Osβ-glu coordinates with nitric oxide signaling to modulate root cell wall pectin phosphorus remobilization under phosphorus deficiency in rice (Oryza sativa L.).

Low phosphorus (P) availability restricts rice growth, and remobilization of internal P pools is important for acclimation to P-limited conditions. Although the root cell wall may act as an internal P reservoir, the genes regulating cell wall P remobilization remain unclear. Here, we examined Osβ-glu, a rice gene associated with cadmium accumulation, in response to P deficiency. Two independent osβ-glu mutants were analysed under P-sufficient and P-deficient conditions. Under P-sufficient conditions, the mutants showed no obvious growth defects. Under P deficiency, however, they displayed altered root-shoot growth allocation, reduced shoot growth, lower soluble and total P levels, and decreased xylem sap P concentration. In contrast, the mutants retained more P in root cell walls and pectin fractions, suggesting impaired remobilization of cell wall-associated P. The mutants also showed lower root PME activity and a higher degree of pectin methylesterification under P deficiency, indicating altered pectin biochemical remodeling. P deficiency induced nitric oxide (NO) accumulation in rice roots, but this induction was weaker in osβ-glu mutants, whereas nitrite content was unchanged. Application of the NO donor sodium nitroprusside reduced genotypic differences in soluble P, cell wall P, and pectin-associated P. These results indicate that Osβ-glu promotes root cell wall P remobilization under P deficiency through an NO-associated pathway.