OsZTL1 is involved in phosphate deficiency tolerance and cell wall phosphorus reutilization in rice

Limited phosphorus (P) supply severely limits rice growth and productivity, and improving P utilization is important for sustainable crop production. However, the regulatory processes involved in mobilization of P from cell-wall pools remain incompletely understood. Here, we investigated the potential function of OsZTL1 in rice adaptation to P limitation.

We compared ZH11 with two osztl1 knockout mutants under P-sufficient and P-deficient conditions and examined P status, root cell-wall fractions, pectin-related traits, root NO-related fluorescence, and gene expression. The NO donor sodium nitroprusside (SNP) was used to probe NO-related responses.

OsZTL1 transcript abundance progressively increased upon P deprivation in both roots and shoots. Disruption of OsZTL1 improved plant performance during P limitation and was accompanied by increased soluble and total P levels in mutant lines compared with ZH11. During P limitation, osztl1 mutants retained less P in the root cell wall and water-extractable pectin-enriched fraction, together with higher pectin uronic acid content and PME activity and a lower degree of pectin methylesterification. These changes coincided with greater root NO-related fluorescence. SNP treatment largely eliminated genotype differences in soluble P, cell-wall P, pectin-associated P, and pectin uronic acid content. Several phosphate starvation-responsive genes showed altered expression in the mutants, while OsPHR1 and OsPHR2 displayed comparable expression among genotypes.

Our findings suggest a function for OsZTL1 in rice acclimation to P limitation and an association with NO-related changes in root cell-wall P reutilization. The SNP results do not establish that NO acts directly downstream of OsZTL1; genetic evidence is needed to test this relationship.