Decreasing Arsenic Concentration In Rice Grain Through Safener-Elicited Glutathione Sequestration

Abstract

Arsenic accumulation in rice grain poses major problems for human safety, global food security, and the future of nutrition, especially in the developing world. In an effort to investigate feasible and effective strategies to prevent arsenic accumulation in rice grain, this study investigates a potential pathway to reduce arsenic accumulation in rice grains through involving glutathione sequestration. I hypothesized that exogenous applications of solutions called safeners, which are similar to herbicides but lack a key functional group that give xenobiotic capabilities, could elicit a defense response in rice plants that leads to increased production of glutathione. Glutathione has the capability to bind with arsenic sequester it into the vacuole of plants, thus offering a potential avenue to sequester arsenic in non-grain tissue which prevents the arsenic from reaching the grain. The effects of 4 safeners were investigated: fenclorim, isoxadifen-ethyl, dimepiperate, and dichlormid. A greenhouse pot study was done to establish comparisons of glutathione concentrations in various plant parts and glutathione defense pathway gene regulation of safener treated plants as compared to untreated controls. Overall, there were no statistically significant differences between the concentrations of reduced or oxidized glutathione in the nodes, leaves, or flag leaves of safener treated plants in comparison to untreated controls. There was some evidence for a localization effect of reduced glutathione to the nodes of plants treated with fenclorim, but this result was not statistically significant. Likewise, there was no significant increase in expression of genes related to glutathione biosynthesis or transport in plants treated with safeners as compared to untreated controls. The lack of significant data suggests there is room to understanding potential avenues for arsenic sequestration in rice. Additionally, further analysis could be necessary to test the efficacy of safener uptake after exogenous application.