Abstract
Arsenic (As) contamination in rice leads to yield decline and causes carcinogenic risk to human health. Although the role of nitric oxide (NO) in reducing As toxicity is known, NO-mediated genetic modulation in the plant during arsenic toxicity has not yet been established. We analyzed the key components of NO metabolism and the correlations between NO interaction and arsenic stress using rice as a relevant model plant. Illumina sequencing was used to investigate the NO-mediated genome-wide temporal transcriptomic modulation in rice root upon AsIII exposure during 12 days (d) of the growth period. Sodium nitroprusside (SNP) was used as NO donor. SNP supplementation resulted in marked decrease in ROS, cell death and As accumulation during AsIII stress. NO was found to modulate metal transporters particularly NIP, NRAMP, ABC and iron transporters, stress related genes such as CytP450, GSTs, GRXs, TFs, amino acid, hormone(s), signaling and secondary metabolism genes involved in As detoxification. We detected NO-mediated change in jasmonic acid (JA) content during AsIII stress. The study infers that NO reduces AsIII toxicity through modulating regulatory networks involved in As detoxification and JA biosynthesis.
Highlights
Arsenic (As) contamination in water has been an issue of grave concern in South East Asian countries, causing health risks for an estimated 65 million people[1]
The present study examined molecular signaling of nitric oxide (NO) and adaptive responses of the plant to cope with arsenic stress conditions
No significant difference in roots length was found in all treatment in comparison to the control on 4th day (Fig. 1C)
Summary
Our results indicated that NO-mediated reduction in ROS content during AsIII stress (Fig. 2B), and that NO modulated expression behavior of stress related genes such as GSTs, GRXs, HSPs and PODs might be a strategy to cope with As toxicity by maintaining glutathione biochemistry and redox potential in the cell[26]. The Os02g0291400 (OsCBL8) and Os10g0411500 (OsSTA242) genes were more down-regulated in the AsIII + SNP treatment than AsIII treatment on 12th day Plant activates their signaling cascade for tolerance and adaptation vis-a-vis heavy metal toxicity, and studies indicated that a complex crosstalk occurs between the different signaling pathways[51,52,53,54]. This work highlighted NO-mediated modulation of genes, especially TFs, CytP450, GSTs, GRXs, HSPs, amino acids and hormone(s) metabolism, indicating a potential role of NO in reduced ROS level, enhanced cell viability and root growth during AsIII stress. Reduction in jasmonic acid content following SNP supplementation further strengthens the JA-mediated protective role of NO during AsIII stress
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