Elevated CO2 differentially mitigates chromium (VI) toxicity in two rice cultivars by modulating mineral homeostasis and improving redox status.

Chromium (Cr) contamination reduces crop productivity worldwide. On the other hand, the expected increase in the future CO 2 levels (eCO 2) would improve plant growth under diverse growth conditions. However, the synergetic effect of eCO 2 has not been investigated at both physiological and biochemical levels in Cr-contaminated soil. This study aims to analyze the mitigating effect of eCO 2 on Cr VI phytotoxicity in two rice cultivars (Giza 181 and Sakha 106). Plants are exposed to different Cr concentrations (0, 200 and 400 mg Cr/kg Soil) at ambient (aCO 2) and eCO 2 (410 and 620 ppm, respectively). Unlike the stress parameters (MDA, H2O2 and protein oxidation), growth and photosynthetic reactions significantly dropped with increasing Cr concentration. However, in eCO 2 conditions, plants were able to mitigate the Cr stress by inducing antioxidants as well as higher concentrations of phytochelatins to detoxify Cr. Notably, the expression levels of the genes involved in mineral nutrition i.e., OsNRAMP1 , OsRT1 , OsHMA3 , OsLCT1 and iron chelate reductase were upregulated in Cr-stressed Giza 181 plants grown under eCO 2. Mainly in Sakha 106, eCO 2 induced ascorbate-glutathione (ASC/GSH)-mediated antioxidative defense system. The present study brings the first ever comprehensive assessment of how future eCO 2 differentially mitigated Cr toxicity in rice. [Display omitted] • Cr exposure induces severe oxidative damage and dysregulates mineral homeostasis. • ECO 2 upregulates the expression of mineral transporter genes in Cr-stressed plants. • ECO 2 modulates the antioxidant defense and metal detoxification systems. • Cultivar-specific responses to the coexistence of Cr and eCO 2 will be noticed. [ABSTRACT FROM AUTHOR]