Metabolic profiling of transgenic wheat over-expressing the high-molecular-weight Dx5 glutenin subunit

The primary aim of this work was to evaluate potential changes in the metabolic network of transgenic wheat grain over-expressing the high-molecular-weight (HMW) glutenin Dx5-subunit gene. GC-MS and multivariate analyses were used to compare the metabolite profiles of developing caryopses of two independently transformed lines over-expressing Dx5 and another two independently transformed lines expressing only the selectable-marker gene (controls). Developing grain at 7, 14 and 21 Days Post-Anthesis (DPA) was studied to observe differences in metabolically active tissues. There was no distinction between the Dx5 transformants and the controls by principal component analysis (PCA) suggesting that their metabolite compositions were similar. Most changes in metabolite levels and starch occurred at 14 DPA but tapered off by 21 DPA. Only 3 metabolites, guanine, 4-hydroxycinnamic acid and Unknown 071306a, were altered due to Dx5 expression after correction for false discovery rates (P < 0.0005). However, discriminant function analysis (DFA) and correlative analyses of the metabolites showed that Dx5-J, which had the highest level of Dx5 protein in ripe caryopses, could be distinguished from the other genotypes. The second aim of this work was to determine the influence of gene transformation on the metabolome. Cross-comparison of the transformed controls to each other, and to the Dx5 genotypes showed that approximately 50% of the metabolic changes in the Dx5 genotypes were potentially due to variations arising from gene transformation and not from the expression of the Dx5-gene per se. This study therefore suggests the extent to which plant transformation by biolistics can potentially influence phenotype.