Immobilisation of organelles and actin bundles in the cortical cytoplasm of the alga Chara corallina Klein ex. Wild

Intercellular permeation and cyclosis-mediated transport of a fluorescent probe in Characeae

Intercellular communication and transport is the essential prerequisite for the function of multicellular organisms. Simple diffusion as a transport mechanism is often inefficient in sustaining the effective exchange of metabolites, and other active transport mechanisms become involved. In this paper, we use the giant cells of characean algae as a model system to explore the role of advection and diffusion in intercellular transport. Using fluorescent dye as a tracer, we study the kinetics of the permeation of the fluorophore through the plasmodesmata complex in the node of tandem cells and its further distribution across the cell. To explore the role of cytoplasmic streaming and the nodal cell complex in the transport mechanism, we modulate the cytoplasmic streaming using action potential to separate the diffusive permeation from the advective contribution. The results imply that the plasmodesmal transport of fluorescent probe through the central and peripheral cells of the nodal complex is differentially regulated by a physiological signal, the action potential. The passage of the probe through the central cells of the nodal complex ceases transiently after elicitation of the action potential in the internodal cell, whereas the passage through the peripheral cells of the node was retained. A diffusion-advection model is developed to describe the transport kinetics and extract the permeability of the node-internode cell wall from experimental data.

Characean internodal cells as a model system for the study of cell organization

Giant internodal cells of characean green algae have been widely used for studying cellular physiology. This review emphasizes their significance for understanding cytoarchitecture and cytoplasmic reorganization. The cytoarchitecture of internodal cells undergoes pronounced, cytoskeleton-dependent changes during development and in response to environmental cues. Under bright light, internodes develop alternating bands of acid and alkaline pH at their surface that correlate with the differential size and abundance of cortical organelles and, in the genus Chara, with the size and distribution of convoluted plasma membrane domains known as charasomes. Wounding induces responses ranging from chloroplast detachment to deposition of wound walls. These properties and the possibility for mechanical manipulation make the internodal cell ideal for exploring plasma membrane domains, organelle interactions, vesicle trafficking, and local cell wall deposition. The significance of this model system will further increase with the application of molecular biological methods in combination with metabolomics and proteomics.

Effects of dichlorobenzonitrile on the formation of cell wall appositions (plugs) in internodal cells of Chara corallina Klein ex. Willd, em. R.D.W. and Nitella flexilis (L.) Ag

The effect of dichlorobenzonitrile (DCB), an inhibitor of cellulose synthesis, on the formation of local cell wall appositions (plugs) was studied in internodal cells of the characeae Chara corallina Klein ex. Wild, em. R.D.W. and Nitella Flexilis (L.) Ag. DCB Significantly reduces size and number of fibrillar, membrane-free plugs induced by 6 × 10^-2 M Cacl₂ . Formation of these plugs leads to an increase in the cellulose content which is abolished in the presence of DCB. Plugs formed during treatment with DCB have a less regular structure, but membrane recycling appears not to be disturbed. Cells are able to recover from DCB treatment and normal plugs are then formed. DCB has only minor effects on size, number and structure of amorphous, membrane-containing plugs induced by chlortetracycline (CTC) although their callose content is significantly enhanced. The data confirm that fibrillar plugs consist mainly of crystalline cellulose and that this polysaccharide does not play any role in the formation of amorphous plugs.