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Title: Comparative transcriptional and proteomic profiling of bread wheat cultivar and its derived transgenic line over-expressing a low molecular weight glutenin subunit gene in the endosperm

item SCOSSA, F.
item L Chingcuanco, Debbie
item Anderson, Olin
item Vensel, William
item D'OVIDIO, R.
item MASCI, S.

Submitted to: Molecular and Cellular Proteomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2008
Publication Date: 7/14/2008
Citation: Scossa, F., Chingcuanco, D.L., Anderson, O.D., Vensel, W.H., Lafiandra, D., D'Ovidio, R., Masci, S. 2008. Comparative transcriptional and proteomic profiling of bread wheat cultivar and its derived transgenic line over-expressing a low molecular weight glutenin subunit gene in the endosperm. Molecular and Cellular Proteomics. 8(14):2948-2966.

Interpretive Summary: The effects of transgene expression in plants, whether direct or indirect, are relevant to basic research questions, industrial applications, and the issue of “Substantial Equivalence” of GM plants, because transgenes can affect other components of plant metabolism. Wheat endosperm proteins are of major importance with regard to the nutritional and technological properties of wheat flours. Consequently, the potential effects of transgene introduction on these proteins deserve consideration. We focused our studies on a transgenic wheat line over-expressing a gene for a low-molecular-weight glutenin subunit (LMW-GS), which is correlated with dough quality. Proteomic data showed a high level of differential expression in most classes of wheat seed proteins. In order to identify the differentially expressed genes during the process of grain filling, and eventually provide insights about the metabolic pathways altered, we carried out microarray comparisons between the wild type cultivar, the “null genotype” (derived from the transgenic line, but has lost the transgene by segregation), and the transformed line expressing the transgenic protein. During seed development, more than 500 candidate differentially expressed unigenes have been identified. Most of them are genes for seed-storage proteins, or coding for proteins involved in trafficking/secretion and amino acid biosynthesis.

Technical Abstract: We have carried out a parallel transcriptional and proteomic comparison of seeds from a transformed bread wheat line that over-expresses a transgenic low molecular weight glutenin subunit gene relative to the corresponding non-transformed genotype. Proteomic analyses showed that, during seed development, several classes of endosperm proteins were differentially accumulated in the transformed endosperm. As a result of the high over-expression of the transgene and subsequent increase in the amount of the corresponding protein subunit, the amounts of the endogenous glutenins and all sub-classes of gliadins were diminished during seed filling in the transgenic genotype. Similarly, we also had evidence that metabolic and other soluble proteins with allergenic properties were less abundant in the transgenic line with respect to the wild-type genotype. In all protein classes, the differential accumulation detected by proteomic analyses, both in mature and developing seeds, was paralleled by the corresponding decreased transcript levels detected by microarray experiments. These results suggest that the most evident effect of the strong over-expression of the transgenic glutenin gene consists in a global compensatory response involving a significant decrease in the amounts of polypeptides belonging to the prolamin superfamily, including seed storage proteins, as well as other seed proteins with allergenic properties. It seems likely that such compensation is a consequence of the diversion of the amino acids reserves and translation machinery to the synthesis of the transgenic glutenin. The data here reported may also represent a starting point for a better understanding of previously unknown mechanisms controlling the synthesis of wheat seed proteins.