Molecular Approaches to Elucidate Starch Metabolizing System and Engineer Modified Starch Properties

Abstract

Amylopectin has a tandem-cluster structure where numerous clusters with highly organized structure are tandem linked, and is synthesized by at least 4 classes of enzymes; AGPase, starch synthase (SS), branching enzyme (BE) and isoamylase (ISA). Rice plants have totally 21 kinds of enzymes, which differently contribute to amylopectin structure. Especially, SSIIa, BEIIb and ISA1 play distinct roles in formation of the backbone of cluster structure in rice endosperm. Defects in these enzymes result in modified physicochemical properties of starch granules. The expression patterns of genes encoding starch metabolizing enzymes are also demonstrated.