Abstract
Cadmium (Cd) is the toxic heavy metal for both plants and humans, and Cd accumulation in rice grains has become a major agricultural problem in Japan. In this study, we investigated the role of OsNRAMP1 in Cd uptake and transport in rice using two cultivars, Sasanishiki (japonica subspecies, low Cd in shoots) and Habataki (indica subspecies, high Cd in shoots).
An OsNRAMP1::GFP fusion protein localized to the plasma membrane in onion epidermal cells. The growth of the yeast expressing OsNRAMP1 was impaired in the presence of CdCl2 compared to the yeast transformed with empty vector. Moreover, the Cd content of the OsNRAMP1-expressing yeast was higher than the vector control. The amino acid sequence of OsNRAMP1 showed 100% identity between Sasanishiki and Habataki. The expression of OsNRAMP1 was detected in the roots and to a lesser extent in the shoots when grown without Cd. Under these conditions, the expression of OsNRAMP1 in the roots of Habataki was 5.8 times higher than that of Sasanishiki. The results suggest that OsNRAMP1 is involved in the cellular uptake and accumulation of Cd in rice.
