Primary leaf-type ferredoxin 1 participates in photosynthetic electron transport and carbon assimilation in rice

Ferredoxins (Fds) play a crucial role in photosynthesis by regulating the distribution of electrons to downstream enzymes. MultipleFdgenes have been annotated in theOryza sativa L. (rice) genome; however, their specific functions are not well understood. Here, we report the functional characterization of riceFd1. Sequence alignment, phylogenetic analysis of seven rice Fd proteins and quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis showed that rice Fd1 is a primary leaf-type Fd. Electron transfer assays involving NADP(+)and cytochrome cindicated that Fd1 can donate electrons from photosystem I (PSI) to ferredoxin-NADP(+)reductase. Loss-of-functionfd1mutants showed chlorosis and seedling lethality at the three-leaf stage. The deficiency of Fd1 impaired photosynthetic electron transport, which affected carbon assimilation. Exogenous glucose treatment partially restored the mutant phenotype, suggesting that Fd1 plays an important role in photosynthetic electron transport in rice. In addition, the transcript levels of Fd-dependent genes were affected infd1mutants, and the trend was similar to that observed infdc2plants. Together, these results suggest that OsFd1 is the primary Fd in photosynthetic electron transport and carbon assimilation in rice.