Unravelling OsPHT2;1 function in Chloroplast Phosphorus Homeostasis and Photosynthetic Efficiency under Low Phosphorus Stress in Rice

Abstract Phosphorus (P) deficiency is a critical factor limiting crop productivity, primarily due to its detrimental effects on photosynthesis and dry matter accumulation. In this study, we investigate the role of the rice gene OsPHT2;1 in mediating chloroplast P homeostasis and its subsequent impact on photosynthetic function under low P conditions. Stomatal conductance is typically positively correlated with net photosynthetic rates; however, P deficiency disrupts this relationship, leading to reduced stomatal opening and diminished photosynthetic efficiency. Our findings show that the OsPHT2;1 mutation leads to a decrease in the plastoquinone (PQ) pool size. This change is associated with altered stomatal conductance and modifications in electron transport dynamics, including an increase in the transmembrane proton gradient and a shift from linear to cyclic electron transport. This disruption significantly impairs the transport of photosynthetic products, particularly triose phosphates, essential for sucrose synthesis in the cytoplasm. Additionally, the reduced PQ pool influences the expression of key genes involved in photostability, highlighting the interplay between P homeostasis and photosynthetic regulation. By elucidating the mechanisms underlying OsPHT2;1's role in chloroplast function, our research underscores its significance in optimizing rice adaptation to low P environments, thereby enhancing crop resilience and productivity.