Location: Crop Improvement and Genetics ResearchTitle: An asparagines residue at the N-terminus affects the maturation process of low molecular weight glutenin subunits of wheat endosperm Author
Submitted to: Biomed Central (BMC) Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2014
Publication Date: 3/14/2014
Citation: Egidi, E., Sestili, F., Janni, M., D'Ovidio, R., Ceriotti, A., Vensel, W.H., Kasarda, D.D., Masci, S. 2014. An asparagines residue at the N-terminus affects the maturation process of low molecular weight glutenin subunits of wheat endosperm. Biomed Central (BMC) Plant Biology. 14:64. DOI: 10.1186/1471-2229-14-64. Interpretive Summary: Wheat, because of its ability to form a cohesive dough mass is widely used in bread, cookie, noodle and pastry making. The role of wheat dough in human nutrition has generated considerable interest in the proteins that are major dough components. The authors describe the explanation for why a modification occurs to a specific protein type before that protein is incorporated into the polymer. This information will allow formation of lines enriched in this protein type and will allow determination of the role of this modification in flour quality.
Technical Abstract: Wheat (Triticum spp.) glutenin polymers are of two main types, high- (HMW-GS) and low- (LMW-GS) molecular weight subunits. The most common are the latter, based on the first amino acid of the mature sequence, are known as LMW-m and LMW-s types. They differ as a result of three extra amino acids (MET-) at the N-terminus of LMW-m types. The encoding gene nucleotide sequences are nearly identical, thus the link between gene and protein sequences is obscure. It has been theorized that asparagine cleavage at position 23 of the coding sequence for the LMW-s type by an asparaginyl endopeptidase might account for the three-residue difference. We performed site-directed mutagenesis of a LMW-s gene to replace asparagine at position 23 with threonine and thus convert it to a candidate LMW-m type gene. Similarly, a candidate LMW-m type gene was mutated at position 23 to replace threonine with asparagine. Next, we produced transgenic durum wheat (T. durum cultivar Svevo) lines by introducing mutated versions of the LMW-m and LMW-s genes, along with the wild type counterpart of the LMW-m gene. Proteomic comparison between the transgenic and null segregant plants enabled identification of transgenic proteins. Our results show that the formation of LMW-s type relies on the presence of an asparagine residue close to the N-terminus and implicates an asparaginyl endopeptidases in protein maturation.