Photosystem I cyclic electron flow via chloroplast NADH dehydrogenase-like complex performs a physiological role for photosynthesis at low light

Cyclic electron transport around photosystem I (PSI) was discovered more than a half-century ago and two pathways have been identified in angiosperms. Recently, substantial progress has been made in understanding the structure of the chloroplast NADH dehydrogenase-like (NDH) complex, which mediates a route of the cyclic electron transport pathways. However, the physiological significance of the chloroplast NDH complex has remained to be clarified. Most studies focused on the role of the NDH-dependent PSI cyclic electron transport in alleviation of oxidative damage. However, the NDH-deficient mutants in tobacco and Arabidopsis are rather resistant to various stress conditions. The present study proposes a significant physiological function of chloroplast NDH at low light intensity, at which oxidative stress is not substantial in rice. This work would be the first paper which documents the significant physiological function of chloroplast NDH at low light intensity.