OsIRT1 and OsIRT2, Rice Transporters Essential for Iron Uptake from the Soil and for Plant Growth

Abstract

Rice cDNA and genomic libraries were screened in order to clone a Fe(II) transporter gene. OsIRT1, highly homologous to the Arabidopsis Fe(II) transporter gene (IRT1 ) was isolated from Fe-deficient rice roots. Expressed in yeast cells, OsIRT1 cDNA reversed the growth defects of the yeast iron-uptake mutant. OsIRT1-promoter and GUS fusion protein was expressed at stele and cortex under iron limiting condition. OsIRT2, similarly, highly homologous to OsIRT1, was isolated. RT-PCR analysis revealed that OsIRT2 was also predominantly expressed in roots under Fe-deficiency. This suggests that OsIRT1 is a functional metal transporter for iron, and is actively engaged in Fe uptake from soils, especially under limiting conditions.