Subcellular Localization and Genetic Polymorphism of Isoform of Starch Branching Enzyme (SBE IIb) in Wheat Grain

Abstract

To elucidate subcellular localization and genetic polymorphism of SBE IIb,the isoform of starch branching enzyme(SBE),in wheat grain and make insight into molecular mechanism of amylopectin biosynthesis.We identified the differences of SBE IIb among 70 wheat varieties using SDS polyacrylamide gel electrophoresis(SDS-PAGE),recovered SBE IIb from polyacrylamide gel and determined its enzymatic activities.The expression levels of SBE IIb were examined during grain-filling period.The result indicated that starch granule-bound protein SGP-2,was granule-associated SBE IIb with molecular weight of 85 kD.It possessed SBE activity when SDS was removed by acetone precipitation,which reached the highest activity at the 21th day after anthesis.SBE IIb expressed at the early developing stage of wheat grain and expression quantity exhibited differences in different developing periods.Notably,the expression profile of SBE IIb showed no differences among 70 varieties.