Takeshi Fujino

Changes in the Three Dimensional Architecture of the Cell Wall During Lignification of Xylem Cells in Eucalyptus tereticornis

The three dimensional architecture of the cell wall during differentiation of xylem cells in Eucalyptus terericornis was visualizes by rapid-freezing and deep-etching electron microscopy. A highly porous structure was demonstrated in cell corner, middle lamellar and primary walls of both cambium and enlarging xylem cells, but disappeared after lignification of the xylem cells. The porosity of the structure was abruptly diminished by the incrustation of lignin as well as dense deposition of cellulose microfibrils in differentiating xylem cells. This study is the first to detect rosettes, cellulose synthesising enzyme complexes, in the differentiating xylem cells of a woody plant, and provides the first account of the visualization of the three dimensional architecture of xylem cell walls before and after lignification.

Ingestion and decomposition of wood and cellulose by the protozoa in the hindgut of Coptotermes formosanus Shiraki (Isoptera : Rhinotermitidae) as evidenced by polarizing and transmission electron microscopy

Ingestion and decomposition of wood and cellulose by the three protozoa in the hindgut of Coptotermes formosanus Shiraki were investigated using polarizing microscopy and transmission electron microscopy (TEM). Most of wood and cellulose fragments were ingested by the two larger protozoa, Pseudotrichonympha grassii Koidzumi and Holomastigotoides hartmanni Koidzumi, but not by the smallest species, Spirotrichonympha leidyi Koidzumi. Little wood fragments were observed in the hindgut fluid. TEM observations of wood fragments in the body of P. grassii and H. hartmanni clearly indicated that wood polysaccharides such as cellulose were completely decomposed to water-soluble materials by the protozoan enzymes, and that lignin residues were released as a loose fibrous materials.

Ultrastructural Changes in the Compound Middle Lamella of Pinus thunbergii During Lignification and Lignin Removal

Summary The structure of the middle lamella in Pinus thunbergii has been studied by the rapid-freeze deep-etching (RFDE) technique in combination with transmission electron microscopy (TEM). The ultrastructure of the compound middle lamella was studied in the early phases of the development of woody tissue in the cambial and differentiating xylem, before the heavy incrustation with lignin had occurred. Lignified middle lamella in the xylem was studied both directly and after delignification. It was found that the structure of the unlignified middle lamella in the cambium/developing xylem consists of a fine irregular network probably containing pectin and hemicellulose. As a result of lignin incrustation, the middle lamella becomes increasingly dense and the surface structure of the fully lignified middle lamella appeared to be compact and partly covered with globular structures. After delignification of the lignified middle lamella a thin network with a different structure was revealed. This network probably mainly consists of hemicellulose. No microfibrils of the type that occurs in the primary and secondary walls were found in the middle lamella.

Cell Wall Dynamics in Tobacco BY-2 Cells

The plant cell wall is composed of several different classes of macromolecules, including polysaccharides, structural proteins and aromatic substances. These components are integrated into a kind of supermolecule by means of weak inter- and intra-molecular interactions, as well as by cross-linking with covalent bonds. Within this architecture are a wide variety of cell wall enzymes, most of which are involved in the construction, maintenance and restructuring of its own architecture. As a result of the actions of these enzymes, the cell wall undergoes drastic changes in its molecular architecture in such a way that allows controlled cell wall expansion and deformation, thereby playing crucial roles in plant growth and morphogenesis. In addition to the morphological roles, the plant cell wall plays a wide range of physiological functions, which include the defense system against pathogens, translocation of nutrients and transduction of chemical signals within plants.

Elimination of artifactual immunogold labeling from secondary walls of woody stem sections

Abstract. Preliminary in situ transmission electron microscopy immunogold localization of a 24-kDa dehydrin-like protein in red-osier dogwood (Cornus sericea L.) stem cross-sections was contaminated with extensive background labeling of secondary cell walls in both positive and negative control samples. Alterations in antibody dilution, buffer salt concentration and stringency of the washing solutions failed to eliminate background cell-wall labeling. A procedure was developed in which lyophilized cold-acclimated C. sericea xylem tissue was pulverized and boiled with sodium dodecyl sulfate (SDS)-protein extraction buffer to remove soluble proteins and to inactivate proteases. Wood powder, treated with SDS-protein extraction buffer, was used to pre-absorb chicken immune serum specific for a 24-kDa dehydrin-like protein prior to immunolocalization assays. Pre-incubation of primary antibodies did not compromise the recognition of the 24-kDa protein, and this technique effectively eliminated background cell-wall labeling.