Arsenic Bio-volatilization by Engineered Yeast Promotes Rice Growth and Reduces Arsenic Accumulation in Grains

Arsenic is listed as the most extensive environmental carcinogens. The present report demonstrated that yeast expressing WaarsM gene encoding arsenic methyltransferase from soil fungus Westerdykella aurantiaca removes arsenic from contaminated soil. We investigated the potential use of yeast as a plant growth-promoting agent to stimulate rice plant growth. The genetically engineered (GE) Saccharomyces cerevisiae showed high arsenic methylation and volatilization activity under arsenic stress. Rice seeds bio-primed with GE yeast showed higher seedling vigor index compared to untreated control. Yeast also promotes the growth of rice plants in control condition while GE yeast significantly (P < 0.05) increased shoot length, ca 29%, root length, ca 47% and panicle length, ca 38%, of plants grown in arsenic-contaminated soil. The application of yeast significantly increases the photosynthetic pigments of rice plants in the control condition while in the presence of arsenic; the photosynthetic pigments were increased in plants inoculated with GE yeast only. Plants inoculated with GE yeast, grown in soil irrigated with arsenic-containing water accumulates about 37%, 36% and 28% lower arsenic in the root, shoot and grains, respectively, compared to non-inoculated plants. Thus, volatilization of arsenic from contaminated soil is possible with GE yeast and could be the instrumental agent for reducing arsenic content from the soil and agricultural products.