A Mutant of Chlamydomonas reinhardtii with Reduced Rate of Photorespiration

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Photorespiration rates under air-equilibrated conditions (0.04% CO_2 and 21% O_2) were measured in Chlamydomonas reinhardtii wild-type 2137, a phosphoglycolate-phosphatase-deficient (pgp1) mutant and a suppressor double mutant (7FR2N) derived from the pgp1 mutant. In both cells grown under 5% CO_2 and adapted air for 24 h in the suppressor double mutant, the maximal rate of photorespiration (phosphoglycolate synthesis) was only about half of that in either the wild type or the pgp1 mutant (18-7F) cells. In the progeny, the reduced rate of photorespiration was accompanied by increased photosynthetic affinity for inorganic carbon and the capacity for growth under air whether accompanied by the pgp1 background or not. Tetrad analyses suggested that these three characteristics all resulted from a nuclear single-gene mutation at a site unlinked to the pgp1 mutation. The decrease in photorespiration was, however, not due to an increase in the CO_2/O_2 relative specificity of ribulose-1, 5-bisphosphate carboxylase/oxygenase of 7FR2N or of any other suppressor double mutants tested. The relationship between the decrease in the rate of photorespiration and the CO_2-concentrating mechanism is discussed.
日本植物生理学会の論文