Identification of nicotianamine synthase genes in Triticum monococcum and their expression under different Fe and Zn concentrations

In graminaceous plants, nicotianamine (NA) is an important component of metal acquisition. NA is synthesized from S-adenosyl-L-methionine (SAM) catalyzed by nicotianamine synthase (NAS). Here, eight Triticum monococcum NAS (TmNAS) genes were cloned and characterized. Amino acid sequence analysis showed that TtnNAS genes had high sequence identity with those from Triticum aestivum, Zea mays, Oryza sativa and Hordewn vulgare. Phylogenetic analysis showed that NAS genes were classified into two distinct groups, e.g. group I and group II. Expression analysis demonstrated that two of the TmNAS genes in group II were highly expressed in shoot tissues, and the other six TmNAS genes in group I were expressed in root tissues. Further analysis indicated that root-specific TmNAS genes were up-regulated under conditions of Fe- or Zn-deficiency growth, while shoot specific TtnNAS genes were up-regulated under conditions of Fe- or Zn-sufficiency. These results help us understand the NAS genes in T. monococcum and provide novel genetic resources for improving Fe and Zn concentrations in common wheat.