Abstract
Little is known about the regulation mechanism of genes related to Fe acquisition in graminaceous plants. To elucidate this mechanism in rice, we carried out time course analysis during Fe-deficiency stress using 22K rice microarray. Several genes encoding putative transcription factors were induced by Fe deficiency. Among them, a bHLH transcription factor gene, named IRO2, expressed strongly in both roots and shoots during Fe deficiency stress. The expression of OsIRO2 was induced only by Fe deficiency not by other metal deficiency. HvIRO2, a homolog from barley, was also Fe-deficiency inducible. Further, in silico search showed that IRO2, gene is widely conserved in graminaceous plants such as wheat, sorghum and maize. CASTing experiment revealed that OsIRO2 preferred to bind 5'-ACCACGTGGTTTTT-3'. Similar sequences to the OsIRO2 binding sequence were found in upstreams of several genes which relate to Fe acquisition, indicating that IRO2 could regulate these genes under Fe-deficient conditions.
