A Specific Protective Mechanism Against Chloroplast Photo‐Reactive Oxygen Species in Phosphate‐Starved Rice Plants

Abstract

AbstractPhosphorus (Pi) starvation prevents a good match between light energy absorption and photosynthetic carbon metabolism, generating photo‐reactive oxygen species (photo‐ROS) in chloroplasts. Plants have evolved to withstand photo‐oxidative stress, but the key regulatory mechanism underlying it remains unclear. In rice (Oryza sativa), DEEP GREEN PANICLE1 (DGP1) is robustly up‐regulated in response to Pi deficiency. DGP1 decreases the DNA‐binding capacities of the transcriptional activators GLK1/2 on the photosynthetic genes involved in chlorophyll biosynthesis, light harvesting, and electron transport. This Pi‐starvation‐induced mechanism dampens both electron transport rates through photosystem I and II (ETRI and ETRII) and thus mitigates the electron‐excessive stress in mesophyll cells. Meanwhile, DGP1 hijacks glycolytic enzymes GAPC1/2/3, redirecting glucose metabolism toward the pentose phosphate pathway with superfluous NADPH production. Phenotypically, light irradiation induces O2− production in Pi‐starved WT leaves but is observably accelerated in dgp1 mutant and impaired in GAPCsRNAi and glk1glk2 lines. Interestingly, overexpressed DGP1 in rice caused hyposensitivity to ROS‐inducers (catechin and methyl viologen), but the dgp1 mutant shows a similar inhibitory phenotype with the WT seedlings. Overall, the DGP1 gene serves as a specific antagonizer against photo‐ROS in Pi‐starved rice plants, which coordinates light‐absorbing and anti‐oxidative systems by orchestrating transcriptional and metabolic regulations, respectively.