INFLUENCE OF PROTEIN-SYNTHESIS INHIBITORS ON THE EXTRACELLULAR CURRENT PATTERN AND ELECTROPHYSIOLOGICAL PROPERTIES OF INTERNODAL CELLS OF CHARA-CORALLINA

Internodal cells of Chara corallina exhibit a spatially controlled pattern of alternating acid and alkaline regions along their surface, corresponding to regions of outward and inward current density, respectively. Incubation of isolated cells in either 25-mu-g.mL-1 cycloheximide or 50-mu-M 2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide resulted in a 70-90% reduction in current density and a 50% decrease in the magnitude of the dark-induced membrane hyperpolarization. When cells were supplied with dissolved inorganic carbon, in the form of either CO2 or HCO3-, 25-mu-g.mL-1 cycloheximide caused a minimal and 30% reduction in photosynthetic O2 evolution, respectively. In vivo protein synthesis, measured by [H-3]-leucine incorporation, showed an 11% decrease in the presence of cycloheximide, while chloramphenicol caused a 91.5% inhibition. It is interesting to note that although exposure to chloramphenicol elicited only a slight decrease in current density, the dark-induced membrane hyperpolarization was inhibited by 50%. All treatments failed to perturb the regions on the cell surface, of zero current, giving stable band location, even though the current density was reduced. The effect of these protein synthesis inhibitors is discussed in terms of the cellular control mechanism involved in regulating the supply of inorganic carbon for photosynthesis.