Abstract
Multidrug and toxic compound extrusion (MATE) proteins are widely present in bacteria, fungi, plants and mammals. Recent studies have showed that a group of plant MATE genes encodes citrate transporter, which are involved in the Al detoxification or Fe translocation from the roots to the shoots. In this study we isolated two homologous genes (ScFRDL1 and ScFRDL2) of this-type MATE in rye. ScFRDL1 shared 94 % identity with barley Al-induced citrate transporter HvAACT1 and ScFRDL2 shared 80 % identity with rice Al-induced gene OsFRDL2. Both genes were expressed in the roots, however, they showed different expression pattern. The expression of ScFRDL1 was unaffected by Al treatment, but induced by Fe-deficiency. By contrast, the expression of ScFRDL2 was induced by Al but not by Fe deficiency. Furthermore, the expression pattern of OsFRDL2 was consistent with citrate secretion pattern. Immunostaining showed that ScFRDL1 is localized at central cylinder in the basal roots. Taken together, our results suggest that ScFRDL1 is involved in efflux of citrate into the xylem for Fe translocation from root to shoot, while ScFRDL2 is involved in Al-activated citrate secretion in rye.
