title: New insights into redox control of starch degradation.
abstract: Starch is one of the major sinks of fixed carbon in photosynthetic tissues of higher plants. Carbon fixation and the synthesis of primary starch occur during the day in the chloroplast stroma, whereas starch degradation typically occurs during the following night to fuel the whole plant with energy and carbon in the absence of photosynthesis. Redox-based regulatory systems play a central role in the modulation of several chloroplastic pathways. Reversible oxidations of cysteine residues are post-translational modifications that orchestrate the precise functioning of chloroplast pathways together with changes in pH, Mg(2+) and concentrations of metabolic intermediates. Leaf starch metabolism has been intensively studied. The enzymes involved in starch synthesis and degradation have been identified and characterized. However, the redox control of the enzymes responsible for starch degradation at night remains elusive, and their response to redox transitions conflicts with the timing of the physiological events. Most of the enzymes of starch degradation are activated by reducing conditions, characteristic of daytime. Thus, redox control may have only a minor role during starch degradation at night, but could become relevant for daily stomatal opening in guard cells or in the re-allocation of fixed carbon in mesophyll cells in response to stress conditions.
authors.affiliation: Institute of Plant Biology, University of Zürich, Zollikerstrasse 107, CH-8008 Zurich, Switzerland.
authors.forename: Diana
authors.initials: D
authors.lastname: Santelia
authors.affiliation: Department of Pharmacy and Biotechnology FaBiT, University of Bologna, Via Irnerio 42, 40126 Bologna, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Trost
authors.affiliation: Department of Pharmacy and Biotechnology FaBiT, University of Bologna, Via Irnerio 42, 40126 Bologna, Italy. Electronic address: francesca.sparla@unibo.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: Sparla
mesh_terms: D005075:Biological Evolution; D002244:Carbon / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D008954:Models, Biological; D010084:Oxidation-Reduction; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D054046:Plant Stomata / Q000378:metabolism; D010944:Plants / Q000201:enzymology* / Q000235:genetics; D013213:Starch / Q000378:metabolism*; D013312:Stress, Physiological
chemical_list: D010940:Plant Proteins; D002244:Carbon; D013213:Starch