Sulfur supplementation enhances nitric oxide efficacy in reversal of chromium-inhibited Calvin cycle enzymes, photosynthetic activity, and carbohydrate metabolism in wheat

Abstract

The present study demonstrated that exogenously-sourced nitric oxide (as SNP, sodium nitroprusside; NO donor) and sulfur (S) protected photosynthesis against chromium (Cr) stress in wheat (Triticumaestivum L. cv. HD 2851). Plants grown with 100 µM Cr exhibited higher reactive oxygen species (ROS) production, resulting in photosynthetic damage. The individual application of 50 µM NO increased carbohydrate metabolism as well as photosynthetic parameters, antioxidant system with higher transcriptional gene levels that encode the key enzymes for the Calvin cycle under Cr stress. These effects were more prominent when NO was applied with 1.0 mM SO42−. An increase in the reduced glutathione (GSH) content obtained with NO was further enhanced by S and resulted in higher protection against Cr stress. The protective effect of NO with S against Cr toxicity on photosynthesis was reversed when buthionine sulfoximine (BSO; GSH biosynthetic inhibitor) was used. Application of BSO reversed the impact of NO plus S on photosynthesis under Cr stress, verifying that the ameliorating effect of NO was through S-assimilation and via GSH production. Thus, the availability of S to NO application can help reduce Cr toxicity and protect photosynthetic activity and expression of the Calvin cycle enzymes in leaves through the GSH involvement.

Effects of Domestic Sewage on the Photosynthesis and Chromium Migration of Coix lacryma-jobi L. in Chromium-Contaminated Constructed Wetlands

“…Glutathione (GSH) generated in plants is a low-molecular-weight antioxidant that can enhance important functions, such as reducing intracellular peroxides, scavenging free radicals, and chelating heavy metals. Fatma et al [20] found that the toxicity of Cr to the photosynthesis of wheat can be mitigated by the exogenous addition of S and NO, essentially by increasing the level of GSH, and thus mitigating the toxic effects of Cr on photosynthesis and the activity of Calvin cycle enzymes in leaves. Whether the effect of Cr (VI) on the photosynthesis of Coix lacryma-jobi L. is mitigated by regulating the GSH content in leaves under the condition of domestic sewage added needs to be studied in depth.…”