Abstract
Photosynthetic electron transport consists of linear electron transport called Z scheme and cyclic electron transport around PSI. In higher plants, cyclic flow consists of redundant pathways mediated by FQR and NDH. We identified Arabidopsis mutant pgr5 affected in the FQR activity using chlorophyll fluorescence imaging.pgr5 cannot induce thermal dissipation of the excessive absorbed light energy from PSII antennae. We also identified a mutant crr2 affected in the NDH activity. crr2 is defective in the maturation step of chloroplast ndhB gene. Photosynthetic electron transport is more mildly affected in crr2than in pgr5. We created a double mutant pgr5 crr2, in which cyclic electron transport activity is completely impaired. In the mutant photosynthetic electron flow is severely affected even at low light intensity. We conclude that cyclic electron flow is essential for ATP synthesis in photosynthesis, as well as to induce thermal dissipation.
