The class III peroxidase gene OsPrx24 is important for root Iron plaque formation and benefits phosphorus uptake in Rice plants under alternate wetting and drying irrigation

Abstract

Alternate wetting and drying irrigation (AWD) benefits root iron plaque (IP) formation and nutrient uptake, but the underlying mechanism is unclear. RNA-sequencing, histochemical staining, confocal laser microscopy, and transgenic techniques were used to evaluate the contributions of ionic-bonded cell-wall-located class III peroxidases (iPrxs) and hydrogen peroxide (H2O2) to IP formation in rice (Oryza sativa) under AWD. AWD significantly enhanced iPrx activity and expression of OsPrx24, a gene encoding iPrx, accompanied by elevated H2O2 accumulation and IP formation. Microscopic analysis indicated that OsPrx24 was mainly expressed in root epidermis, where H2O2 accumulation and IP precipitation also occurred. In an OsPrx24-overexpression line (OsPrx24-OX), the H2O2 concentration was 28.2% lower, and IP formation was 42.6% higher than in the wild type (WT). Treatment with both an iPrx inhibitor and an H2O2 scavenger reduced the IP content, but it was higher in OsPrx24-OX than in the WT under these treatment conditions. Phosphorus concentrations were higher and more IP was found in the roots of OsPrx24-OX than the WT. The results imply that OsPrx24 participates in IP formation by regulating iPrx activity and H2O2 concentration under AWD. The results enhance our understanding of IP formation and nutrient uptake in rice.