Editing Silicon Transporter Genes to Reduce Arsenic Accumulation in Rice.

Rice is a dominant source of inorganic arsenic (As) exposure for populations consuming rice as a staple food. Decreasing As accumulation in rice grain is important for improving food safety. Arsenite [As(III)], the main form of As in paddy soil porewater, is taken up inadvertently by OsLsi1 and OsLsi2, the two key transporters for silicon (Si) uptake in rice roots. Here, we investigated whether editing or can decrease As accumulation in rice grain without compromising grain yield. We used the CRISPR-Cas9 technology to edit the promoter region of and the C-terminal coding sequence of and , and we generated a total of 27 mutants. Uptake and accumulation of Si and As were evaluated in both short-term hydroponic experiments and in a paddy field. Deletion of 1.2-2 kb of the promoter suppressed expression in roots and Si uptake markedly and did not affect As(III) uptake or grain As concentration. Some of the and coding sequence mutants showed large decreases in the uptake of Si and As(III) as well as large decreases in Si accumulation in rice husks. However, only mutants showed significant decreases (by up to 63%) in the grain total As concentration. Editing mainly affected the accumulation of inorganic As in rice grain with little effect on the accumulation of dimethylarsenate (DMA). Grain yields of the mutants were comparable to those of the wild type. Editing provides a promising way to reduce As accumulation in rice grain without compromising the grain yield.