Arsenic is potent toxicant and classified as class i carcinogen by the u.s. environmental protection agency (u.s. epa). higher arsenic accumulation in crops causes serious health hazards, including cancer, especially in southeast asian countries. to cope up with arsenic toxicity, organisms develop various mechanism in which arsenic methylation is widespread phenomenon in nature. in the present study, we identified novel arsenic methyltransferase (waarsm) gene from soil fungus, westerdykella aurantiaca, isolated from arsenic-contaminated agricultural soil of west-bengal, india. to study the role of waarsm in planta, we genetically engineered arabidopsis thaliana with waarsm gene. the transgenic plants accumulate 36% and 16% less arsenic in seeds and shoots, respectively compared to (wild-type) wt plants which prove its ability to decrease arsenic accumulation in food crops grows in arsenic affected areas. arsenic accumulation in rice grains is worldwide concern and influences the nutritional status of rice grains. in the present study, waarsm was expressed in japonica rice (oryza sativa) and found that transgenic plants produce methylated and volatile arsenicals. transgenic line, grown on soil irrigated with arsenic-containing water accumulates 50% and 52% lesser arsenic than nt in shoot and root, respectively; while arsenic concentration in polished seeds and husk of transgenic line was reduced by 52% compared to nt. this is the first report of arsenic volatilization in rice by arsm gene of eukaryotic origin. in conclusion, our study demonstrates that the expression of fungal waarsm gene in rice induces arsenic methylation and volatilization as well as altering arsenic speciation in the plant. considering, no gene encoding arsm has yet been identified in the higher plant’s genome, including rice genome, the present project provides a strategy to generate transgenic rice that accumulate less arsenic in the grains and will have tremendous societal impact related to public health consequences.