Abstract
The alternative electron transfer pathway is considered to remove excessive reducing power and to induce NPQ. We showed that PSΙcyclic electron flow is essential for this process. To isolate mutants defective in other alternative pathways, we screened high-chlorophyll-fluorescence mutants in CO2-free and 5% O2 air. CE46-48 exhibited reduction in ΦPSΙΙ and NPQ in CO2-free air. This phenotype was remarkable during photosynthesis induction phase. In CE46-48, NDH activity was not affected. In CE46-48 pgr5 double mutant, NPQ induction was severely impaired, the phenotype which did not depend on O2 concentration. Although pgr5 crr2 double mutant was severely affected in photosynthesis, pgr5 CE46-48 double mutant can grow normally. These results suggest that CE46-48 is defective in an alternative electron transfer pathway, other than PSΙ cyclic electron flow. The pathway mainly functions during photosynthesis induction phase. We are analyzing CE46-48 focusing on water water cycle activity.
