SPATIAL-DISTRIBUTION OF BETA-AMYLASE IN GERMINATING BARLEY-SEEDS BASED ON THE AVIDIN-BIOTIN-PEROXIDASE COMPLEX METHOD

In comparison with two wild type barley cultivars, Sundance and Bomi, biochemical data show that the high-lysine mutant Hiproly contains abundant amounts of lysine-rich beta-amylase, whereas mutant Riso 1508, also a high-lysine mutant, contains negligible amounts of this enzyme. Immunocytochemical studies of germinating barley seeds, using both mono- and polyclonal antibodies to beta-amylase, support the biochemical findings of enzyme abundance in developing seeds. Three immunostaining methods for localization of beta-amylase were tested; of these, the avidin-biotin-peroxidase complex method, a relatively new procedure for study of plant tissues, is by far the most sensitive. Beta-Amylase occurs predominantly in cytoplasm of the endosperm, with a minor, but previously unknown localization in the aleurone of the mid-region of the seeds. A spatial distribution of beta-amylase is seen. Endosperm in the upper and lower-regions has the greatest amount of beta-amylase, with the amount decreasing toward the mid-region. In the mid-region, a limited aleurone localization of beta-amylase is found in all four barley strains. The function of this aleurone localization is unclear. In the endosperm, the abundance of beta-amylase appears to be inversely correlated with number of starch grains per unit area in Hiproly but not in Riso 1508, yet the rate of germination of the two mutants is essentially identical. Whether beta-amylase has a role in starch metabolism in these germinating barley seeds is unclear.