The Natural Resistance Associated Macrophage Proteins (NRAMP) play roles in metal transport in plants. Previous studies have shown that OsNrat1 (OsNramp4) in rice (Oryza sativa) encodes an aluminum transporter, which is required for rice aluminum tolerance.
Researchers from Guangxi University, led by Muxue Lu, characterized an NRAMP member in sorghum (Sorghum bicolor), SbNrat1, which is homologous to OsNrat1. SbNrat1 was found to be expressed in both roots and shoots, and its expression is not induced by aluminum treatment.
When expressed in yeast, the SbNrat1 protein transports the trivalent aluminum ion, but not manganese and cadmium. To further prove its homology to OsNrat1, it was introduced into the rice osnrat1 mutant. SbNrat1's expression in the mutant rescued its sensitivity to aluminum. However, no correlation between aluminum tolerance and SbNrat1 expression levels was found.
These data indicate that the SbNrat1 functions as an aluminum transporter and is involved in basic aluminum tolerance in sorghum.