OsNRAMP1 contributes to cadmium and manganese uptake in rice.

Rice is a major dietary source of the toxic metal, cadmium (Cd). Previous studies reported that the rice transporter, OsNRAMP1, (Natural resistance-associated macrophage protein 1) could transport iron (Fe), Cd and arsenic (As) in heterologous yeast assays. However, thein plantafunction of OsNRAMP1 remains unknown. Here, we showed that OsNRAMP1 was able to transport Cd and manganese (Mn) when expressed in yeast, but did not transport Fe or As.OsNRAMP1was mainly expressed in roots and leaves and encoded a plasma membrane-localized protein.OsNRAMP1expression was induced by Cd treatment and Fe deficiency. Immunostaining showed that OsNRAMP1 was localized in all root cells, except the central vasculature, and in leaf mesophyll cells. The knockout ofOsNRAMP1resulted in significant decreases in root uptake of Cd and Mn and their accumulation in rice shoots and grains, and increased sensitivity to Mn deficiency. The knockout ofOsNRAMP1had smaller effects on Cd and Mn uptake than knockout ofOsNRAMP5, while knockout of both genes resulted in large decreases in the uptake of the two metals. Taken together, OsNRAMP1 contributes significantly to the uptake of Mn and Cd in rice, and the functions of OsNRAMP1 and OsNRAMP5 are similar but not redundant.