Chapter

Photosynthesis

Volume 34 of the series Advances in Photosynthesis and Respiration pp 625-650

Date:

The Uptake of CO2 by Cyanobacteria and Microalgae

  • Hideya FukuzawaAffiliated withDivision of Integrated Life Science, Graduate School of Biostudies, Kyoto University
  • , Teruo OgawaAffiliated withInstitute of Plant Physiology and Ecology Email author 
  • , Aaron KaplanAffiliated withDepartment of Plant and Environmental Sciences, The Hebrew University of Jerusalem

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Summary

Cyanobacteria and eukaryotic algae possess a CO2-concentrating mechanism (CCM), which involves the transport of inorganic carbon (Ci) driven by light energy and the fixation of CO2 in the subcellular compartments (carboxysomes in cyanobacteria and pyrenoids in green algae) where most of the ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) is confined. Physiological and molecular analysis identified five Ci uptake-systems in cyanobacteria. Two of them are CO2-uptake systems driven by the thylakoid membrane-located NAD(P)H dehydrogenase (NDH-1) complexes. Three bicarbonate transporters, BCT1 (an ABC-type transporter composed of Cmp proteins), SbtA and BicA, are localized on the cytoplasmic membranes. One of the main features of the CCMs is a marked rise in the ability to take up Ci observed when high-CO2-grown cells are transferred to CO2-limiting conditions in the light. Many low-CO2 (LC)-inducible genes including those involved in Ci uptake have been identified in cyanobacteria and green algae. Chlamydomonas reinhardtii is a model eukaryotic alga and has been used extensively for the study of the CCM. Candidate genes responsible for Ci uptake in C. reinhardtii, and that encode proteins homologous to transporters in other organisms, were found among LC-inducible genes identified by DNA microarray analysis. These genes include LciA and LciB, whose transcripts are not accumulated in the pmp1 mutant defective in Ci-transport upon exposure to LC. The CCM1 (CIA5) is essential for the control of CCM induction and the expression of CO2-responsive genes through putative LC signal transduction pathways. We present recent studies on the mechanisms of CO2-sensing and of induction of gene expression by LC. Other microalgae such as coccolithophorids, diatoms and dinoflagellates also possess CCMs. We summarize the present state of the art on the CCMs of these major aquatic primary producers and other CCM-related topics such as cycling of Ci, CO2-mediated interspecies communication, stable carbon isotope fractionation and biotechnological implications.