Journal Article

Antisense Inhibition of Isoamylase Alters the Structure of Amylopectin and the Physicochemical Properties of Starch in Rice Endosperm

Naoko Fujita, Akiko Kubo, Dong-Soon Suh, Kit-Sum Wong, Jay-Lin Jane, Kenjiro Ozawa, Fumio Takaiwa, Yumiko Inaba and Yasunori Nakamura

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 6, pages 607-618
Published in print June 2003 | ISSN: 0032-0781
Published online June 2003 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcg079
Antisense Inhibition of Isoamylase Alters the Structure of Amylopectin and the Physicochemical Properties of Starch in Rice Endosperm

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This is the first report on regulation of the isoamylase1 gene to modify the structure of amylopectin and properties of starch by using antisense technology in plants. The reduction of isoamylase1 protein by about 94% in rice endosperm changed amylopectin into a water-insoluble modified amylopectin and a water-soluble polyglucan (WSP). As compared with wild-type amylopectin, the modified amylopectin had more short chains with a degree of polymerization of 5–12, while their molecular sizes were similar. The WSP, which structurally resembled the phytoglycogen in isoamylase-deficient sugary-1 mutants, accounted for about 16% of the total α-polyglucans in antisense endosperm, and it was distributed throughout the whole endosperm unlike in sugary-1 mutant. The reduction of isoamylase activity markedly lowered the gelatinization temperature from 54 to 43°C and the viscosity, and modified X-ray diffraction pattern and the granule morphology of the starch. The activity of pullulanase, the other type of starch debranching enzyme, in the antisense endosperm was similar to that in wild-type, whereas it is deficient in sugary-1 mutants. These results indicate that the isoamylase1 is essential for amylopectin biosynthesis in rice endosperm, and that alteration of the isoamylase activity is an effective means to modify the physicochemical properties and granular structure of starch.

Keywords: Keywords: Amylopectin — Isoamylase — Phytoglycogen — Pullulanase — Rice — Starch.; Abbreviations: AGPase, ADPglucose pyrophosphorylase; BE, starch branching enzyme; DBE, starch debranching enzyme; DMSO, dimethylsulfoxide; DP, degree of polymerization; DSC, differential scanning calorimetry; Glu-B1 promoter, glutelin B1 promoter; HPAEC-PAD, high-performance anion-exchange chromatography with pulsed amperometric detection; HPSEC-MALLS-RI, high-performance size-exclusion chromatography equipped with laser-light scattering and refractive index detectors; ISA, isoamylase; Mw, weight-average molecular weight; PUL, pullulanase; RVA, rapid visco analyzer; Rz, z-average radii of gyration; SEM, scanning electron micrograph; SS, soluble starch synthase; WSP, water-soluble polyglucans.

Journal Article.  8389 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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