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Updated: Sep 20, 2026

Reactivation of Demembranated Cell Models in Chlamydomonas reinhardtii
Published on: May 6, 2022
An anaplerotic role for mitochondrial carbonic anhydrase in Chlamydomonas reinhardtii
Mario Giordano1, Alessandra Norici, Magnus Forssen
1Dipartimento di Scienze del Mare, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy. giordano@unian.it
Abstract:
Previous studies of the mitochondrial carbonic anhydrase (mtCA) of Chlamydomonas reinhardtii showed that expression of the two genes encoding this enzyme activity required photosynthetically active radiation and a low CO(2) concentration. These studies suggested that the mtCA was involved in the inorganic carbon-concentrating mechanism. We have now shown that the expression of the mtCA at low CO(2) concentrations decreases when the external NH(4)(+) concentration decreases, to the point of being undetectable when NH(4)(+) supply restricts the rate of photoautotrophic growth. The expression of mtCA can also be induced at supra-atmospheric partial pressure of CO(2) by increasing the NH(4)(+) concentration in the growth medium. Conditions that favor mtCA expression usually also stimulate anaplerosis. We therefore propose that the mtCA is involved in supplying HCO(3)(-) for anaplerotic assimilation catalyzed by phosphoenolpyruvate carboxylase, which provides C skeletons for N assimilation under some circumstances.
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