procedure was used to localize tissue calcium in situ. An accumulation of Ca in the upper halves of horizontal, gravistimulated coleoptiles is seen within 10 min of stimulus onset. A pronounced redistribution of Ca to the upper side occurs within 30 min; although the localization of this cation is not uniform along the organ axis and in the apical region, Ca appears to accumulate along the lower side. The observed asymmetric distribution of Ca in these tissues precedes large-scale visible bending by 20–30 min, but is temporally well-correlated with differential growth responses in the coleoptile, as measured by more sensitive quantitative techniques. Gravitropic curvature is well developed by 3 h and is accompanied by further redistribution of Ca to tissues along the upper coleoptile half, centered around the bend. Ultrastructural localization studies indicate that Ca asymmetry results primarily from changes in the distribution of Ca within the apoplastic compartment. Large amounts of Ca accumulate at the cuticle in epidermal cell walls and in the walls of the underlying parenchyma cells at the upper side of the organ in the region of maximal bending. The differential growth response resulting in the establishment of gravitropic curvature may largely be the consequence of antagonistic effects of Ca on auxin-mediated cell wall loosening and elongation growth processes at the upper side of the organ.     

Centripetal Disposition of Bundle Sheath Chloroplasts During the Leaf Development of Eleusine coracana

Distribution of chloroplasts in bundle sheath cells was examinedby light and electron microscopy during the leaf developmentof finger millet (Eleusine coracana Gaertn.), an NAD malic enzymetype C₄ plant with centripetal arrangement of bundle sheathchloroplasts. Young chloroplasts are almost evenly distributedalong the cell walls in bundle sheath cells of folded immatureleaves. In elongating leaves and above the elongation zone thebundle sheath chloroplasts tend to lie along the radial wallsand the walls adjacent to the vascular bundle. They furthermigrate near to the vascular bundle and finally establish acentripetal arrangement. Mitochondria, microbodies and nucleusmigrate along with the chloroplasts. Etioplasts and other organellesare centripetally located in the bundle sheath cells of etiolatedseedlings grown in the dark. Bundle sheath chloroplast, C₄ plant, chloroplast, chloroplast orientation, Eleusine coracana, finger millet     

毛竹茎细胞壁半纤维素多糖的免疫细胞化学定位研究

本文以毛竹(Phyllostachys pubescens)为材料,采用免疫细胞化学标记方法对两种细胞壁半纤维素多糖成分,即木聚糖(Xylan)和(1-3)(1-4)-β-葡聚糖［(1-3)(1-4)-β-glucan］在毛竹茎中的分布进行了观察。结果表明,应用免疫细胞化学方法可以准确、有效地观察这两种半纤维素多糖成分在细胞壁中的分布;木聚糖分布在已木质化的组织细胞的细胞壁中,与细胞壁木质化有密切关系;(1-3)(1-4)-β-葡聚糖在幼竹茎基本组织中分布于短薄壁细胞细胞壁中及长薄壁细胞胞间层,而在老龄竹茎基本组织中,仅分布于短薄壁细胞细胞壁中,而长薄壁细胞细胞壁却无此成分,反映出长、短薄壁细胞细胞壁组成上的差异。     

侵染细胞质膜附近小泡的来源及其作用

箭舌豌豆根瘤幼龄侵染细胞的壁和质膜比较光滑,成熟侵染细胞与此不同,不仅细胞壁厚薄均,有较多的胞间连丝,而且质膜常常内陷形成各种突起,然后离质膜形成小泡。这些位于质膜附近的小泡体积较小,多呈圆形,既可单独存在,也可多个聚在一起。在向细胞中央移动中,有的小泡靠近细胞质膜,甚至与细菌周期融合,有的小泡不民附近的小液泡融合变为较大液泡,并常用降解程度不同的细菌位于其中,在衰老侵染细胞中,细胞壁附近有小泡,     

The exchange factor Cdc24 is required for cell fusion during yeast mating

During Saccharomyces cerevisiae mating, chemotropic growth and cell fusion are critical for zygote formation. Cdc24p, the guanine nucleotide exchange factor for the Cdc42 G protein, is necessary for oriented growth along a pheromone gradient during mating. To understand the functions of this critical Cdc42p activator, we identified additional cdc24 mating mutants. Two mating-specific mutants, the cdc24-m5 and cdc24-m6 mutants, each were isolated with a mutated residue in the conserved catalytic domain. The cdc24-m6 mutant responds normally to pheromone and orients its growth towards a mating partner yet accumulates prezygotes during mating. cdc24-m6 prezygotes have two apposed intact cell walls and do not correctly localize proteins required for cell fusion, despite normal exocytosis. Our results indicate that the exchange factor Cdc24p is necessary for maintaining or restricting specific proteins required for cell fusion to the cell contact region during mating.     

Immunogold localization of xyloglucan and rhamnogalacturonan I in the cell walls of suspension-cultured sycamore cells

Plant cell walls serve several functions: they impart rigidity to the plant, provide a physical and chemical barrier between the cell and its environment, and regulate the size and shape of each cell. Chemical studies have provided information on the biochemical composition of the plant cell walls as well as detailed knowledge of individual cell wall molecules. In contrast, very little is known about the distribution of specific cell wall components around individual cells and throughout tissues. To address this problem, we have produced polyclonal antibodies against two cell wall matrix components; rhamnogalacturonan I (RG-I), a pectic polysaccharide, and xyloglucan (XG), a hemicellulose. By using the antibiodies as specific markers we have been able to localize these polymers on thin sections of suspension-cultured sycamore cells (Acer pseudoplatanus). Our results reveal that each molecule has a unique distribution. XG is localized throughout the entire wall and middle lamella. RG-I is restricted to the middle lamella and is especially evident in the junctions between cells. These observations indicate that plant cell walls may have more distinct chemical (and functional?) domains than previously envisaged.     

Evidence for the attachment of Hsp150/Pir2 to the cell wall of Saccharomyces cerevisiae through disulfide bridges

Here we present evidence that Hsp150/Pir2, a member of the Pir family of cell wall proteins, can be extracted from the purified cell walls of Saccharomyces cerevisiae by treatment with beta-mercaptoethanol, demonstrating that at least part of this protein is attached to the cell wall through disulfide bridges. We also present evidence that Pir4, another member of this family, is partly secreted to the growth medium. Finally we propose a hypothesis to explain the relationship between the differently localized forms of particular members of the Pir family of cell wall proteins.     

Mice recognize the center of an enclosure

In recent years, it has been shown that animals can localize the geometric center of an area by reference to the shape of the environment. We trained a group of mice (experimental group) to search for a pellet hidden under sand in the center of a square-shaped dry maze. Three weeks later, they were tested in a triangular enclosure half the size of the training area and a circular enclosure double the size of the training area to see transfer to these enclosures. We compared their searching behavior with that of subjects that had received no training. The results show that the experimental group searched the geometric center of each enclosure in both transfer tests, while the untrained control group walked along the walls. This indicates that the experimental group localized the center not by reference to the absolute distance from the corners but by equal distances from all walls (geometric center).     

SOME ULTRASTRUCTURAL OBSERVATIONS ON ENDODERMAL CELL DEVELOPMENT IN ZEA MAYS ROOTS

The fine structure of primary, secondary, and tertiary stages of Zea endodermal cell development was investigated. The casparian strip formed in situ in the anticlinal walls and remained at a fixed point relative to the endodermis-pericycle boundary. The only protoplasmic structure that had a constant spatial association with the developing strip was the plasmalemma. Plasmodesmata appeared to be more numerous on the tangential walls than on radial walls; only rarely were they located in the casparian strip. The suberized lamella developed on inner and outer tangential walls before it appeared on the radial walls. No cytoplasmic organelles were found to have any particular spatial association with this layer. The suberized lamella was about 0.04 μm thick except near plasmodesmata and along the adaxial margin of the casparian strip, where it was thicker. Occasionally it failed to form along the abaxial margin of the strip. The adherent affinity between plasmalemma and casparian strip was lost after the strip was covered by suberized lamella. The secondary wall became asymmetrically thickened by differential deposition of successive lamellae. A thin layer of secondary wall material extended across the floor of each pit. Pit cavities often contained mitochondria, and plasmodesmata were restricted to the pits. The plasmodesmata were constricted where they entered the thin layer of secondary wall material and where they penetrated the suberized lamella. The various stages of cell development tended to be asynchronous. No passage cells were observed. Endodermal cell development in Zea closely resembles that described for barley.     

Ultrastructural Localization of a Bean Glycine-Rich Protein in Unlignified Primary Walls of Protoxylem Cells

A polyclonal antibody was used to localize a glycine-rich cell wall protein (GRP 1.8) in French bean hypocotyls with the indirect immunogold method. GRP 1.8 could be localized mainly in the unlignified primary cell walls of the oldest protoxylem elements and also in cell corners of both proto- and metaxylem elements. In addition, GRP 1.8 was detected in phloem using tissue printing. The labeled primary walls of dead protoxylem cells showed a characteristically dispersed ultrastructure, resulting from the action of hydrolases during the final steps of cell maturation and from mechanical stress due to hypocotyl growth. Primary walls of living protoxylem and adjacent parenchyma cells were only weakly labeled. This was true also for the secondary walls of proto- and metaxylem cells, which in addition showed high background labeling. Inhibition of lignification with a specific and potent inhibitor of phenylalanine ammonia-lyase did not lead to enhanced labeling of secondary walls, showing that lignin does not mask the presence of GRP 1.8 in these walls. Dictyosomes of living proto- and metaxylem cells were not labeled, but dictyosomes of xylem parenchyma cells without secondary walls, adjacent to strongly labeled protoxylem elements, were clearly labeled. These observations suggest that GRP 1.8 is not produced by xylem vessels but by xylem parenchyma cells that export the protein to the wall of protoxylem vessels.     

Irregular growth forms and cell wall modifications,polygalacturonase detection,and endocell formation in <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">radicis-lycopersici</Emphasis> infecting tomato plants,as studied ultrastructurally and cytochemically

Pathogen cells of Fusarium oxysporum f.sp. radicis-lycopersici infecting container-grown tomato plants were characterized ultrastructurally, using gold-complexed probes, chitinase and wheat germ agglutinin to localize chitin, and polyclonal antibodies to a polygalacturonase to localize this enzyme. It was isolated and purified from the pathogen growing in culture. Many fungal cells were of irregular forms (microhyphal, frondose) with modified, thin or imperceptible lucent wall layers, in which were often included components seemingly of host origin. Gold particles of the polygalacturonase probe were concentrated on portions of penetration hyphae and in areas of associated altered host wall. Fine filamentous-like structures, often linked to fungal cells, reached into extracellular matter and into host walls. Examination of 0.2–0.25 μm-thick sections at 120 kV, and tilted at various angles, indicated that fungal cells frequently had a pronounced wavy contour. Labelling of thin walls for chitin was mostly nil, particularly in contact with host walls, as of also thicker walls in similar situations, or it was then associated with the outside opaque layer. Cells of diverse dimensions with thin or thicker walls and with altered or normal content, contained endocells. Walls of the encodcells and of the enclosing cells often labelled differently for chitin with both probes. Endocells mostly did not originate from proliferation of a living into a dead cell but often ensuing as an apparent fragmentation of the cell content or following its retraction. The bearing of these observations on the host-pathogen relationship, particularly concerning the role of thin-walled hyphae and irregular forms, is discussed.     

Effect of Rust Infection on Cell Walls of Barley and Wheat; Immunocytochemistry Using Anti-Barley Thionin as a Probe

Polyclonal antiserum prepared against barley cell wall thionin was used to localize and quantitate immunoreactive material on the cellular level in healthy and rust-infected leaves of barley and wheat. Three types of sites were used for the immunocytochemical analysis: as control sites, mesophyll cell walls were selected in uninoculated leaves, and in leaves that were inoculated with rust but where the sites were not in contact with the pathogen: these were compared with mesophyll cell walls that were in contact with intercellular rust hyphae in inoculated leaves.
Similar amounts of cell wall thionin were detected in all 3 barley cultivars before inoculation. At sites where intercellular hyphae of Puccinia hordei had made contact with mesophyll cell walls, less thionin was found in the compatible host cv. Larker, but in incompatible hosts (cvs. Gold and Bolivia) the thionin concentration did not differ from that of the controls.
Two cultivars of wheat were studied with respect to immunoreactive material in their mesophyll cell walls, the universal rust suscept cv. Little Club and the highly rust-resistant cv. Khapli. Before inoculation, leaves of cv. Khapli contained about twice the amount of immunoreactive material in mesophyll cell walls than those of cv. Little Club. This relation was unchanged in walls that had made contact with P. graminis tritici , but in non-contacted walls of infected cv. Little Club leavest, he concentration of this material had risen to levels typical for those of cv. Khapli. Tests for immunoreactive material with pre-embedding cytochemistry yielded negative results, indicating that it is not exposed on the surface of mesophyll walls in barley and wheat.     

Structural cell-wall proteins in protoxylem development: evidence for a repair process mediated by a glycine-rich protein

Polyclonal antibodies were used to localize structural cell-wall proteins in differentiating protoxylem elements in etiolated bean and soybean hypocotyls at the light- and electron-microscopic level. A proline-rich protein was localized in the lignified secondary walls, but not in the primary walls of protoxylem elements, which remain unlignified, as shown with lignin-specific antibodies. Secretion of the proline-rich protein was observed during lignification in different cell types. A glycine-rich protein (GRP1.8) was specifically localized in the modified primary walls of mature protoxylem elements and in cell corners between xylem elements and xylem parenchyma cells. The protein was secreted by Golgi bodies both in protoxylem cells after the lignification of their secondary walls and in the surrounding xylem parenchyma cells. The modified primary walls of protoxylem elements were visualized under the light microscope as filaments or sheets staining distinctly with the protein stain Coomassie blue. Electron micrographs of these walls show that they are composed of an amorphous material of moderate electron-density and of polysaccharide microfibrils. These materials form a three-dimensional network, interconnecting the ring- or spiral-shaped secondary wall thickenings of protoxylem elements and xylem parenchyma cells. The results demonstrate that the modified primary walls of protoxylem cells are not simply breakdown products due to partial hydrolysis and passive elongation, as believed until now. Extensive repair processes produce cell walls with unique staining properties. It is concluded that these walls are unusually rich in protein and therefore have special chemical and physical properties.     

Cytochemical localization of calcium in cap cells of primary roots of Zea mays L

The distribution of calcium (Ca) in caps of vertically- and horizontally-oriented roots of Zea mays was monitored to determine its possible role in root graviresponsiveness. A modification of the antimonate precipitation procedure was used to localize Ca in situ. In vertically-oriented roots, the presumed graviperceptive (i.e., columella) cells were characterized by minimal and symmetric staining of the plasmalemma and mitochondria. No precipitate was present in plasmodesmata or cell walls. Within 5 min after horizontal reorientation, staining was associated with the portion of the cell wall adjacent to the distal end of the cell. This asymmetric staining persisted throughout the onset of gravicurvature. No staining of lateral cell walls of columella cells was observed at any stage of gravicurvature, suggesting that a lateral flow of Ca through the columella tissue of horizontally-oriented roots does not occur. The outermost peripheral cells of roots oriented horizontally and vertically secrete Ca through plasmodesmata-like structures in their cell walls. These results are discussed relative to proposed roles of root-cap Ca in root gravicurvature.     

Formation of intercellular gas space in the diaphragm during the development of aerenchyma in the leaf petiole of Sagittaria trifolia

The development of aerenchyma in the petiole of Sagittaria trifolia L. was studied by means of light-microscopy, scanning electron microscope, transmission electron microscope and immunofluorescence, focusing on the formation of intercellular spaces in diaphragms and its relationship with the organization of cortical microtubule arrays. A complex and organized honeycomb-like schizogenous aerenchyma formed by cylinders and vascular diaphragms was observed in the petiole of S. trifolia at different developmental stages. Cell division was the primary factor contributing to the increased volume of air spaces at early stages, while cell enlargement became the primary factor at later stages. The cortical microtubules localize at the sites where intercellular spaces and the secondary cell walls will be formed or deposited during the formation of intercellular spaces by the separation of diaphragm cells. Cortical microtubules were observed at the boundary of diaphragm cells and the fringes of intercellular spaces at later developmental stages where cell expansion occurs rapidly. These observations support the hypothesis that reorganization of cortical microtubule arrays might be related to the formation of air spaces in diaphragms and are involved in the deposition of secondary cell walls.     

Chromosomal localization of the gene for the human trifunctional enzyme, methylenetetrahydrofolate dehydrogenase-methenyltetrahydrofolate cyclohydrolase-formyltetrahydrofolate synthetase.

A trifunctional protein in man, 5,10-methylenetetrahydrofolate dehydrogenase-5,10-methenyltetrahydrofolate cyclohydrolase-10-formyltetrahydrofolate synthetase, catalyzes three consecutive steps in the interconversion of tetrahydrofolate derivatives; these derivatives supply one-carbon units for intermediary metabolism. Somatic cell hybridization and in situ hybridization were used to localize the functional gene coding for this protein--to human chromosome 14q24, near the c-fos and TGF-beta 3 loci. A second hybridizing sequence, possibly a pseudogene, was identified near the centromere of the X chromosome, at Xp11.