Characterisation of the malting barley transcriptome using SAGE

Long Serial Analysis of Gene Expression (SAGE) is a technique that enables the analysis of a large number of expressed transcripts using a quantitative approach. Efficient analysis of the transcripts is achieved by concatenation of short 21 bp tags into longer clones for sequencing. To characterise the transcriptional profile of grain during the malting process we constructed eight LongSAGE libraries from Barley var. Tallon. One library was constructed from mature un-steeped seed and seven libraries were generated from barley grain at specific time points during malting, 0, 12, 24, 48, 72, 96 and 120 hours post steeping. A total of 155,206 Long SAGE tags, representing 41,909 different tags, were analysed. Tags were identified from BLASTN searches, initially within the barley cDNA database and then within the publicly available barley EST databases. EST’s were searched against the NCBI non-redundant database to assign an annotation. The twenty most abundant tags from each library were examined to identify the putative functional role of highly abundant transcripts. The largest functional groups include transcripts coding for stress response and cell defense, ribosomal proteins and storage proteins. The most abundant tag shows significant up-regulation across the malting time course. The SAGE analysis presented in this study provides an insight into the biological and physiological activity of barley seed germination and malting.