title: Properties of a novel type of starch found in the double mutant "sweet wheat".
abstract: The double mutant "sweet wheat" (SW), which produces substantial amounts of sugars in immature seeds, is missing two starch synthases, namely granule-bound starch synthase I (GBSSI) and starch synthase IIa (SSIIa). The lack of these two enzymes causes major changes in the attributes of SW seed, starch, and starch granules. SW seeds appear normal during early stages of development, but become shrunken when seeds begin to mature and dry. However, even in immature seed, starch granules are small and misshapen, and high levels of maltose are present throughout seed development. The crystallinity of SW starch is altered in that a major peak typical of the cereal A-type diffraction pattern is absent, and the gelatinization temperature of SW starch is considerably lower than that of wild-type starch. Amylopectin from SW seed has a substantially lower molecular weight than that from wild-type seed, and a low molecular weight peak with a bimodal distribution is found only in SW starch. This peak contains linear malto-oligosaccharides as well as short, branched glucans. SW starch has an increased proportion of branches with DP<10, and chains with DP 2 and 3 are particularly increased. These changes suggest that sweet wheat starch is being modified in an atypical manner by isoamylases and/or β-amylases.
authors.affiliation: NARO Tohoku Agriculture Research Center, Morioka 020-0198, Japan; Bioriginal Food and Science Corporation, Saskatoon, Canada S7J 0R1.
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Vrinten
authors.affiliation: Nippon Flour Mills Co., Ltd., Atsugi 243-0041, Japan.
authors.forename: Tomoya
authors.initials: T
authors.lastname: Shimbata
authors.affiliation: Ezaki Glico Co., Ltd., Osaka 555-8502, Japan.
authors.forename: Michiyo
authors.initials: M
authors.lastname: Yanase
authors.affiliation: Nippon Flour Mills Co., Ltd., Atsugi 243-0041, Japan.
authors.forename: Ai
authors.initials: A
authors.lastname: Sunohara
authors.affiliation: NARO Tohoku Agriculture Research Center, Morioka 020-0198, Japan.
authors.forename: Mika
authors.initials: M
authors.lastname: Saito
authors.affiliation: Nippon Flour Mills Co., Ltd., Atsugi 243-0041, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Inokuma
authors.affiliation: Nippon Flour Mills Co., Ltd., Atsugi 243-0041, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takiya
authors.affiliation: Ezaki Glico Co., Ltd., Osaka 555-8502, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Takaha
authors.affiliation: NARO Tohoku Agriculture Research Center, Morioka 020-0198, Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Nakamura
mesh_terms: D007517:Isoamylase / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000378:metabolism*; D013213:Starch / Q000096:biosynthesis* / Q000235:genetics; D013214:Starch Synthase / Q000235:genetics / Q000378:metabolism; D014908:Triticum / Q000235:genetics / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D013213:Starch; C434607:granule-bound starch synthase I; C111377:starch synthase II; D013214:Starch Synthase; D007517:Isoamylase