Malting is a controlled germination of the barley grain in preparation for brewing, distilling, or food manufacturing. Exposure to moisture leads to the activation and synthesis of enzymes that modify the endosperm's physical structure suitable for downstream use. Different barley varieties, defined by a distinct genotype, exhibit different malting characteristics in response to water and the abundance of key enzymes that are expressed. Identifying the proteins that control this response is important to barley breeders in developing varieties with desirable malting characteristics.
In this analysis, two InterGrain barley genotypes: (1) Flinders, an established premium variety, and (2) IGB1467, a trial breeding line with a unique phenotype of malting at lower moisture content was used to uncover differences in the grain proteomes. Data independent acquisition (DIA) mass spectrometry (MS) via Sequential Window Acquisition of all THeoretical fragment-ion (SWATH) was used to achieve an unbiased quantitative characterisation of the malt barley proteomes. Protein abundance patterns were measured at three time points during water uptake (imbibition). Subsequent computational biology analysis was performed to define the significant protein abundance differences between the two malt barley genotypes that differ in response to water.
A total of 7,073 unique peptides mapped to 2,316 proteins identified with 1,519 proteins quantified at a minimum of two peptides per protein and a 1% false discovery rate. Unsupervised principal component analysis (PCA) revealed proteome alteration associated with genotype and time points of ~24% and ~18%, respectively. Gene Ontology (GO) analysis revealed significant up-regulation of "Hydrolase activity" and down-regulation of "Nutrient reservoir activity" pathways in both genotypes. Malt barley proteome profiling provides insight into how the expression of different protein classes and isoforms differ between genotypes and influences industry-relevant water uptake phenotype.