Osβ-glu coordinates with nitric oxide signaling to modulate root cell wall pectin phosphorus remobilization under...

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.