Rice 2C protein phosphatase, OsNY1, and magnesium oxide positively regulate arsenic tolerance by root cells...

The protein phosphatase type 2 C (PP2C) plays an irreplaceable role in growth regulation and responses to various stresses. OsNY1 is a protein phosphatase in polyploid rice. We found that ny1 knockout mutants exhibit increased sensitivity to arsenic (As). Compared with wild-type (H1) plants, ny1 growth under As stress was significantly inhibited, with lower SOD, POD, and CAT activities. Moreover, root lignin contents, total soluble sugar, and GSH contents were significantly lower than in H1. In contrast, MDA, H₂O_2, and As contents were significantly higher than in H1 (As contents in the above-ground sections and roots of ny1 were 29.69% and 23.51% greater than that of H1, respectively). SEM and WE-CLSM results indicate that under As stress, ny1 exhibits greater disruption of root cells, with growth inhibition observed in both the elongation zone and meristematic region of the root system. Transcriptome results indicate that under As stress, ny1 exhibits significant changes in heavy metal ion response, heavy metal ion detoxification, protein phosphorylation, protein serine/threonine kinase activity, heatshock proteins, ATP binding, and DNA replication and repair-related DEGs. Additionally, nano-sized magnesium oxide particles (MgO-NPs) can reduce As uptake while increasing magnesium absorption, thereby enhancing antioxidant enzyme activity and alleviating As toxicity in rice. This study demonstrated that the type 2 C protein phosphatase OsNY1 positively regulates As tolerance in polyploid rice, and that MgO-NPs can alleviate As toxicity in both wild-type and mutant lines.