title: Starch Granule Re-Structuring by Starch Branching Enzyme and Glucan Water Dikinase Modulation Affects Caryopsis Physiology and Metabolism.
abstract: Starch is of fundamental importance for plant development and reproduction and its optimized molecular assembly is potentially necessary for correct starch metabolism. Re-structuring of starch granules in-planta can therefore potentially affect plant metabolism. Modulation of granule micro-structure was achieved by decreasing starch branching and increasing starch-bound phosphate content in the barley caryopsis starch by RNAi suppression of all three Starch Branching Enzyme (SBE) isoforms or overexpression of potato Glucan Water Dikinase (GWD). The resulting lines displayed Amylose-Only (AO) and Hyper-Phosphorylated (HP) starch chemotypes, respectively. We studied the influence of these alterations on primary metabolism, grain composition, starch structural features and starch granule morphology over caryopsis development at 10, 20 and 30 days after pollination (DAP) and at grain maturity. While HP showed relatively little effect, AO showed significant reduction in starch accumulation with re-direction to protein and β-glucan (BG) accumulation. Metabolite profiling indicated significantly higher sugar accumulation in AO, with re-partitioning of carbon to accumulate amino acids, and interestingly it also had high levels of some important stress-related metabolites and potentially protective metabolites, possibly to elude deleterious effects. Investigations on starch molecular structure revealed significant increase in starch phosphate and amylose content in HP and AO respectively with obvious differences in starch granule morphology at maturity. The results demonstrate that decreasing the storage starch branching resulted in metabolic adjustments and re-directions, tuning to evade deleterious effects on caryopsis physiology and plant performance while only little effect was evident by increasing starch-bound phosphate as a result of overexpressing GWD.
authors.affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark.
authors.forename: Shahnoor S
authors.initials: SS
authors.lastname: Shaik
authors.affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Obata
authors.affiliation: Department of Molecular Biology and Genetics, Aarhus University, Forsøgsvej 1, 4200 Slagelse, Denmark.
authors.forename: Kim H
authors.initials: KH
authors.lastname: Hebelstrup
authors.affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany.
authors.forename: Kevin
authors.initials: K
authors.lastname: Schwahn
authors.affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany.
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, Ørsteds Plads, 2800, Lyngby, Denmark.
authors.forename: Ramona V
authors.initials: RV
authors.lastname: Mateiu
authors.affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark.
authors.forename: Andreas
authors.initials: A
authors.lastname: Blennow
mesh_terms: D015061:1,4-alpha-Glucan Branching Enzyme / Q000378:metabolism; D000688:Amylose / Q000378:metabolism; D002236:Carbohydrate Conformation; D002523:Edible Grain / Q000378:metabolism; D056625:Endosperm / Q000378:metabolism; D001467:Hordeum / Q000378:metabolism*; D010755:Organophosphates / Q000378:metabolism; D064587:Osmoregulation; D010316:Particle Size; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D025341:Principal Component Analysis; D013213:Starch / Q000737:chemistry* / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D010755:Organophosphates; D010940:Plant Proteins; D013213:Starch; D000688:Amylose; D015061:1,4-alpha-Glucan Branching Enzyme; D017853:Phosphotransferases (Alcohol Group Acceptor)