Complexity of the Barley α-Amylase Gene Families: Determination of Gene Numbers for each Family and mRNA Levels for Individual Members

Abstract

The barley α-amylase genes have served as a model system for investigating the roles of the phytohormone GA₃ in regulating gene expression. These genes are expressed in the aleurone layer, a tissue that surrounds the starchy endosperm of the grain. During germination, in response to GA synthesized by the embryo, the aleurone cells switch protein synthesis towards production and secretion of large quantities of hydrolytic enzymes that degrade the storage components in the starchy endosperm into products used for growth by the embryo. Although the magnitude of response to GA may vary when aleurone layers from different cultivars of barley are compared, the mechanism appears to be a general one and applies to other cereals, such as wheat [1] and oats [30]. Our experiments, as well as those of many other investigators in the field, use aleurone layers from H. vulgare L. cv Himalaya because this cultivar has a dramatic response to the exogenous application of GA₃.