TY - JOUR A1 - Compart, Julia A1 - Li, Xiaoping A1 - Fettke, Jörg T1 - Starch-A complex and undeciphered biopolymer JF - Journal of plant physiology : biochemistry, physiology, molecular biology and biotechnology of plants N2 - Starch is a natural storage carbohydrate in plants and algae. It consists of two relatively simple homo-biopolymers, amylopectin and amylose, with only alpha-1,4 and alpha-1,6 linked glucosyl units. Starch is an essential source of nutrition and animal food, as well as an important raw material for industry. However, despite increasing knowledge, detailed information about its structure and turnover are largely lacking. In the last decades, most data were generated using bulk experiments, a method which obviously presents limitations regarding a deeper understanding of the starch metabolism. Here, we discuss some unavoidable questions arising from the existing data. We focus on a few examples related to starch biosynthesis, degradation, and structure where these limitations strongly emerge. Closing these knowledge gaps will also be extremely important for taking the necessary steps in order to set up starch-providing crops for the challenges of the ongoing climate changes, as well as for increasing the usability of starches for industrial applications by biotechnology. KW - Starch KW - Starch structure KW - Organization model KW - Starch metabolism KW - Analytical limitations Y1 - 2021 U6 - https://doi.org/10.1016/j.jplph.2021.153389 SN - 0176-1617 SN - 1618-1328 VL - 258 SP - 258 EP - 259 PB - Elsevier CY - München ER - TY - JOUR A1 - Fettke, Jörg A1 - Nunes-Nesi, Adriano A1 - Fernie, Alisdair R. A1 - Steup, Martin T1 - Identification of a novel heteroglycan-interacting protein, HIP 1.3, from Arabidopsis thaliana JF - Journal of plant physiology : biochemistry, physiology, molecular biology and biotechnology of plants N2 - Plastidial degradation of transitory starch yields mainly maltose and glucose. Following the export into the cytosol, maltose acts as donor for a glucosyl transfer to cytosolic heteroglycans as mediated by a cytosolic transglucosidase (DPE2; EC 2.4.1.25) and the second glucosyl residue is liberated as glucose. The cytosolic phosphorylase (Pho2/PHS2; EC 2.4.1.1) also interacts with heteroglycans using the same intramolecular sites as DPE2. Thus, the two glucosyl transferases interconnect the cytosolic pools of glucose and glucose 1-phosphate. Due to the complex monosaccharide pattern, other heteroglycan-interacting proteins (Hips) are expected to exist. Identification of those proteins was approached by using two types of affinity chromatography. Heteroglycans from leaves of Arabidopsis thaliana (Col-0) covalently bound to Sepharose served as ligands that were reacted with a complex mixture of buffer-soluble proteins from Arabidopsis leaves. Binding proteins were eluted by sodium chloride. For identification, SDS-PAGE, tryptic digestion and MALDI-TOF analyses were applied. A strongly interacting polypeptide (approximately 40 kDa; designated as HIP1.3) was observed as product of locus At1g09340. Arabidopsis mutants deficient in HIP1.3 were reduced in growth and contained heteroglycans displaying an altered monosaccharide pattern. Wild type plants express HIP1.3 most strongly in leaves. As revealed by immuno fluorescence, HIP1.3 is located in the cytosol of mesophyll cells but mostly associated with the cytosolic surface of the chloroplast envelope membranes. In an HIP1.3-deficient mutant the immunosignal was undetectable. Metabolic profiles from leaves of this mutant and wild type plants as well were determined by GC-MS. As compared to the wild type control, more than ten metabolites, such as ascorbic acid, fructose, fructose bisphosphate, glucose, glycine, were elevated in darkness but decreased in the light. Although the biochemical function of HIP1.3 has not yet been elucidated, it is likely to possess an important function in the central carbon metabolism of higher plants. KW - Arabidopsis thaliana KW - Carbohydrate binding proteins KW - Cytosolic heteroglycans KW - Maltose metabolism KW - Starch metabolism Y1 - 2011 U6 - https://doi.org/10.1016/j.jplph.2010.09.008 SN - 0176-1617 VL - 168 IS - 12 SP - 1415 EP - 1425 PB - Elsevier CY - Jena ER - TY - JOUR A1 - Mahlow, Sebastian A1 - Orzechowski, Slawomir A1 - Fettke, Jörg T1 - Starch phosphorylation: insights and perspectives JF - Cellular and molecular life sciences N2 - During starch metabolism, the phosphorylation of glucosyl residues of starch, to be more precise of amylopectin, is a repeatedly observed process. This phosphorylation is mediated by dikinases, the glucan, water dikinase (GWD) and the phosphoglucan, water dikinase (PWD). The starch-related dikinases utilize ATP as dual phosphate donor transferring the terminal gamma-phosphate group to water and the beta-phosphate group selectively to either C6 position or C3 position of a glucosyl residue within amylopectin. By the collaborative action of both enzymes, the initiation of a transition of alpha-glucans from highly ordered, water-insoluble state to a less order state is realized and thus the initial process of starch degradation. Consequently, mutants lacking either GWD or PWD reveal a starch excess phenotype as well as growth retardation. In this review, we focus on the increased knowledge collected over the last years related to enzymatic properties, the precise definition of the substrates, the physiological implications, and discuss ongoing questions. KW - Starch metabolism KW - Glucan, water dikinase KW - Phosphoglucan, water dikinase KW - Starch phosphorylation KW - Starch degradation Y1 - 2016 U6 - https://doi.org/10.1007/s00018-016-2248-4 SN - 1420-682X SN - 1420-9071 VL - 73 SP - 2753 EP - 2764 PB - Springer CY - Basel ER - TY - JOUR A1 - Malinova, Irina A1 - Steup, Martin A1 - Fettke, Jörg T1 - Starch-related cytosolic heteroglycans in roots from Arabidopsis thaliana JF - Journal of plant physiology : biochemistry, physiology, molecular biology and biotechnology of plants N2 - Both photoautotrophic and heterotrophic plant cells are capable of accumulating starch inside the plastid. However, depending on the metabolic state of the respective cell the starch-related carbon fluxes are different. The vast majority of the transitory starch biosynthesis relies on the hexose phosphate pools derived from the reductive pentose phosphate cycle and, therefore, is restricted to ongoing photosynthesis. Transitory starch is usually degraded in the subsequent dark period and mainly results in the formation of neutral sugars, such as glucose and maltose, that both are exported into the cytosol. The cytosolic metabolism of the two carbohydrates includes reversible glucosyl transfer reactions to a heteroglycan that are mediated by two glucosyl transferases. DPE2 and PHS2 (or, in all other species, Pho2). In heterotrophic cells, accumulation of starch mostly depends on the long distance transport of reduced carbon compounds from source to sink organs and, therefore, includes as an essential step the import of carbohydrates from the cytosol into the starch forming plastids. In this communication, we focus on starch metabolism in heterotrophic tissues from Arabidopsis thaliana wild type plants (and in various starch-related mutants as well). By using hydroponically grown A. thaliana plants, we were able to analyse starch-related biochemical processes in leaves and roots from the same plants. Within the roots we determined starch levels and the morphology of native starch granules. Cytosolic and apoplastic heteroglycans were analysed in roots and compared with those from leaves of the same plants. A. thaliana mutants lacking functional enzymes either inside the plastid (such as phosphoglucomutase) or in the cytosol (disproportionating isoenzyme 2 or the phosphorylase isozyme, PHS2) were included in this study. In roots and leaves from the three mutants (and from the respective wild type organ as well), starch and heteroglycans as well as enzyme patterns were analysed. KW - Cytosolic heteroglycans KW - Cytosolic glucosyl transferases KW - Photoautotrophic tissues KW - Heterotrophic tissues KW - Starch metabolism Y1 - 2011 U6 - https://doi.org/10.1016/j.jplph.2010.12.008 SN - 0176-1617 VL - 168 IS - 12 SP - 1406 EP - 1414 PB - Elsevier CY - Jena ER - TY - JOUR A1 - Muntaha, Sidratul Nur A1 - Li, Xiaoping A1 - Compart, Julia A1 - Apriyanto, Ardha A1 - Fettke, Jörg T1 - Carbon pathways during transitory starch degradation in Arabidopsis differentially affect the starch granule number and morphology in the dpe2/phs1 mutant background JF - Plant physiology and biochemistry : an official journal of the Federation of European Societies of Plant Physiology N2 - The Arabidopsis knockout mutant lacking both the cytosolic disproportionating enzyme 2 (DPE2) and the plastidial phosphorylase (PHS1) had a dwarf-growth phenotype, a reduced and uneven distribution of starch within the plant rosettes, and a lower starch granule number per chloroplast under standard growth conditions. In contrast, a triple mutant impaired in starch degradation by its additional lack of the glucan, water dikinase (GWD) showed improved plant growth, a starch-excess phenotype, and a homogeneous starch distribution. Furthermore, the number of starch granules per chloroplast was increased and was similar to the wild type. We concluded that ongoing starch degradation is mainly responsible for the observed phenotype of dpe2/phs1. Next, we generated two further triple mutants lacking either the phosphoglucan, water dikinase (PWD), or the disproportionating enzyme 1 (DPE1) in the background of the double mutant. Analysis of the starch metabolism revealed that even minor ongoing starch degradation observed in dpe2/phs1/pwd maintained the double mutant phenotype. In contrast, an additional blockage in the glucose pathway of starch breakdown, as in dpe2/phs1/ dpe1, resulted in a nearly starch-free phenotype and massive chloroplast degradation. The characterized mutants were discussed in the context of starch granule formation. KW - Starch granules KW - Starch metabolism KW - Starch granule number per KW - chloroplast KW - Starch morphology KW - LCSM KW - Arabidopsis thaliana Y1 - 2022 U6 - https://doi.org/10.1016/j.plaphy.2022.03.033 SN - 0981-9428 SN - 1873-2690 VL - 180 SP - 35 EP - 41 PB - Elsevier CY - Paris ER - TY - JOUR A1 - Orawetz, Tom A1 - Malinova, Irina A1 - Orzechowski, Slawomir A1 - Fettke, Jörg T1 - Reduction of the plastidial phosphorylase in potato (Solanum tuberosum L.) reveals impact on storage starch structure during growth at low temperature JF - Plant physiology and biochemistry : an official journal of the Federation of European Societies of Plant Physiology N2 - Tubers of potato (Solanum tuberosum L.), one of the most important crops, are a prominent example for an efficient production of storage starch. Nevertheless, the synthesis of this storage starch is not completely understood. The plastidial phosphorylase (Phol; EC 2.4.11) catalyzes the reversible transfer of glucosyl residues from glucose-1-phosphate to the non-reducing end of alpha-glucans with the release of orthophosphate. Thus, the enzyme is in principle able to act during starch synthesis. However, so far under normal growth conditions no alterations in tuber starch metabolism were observed. Based on analyses of other species and also from in vitro experiments with potato tuber slices it was supposed, that Phol has a stronger impact on starch metabolism, when plants grow under low temperature conditions. Therefore, we analyzed the starch content, granule size, as well as the internal structure of starch granules isolated from potato plants grown under low temperatures. Besides wild type, transgenic potato plants with a strong reduction in the Phol activity were analyzed. No significant alterations in starch content and granule size were detected. In contrast, when plants were cultivated at low temperatures the chain length distributions of the starch granules were altered. Thus, the granules contained more short glucan chains. That was not observed in the transgenic plants, revealing that Pho1 in wild type is involved in the formation of the short glucan chains, at least at low temperatures. (C) 2016 Elsevier Masson SAS. All rights reserved. KW - Potato KW - Solanum tuberosum L. KW - Plastidial phosphorylase KW - Starch synthase KW - Starch metabolism KW - Starch granule Y1 - 2016 U6 - https://doi.org/10.1016/j.plaphy.2016.01.013 SN - 0981-9428 VL - 100 SP - 141 EP - 149 PB - Elsevier CY - Paris ER -