Proteomics of flour from domesticated varieties and wild barley reveals differences in their hordein compositions

Proteomic studies in barley have been predominantly focused on malting barley for the brewing industry. In this study, protein contents and detailed protein compositions of grains of Wild Barley (WB) ( Hordeum spontaneum ) and two varieties of domesticated barley ( Hordeum vulgare), Golden Promise (GP), bred for brewing, and PS3, bred for food, were investigated to reveal compositional differences in the hordeins, the major storage proteins of barley. For proteomic profiling a sensitive LC-MS/MS Orbitrap system was used in combination with a one-step denaturing and reducing phenol extraction. The extracts were subjected to label-free bottom-up proteomics. Differences were revealed not only in the overall composition of groups of storage proteins, but also in individual hordeins. WB and PS3 contained higher amounts of D-hordein than GP, while GP had higher levels of B-hordein. Furthermore, the differences in protein composition were evaluated to identify links between the proteome and genotypes’ use case and the transition from wild barley.