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ARS Home » Pacific West Area » Aberdeen, Idaho » Small Grains and Potato Germplasm Research » Research » Publications at this Location » Publication #264774
Title: Molecular and chemical characterization of a new waxy allele in barley (Hordeum vulgare L.)

Author
item Hu, Gongshe
item Burton, Charlotte
item HONG, ZONGLIE - University Of Idaho

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2014
Publication Date: 8/15/2014
Citation: Hu, G., Burton, C.S., Hong, Z. 2014. Molecular and chemical characterization of a new waxy allele in barley (Hordeum vulgare L.). Cereal Chemistry. 91(5):438-444.

Interpretive Summary: A diet high in ß-glucan has beneficial effects on human health, such as reduction of serum cholesterol. Consequently, barley scientists are interested in increasing the amount of ß-glucan in grain. In this work, we identified and thoroughly characterized a barley mutant ‘M38’ which has high grain ß-glucan content. The high grain ß-glucan content was associated with thickened endosperm cell wall and reduced amylose accumulation. Our research also showed that the mutation is a new allele of the previously characterized Waxy gene, encoding an endosperm-specific granule-bound starch synthase I (GBSSI). The alteration of a nucleotide in the mutant resulted in the substitution of glycine with serine at position 263 in the putative ADP-glucose binding domain. This change may affect the enzyme activity of GBSSI. Our study indicated that the two pathways involved in ß-glucan and amylose biosynthesis are regulated in a reciprocal manner. This mechanism, absent in corn and rice, allows channeling of carbohydrate supply to ß-glucan accumulation when amylose biosynthesis was down-regulated by the M38 mutation in barley. We believe that the manuscript provided a novel insight in polysaccharide biosynthesis pathways in cereal endosperm cells. Such basic understanding will contribute to scientific efforts to breed barley with enhanced health benefits.

Technical Abstract: Barley M38 mutant was first selected for its high level of mixed-linkage (1,3), (1,4) beta-D-glucan (MLG) in the grain. This elevated level of MLG was found to be associated with thickened endosperm cell wall and reduced amylose accumulation. The M38 mutation was mapped to a genetic locus flanked by two molecular markers, sKT-3 and EBmac655 on chromosome 7. Molecular cloning of the M38 locus revealed its identity as a new allele of the previously characterized Waxy gene, encoding an endosperm-specific granule-bound starch synthase I (GBSSI). The M38 locus contains two alterations in nucleotide sequence from the Waxy gene. One of the nucleotide alterations would not change its protein product. The other alteration would result in the substitution of glycine at position 263 with serine in the putative ADP-glucose binding domain. This amino acid substitution alters loop structures on the exterior surface of the folded protein and may affect its enzyme activity. It appears that the two pathways involved in MLG and amylose biosynthesis are regulated in a reciprocal manner. This mechanism, absent in corn and rice, allows channeling of carbohydrate supply to the MLG accumulation when amylose biosynthesis was down-regulated by the M38 mutation in barley. A better understanding of the regulation of polysaccharide biosynthesis pathways would help improve grain traits in breeding programs and may also have potential implications in malting, biofuel, and feed.