Genome-wide identification, characterization and relative expression analysis of putative iron homeostasis genes: NAS, NAAT, and DMAS in hexaploid wheat and its progenitors

The present study used different in silico approaches to identify and characterize the putative iron homeostasis genes in hexaploid wheat (Chinese Spring) and its diploid wild progenitors (Triticum urartu, Aegilops speltoides, and Aegilops tauschii). A total of six NAAT genes, three NAAT1 and other three NAAT2 types on long arms of group 1 chromosomes, three DMAS genes on group 4 chromosomes and twenty NAS genes on group 2, 3, 4, 5 and 6 chromosomes were identified and characterized in hexaploid wheat whereas, two NAAT genes from T. urartu (TuNAAT1 and TuNAAT2) and one each from Ae. speltoides (Ae.spelNAAT2) and Ae. tauschii (Ae.tausNAAT1), a single DMAS gene each from T. urartu, Ae. speltoides and Ae. tauschii and five NAS genes each from the diploid wild progenitors was reported on similar group of chromosomes. Structure analysis among the hexaploid wheat and wild progenitors revealed differences in lengths of NAAT and DMAS genes. This variation in the length of homologous genes was found to be associated with variation in the length of intron sequences which may influence the expression pattern of these genes. Further, gene expression analyses (quantitative RT-PCR) of four of the iron homeostasis genes, namely, TaNAAT, TaDMAS, TaIDEF2, and TaNAS9-2AS was performed in hexaploid wheat. Expression of three genes, TaNAAT, TaDMAS, and TaNAS9-2AS in wheat roots was found to be directly regulated by the iron deficiency and age of the plants, whereas TaIDEF2 was appeared to be post transcriptionally regulated. The identification and characterization of these genes, provides a useful genetic resource for better understanding of iron homeostasis genes in hexaploid wheat. This information could be used in subsequent wheat biofortification programmes using molecular breeding approaches.