Abstract
Little is known about the regulation mechanism of genes related to Fe acquisition in graminaceous plants. To elucidate this mechanism in rice, we analyzed bHLH transcription factor named OsIRO2, which was found by rice microarray analysis. OsIRO2 expressed strongly in both shoots and roots during Fe deficiency stress. The expression of OsIRO2 was induced only by Fe deficiency and not induced by Zn, Cu and Mn deficiency. Cyclic Amplification and Selecting Targets (CASTing) experiment revealed that OsIRO2 preferred to bind 5'-ACCACGTGGTTTT-3'. Gel mobility shift assay showed that the G-box (CACGTG) was the core sequence for binding of OsIRO2 and the sequence around the G-box increased the binding of OsIRO2. Similar sequences to the OsIRO2 binding sequence were found in upstreams of several genes which related to Fe acquisition, indicating that OsIRO2 could regulate these genes. We made transgenic rice plants overexpressing or repressing OsIRO2.
