Mitochondrial and peroxisomal NAD + uptake are important for improved photosynthesis and seed yield under elevated CO 2 concentrations.

As sessile organisms, plants must adapt their physiology and developmental processes to cope with challenging environmental circumstances, such as the ongoing elevation in atmospheric carbon dioxide (CO 2 ) levels. Nicotinamide adenine dinucleotide (NAD + ) is a cornerstone of plant metabolism and plays an essential role in redox homeostasis. Given that plants impaired in NAD metabolism and transport often display growth defects, low seed production and disturbed stomatal development/movement, we hypothesized that subcellular NAD distribution could be a candidate for plants to exploit the effects of CO 2 fertilization. We report that an efficient subcellular NAD + distribution is required for the fecundity-promoting effects of elevated CO 2 levels. Plants with reduced expression of either mitochondrial (NDT1 or NDT2) or peroxisomal (PXN) NAD + transporter genes grown under elevated CO 2 exhibited reduced total leaf area compared with the wild-type while PXN mutants also displayed reduced leaf number. NDT2 and PXN lines grown under elevated CO 2 conditions displayed reduced rosette dry weight and lower photosynthetic rates coupled with reduced stomatal conductance. Interestingly, high CO 2 doubled seed production and seed weight in the wild-type, whereas the mutants were less responsive to increases in CO 2 levels during reproduction, producing far fewer seeds than the wild-type under both CO 2 conditions. These data highlight the importance of mitochondrial and peroxisomal NAD + uptake mediated by distinct NAD transporter proteins to modulate photosynthesis and seed production under high CO 2 levels.