Molecular Mechanism of Organic Pollutant-Induced Reduction of Carbon Fixation and Biomass Yield in Oryza sativa L.

Abstract

Photosynthetic carbon fixation is fundamental for plant growth and is a key process driving the global carbon cycle. This study explored the mechanism of disturbed carbon fixation in Oryza sativa L. by organic pollutants 2,3,4,5-tetrachlorobiphenyl (CB 61), 4′-hydroxy-2,3,4,5-tetrachlorobiphenyl (4′-OH-CB 61), 2,2′,4,4′-tetrabromo diphenyl ether (BDE 47), tricyclazole (TRI), and pyrene. The biomass of rice exposed to 4′-OH-CB 61, TRI, and BDE 47 was on average 80.63% of that of the control (p < 0.05), and the inhibition of net photosynthetic rate was 59.15% by 4′-OH-CB 61. Proteomics confirmed that 4′-OH-CB 61 significantly downregulated the enzymes in the photosynthetic carbon fixation pathway, which was attributed to the decrease in ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), the rate-limiting enzyme in the Calvin cycle. In detail, decreased Rubisco activity (6.96–33.44%) and downregulated OsRBCS2-5 encoding small Rubisco subunits (?6.80 < log₂FC < ?2.13) by 4′-OH-CB 61, TRI, and BDE 47 were in line with biomass yield reduction. Molecular docking and dynamic simulation suggested that the three pollutants potentially competed with CO₂ for binding to the active sites in Rubisco, leading to reduced CO₂ capture efficiency. These results revealed the molecular mechanism of organic pollution-induced rice yield reduction, contributing to improving the understanding of crop growth and carbon sequestration capacity of organics-contaminated soils globally.