Identification and Functional Characterization of OsSULTR3;1 in Grain Selenium Accumulation in Rice

Rice is a major source of selenium (Se) globally; however, about one billion people experience Se deficiencies. Plants uptake and transport both sulfur (S) and Se using sulfate transporters (SULTRs). Our study aimed to identify rice SULTR genes involved in grain Se accumulation. Expression analysis of 12 rice SULTR genes in tissues at different developmental stages, and under Se and S treatments, revealed that OsSULTR3;1 is strongly expressed in rice grains and mainly induced by Se. Through heterologous expression of OsSULTR3;1 in yeast and the creation of OsSULTR3;1 overexpression and knockout lines, we showed that OsSULTR3;1 is responsible for the active uptake of both selenate and selenite. OsSULTR3;1 knockout and overexpression lines reduced and increased grain Se content by 69.6%, 68.7%, 33.3%, and 78.5%, 15.5%, and 57.5%, respectively, compared with the wild type. Our findings validate the function of OsSULTR3;1 in grain Se accumulation and provide information for breeding Se-enriched rice cultivars.