The relationship of limit dextrinase, limit dextrinase inhibitor and malt quality parameters in barley and their genetic analysis

Identification of the Key Transcription Factors Regulating the Expression of the Genes Associated with Barley Malt Quality during Malting

Barley malt is produced through a malting process; it begins with steeping followed by germination and kilning, in which dramatic changes happen for a large number of physiological and biochemical traits in barley seeds. The objectives of this study were to comprehensively investigate the phenotypic changes during malting, and identify the key regulators that modulate the expression of genes associated with malt quality traits. The results showed that there was a significant positive correlation between gibberellic acid (GA) content and the activities of some hydrolytic enzymes, including α-amylases, β-amylases, and limit dextrinase (LD), and a significant negative correlation between GA and β-glucan content. Starch content had little change, but starch granules were pitted severely during malting. Weighted gene coexpression analysis (WGCNA) identified the genes associated with the greatest changes of the examined malt traits during malting. The correlation analysis and protein-protein interaction (PPI) analysis detected several key transcriptional factor (TF) regulating genes associated with malt quality. These genes and TFs regulating malting traits are potentially useful in barley breeding for malt quality improvement.

Application of Mass Spectrometry-Based Proteomics to Barley Research

Barley (Hordeum vulgare) is the fourth most cultivated crop in the world in terms of production volume, and it is also the most important raw material of the malting and brewing industries. Barley belongs to the grass (Poaceae) family and plays an important role in food security and food safety for both humans and livestock. With the global population set to reach 9.7 billion by 2050, but with less available and/or suitable land for agriculture, the use of biotechnology tools in breeding programs are of considerable importance in the quest to meet the growing food gap. Proteomics as a member of the "omics" technologies has become popular for the investigation of proteins in cereal crops and particularly barley and its related products such as malt and beer. This technology has been applied to study how proteins in barley respond to adverse environmental conditions including abiotic and/or biotic stresses, how they are impacted during food processing including malting and brewing, and the presence of proteins implicated in celiac disease. Moreover, proteomics can be used in the future to inform breeding programs that aim to enhance the nutritional value and broaden the application of this crop in new food and beverage products. Mass spectrometry analysis is a valuable tool that, along with genomics and transcriptomics, can inform plant breeding strategies that aim to produce superior barley varieties. In this review, recent studies employing both qualitative and quantitative mass spectrometry approaches are explored with a focus on their application in cultivation, manufacturing, processing, quality, and the safety of barley and its related products.

Isobaric Tags for Relative and Absolute Quantitation Proteomic Analysis of Germinating Barley under Gibberellin and Abscisic Acid Treatments

The degradation of starch in barley grains is a primary step of beer production. The addition of an appropriate amount of gibberellin (GA) promotes the production of fermentable sugars, beneficial to the brewing industry. However, the response of proteomics in germinating barley to GA and abscisic acid (ABA) treatments is not thoroughly understood. In this study, isobaric tags for relative and absolute quantitation (iTRAQ) proteomics analysis was performed to illustrate the change of proteins in Tibetan wild barley XZ72 and XZ95 under GA and ABA treatments during germination. XZ72 had more proteins upregulated than XZ95 under GA treatment, while under ABA treatments, XZ95 had more proteins upregulated than XZ72. Concerning the proteins involved in energy metabolism under GA treatment, XZ72 had more proteins upregulated than XZ95. Among the 174 proteins related to starch metabolism, 31 proteins related to starch hydrolysis, such as α-amylase, α-glucosidase, and β-fructofuranosidase, showed higher relative abundance in control and GA treatments in XZ72 than in XZ95. Analysis of correlation between proteins and metabolites indicated that higher hydrolase activity is beneficial for the accumulation of fermentable sugars during germination. On the other hand, 26 starch-synthesis-related proteins were upregulated in XZ95 under ABA treatment. It may be suggested that GA-induced proteins act as accelerators of starch degradation, while ABA-induced proteins inhibit starch degradation. The current results showed that XZ72 is highly capable of allocating the starch-hydrolyzing enzymes, which play important roles in starch breakdown.