Nitric Oxide Could Allay Arsenic Phytotoxicity in Tomato (Solanum lycopersicum L.) by Modulating Photosynthetic Pigments, Phytochelatin Metabolism, Molecular Redox Status and Arsenic Sequestration

Background: Plants do not always have the genetic capacity to tolerate high quantities of (As) which does not only arrest the plant growth, but commit potential health risks by dietary bioaccumulation. However, the interplay between the tomato plants and As-NO driven molecular cell dynamics are obscure. Hence, seedlings were treated with As (10 mg/L) alone or in combination with 100 µM sodium nitroprusside (SNP, NO donor) and 200 µM 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO, NO scavenger). Results: SNP immobilized the As in the roots and reduced the shoot translocation by up-regulating the transcriptional expression of the PCS , GSH1 , MT2 and ABC1 . SNP further restored the growth retardation by modulating the chlorophyll and proline metabolism, increasing NO accumulation and stomatal conductance along with a clear crosstalk between the activity of antioxidants as well as glyoxalase I and II leading endogenous H 2 O 2 and MG decrease. Conclusion: Higher PCs and glutathione accumulation helped to protect photosynthetic apparatus, however, cPTIO reversed the protective effects of SNP, authenticating the role of NO in the As toxicity alleviation.