Figure 10.

Model of PGDH3’s role in providing an additional stromal electron sink for photosynthesis. A, In WT chloroplasts, PGDH3 facilitates the transfer of electrons from the CBBC intermediate, 3-PGA, to NADH. As a byproduct serine is produced. Electrons can be further transferred to malate by NAD-dependent MDH for export into the cytosol. B, In pgdh3 mutants, 3-PGA accumulates and less plastid NADH gets produced as an electron sink. Consequently, the CBBC cycle slows down, the NADP(H) pool becomes over reduced, and PSI becomes increasingly acceptor side limited. OAA, oxaloacetate. PSII/I, photosystem II/I. Cyt b₆f, cytochrome b₆f complex. PC, plastocyanin. FD, ferredoxin.