Abstract
Photosynthetic organisms produce phosphoglycolate by photorespiration (by the oxygenase activity of rubisco) under air. The compound is a strong inhibitor of photosynthesis, and phosphoglycolate phosphatase (PGPase) deficient mutants cannot grow under air, even in Chlamydomonas that has CO2-concentrating mechanism (CCM) to suppress photorespiration. The activity of Chlamydomonas PGPase (PGP1) increases shortly after transfer to low CO2, following the increase in the mRNA level, similar to CCM enzymes, although the mechanism of Pgp1 expression is not clear. In order to help define the mechanism, as Pgp1 is likely to play an important role in the regulation of both photorespiration and CCM, we determined and compared the DNA sequences of Pgp1 gene and the 5'-upstream region in both wild-type 2137 and pgp1-1 mutant N142, and also compared the Pgp1 upstream sequence with those of photorespiratory and CCM enzymes. Possible isozymes of PGPase are also discussed based on their gene sequences.
