title: Starch-branching enzymes preferentially associated with A-type starch granules in wheat endosperm.
abstract: Two starch granule-bound proteins (SGP), SGP-140 and SGP-145, were preferentially associated with A-type starch granules (>10 microm) in developing and mature wheat (Triticum aestivum) kernels. Immunoblotting and N-terminal sequencing suggested that the two proteins were different variants of SBEIc, a 152-kD isoform of wheat starch-branching enzyme. Both SGP-140 and SGP-145 were localized to the endosperm starch granules but were not found in the endosperm soluble fraction or pericarp starch granules younger than 15 d post anthesis (DPA). Small-size starch granules (<10 microm) initiated before 15 DPA incorporated SGP-140 and SGP-145 throughout endosperm development and grew into full-size A-type starch granules (>10 microm). In contrast, small-size starch granules harvested after 15 DPA contained only low amounts of SGP-140 and SGP-145 and developed mainly into B-type starch granules (<10 microm). Polypeptides of similar mass and immunologically related to SGP-140 and/or SGP-145 were also preferentially incorporated into A-type starch granules of barley (Hordeum vulgare), rye (Secale cereale), and triticale (x Triticosecale Wittmack) endosperm, which like wheat endosperm have a bimodal starch granule size distribution.
authors.affiliation: Plant Biotechnology Institute, National Research Council of Canada, 110 Gymnasium Place, Saskatoon, Saskatchewan, Canada S7N 0W9.
authors.forename: M
authors.initials: M
authors.lastname: Peng
authors.forename: M
authors.initials: M
authors.lastname: Gao
authors.forename: M
authors.initials: M
authors.lastname: Båga
authors.forename: P
authors.initials: P
authors.lastname: Hucl
authors.forename: R N
authors.initials: RN
authors.lastname: Chibbar
mesh_terms: D015061:1,4-alpha-Glucan Branching Enzyme / Q000032:analysis* / Q000378:metabolism; D000595:Amino Acid Sequence; D003594:Cytoplasmic Granules / Q000201:enzymology* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004792:Enzyme Precursors / Q000032:analysis* / Q000378:metabolism; D015151:Immunoblotting; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010940:Plant Proteins / Q000032:analysis* / Q000378:metabolism; D012639:Seeds / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D013213:Starch / Q000378:metabolism* / Q000648:ultrastructure; D013214:Starch Synthase / Q000032:analysis / Q000378:metabolism; D014908:Triticum / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism
chemical_list: D004792:Enzyme Precursors; D010940:Plant Proteins; D013213:Starch; D015061:1,4-alpha-Glucan Branching Enzyme; D013214:Starch Synthase