Biosynthesis and biological function of mixed-linkage glucan in cereals

Authors: JAMALIZADEH, LEILA - University Of Idaho; Hu, Gongshe; HONG, ZONGLIE - University Of Idaho

Submitted to: Trends in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2022
Publication Date: N/A
Citation: N/A

Interpretive Summary: Mixed-linkage (1,3; 1,4) Beta-D-glucan (simply called beta-glucan) is a very important quality trait in cereal. Beta-glucan has been clinically proved that it greatly benefits human health. High content beta-glucan varieties in barley and oat has a good marketing demand. This paper systemically summarized the comprehensive researches related to beta-glucan in cereal including the characterizations in genetics, molecular biology, metabolic pathways, major genes contribution to the beta-glucan content, health benefits, and marketing value of beta-glucan. The paper will help researchers to update the current information and to use the information in designing their future experiments and help breeders to develop high value varieties more effectively.

Technical Abstract: Mixed-linkage (1,3; 1,4) beta-D-glucan, commonly known as beta-glucan, consists of repeating units of D-glucose which are joined together by beta-glycosidic bonds. The unique arrangements of beta-(1,4) and beta-(1,3) glycosidic bounds in the backbone of beta-glucan lead to producing kinks and bends in its three-dimensional (3-D) structure and this asymmetric structure is believed to increase the solubility of beta-glucan in aqueous solution. Beta-glucan is a dietary fiber found in cereal crops such as oats and barley and is of great beneficial effects on human health. As a soluble fiber, Beta-glucan can be digested partially and absorbed slowly in the human intestines. When used as the main source of polysaccharides in foods, beta-glucan does not result in blood sugar spikes after meals, which contrasts with starch and sucrose that can be absorbed quickly and cause blood sugar spikes. Supplementation of beta-glucan in diets is an effective way in reducing blood sugar and cholesterol levels and is highly recommended for patients with heart and diabetic conditions. This review will be focused on beta-glucan in cereals, especially barley. Current barley cultivars contain about 7-8% beta-glucan in grain. Mutant lines with altered levels of beta-glucan have been successfully isolated from mutagenized populations of barley. The biosynthesis of beta-glucan in plants are catalyzed by enzymes that are encoded by the cellulose synthesis-like superfamily (Csl) genes, Csl F, H and J. Mutations in these Csl genes or other genes that are involved in polysaccharide synthesis pathways have been shown to alter the levels of beta-glucan in barley. A better understanding of the genetic and biochemical basis of beta-glucan biosynthesis and accumulation would be very helpful in development of new barley cultivars with elevated or reduced levels of beta-glucan in grain.