A total of 48 full length DNA sequences representing six TaGS1.1 and TaGS2 alleles, were isolated from 8 hexaploid wheat accessions on Illumina-MiSeq next generation sequencing platform. The sequences were consolidated through multiple gene de novo sequence assembly and consensus alignment with the genome-specific references. Phylogenetic analysis revealed a clear divergence at molecular level between cytosolic TaGS1.1 and plastid TaGS2 and even wider genetic divergence among the plastid GS alleles. A modelling system based on a translation of the full length TaGS1.1 and TaGS2 mRNA sequences showed that the dominant amino acid residues in the active sites were Aspartic acid, Glutamic acid and Arginine (TaGS1.1, TaGS2); Threonine, Tryptophan and Leucine (TaGS2). Prediction of active site mutation and relative sequence conservation point to sharply contrasting inter-allelic mutation sensitivity at the catalytic sites. Comparative assessment of GS orthologues between the isolated wheat sequences and other plant species revealed a syntenic relationship between the wheat and barley GS2 sequences. Kukri GS2B for example, depicts homology with Glycine max GS2, Solanum tuberosum GLN and Zea mays GS1.2. Functional prediction of protein catalytic domain across all the GS alleles suggests key roles for these genes in the glutamine biosynthetic processes, chemical reactions and pathways resulting in the formation of glutamine, 2-amino-4-carbamoylbutanoic acid. The allelic variation signals highlighted in this study will be crucial in determining whether functional variation existing between the GS alleles at molecular level will result in structural differences that significantly regulate nitrogen (N) linked metabolism in hexaploid wheat.
