| Summary: | Effective maintenance of plant iron (Fe) homoeostasis relies on a network of transcription factors (TFs) that respond to environmental conditions and regulate Fe uptake, translocation, and storage. The iron-related transcription factor 3 (IRO3), as well as haemerythrin motif-containing really interesting new gene (RING) protein and zinc finger protein (HRZ), are major regulators of Fe homeostasis in diploid species like <i>Arabidopsis</i> (<i>Arabidopsis thaliana</i>) and rice (<i>Oryza sativa</i> L.), but remain uncharacterised in hexaploid bread wheat (<i>Triticum aestivum</i> L.). In this study, we have identified, annotated, and characterised three <i>TaIRO3</i> homoeologs and six <i>TaHRZ1</i> and <i>TaHRZ2</i> homoeologs in the bread wheat genome. Protein analysis revealed that TaIRO3 and TaHRZ proteins contain functionally conserved domains for DNA-binding, dimerisation, Fe binding, or polyubiquitination, and phylogenetic analysis revealed clustering of TaIRO3 and TaHRZ proteins with other monocot IRO3 and HRZ proteins, respectively. Quantitative reverse-transcription PCR analysis revealed that all <i>TaIRO3</i> and <i>TaHRZ</i> homoeologs have unique tissue expression profiles and are upregulated in shoot tissues in response to Fe deficiency. After 24 h of Fe deficiency, the expression of <i>TaHRZ</i> homoeologs was upregulated, while the expression of <i>TaIRO3</i> homoeologs was unchanged, suggesting that TaHRZ functions upstream of TaIRO3 in the wheat Fe homeostasis TF network.
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