title: Starch granule initiation and growth are altered in barley mutants that lack isoamylase activity.
abstract: Two mutant lines of barley, Risø 17 and Notch-2, were found to accumulate phytoglycogen in the grain. Like the sugary mutants of maize and rice, these phytoglycogen-accumulating mutants of barley lack isoamylase activity in the developing endosperm. The mutants were shown to be allelic, and to have lesions in the isoamylase gene, isa1 that account for the absence of this enzyme. As well as causing a reduction in endosperm starch content, the mutations have a profound effect on the structure, number and timing of initiation of starch granules. There are no normal A-type or B-type granules in the mutants. The mutants have a greater number of starch granules per plastid than the wild-type and, particularly in Risø 17, this leads to the appearance of compound starch granules. These results suggest that, as well as suppressing phytoglycogen synthesis, isoamylase in the wild-type endosperm plays a role in determining the number, and hence the form, of starch granules.
authors.affiliation: Department of Plant Science, University of Adelaide, Waite Campus, Glen Osmond, SA 5064, Australia.
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Burton
authors.forename: Helen
authors.initials: H
authors.lastname: Jenner
authors.forename: Luke
authors.initials: L
authors.lastname: Carrangis
authors.forename: Brendan
authors.initials: B
authors.lastname: Fahy
authors.forename: Geoffrey B
authors.initials: GB
authors.lastname: Fincher
authors.forename: Chris
authors.initials: C
authors.lastname: Hylton
authors.forename: David A
authors.initials: DA
authors.lastname: Laurie
authors.forename: Mary
authors.initials: M
authors.lastname: Parker
authors.forename: Darren
authors.initials: D
authors.lastname: Waite
authors.forename: Sonja
authors.initials: S
authors.lastname: van Wegen
authors.forename: Tamara
authors.initials: T
authors.lastname: Verhoeven
authors.forename: Kay
authors.initials: K
authors.lastname: Denyer
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D017343:Genes, Plant; D005936:Glucans / Q000378:metabolism; D001467:Hordeum / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D007517:Isoamylase / Q000235:genetics*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009154:Mutation; D018087:Plastids / Q000378:metabolism; D013213:Starch / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D018744:DNA, Plant; D005936:Glucans; D013213:Starch; D007517:Isoamylase