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.