HvBGlu3, a GH1 β-glucosidase enzyme gene, negatively influences β-glucan content in barley grains

Barley grains are rich in beta-glucan, an important factor affecting end-use quality. Previously, we identified several stable marker-trait associations (MTAs) and novel candidate genes associated with beta-glucan content in barley grains using GWAS (Genome Wide Association Study) analysis. The gene HORVU3Hr1G096910, encoding beta-glucosidase 3, named HvBGlu3, is found to be associated with beta-glucan content in barley grains. In this study, conserved domain analysis suggested that HvBGlu3 belongs to glycoside hydrolase family 1 (GH1). Gene knockout assay revealed that HvBGlu3 negatively influenced beta-glucan content in barley grains. Transcriptome analysis of developing grains of hvbglu3 mutant and the wild type indicated that the knockout of the gene led to the increased expression level of genes involved in starch and sucrose metabolism. Glucose metabolism analysis showed that the contents of many sugars in developing grains were significantly changed in hvbglu3 mutants. In conclusion, HvBGlu3 modulates beta-glucan content in barley grains by mediating starch and sucrose metabolism in developing grains. The obtained results may be useful for breeders to breed elite barley cultivars for food use by screening barley lines with loss of function of HvBGlu3 in barley breeding.