Analysis of the barley malt rootlet proteome

Authors: Mahalingam, Ramamurthy

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2019
Publication Date: 12/6/2019
Citation: Mahalingam, R. 2019. Analysis of the barley malt rootlet proteome. International Journal of Molecular Sciences. 21(1):179. http://dx.doi.org/10.3390/ijms21010179.
DOI: https://doi.org/10.3390/ijms21010179

Interpretive Summary: Majority of the barley production globally is used by the malting and brewing industry. A major byproduct of the malting industry is the rootlets that is mostly used as animal feed. In this study we examined the rootlets from two different stages of malting – germination and kilning to define their proteome composition. In collaboration with bioinformaticians from Iowa state University we developed high resolution Gene Ontologies (GO) for all the genes in the barley genome. This enabled us to identify GOs significantly enriched in the barley rootlets with high confidence. Using biochemical pathway enrichment analysis supported by two different databases (KEGG and Plant Reactome) we identified that rootlets have significantly higher amounts of proteins and amino acids justifying their use as animal feed. Enrichment of proteins associated with auxin and jasmonic acid was further corroborated by measuring these metabolites in the rootlets. Furthermore, this analysis identified enrichment of pathways associated with antioxidants and health promoting secondary metabolites. This study shows the potential use of this malting industry byproduct for extracting valuable health promoting metabolites.

Technical Abstract: Globally, malting of barley for beer brewing is a major use of this cereal. One of the byproducts of the malting industry are the rootlets that are used as animal feed. In this study we used the rootlets derived from two stages of the malting process, germination and kilning, from a popular malting barley variety to analyze the proteome. A label-free shotgun proteomics strategy was used to identify more than 800 proteins from the barley rootlets. A high coverage and high confidence Gene Ontology annotations of the barley genome was generated to facilitate the functional annotation of the proteins identified in the rootlets. Analysis of these proteins using KEGG and Plant Reactome databases indicated enrichment of pathways associated with protein biosynthesis, secondary metabolism and antioxidants. Enrichment of jasmonic acid and auxin pathways were supported by increased levels of these phytohormones in the rootlets. As a rich source of proteins and amino acids use of these by-products of the malting industry for animal feed is validated. This study also indicates rootlets as a potential source of naturally occurring phenylpropanoids and antioxidants which can be further exploited in the development of functional foods.