title: Chlorella starch branching enzyme II (BEII) can complement the function of BEIIb in rice endosperm.
abstract: In monocots, starch branching enzyme II (BEII) was functionally differentiated into BEIIa and BEIIb after separation from the dicots, and in cereals BEIIb plays a distinct role in amylopectin biosynthesis in the endosperm. The present study was conducted to examine to what extent a green algal BEII has an overlapping function with BEIIb in starch biosynthesis by introducing the Chlorella BEII gene into an amylose-extender (ae) mutant of rice. Chlorella BEII was found to complement the contribution of the rice endosperm BEIIb to the structures of amylopectin and starch granules because these mutated phenotypes were recovered almost completely to those of the wild type by the expression of Chlorella BEII. When the recombinant BE enzymes were incubated with the rice ae amylopectin, the branching pattern of Chlorella BEII was much more similar to that of rice BEIIb rather than rice BEIIa. Detailed analyses of BE reaction products suggests that BEIIb and Chlorella BEII only transfer chains with a degree of polymerization (DP) of 6 and 7, whereas BEIIa preferably transfers short chains with a DP of about 6-11. These results show that the Chlorella BEII is functionally similar to rice BEIIb rather than BEIIa.
authors.affiliation: CREST, Japan Science and Technology Corporation, Kawaguchi, Saitama, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Sawada
authors.forename: Perigio B
authors.initials: PB
authors.lastname: Francisco
authors.forename: Satomi
authors.initials: S
authors.lastname: Aihara
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Utsumi
authors.forename: Mayumi
authors.initials: M
authors.lastname: Yoshida
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Oyama
authors.forename: Mikio
authors.initials: M
authors.lastname: Tsuzuki
authors.forename: Hikaru
authors.initials: H
authors.lastname: Satoh
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Nakamura
mesh_terms: D015061:1,4-alpha-Glucan Branching Enzyme / Q000235:genetics / Q000378:metabolism*; D000687:Amylopectin / Q000096:biosynthesis; D002708:Chlorella / Q000201:enzymology* / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics
chemical_list: D010940:Plant Proteins; D000687:Amylopectin; D015061:1,4-alpha-Glucan Branching Enzyme; C112590:starch-branching enzyme II