Abstract
Fe deficiency is a major abiotic stress in crop production. Although responses to Fe deficiency in graminaceous plants, such as increased production and secretion of mugineic acid family phytosiderophores (MAs), have been described, the gene regulation mechanisms related to these responses are largely unknown. We characterized the Fe-deficiency-inducible bHLH transcription factor OsIRO2. In rice, the overexpression of OsIRO2 resulted in higher MAs secretion and higher tolerance to Fe deficiency, while repression of OsIRO2 resulted in lower MAs secretion and hypersensitivity to Fe deficiency. Microarray analysis demonstrated that OsIRO2 regulates 59 Fe-deficiency-induced genes, including the genes involved in Fe(III)MAs transport system. Some of those genes, including two transcription factors, possessed the OsIRO2-binding sequence in their upstream regions. OsIRO2 possesses a homologous sequence of the Fe-deficiency-responsive cis-acting elements (IDEs) in its upstream region. We propose a novel gene regulation network for Fe-deficiency responses, including OsIRO2, IDEs, and the two transcription factors.
