Remediation of Chromium Toxicity Through Exogenous Salicylic Acid in Rice (Oryza sativa L.)

Abstract

This work investigates whether and how salicylic acid (SA) alleviates chromium (Cr) toxicity in rice. Addition of SA under Cr stress markedly increased growth parameters, total protein content, and membrane stability but reduced the concentration and translocation of Cr in shoots but not in roots, suggesting that SA does have critical roles in Cr detoxification associated with Cr sequestration in roots. Further, Fe along with the expression of two Fe transporters (OsIRT1, OsNRAMP1) showed no significant changes in roots due to SA supplementation under Cr stress, indicating that regulation of Fe uptake is not involved in Cr reduction in rice plants through SA. At molecular level, OsPCS1 (phytochelatin synthase) and OsMT1 (metallothionein) and OsHMA3 (P-type ATPase 3) transcripts significantly upregulated following SA supplementation under Cr stress, suggesting that these chelating agents may bind to Cr leading to elevated Cr retention in roots. Furthermore, increased CAT, POD, SOD, and GR leading to decreased H2O2 along with elevated metabolites (cysteine, methionine, glutathione, proline, ascorbic acid) in roots implies active involvement of ROS scavenging and plays partial role in SA-mediated alleviation of Cr toxicity in rice plants. These findings will be useful for bioremediation of Cr toxicity in rice and other crops.