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Title: Temporal analyses of barley malting stages using shot-gun proteomics

item Mahalingam, Ramamurthy

Submitted to: Proteomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2018
Publication Date: 8/8/2018
Citation: Mahalingam, R. 2018. Temporal analyses of barley malting stages using shot-gun proteomics. Proteomics.

Interpretive Summary: Barley malt is the most important raw material for the brewing industry. Barley malting quality is a complex trait involving multiple biochemical pathways. Malting quality has been mainly assessed using a set of handful of traits. Identifying novel malting associated traits will greatly improve the assessment of malting quality. In this study, we are using the state-of-the-art proteomics technology to identify changes occurring in the proteome during the various stages of malting. This is one of the first report to have identified more than 1400 proteins that vary in their abundance in one or more stages during barley malting. This repertoire of proteins will provide a novel resource for further characterization of hitherto unknown malting quality associated enzymes and regulatory proteins.

Technical Abstract: Malt derived from barley malting is an essential raw material for beer brewing. In this study, we performed the first dynamic proteome survey during barley malting using a gelfree proteomics approach. This strategy entails in-solution tryptic digestion of precipitated proteins and analysis of peptides by nano-liquid chromatography coupled with tandem mass spectrometry. A total of 1418 proteins were identified from the five malting stages-end of steep, 1, 3, 5 days after germination, and end of kilning cycle. About 900 proteins identified in this analysis were annotated as uncharacterized or predicted proteins. Integrating information from Uniprot90, Uniprot50, Pfam and Interpro databases and gene ontologies from EnsemblPlants, 796 of the predicted and uncharacterized proteins were provided some functional annotation. Nearly 67% of the identified proteins were present during all the five stages of malting indicating that major metabolic pathways that are activated during the onset of germination show minimal flux. GO enrichment analysis indicated over-representation of proteins associated with translation, carbohydrate metabolism and enzyme regulator activity during malting. Spectral counting analysis of proteins identified in all stages indicated 81 differentially abundant proteins with representative members from all the enriched GO categories. Proteins with high abundance especially during the kilning stage provide novel targets for malting barley breeding and unique markers for predicting malting quality.