Effects of microtubule agents on the spatial and electrical properties of the plasma membrane inChara corallina

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.

Effect of a Single Excitation Stimulus on Photosynthetic Activity and Light-dependent pH Banding in Chara Cells

Using pH microelectrodes and a Microscopy PAM (pulse-amplitude modulated) chlorophyll fluorometer, it is shown that a propagation of an action potential in Chara corallina leads to transient suppression of spatially periodic pH profiles along the illuminated cell. The suppression was manifested as a large pH decrease in the alkaline zones and a slight pH increase in the acid zones. The propagating action potential diminished the maximum yield of chlorophyll fluorescence (F(m)') in the alkaline cell regions, as well as the quantum yield of photosystem II photochemistry, without affecting F(m)' in the acid cell regions. The results indicate an interference of membrane excitation in the mechanisms responsible for pH banding patterns in Characean algae. Apparently, the electrical excitation of the plasma membrane in the alkaline cell regions initiates a pathway that can modulate membrane events at the thylakoid membrane.

Spatial organization of transport domains and subdomain formation in the plasma membrane of Chara corallina

Pattern formation mechanisms in developing organisms determine cellular differentiation and function. However, the components that interact during the manifestation of a spatial pattern are in general unknown. Characean algae represent a model system to study pattern formation. These algae develop alternating acid and alkaline transport domains that influence the pattern of growth. In the present study, it will be demonstrated that a diffusion mechanism is implicated in acid and alkaline domain formation and this growth pattern. Experiments on the characean growth pattern were performed that resulted in pronounced, however, unpredictable modifications in the original pattern. A major component involved in this pattern-forming mechanism emerged from the nonlinear kinetics of the H(+)-ATPase that is located in the plasma membrane of these algae. Based on these kinetics, a mathematical model was developed and numerically analyzed. As a result, the contribution of a diffusional component to the characean acid/alkaline pattern appeared most likely.