Abstract：Severe crop yield losses are caused by the rhizotoxicities of aluminum (Al3+) and protons (H+) in acid soil. Some plant species and cultivars have evolved mechanisms for detoxifying Al3+ and H+, but little is known about molecular mechanisms of their tolerance. Here, we reported a gene, MsSTAR2(GenBank accession no. KC430619), encoded a transmembrane domain of a bacterial-type ABC transporter in Medicago sativa L., and shared a high similarity with rice(Oryza sativa) OsSTAR2 and Arabidopsis thaliana AtALS3, which had been implicated in aluminum tolerance. MsSTAR2 was constitutively expressed in all tissues and it was predominantly expressed at leaves. Different with OsSTAR2 and AtALS3, either Al3+ or H+ increased the expression of MsSTAR2, but the gene didn't respond to other metal ions, such as Cd and Mn. Furthermore, we found that there was no positive correlation between the amount of gene expression and aluminum resistance in Medicago Sativa L. All these results indicated that MsSTAR2 is an aluminum-activated gene in Medicago Sativa L., and it may induce the protection mechanism caused by aluminum damage, which probably functions as a bacterial-type ABC transporter by forming a complex with a nucleotide binding domain protein.
