Presence Of Cell Wall Research Articles

Membrane- and cell wall-associated heat shock proteins in two genotypes of barley seedlings

ABSTRACT The heat-shock (HS) response of two genotypes (cv. Onice, winter type, and cv. Georgie, spring type) of barley (Hordeum vulgare L.) was compared. Protein synthesis was markedly reduced by HS in roots and coleoptiles of both genotypes. The reduction in cv. Onice was higher than in cv. Georgie. The pattern of cytosolic, membrane and cell wall HSPs was analysed by SDS-PAGE in coleoptiles and roots of the two genotypes. Differences and similarities in coleoptiles and roots of the same genotype and between the two genotypes were observed. In roots of the genotype Onice, LMW and HMW HSPs isolated from the cytosol, membranes and cell walls were resolved into a diverse array of polypeptides by two-dimensional gel electrophoresis. Present results confirm the de novo synthesis of cytosolic and membrane HSPs, and demonstrate, for the first time, their presence in cell walls.

Lipid lateral mobility in the plasma membrane of whole plant cells.

Fluorescence photobleaching recovery was used to measure the apparent lateral diffusion coefficient and mobile fraction of a fluorescent lipid probe in the plasma membranes of whole plant cells, i.e., in the presence of cell walls. Interfering fluorescence from the cell wall was reduced by extensive washing and then subtracted from the recovery recordings. Mobility characteristics of plasma membrane lipids in whole cells were found to be very similar to those in protoplasts.

Intercellular movement of protoplasm in vivo in developing endosperm of wheat caryopses

Earlier work in our laboratory indicated that protoplasmic constituents can migrate from one cell to another in certain tissues of higher plants. Further investigations have been conducted using garlic bulbs and wheat nucellus for microscopic observation of intercellular protoplasmic movement in vivo. These gave preliminary indications of the dynamic characteristics of migrating nuclei and cytoplasm. The present paper gives recent results providing new evidence for intercellular protoplasmic movement that is neither hindered by the presence of cell wall nor the narrowness of channels of intercellular connection. By careful manipulation, intact endosperm sacs could be taken from developing caryopses (6–8 days after fertilization) without apparent injury to constituent cells. Shortly after the living specimen is mounted on the microscopic stage, asynchronous intercellular protoplasmic movement can be observed here and there. It can be seen that protoplasm extrudes in rapid but intermittent movements from one cell to the next by vigorous contraction. Although various cell constituents may move together, they can also be quite independent of each other. The moving units, though undergoing violent deformation, resume their normal shape and structure following intercellular migration. Evidently this kind of movement is a naturally occurring and active phenomenon closely related to the physiological state of the tissue. Electron microscopic studies reveal that a limited number of plasmodesmatal channels undergo modification and enlarge to 100–400 nm, through which the protoplasmic constituents pass.

Cell-free synthesis of mycolic acids in Mycobacterium aurum: radioactivity distribution in newly synthesized acids and presence of cell wall in the system

Distribution of radiolabelling in different parts of the newly synthesized mycolic acids, by a cell-free system from Mycobacterium aurum previously described, is examined, [1- 14C]acetate being the precursor. By oxidation cleavage of mycolic acids and examination of the fragments, it was shown that acetate was not uniformly incorporated into the molecule: the methyl terminal part was not labelled, while the central fragments — between unsaturations or between oxygenated functions (oxo or ester) and unsaturations — presented the major part of radioactivity, suggesting the elongation of a preformed compound that the cell-free extract was unable to synthesize. Moreover, the side-chain R2-CH 2-COOH was only weakly labelled compared to the central fragments. Since non-hydroxylated fatty acids were not synthesized by the system, it is suggested that de novo C 18 fatty acids may be elongated with C 2 units by the cell-free extract into C 22 fatty derivative, only a low level of labelling being recorded (two C 2 units for all the molecule). A scheme is proposed to summarize the main results. Identification of meso-DAP which is a characteristic amino-acid of the peptidoglycan in Actinomycetes and analysis of the profiles of total fatty esters, demonstrated that the cell-free extract is partly constituted by fragments of the cell wall as has already been noticed by examination of micrographs of the extract.

Relationship Between the Increased Sensitivity of Heat Injured Clostridium perfringens Spores to Surface Active Antibiotics and to Sodium Chloride and Sodium Nitrite

Spores of Clostridium perfringens NCTC 8798 became increasingly sensitive to inhibition by sodium chloride, sodium nitrite and a mixture of polymyxin and neomycin when heated at 70–100°C. That the increased sensitivity to each agent was caused by the same cellular damage was suggested by: (1) the temperature coefficients for induction of cellular damage leading to increased sensitivity to all three agents were the same; (2) in the absence of the agents, the spores regained resistance to all three at about the same time and in each case in the presence of cell wall‐, protein‐ and DNA‐synthesis inhibitors; (3) combinations of the agents were generally no more inhibitory to the heated spores than were the individual agents.

Concanavalin A affects polysaccharidic wall formation and mitotic activity in Polyphysa (Acetabularia) cliftonii protoplasts

Cell wall formation, terminating the differentiation of protoplasts from nucleate cap ray cytoplasm of Polyphysa (Acetabularia) cliftonii, is inhibited by concanavalin A (ConA), depending on its concentration. The effect is completely reversible by application of the hapten sugar αMM, but not by NAcGal. It is concluded that ConA binds to certain glycosylated surface components, thus preventing the growth of the wall-polysaccharide chains, predominantly cellulose, or their attachment to ‘priming’ components. Normally, cell wall formation and nuclear divisions are strictly correlated. ConA, however, dissociates cell wall formation from the mitotic events reversibly in that it suppresses wall formation and leaves mitosis unmolested. In general, therefore, ConA revealed no mitogenic effect in the plant system under investigation. In special, the ConA effect might be regarded as a strong stimulation of mitotic events in relation to the normally existing correlation between mitosis and the presence of cell wall.

Presence of Cell Walls Like those of Bacteria in Rickettsiae

Presence of Cell Walls Like those of Bacteria in Rickettsiae