Over-expression of (1,3;1,4)-β-D-glucanase isoenzyme EII gene results in decreased (1,3;1,4)-β-D-glucan content and increased starch level in barley grains

Abstract

Background: High content of (1,3;1,4)-β-d-glucan in barley grains is regarded as an undesirable factor affecting malting potential, brewing yield and feed utilization. Production of thermostable bacterial (1,3;1,4)-β-glucanase in transgenic barley grain or supplementation of exogenous bacterial (1,3;1,4)-β-glucanase has been used to improve malt and feed quality. The aim of the present study was to investigate the effect of over-expression of an endogenous (1,3;1,4)-β-glucanase on β-glucan content and grain composition in barley.

Results: A construct containing full-length HvGlb2 cDNA encoding barley (1,3;1,4)-β-glucanase isoenzyme EII under the control of a promoter of barley D-Hordein gene Hor3-1 was introduced into barley cultivar Golden Promise via Agrobacterium-mediated transformation, and transgenic plants were regenerated after hygromycin selection. The T₂ generation of proHor3:HvGlb2 transgenic lines showed increased activity of (1,3;1,4)-β-glucanase in grains. Total β-glucan content was reduced by more than 95.73% in transgenic grains compared with the wild-type control. Meanwhile, over-expression of (1,3;1,4)-β-glucanase led to an increase in 1000-grain weight, which might be due to elevated amounts of starch in the grain.

Conclusion: Manipulating the expression of (1,3;1,4)-β-glucanase EII can control the β-glucan content in grain with no apparent harmful effects on grain quality of transgenic plants. © 2016 Society of Chemical Industry.

Keywords: (1,3;1,4)-β-d-glucan; (1,3;1,4)-β-glucanase; starch; transgenic barley.