Nitrate inhibits the remobilization of cell wall phosphorus under phosphorus-starvation conditions in rice (Oryza sativa)

NO3 (-) not only inhibited the reutilization of cell wall P via decreasing root cell wall pectin content and PME activity, but also hampered the P translocation from root to shoot. The rice cultivars 'Kasalath' (Kas) and 'Nipponbare' (Nip) were used to demonstrate that the nitrogen source NO3 (-) inhibits internal phosphorus (P) reutilization in rice under P-absence conditions. Analysis using Kas showed that the expression of - P-induced marker genes OsIPS1/2 and OsSPX1/2/3/5 are significantly higher under 1 mM NO3- - P (1N - P) treatment than 0 mM NO3- - P (0N - P) treatment. The absence of NO3 (-) from the nutrient solution significantly increased cell wall P release by increasing pectin synthesis and increasing the activity of pectin methylesterase (PME), and also significantly improved the translocation of soluble P from the root to the shoot by increasing xylem sap P content under P-absence conditions. The rice seedlings grown in 0 mM NO3 (-) accumulated significantly higher nitric oxide (NO) in the roots than those grown in 1 mM NO3 (-). Exogenously applying the NO donor sodium nitroprusside (SNP) revealed that NO is a major contributor to differential cell wall P remobilization in rice by mediating pectin synthesis and demethylation under different NO3 (-) concentrations (0 and 1 mM) under P-deprived conditions.