Characterization of a novel barley β-amylase gene expressed only during early grain development

Abstract A developmentally regulated, novel β-amylase gene ( ESDbamy ) from Hordeum vulgare L. has 76% amino acid similarity with a previously described barley β-amylase. However, the 3' -end sequences of these β-amylases were different. The glycine-rich repeats, which are signature sequences of endosperm-type β-amylases, are absent in this novel ESDbamy gene. ESDbamy is highly expressed in the caryopsis during early development; however, it is not expressed in other tissues. Early seed development-specific (ESD) β-amylase mRNA levels and enzyme activities were higher in a shrunken endosperm mutant, seg8, than in the wild type. Seg8 has defective endosperm development, reduced starch synthesis and elevated monosaccharide concentrations