Abstract
Cyclic electron flow around PSΙ is essential to induce of NPQ by recycling electrons from reduced ferredoxin or NADPH to plastoquinone. PSΙ cyclic electron flow consists of two redundant pathways depending on FQR and NDH activities. Arabidopsis mutants lacking FQR activity, pgr5, and lacking NDH activity, crr mutants, were isolated and characterized. To screen mutants affected in alternative electron flow functioning with these pathways, we isolated mutants displaying the high chlorophyll fluorescence under CO2-free, 5%-O2 condition. In CE46-48 mutant, NPQ induction and ΦPSΙΙ were lowered than in the wild type under CO2-free, 5%-O2 condition. While NPQ induction was impaired during the induction phase of photosynthesis, it was rather normal during steady steate. CE46-48 may be defective in the alternative electron flow that are independent from FQR or NDH. We are investigating the impact on the activity of O2 reduction by PSΙ.
