The OsNRAMP1 iron transporter is involved in Cd accumulation in rice

Abstract

Cadmium (Cd) is a heavy metal toxic to humans and the accumulation of Cd in the rice grain is a major agricultural problem, particularly in Asia. The role of the iron transporter OsNRAMP1 in Cd uptake and transport in rice was investigated here. An OsNRAMP1:GFP fusion protein was localized to the plasma membrane in onion epidermal cells. The growth of yeast expressing OsNRAMP1 was impaired in the presence of Cd compared with yeast transformed with an empty vector. Moreover, the Cd content of OsNRAMP1-expressing yeast exceeded that of the vector control. The expression of OsNRAMP1 in the roots was higher in a high Cd-accumulating cultivar (Habataki) than a low Cd-accumulating cultivar (Sasanishiki) regardless of the presence of Cd, and the amino acid sequence of OsNRAMP1 showed 100% identity between Sasanishiki and Habataki. Over-expression of OsNRAMP1 in rice increased Cd accumulation in the leaves. These results suggest that OsNRAMP1 participates in cellular Cd uptake and Cd transport within plants, and the higher expression of OsNRAMP1 in the roots could lead to an increase in Cd accumulation in the shoots. Our results indicated that OsNRAMP1 is an important protein in high-level Cd accumulation in rice.

Uptake and Accumulation of Cadmium and Relative Gene Expression in Roots of Cd-resistant Salix matsudana Koidz

“…3), suggesting that ZIP1 may play crucial roles in the early absorption of Cd. NRAMP1 can be considered a kind of Fe transporter in plants, and its expression can be induced by Fe deficiency in roots [19]. Cailliatte et al [18] demonstrated that the metal transporter NRAMP1 was high-affinity Mn uptake that is essential for growth in conditions of low Mn availability.…”

“…NRAMP1 is localized in the plasma membrane of root cells, functioning as a high-affinity transporter for Mn uptake [17]. AtNRAMP1 expression induced by Fe deficiency in roots is thought to control Fe homeostasis in plants [18][19] and may be involved in an enhanced influx of Cd into the cells, causing Cd toxicity [20][21]. HMA3 may be involved in the detoxification of metals by chelating Cd into the vacuole [22].…”

Two models of Cd uptake by common plants and Hyperaccumulators

“…The difference between the models of common plants and Cd-hyperaccumulators laid in the different effects of OsNramp1 and OsNramp5 on Cd accumulation. For instance, OsNramp1 localized in the plasma membrane and the level of OsNramp1 expression was higher in high-Cd-accumulating indica cultivars such as Habataki than in low-Cd-accumulating japonica cultivars such as Sasanishiki [6]. The reflection of these in the models was that the effect of OsNramp1 on Cd that existing in a free state are different.…”

“…OsNramp1 expression was observed mainly in roots and was higher in the roots of a high-Cdaccumulating cultivar than in those of a low-Cd-accumulating cultivar [1]. OsNramp5 was mainly expressed in the roots and localized in the plasma membrane of exodermis and endodermis cells of the roots [2].…”

“…1 is constituted by 27 nodes and 50 edges. A brief description of the biology represented by the network is as follows: The Nramp family of metal transporters has been identified in several plant species, rice possesses seven putative Nramp genes [1]. Different Nramp genes have different subcellular localizations, thus have different effects on cadmium accumulation.…”