Regulation of the CO2-concentrating mechanism in Chlorella vulgaris UAM 101 by glucose

In the green alga Chlorella vulgaris UAM 101, a CO2-concentrating mechanism is induced when the cells are growing under low CO2 conditions. We have investigated the effect of glucose on the induction of this mechanism. Cells adapted to low CO2 in the presence of glucose showed a reduced ability to transport and fix external inorganic carbon. This reduction was correlated with a decrease in internal carbonic anhydrase activity. 3-O-methyl-glucose, a nonmetabolizable analog of glucose, caused a more dramatic repression of these phenomena. Immunoblot analyses of total cell protein of Chlorella vulgaris UAM 101 against large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase and ribulose 1,5-bisphosphate-carboxylase/oxygenase activase polyclonal antibodies showed that the expression of these two polypeptides was affected by neither CO2 level, nor glucose or 3-O-methyl-glucose. Ultrastructure studies showed that the low CO2-induced development of the pyrenoid was also affected by glucose. Immunocytochemical data demonstrated that ribulose-1,5-bisphosphate carboxylase/oxygenase was exclusively located in the pyrenoid matrix. This localization and the density of labeling of the pyrenoid region were affected by neither CO2 level nor the presence of glucose.