Cloning, Characterization Of Low-molecular-weight Glutenin Subunits Genes From Wheat Related Species And Their Prokaryote Expression Vectors’ Construction

The gluten proteins in wheat endosperm confer the unique visco-elastic properties todough and make it suitable to be processed into kinds of food. Glutenins consist ofhigh-molecular-weight glutenin subunits (HMW-GS) and low-molecular-weight gluteninsubunits (LMW-GS), which are considered to be major determinants of the unique doughproperties. However, the relationships of certain alleles of LMW-GS with dough qualitiesare still not entirely understood, because of the complexity of the LMW-GS gene familyand the extensive allelic diversity of LMW-GS in common wheat. More recently, somestudies have been focused on the isolation of LMW-GS genes from wheat related species.In this study, according to sequence homology of LMW-GS gene of Triticeae fromdifferent species, four novel LMW-GS genes from the genome of Triticum zhukovskyi andTriticum compactum were cloned and characterized. Sequence comparison between themand other known LMW-GS genes was carried and their protein secondary structure wasalso predicted. The results showed that all these four genes belong to i-type LMW-GSgenes and therefore were designated TzLMW-i1, TzLMW-i2, TcLMW-i1andTcLMW-i2,respectively. Compared with other LMW-i subunits, these four novel i-typeLMW-GS have eight conserved Cys residues. Interestingly, TzLMW-i2has an additionalcysteine residue in its C-terminal cysteine-rich region which may confer additionalinter-molecular disulfide bond and may act as―chain brancher‖in the gluten proteinnetwork. Moreover, the TcLMW-i2subunit has a longer N-terminal repetitive domain thanother i-type LMW-GS. It has been suggested that longer sequences of the repetitivedomain of LMW-GS possibly contributes to the formation of inter-chain hydrogen bonds,particularly with HMW-GS, and this is important in stabilizing protein-protein interactionsin gluten and influencing the gluten structure and dough functionality. Finally, we alsobuilt four new prokaryotic expression vector of the cloned four LMW-GS in order toexpress these recombinant proteins with the aim to clarify their role in the formation of thegluten network.