title: Expression of Escherichia coli branching enzyme in caryopses of transgenic rice results in amylopectin with an increased degree of branching.
abstract: Physiochemical properties of starch are dependent on several factors including the relative abundance of amylose and amylopectin, and the degree of branching of amylopectin. Utilizing Agrobacterium-mediated transformation, a construct containing the coding region of branching enzyme of Escherichia coli, under transcriptional control of the rice (Oryza sativa L.) starch-branching enzyme promoter was introduced into rice cv. Nakdong. To enhance glgB expression, the first intron of rice starch-branching enzyme and the matrix attachment region (MAR) sequence from chicken lysozyme were included in the expression vector. Eleven independent transgenic rice plants were generated. Southern blot analysis indicated that the copy number of glgB integrated into transgenic rice varied from one to five. High-performance liquid chromatographic analysis of starch from transgenic lines revealed that amylopectin from transgenic lines exhibited greater branching than that of non-transgenic rice. The A/B1 ratio in amylopectin increased from 1.3 to 2.3 and the total branching ratio, A+B1/B-rest, increased from 6 to 12 in transgenic rice. The observed increase in the short-chain fractions with a degree of polymerization between 6 and 10 is expected to have a significant effect on retrogradation. Our study demonstrates that amylopectin branching can be altered in vivo, thus changing the physicochemical properties of starch.
authors.affiliation: Department of Bioscience and Bioinformatics, Myongji University, 449-728 Yongin, Korea.
authors.forename: Won-Seok
authors.initials: WS
authors.lastname: Kim
authors.forename: Jukon
authors.initials: J
authors.lastname: Kim
authors.forename: Hari B
authors.initials: HB
authors.lastname: Krishnan
authors.forename: Baek Hie
authors.initials: BH
authors.lastname: Nahm
mesh_terms: D015061:1,4-alpha-Glucan Branching Enzyme / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000687:Amylopectin / Q000096:biosynthesis* / Q000737:chemistry*; D001483:Base Sequence; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D015870:Gene Expression; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D010957:Plasmids
chemical_list: D000687:Amylopectin; D015061:1,4-alpha-Glucan Branching Enzyme