Natural Variation in NRAT1 Alters Expression and Function of a Key Gatekeeper for Rice Aluminum Tolerance

Rice is the most Al tolerant cereal crop, and offers a good model for identifying Al tolerance genes and mechanisms in other species. Here we investigated natural variation in the rice Nrat1 gene encoding a root plasma membrane Al uptake transporter. DNA sequence variation in the Nrat1 coding and regulatory regions was associated with changes in Nrat1 expression and Nrat1 Al transport properties, resulting in significant differences in the Al content of root cell wall and cell sap in 24 diverse rice lines. Expression of the tolerant OsNrat1 allele in yeast resulted in higher Al uptake than did the sensitive allele, and conferred greater Al tolerance when expressed in transgenic Arabidopsis. These findings confirm the important role of Nrat1 in conferring Al tolerance in rice and demonstrate its ability to enhance Al tolerance in Arabidopsis where it is not naturally associated with Al tolerance. This suggests that the Nrat1 gene or its orthologs may be useful tools for enhancing Al tolerance in a wide range of plant species.