Molecular Basis and Regulation of Ammonium Transporter in Rice

Rice grows in flooded paddy fields and takes up ammonium as the preferred nitrogen (N) source. Ammonium uptake is facilitated by a family of integral membrane proteins known as ammonium transporters found in all domains of life. However, the molecular mechanism and functional characteristics of the ammonium transporters (AMT) in rice have not been determined in detail yet. In this review, we report a genome-wide search for AMT genes in rice, resulting in the increase of the number of potential AMT proteins to at least 12, including members of both the alpha and beta sub-groups. Analysis of the predicted protein sequences for the 12 OsAMT proteins identified many conserved phosphorylation sites in both the alpha and beta group members, which could potentially play a role in controlling the activity of the transporters. Present knowledge of the expression of rice AMT genes is also summarized in detail. Future studies should focus on the structural and functional characteristics of OsAMT proteins to provide insight into the mechanism of ammonium uptake and its regulation in rice. Such research could improve utilization and decrease wastage of N fertilizer in rice cultivation.