Adaptation to different concentrations of CO₂ in a Chlamydomonas mutant with reduced rate of photorespiration: Photosynthetic response and cDNA macro array analysis

Abstract

The rate of photorespiration is only a half of wild type in both high CO₂-grown and air-adapted cells of the Chlalmydomonas mutant with reduced rate of photorespiration (RPR1). The photosynthetic affinity for CO₂ is apparently higher in high CO₂ cells of RPR1 than that of wild type, but is not so clear in low-CO₂-adapted cells. We expect that the reduced rate of photorespiration in RPR1 is a result of enhanced CCM function caused by lowered CO₂ sensitivity. In this report, to help define the mutation in RPR1, we compared photosynthetic adaptation to different concentrations of CO₂ and cDNA macro array analysis for 5% CO₂ and air-adapting cells of wild type and RPR1-N21. We found a biphasic photosynthetic response to the adapted CO₂ concentrations in both wild type and N21. The relationship to CCM, the mutant gene of N21, and the results of cDNA macro array analysis will be discussed.