A novel NAC transcription factor IDEF2 that recognizes the iron deficiency-responsive element 2 regulates the genes involved in iron homeostasis in plants

Abstract

Many genes related to iron uptake and translocation are up-regulated by iron deficiency and possess iron deficiency-responsive cis-elements, IDE1 and IDE2. We identified a novel transcription factor of rice, IDEF2, which specifically binds to IDE2 by yeast one-hybrid screening. IDEF2 recognized a part of IDE2 as the binding core sequence, which is different from any reported cis-elements bound by NAC domain transcription factors. Interestingly, IDEF2 also recognized a part of CaMV 35S promoter, which is not similar to IDE2. Repression of IDEF2 by RNAi caused aberrant iron homeostasis in rice. Among the iron-deficiency inducible genes, several genes including OsYSL2 were less induced by iron deficiency in the RNAi rice. OsYSL2 is Fe(II)-nicotianamine transporter and important for iron translocation. IDEF2 bound to OsYSL2 promoter region containing the IDEF2 binding core sequence, suggesting direct regulation of OsYSL2 expression. These results reveal novel cis-element/trans-factor interactions functionally associated with iron homeostasis.