Starch biosynthesis in cereal endosperm.
Stored starch generally consists of two d-glucose homopolymers, the linear polymer amylose and a highly branched glucan amylopectin that connects linear chains. Amylopectin structurally contributes to the crystalline organization of the starch granule in cereals. In the endosperm, amylopectin biosynthesis requires the proper execution of a coordinated series of enzymatic reactions involving ADP glucose pyrophosphorylase (AGPase), soluble starch synthase (SS), starch branching enzyme (BE), and starch debranching enzyme (DBE), whereas amylose is synthesized by AGPase and granule-bound starch synthase (GBSS). It is highly possible that plastidial starch phosphorylase (Pho1) plays an important role in the formation of primers for starch biosynthesis in the endosperm. Recent advances in our understanding of the functions of individual enzyme isoforms have provided new insights into how linear polymer chains and branch linkages are synthesized in cereals. In particular, genetic analyses of a suite of mutants have formed the basis of a new model outlining the role of various enzyme isoforms in cereal starch production. In our current review, we summarize the recent research findings related to starch biosynthesis in cereal endosperm, with a particular focus on rice.
Jeon
Jong-Seong
JS
Plant Metabolism Research Center & Graduate School of Biotechnology, Kyung Hee University, Yongin 446-701, Republic of Korea. jjeon@khu.ac.kr <jjeon@khu.ac.kr>
Ryoo
Nayeon
N
Hahn
Tae-Ryong
TR
Walia
Harkamal
H
Nakamura
Yasunori
Y
D002523:Edible Grain / Q000201:enzymology* / Q000235:genetics; D056625:Endosperm / Q000201:enzymology* / Q000235:genetics; D004798:Enzymes / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D012275:Oryza / Q000201:enzymology / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D013213:Starch / Q000096:biosynthesis* / Q000235:genetics
D004798:Enzymes; D010940:Plant Proteins; D013213:Starch