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Plant Physiology 90:1195-1200 (1989) © 1989 American Society of Plant Biologists Adaptation of Chlamydomonas reinhardtii High-CO2-Requiring Mutants to Limiting CO21Department of Botany, Iowa State University, Ames, Iowa 50011
Photosynthetic characteristics of four high-CO2-requiring mutants of Chlamydomonas reinhardtii were compared to those of wild type before and after a 24-hour exposure to limiting CO2 concentrations. The four mutants represent two loci involved in the CO2-concentrating system of this unicellular alga. All mutants had a lower photosynthetic affinity for inorganic carbon than did the wild type when grown at an elevated CO2 concentration, indicating that the genetic lesion in each is expressed even at elevated CO2 concentrations. Wild type and all four mutants exhibited adaptive responses to limiting CO2 characteristic of the induction of the CO2-concentrating system, resulting in an increased affinity for inorganic carbon only in wild type. Although other components of the CO2-concentrating system were induced in these mutants, the defective component in each was sufficient to prevent any increase in the affinity for inorganic carbon. It was concluded that the genes corresponding to the ca-1 and pmp-1 loci exhibit at least partially constitutive expression and that all components of the CO2-concentrating system may be required to significantly affect the photosynthetic affinity for inorganic carbon.
2 Present address: Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki 305, Japan. 1 This work was supported by grant CRCR-1-1591 from the Competitive Research Grants Office of the U.S. Department of Agriculture. This article has been cited by other articles:
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