FNR1

FNR1, or ferredoxin-NADP+ reductase 1, is a gene that encodes a plastid-localized enzyme involved in the photosynthetic light reactions of plants. In Arabidopsis thaliana, FNR1 is one of two chloroplast-targeted FNR genes, alongside FNR2.

The encoded enzyme catalyzes the transfer of electrons from ferredoxin to NADP+, producing NADPH that fuels carbon fixation in the Calvin cycle and helps in antioxidative metabolism. FNR1 binds flavin adenine dinucleotide (FAD) as a cofactor and functions on the stromal side of the thylakoid membrane in the chloroplast.

Expression of FNR1 is highest in photosynthetic tissues and is influenced by light conditions. The FNR1 and FNR2 genes show partial functional redundancy, with overlapping expression patterns and compensation under certain conditions.

Genetic studies indicate that loss-of-function mutations in FNR1 alone often result in mild phenotypes due to redundancy with FNR2, whereas double mutants display reduced NADPH production, slower growth, and heightened sensitivity to light stress.

FNR1 is part of a conserved plant gene family involved in photosynthesis and redox balance, illustrating how gene duplication supports adaptation to varying light environments.