title: Leaf starch degradation comes out of the shadows.
abstract: During the day, plants accumulate starch in their leaves as an energy source for the coming night. Based on recent findings, the prevailing view of how the transitory starch is remobilized needs considerable revision. Analyses of transgenic and mutant plants demonstrate that plastidic glucan phosphorylase is not required for normal starch breakdown and cast doubt on the presumed essential role of alpha-amylase but do show that beta-amylase is important. Repression of the activity of a plastidic beta-amylase, the export of its product (maltose) or further metabolism of maltose by a newly identified transglucosidase impairs starch degradation. Breakdown of particulate starch also depends on the activity of glucan-water dikinase, which phosphorylates glucosyl residues within the polymer.
authors.affiliation: Institute of Plant Biotechnology, University of Stellenbosch, Private Bag X1, 7602 Matieland, Stellenbosch, South Africa. lloyd@sun.ac.za
authors.forename: James R
authors.initials: JR
authors.lastname: Lloyd
authors.forename: Jens
authors.initials: J
authors.lastname: Kossmann
authors.forename: Gerhard
authors.initials: G
authors.lastname: Ritte
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D003624:Darkness; D005947:Glucose / Q000378:metabolism; D008027:Light; D008320:Maltose / Q000378:metabolism; D010641:Phenotype; D018515:Plant Leaves / Q000378:metabolism*; D013213:Starch / Q000378:metabolism*; D000516:alpha-Amylases / Q000378:metabolism; D001614:beta-Amylase / Q000378:metabolism
chemical_list: D008320:Maltose; D013213:Starch; D000516:alpha-Amylases; D001614:beta-Amylase; D005947:Glucose