Starch formation inside plastids of higher plants

Abstract

Starch is a water-insoluble polyglucan synthesized inside the plastid stroma within plant cells, serving a crucial role in the carbon budget of the whole plant by acting as a short-term and long-term store of energy. The highly complex, hierarchical structure of the starch granule arises from the actions of a large suite of enzyme activities, in addition to physicochemical self-assembly mechanisms. This review outlines current knowledge of the starch biosynthetic pathway operating in plant cells in relation to the micro- and macro-structures of the starch granule. We highlight the gaps in our knowledge, in particular, the relationship between enzyme function and operation at the molecular level and the formation of the final, macroscopic architecture of the granule.

Keywords: Amylopectin; Amyloplasts; Amylose; Cereals; Chloroplasts; Debranching enzymes; Endosperm; Granule morphology; Malto-oligosaccharides; Phytoglycogen; Plastids; Starch; Starch branching enzyme; Starch structure models; Starch synthase.