Regulation of the Synthesis of Ribulose‐1,5‐Bisphosphate Carboxylase and Its Subunits in the Flagellate Chlorogonium elongatum

Shifting of heterotrophically cultured cells of Chlorogonium elongatum to autotrophic culture conditions results in a more than tenfold increase in the level of the chloroplastic enzyme ribulose-1,5-bisphosphate carboxylase. This increase in enzyme amount is caused by an increased synthesis of the enzyme de novo under both growth conditions. The synthesis of the enzyme is mainly under the control of two factors. Light promotes the synthesis, while acetate, the carbon source of this organisms, has a strong inhibitory effect on this process. Since a mutant lacking chlorophyll shows a normal response to the change of culture conditions the chlorophylls can be ruled out as photoreceptors.