THE MOLECULAR AND BIOCHEMICAL ANALYSES OF CO2-CONCENTRATING MECHANISMS IN CYANOBACTERIA AND MICROALGAE

The supply of dissolved inorganic carbon for photosynthesis in the aquatic environment is much more variable than that experienced by terrestrial plants. In response to this variability, cyanobacteria and many species of microalgae acclimate to rapid changes in the availability of dissolved inorganic carbon by the induction of high affinity/high capacity CO2-concentrating systems (CCMs). Biochemical and molecular analyses of the acclimation response have recently identified several components that are required for efficient operation of the CCMs and CO2 assimilation. This has been accomplished using in vivo labelling studies, and characterization of high inorganic carbon (C(i)) requiring cyanobacterial and algal mutants. The identification and regulation of expression of polypeptides synthesized in response to limiting C(i) concentrations, and the proposed role of the carboxysome and the pyrenoid in the functioning of the CCMs are examined.