Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 14, 2013
Publication Date: June 21, 2013
Citation: Anderson, O.D. 2013. The B-hordein prolamin family of barley. Genome. 56:179-185. Interpretive Summary: The barley grain is used for both human and animal feed and in beer making. The major proteins of the grain are prolamins - proteins high in the amino acids proline and glutamine. Of the several classes of prolamins, the B-hordeins comprise up to 80% of the total prolamin fraction. The prolamins are also a causative factor in celiac disease - an autoimmune disorder with no known treatment except avoidance of wheat and barley containing foods. No complete description of the B-hordeins or their genes has previously been reported, which complicates planning strategies to avoid the celiac response. The current report describes the complete B-hordein protein and gene family of a single barley cultivar and shows different levels of expression for the individual B-hordein genes.
Technical Abstract: The spectrum of B-hordein prolamins and genes in the single barley cultivar Barke is described from an in silico analysis of 1452 B-hordein ESTs and available genomic DNA. Eleven unique B-hordein proteins are derived from EST contigs. Ten contigs encode apparent full-length B-hordeins and the eleventh contains a premature stop codon that will lead to a truncated B-hordein. The number of ESTs assigned to each sequence is used as an estimate of relative gene transcription and expression. Three of the sequences account for 79% of the total ESTs, with one sequence comprising 32% of the total ESTs and has a variant C-terminus caused by an undefined sequence change history near the 3’ coding terminus. The 70x difference in EST distribution among sequences points to the importance of understanding differential rates of expression within closely related gene families. Analysis of available genomic sequences confirms the EST assembly and reveals one full-length and two partial sequences of pseudogenes as evidenced by no matching ESTs for three of the sequences and premature stop codons and frame shifts in two sequences. Thus, the complete B-hordein gene family for cv Barke is comprised of active genes encoding ten full-length and one truncated B-hordein plus three pseudogenes.