Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2010
Publication Date: 12/22/2010
Citation: Vinje, M.A., Willis, D.K., Duke, S.H., Henson, C.A. 2010. Differential RNA expression of Bmy1 during seed development and the association with beta-amylase accumulation, activity, and total protein. Plant Physiology and Biochemistry. 49:39-45.
Interpretive Summary: Malting barley commands a premium price in the market place primarily due to it's special abilities to convert the complex carbohydrates in the seed to simple sugars that brewer's yeast can digest. Plant breeders have long searched for inexpensive tools that can rapidly distinguish barleys with good malting potential from those without such potential. One of the more recent tools being used internationally and under consideration for use by North American plant breeders is specific sequence variation in the DNA that produces a critical enzyme that converts starch to simple sugars. The research reported here was conducted to determine if the sequence variation was useful in predicting how much of this critical enzyme would be present in the mature seed. We demonstrated that the sequence variation did not predict or determine the amount of this enzyme in the mature seed and that the amount of the enzyme accumulated was determined by how much total protein the seed produced. The impact of this work is that North American barley breeders will be unlikely to use this documented DNA sequence variation as a selection tool to develop new malting barley cultivars because it would result for the selection of high protein content, which is a negative quality factor for malting barley.
Technical Abstract: Four genotypes carrying different Bmy1 intron III alleles were analyzed for differences in Bmy1 RNA expression in developing seeds at 17, 19, and 21 days after anthesis (DAA). Ashqelon and PI 296897, wild barleys which carry the Bmy1.c and Bmy1.d intron III alleles, respectively, had 2.5 to 3- fold higher Bmy1 RNA expression than Legacy and Harrington, cultivated barleys which carry the Bmy1.a and Bmy1.b intron III alleles, respectively. The large insertion/deletions (indels) located within the promoter and the third intron of Bmy1 do not appear to affect the levels of Bmy1 transcript accumulation. However, the approximately 503 bp upstream of the Bmy1 gene is highly conserved among cultivated and wild barleys and may possibly contain the requisite transcription factor binding sites necessary for Bmy1 expression. The expression pattern of Bmy1 and the putative transcription factor binding sites observed in the promoter indicate that Bmy1 may be under the control of seed storage protein transcription factors. Beta-amylase activity levels calculated on protein basis were not significantly different at maturity between any of the four genotypes whereas Ashqelon and PI 296897 had significantly higher activity levels at maturity when calculated on a fresh weight basis. The wild barley genotypes Ashqelon and PI 296897 produce more total proteins during seed development causing them to have higher Bmy1 expression, more Bmy1 protein and thus higher Beta-amylase activity on a fresh weight basis.