A rice FRD3-like (OsFRDL1) gene is expressed in the cells involved in long-distance transport

We identified four putative AtFRD3-like genes (OsFRDL) in the rice genome that exhibited 39.1 to 56.7% amino acid sequence similarities to Arabidopsis FRD3. Of these, we cloned three OsFRDL genes from a cDNA library prepared from iron-deficient rice roots: OsFRDL1, OsFRDL2, and OsFRDL3. OsFRDL1 was expressed weakly in Fe-sufficient roots, and slight expression was induced in the roots of Fe-deficient plants. OsFRDL2 was expressed constitutively in both roots and leaves, and Fe deficiency reduced its expression in leaves. OsFRDL3 was expressed in leaves, but not in roots; Fe deficiency induced slight expression in leaves. An OsFRDL1-sGFP fusion protein was localized in the plasma membrane in onion epidermal cells. The promoter GUS analysis showed that OsFRDL1 was localized in the cells involved in long-distance transport, in both Fe-sufficient and Fe-deficient plants. Furthermore, OsFRDL1 expression was observed during the reproductive stage. These results suggest that OsFRDL1 is a transporter that resides in the plasma membrane of cells involved in long-distant transport.