Arsenic (As) contamination of paddy rice in South and South-East Asia has raised much concern as rice is the subsidence diet for millions. The mechanism of As tolerance was investigated on contrasting rice genotypes, selected for As tolerance and accumulation. The rice genotypes responded differentially under arsenate As(V)] and arsenite As(III)] stress in terms of gene expression, antioxidant defence and thiol metabolic pathway. Arsenic induced oxidative stress was more pronounced in sensitive rice, while most of antioxidant enzymes, amino acids, thiolic content and their biosynthesis...