Selenate mitigates arsenite toxicity in rice (Oryza sativa L.) by reducing arsenic uptake and ameliorates amino acid content and thiol metabolism

• Selenium supplementation reduced arsenic accumulation in rice.
• Essential amino acids were enhanced in As+Se treatment.
• As+Se treatment increased non-protein thiols and phytochelatins in rice.
• Stress related nonessential amino acids were positively correlated to As accumulation.

Arsenic (As) is a toxic element with the potential to cause health effects in humans. Besides rice is a source of both amino acids (AAs) and mineral nutrients, it is undesired source of As for billions of people consuming rice as the staple food. Selenium (Se) is an essential metalloid, which can regulate As toxicity by strengthening antioxidant potential. The present study was designed to investigate AsIII stress mitigating effect of SeVI in rice. The level of As, thiolic ligands and AAs was analyzed in rice seedlings after exposure to AsIII/SeVI alone and AsIII+SeVI treatments. Selenate supplementation (AsIII 25 μM+SeVI 25 μM) decreased total As accumulation in both root and shoot (179 & 144%) as compared to AsIII alone treatment. The AsIII+SeVI treatment also induced the levels of non-protein thiols (NPTs), glutathione (GSH) and phytochelatins (PCs) as compared to AsIII alone treatment and also modulated the activity of enzymes of thiol metabolism. The content of amino acids (AAs) was significantly altered with SeVI supplementation. Importantly, essential amino acids (EAAs) were enhanced in AsIII+SeVI treatment as compared to AsIII alone treatment. In contrast, stress related non-essential amino acids (NEAAs) like GABA, Glu, Gly, Pro and Cys showed enhanced levels in AsIII alone treatment. In conclusion, rice supplemented with SeVI tolerated As toxicity with reduced As accumulation and increased the nutrition quality by increasing EAAs.