TERRAPUB AGri-Bioscience Monographs (AGBM)


Vol. 4 (No. 1), pp. 1-18, 2014 doi: 10.5047/agbm.2014.00401.0001

Starch Biosynthesis in Rice Endosperm

Naoko Fujita

Department of Biological Production, Faculty of Bioresource Sciences, Akita Prefectural University, 241-438 Kaidobata-nishi, Shimoshinjo-nakano, Akita 010-0195, Japan
e-mail: naokof@akita-pu.ac.jp

(Received on March 31, 2013; Accepted on August 30, 2013; Online published on February 26, 2014)

Abstract: Starches are the most important form of carbohydrates for most organisms on earth. However, the starch structure and biosynthesis mechanisms have not been completely resolved. At least four classes of enzymes catalyze the reactions of starch biosynthesis in plants: starch synthase (SS) elongates α-glucan chains of starch, ADP-glucose pyrophosphorylase (AGPase) supplies the substrate for SS, branching enzyme (BE) forms the α-1,6-glycosidic bonds of amylopectin, and debranching enzyme (DBE) trims improper branchesgenerated by BE. Many isozymes of these enzymes encoding different genes exist ingreen plants. To understand the starch biosynthesis mechanisms, the author tried to isolate rice mutant lines and transgenic rice lines of the genes that account for starchbiosynthetic enzymes. Through the biochemical and physiological analyses of these materials during the last 15 years, the function of the isozymes expressed in the endospermof rice has been better understood. We built the model of amylopectin biosynthesis basedon the function of each isozyme. The unique starches that accumulate in the endospermof mutant lines are quite different from those of the wild type. In the near future, theauthor hopes that unique starches that accumulate in the mutant lines will be useful forindustrial applications.

Keywords: amylopectin, mutant lines, rice, starch biosynthesis, transgenic rice lines


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