Description and functional analysis of the transcriptome from malting barley

The present study aimed to establish an early model of the malting barley transcriptome, which describes the expression of genes and their ontologies, identify the period during malting with the largest dynamic shift in gene expression for future investigation, and to determine the expression patterns of all starch degrading enzyme genes relevant to the malting and brewing industry. Large dynamic increases in gene expression occurred early in malting with differential expressed genes enriched for cell wall and starch hydrolasesamongst many malting related categories. Twenty-five of forty starch degrading enzyme genes were differentially expressed in the malting barley transcriptome including eleven α-amylase genes, six β-amylase genes, three α-glucosidase genes, and all five starch debranching enzyme genes. Four new or novel α-amylase genes, one β-amylase gene (Bmy3), three α-glucosidase genes, and two isoamylase genes had appreciable expression that requires further exploration into their potential relevance to the malting and brewing industry. Five samples of Conrad, a North American 2-row spring malting cultivar, were obtained from the USDA-ARS Cereal Crops Research Unit (CCRU) in Madison, WI that originated from 2014 and 2015 crop years grown in four different barley producing regions (two in Montana, one in Idaho, and one in North Dakota). These five samples were pooled together equally (120 g w/w) and homogenized. Three micromalting replications were drawn from the pooled sample and each replication was micromalted using 110 g dry weight. Micromalting was performed using the CCRU's Traditional Malting System, which consists of steeping (4 h water immersion [16 °C] followed by 4 h air rest [18 °C] repeated until final moisture is at 45% [Total steep = 38 h]), germinating (120 h [17 °C] while rotating for 3 min every 30 min, and kilning (lowers moisture to ~4% using increasingly hotter air). Kilning was only performed to obtain malt quality data on the remaining samples after collections were finished. Dry samples were unmalted mature grain and out of steep samples were considered 0 days of germination (0 DoG). Remaining samples (1–5 DoG) were collected every 24 h after steeping (0 DoG). Samples were collected at the same time every day, flash frozen in liquid nitrogen, and stored at −80 °C. Total RNA was isolated from all seven micromalting time points (Dry, 0–5 DoG) with three micromalting replications.