ltarrysmith@student.unimelb.edu.au

Crops adapt to low iron (Fe) soils through a complex network of transcription factors that regulate Fe uptake, translocation, and storage. The Hemerythrin motif-containing Really Interesting New Gene (RING)- and Zinc finger protein (HRZ) is a master negative regulator within the plant Fe homeostasis network and knockdown of OsHRZ expression increases tolerance to Fe deficiency and grain Fe concentrations in rice (Oryza sativa L.).

This study describes the identification, annotation, and characterisation of six TaHRZ1 and TaHRZ2 homoeologs in the bread wheat (Triticum aestivum L.) genome1. In silico phylogenetic and protein analyses demonstrated that TaHRZ proteins possess Fe binding and polyubiquitination activity, and segregate into two groups: TaHRZ1 and TaHRZ2.

Reverse transcription PCR analyses revealed unique tissue expression profiles for each TaHRZ homoeolog, and rapid upregulation of all TaHRZs under Fe deficiency, suggesting the TaHRZs function as master negative regulators of wheat Fe homeostasis. We are now using gene editing to knock-out individual TaHRZ homoeologs in bread wheat and assess the effect on grain Fe concentration and plant tolerance to Fe deficiency.

Together this research represents a culmination of novel wheat genomic resources and breeding techniques and highlights a novel and possibly transgene-free strategy for future wheat Fe biofortification.

1Carey-Fung O, Beasley JT, Johnson AAT. Annotation and Molecular Characterisation of the TaIRO3 and TaHRZ Iron Homeostasis Genes in Bread Wheat (Triticum aestivum L.). Genes (Basel). 2021 Apr 27;12(5):653.