title: Antisense inhibition of isoamylase alters the structure of amylopectin and the physicochemical properties of starch in rice endosperm.
abstract: 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 alpha-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 degrees 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.
authors.affiliation: Department of Biological Production, Akita Prefectural University, Akita-city, Akita, 010-0195 Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Fujita
authors.forename: Akiko
authors.initials: A
authors.lastname: Kubo
authors.forename: Dong-Soon
authors.initials: DS
authors.lastname: Suh
authors.forename: Kit-Sum
authors.initials: KS
authors.lastname: Wong
authors.forename: Jay-Lin
authors.initials: JL
authors.lastname: Jane
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Ozawa
authors.forename: Fumio
authors.initials: F
authors.lastname: Takaiwa
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Inaba
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Nakamura
mesh_terms: D000687:Amylopectin / Q000096:biosynthesis* / Q000235:genetics* / Q000648:ultrastructure; D015536:Down-Regulation / Q000235:genetics; D005782:Gels / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D005936:Glucans / Q000378:metabolism; D007517:Isoamylase / Q000037:antagonists & inhibitors* / Q000172:deficiency / Q000235:genetics; D008855:Microscopy, Electron, Scanning; D015394:Molecular Structure; D008970:Molecular Weight; D009154:Mutation / Q000235:genetics; D020320:Oligoribonucleotides, Antisense / Q000494:pharmacology; D012275:Oryza / Q000201:enzymology* / Q000235:genetics* / Q000648:ultrastructure; D012995:Solubility; D013213:Starch / Q000235:genetics* / Q000378:metabolism* / Q000648:ultrastructure; D013696:Temperature; D014783:Viscosity
chemical_list: D005782:Gels; D005936:Glucans; D020320:Oligoribonucleotides, Antisense; C009109:pullulan; D013213:Starch; D000687:Amylopectin; D007517:Isoamylase