Increased expression of HvGAMYB in transgenic barley increases hydrolytic enzyme production by aleurone cells in response to gibberellin

Abstract

HvGAMYB is a transcription factor protein, which is part of the gibberellin (GA) signal transduction pathway in barley aleurone cells. It activates GA-regulated genes to cause synthesis of alpha-amylase and other hydrolytic enzymes. In aleurone cells, HvGAMYB is up-regulated by GA prior to hydrolytic enzyme gene expression. In this study we tested the hypothesis that over-expression of HvGAMYB by inserting additional gene copies might increase production of the GA-induced aleurone enzymes. Transgenic lines of barley cv.Golden Promise with extra copies of the HvGAMYB gene were previously created and shown to produce increased amounts of HvGAMYB. In this study grains which were null and homozygous for the transgene were compared, and it was found that increased expression of HvGAMYB resulted in increased amounts of two GA-induced hydrolytic enzymes in both germinating grains and in GA-treated de-embryonated grains. Enzyme production by malting barley is an important quality parameter and these results indicate that it might be possible to increase the production of all GA-induced enzymes in aleurone by increasing the production of HvGAMYB. Such an outcome would be a valuable adjunct to conventional breeding programs.