Pyruvate, phosphate dikinase regulatory protein impacts light response of C4 photosynthesis in Setaria viridis

• DOI: 10.1093/plphys/kiac333
• Publication Date: 2022-07-25T14:51:45Z
• Authors: Kuenzang Om; Nico N Arias; Chaney C Jambor; Alexandra MacGregor; Ashley N Rezachek; Carlan Haugrud; Hans-Henning Kunz; Zhonghui Wang; Pu Huang; Quan Zhang; Josh Rosnow; Thomas P Brutnell; Asaph B Cousins; Chris J Chastain
• Keywords: C4 Photosynthesis

Abstract In C4 plants, the pyruvate (Pyr), phosphate dikinase regulatory protein (PDRP) regulates activity of pathway enzyme Pyr, (PPDK) in a light-/dark-dependent manner. The importance this action to function and overall photosynthesis is unknown. To resolve question, we assessed vivo PPDK phospho-regulation whole leaf photophysiology CRISPR–Cas9 PDRP knockout (KO) mutant NADP-ME grass green millet (Setaria viridis). was undetectable extracts from KO lines. Likewise, phosphorylated at PDRP-regulatory Thr residue immunologically extracts. rapid constitutively high lines, irrespective light or dark pretreatment leaves. Gas exchange analysis net CO2 assimilation revealed leaves had markedly slower induction kinetics when transition high-light low-light high-light. initial 30 min phase, an ∼15% lower rate versus wild-type (WT). Despite impaired kinetics, found growth vigor lines be visibly indistinguishable WT grown normal air under standard chamber conditions. However, plants fluctuating regime exhibited gradual multi-day decline Fv/Fm, indicative progressive photosystem II damage due absence PDRP. Collectively, our results demonstrate that one PDRP’s functions ensure optimal photosynthetic during dynamic changes incident light.