Sodium nitroprusside ameliorates lead toxicity in rice (Oryza sativa L.) by modulating the antioxidant scavenging system, nitrogen metabolism, lead sequestration mechanism, and proline metabolism

As a toxic anthropogenic pollutant, lead (Pb) can be harmful to both plants and animals. Here, the effects of the application of nitric oxide (NO) donor, sodium nitroprusside (SNP, 0, 50, and 100 mu M), on the morphological, biochemical, and molecular responses of rice plants under Pb (0, 150, and 300 mu M) toxicity in hydroponic conditions were investigated. Pb stress decreased biomass, photosynthetic pigments, Fv/Fm value, and nitrogen (N) and increased the accumulation of hydrogen peroxide (H2O2), methylglyoxal (MG), malondialdehyde (MDA), and electrolyte leakage (EL) in rice seedlings. However, by improving the metabolism of chlorophyll and proline, SNP increased the content of chlorophyll and proline, restored the performance of the photosynthetic apparatus, and stimulated the growth of Pb-stressed rice seedlings. SNP by reducing the expression of HMA2 and increasing the expression of HMA3 and HMA4 caused the immobilization of Pb in the roots and reduced its transfer to the leaves. Adding SNP increased the activity of antioxidant enzymes and glyoxalase cycle and decreased H2O2, MG, MDA, and EL in the leaves of Pb-stressed rice seedlings. By upregulating the expression of genes GSH1, PCS, and ABCC1, SNP increased the accumulation of GSH and PCs in the roots and leaves and increased the plant's tolerance to Pb stress. By modulating the activity of enzymes involved in N metabolism, SNP increased the concentration of N and nitrate and decreased the concentration of ammonium in the leaves of Pb-stressed seedlings. Our study provides evidence that NO may become a promising tool for increasing the tolerance of rice plants to Pb toxicity.

Automated summary

This study investigated the effects of nitric oxide (NO) on rice plants under lead (Pb) toxicity. The results showed that NO improved chlorophyll and proline metabolism, leading to enhanced growth and photosynthetic performance of rice plants under Pb stress. Additionally, NO reduced the accumulation of oxidative stress markers and promoted the immobilization of Pb in the roots. These findings suggest that NO could be a promising tool for enhancing the tolerance of rice plants to Pb toxicity.