Wheat has the most NAS genes
Nicotianamine synthase (NAS) genes control the production of nicotianamine, a non-protein amino acid that chelates divalent metal cations such Fe2+ and facilitates their transport in plant tissues. In graminaceous plants, a significant proportion of nicotianamine is converted to phytosiderophores that are secreted from roots for absorption of Fe3+ from soils. Here we describe the discovery of 21 NAS genes in bread wheat – the largest NAS gene family found in any plant species to date – and demonstrate that most members of this gene family are active during germination, seedling growth, reproductive development and under Fe deficiency.
To learn more read the full paper here:
Bonneau J, Baumann U, Beasley J, Li Y, Johnson AAT (2016) Identification and molecular characterization of the nicotianamine synthase gene family in bread wheat. Plant Biotech Journal doi: 10.1111/pbi.12577. Bonneau et al. 2016 PDF.