jesse.beasley@unimelb.edu.au

Nicotianamine (NA) is a chelator of divalent metal cations that is synthesized by nicotianamine synthase enzymes (NAS) in all higher plants. We have previously described the identification of 21 TaNAS genes present in the bread wheat (Triticum aestivum L.) cultivar (cv.) Chinese Spring genome1.

This study utilized up-to-date online wheat genomic resources to discover 33 TaNAS genes present in cv. Chinese Spring genome and an additional eight TaNAS genes throughout the genomes of ten other bread wheat cvs. The expression of most TaNAS genes was higher in wheat roots relative to other tissues, although some individual TaNAS genes displayed ubiquitous expression across tissues and developmental stages. The amino acid sequence of all TaNAS proteins contained two motifs for cytoplasmic vesicular localization, and extended N-terminal regions in TaNAS2-A1, TaNAS2-A2, TaNAS2-D3, TaNAS6-A1, TaNAS6-D1, TaNAS7-A1, TaNAS7-B1, and TaNAS8-D1 predicted subcellular localisation to mitochondria and/or chloroplasts.

To explore the effect of TaNAS overexpression on grain nutrition and plant growth we transformed bread wheat (cv. Fielder) with six independent constructs containing TaNAS coding sequences (TaNAS1-A1, TaNAS3-B1, TaNAS4-A1, TaNAS6-DL1, TaNAS6-DS1, and TaNAS7-A1) that represent a range of TaNAS protein structures and gene expression profiles. We isolated three single insert homozygous TaNAS events and a respective null segregant (NS) control for each construct and assessed plant growth and grain nutrition of T3 transgenic plants under both glasshouse and field conditions.

This study demonstrates the value of genomic resources for characterizing important gene families in bread wheat and provides further evidence of NA biofortification as a promising strategy for enhancing grain nutritional quality2.

1Bonneau JP, Baumann U, Beasley JT, Li Y, Johnson AAT. Identification and molecular characterization of the nicotianamine synthase gene family in bread wheat. Plant Biotechnol J. 2016 Dec;14(12):2228-2239.

2Beasley JT, Bonneau JP, Moreno-Moyano LT, Callahan DL, Howell KS, Tako E, Taylor J, Glahn RP, Appels R, Johnson AAT. Multi-year field evaluation of nicotianamine biofortified bread wheat. Plant J. 2022 Mar;109(5):1168-1182.