title: The analysis of the different functions of starch-phosphorylating enzymes during the development of Arabidopsis thaliana plants discloses an unexpected role for the cytosolic isoform GWD2.
abstract: The genome of Arabidopsis thaliana encodes three glucan, water dikinases. Glucan, water dikinase 1 (GWD1; EC 2.7.9.4) and phosphoglucan, water dikinase (PWD; EC 2.7.9.5) are chloroplastic enzymes, while glucan, water dikinase 2 (GWD2) is cytosolic. Both GWDs and PWD catalyze the addition of phosphate groups to amylopectin chains at the surface of starch granules, changing its physicochemical properties. As a result, GWD1 and PWD have a positive effect on transitory starch degradation at night. Because of its cytosolic localization, GWD2 does not have the same effect. Single T-DNA mutants of either GWD1 or PWD or GWD2 have been analyzed during the entire life cycle of A. thaliana. We report that the three dikinases are all important for proper seed development. Seeds from gwd2 mutants are shrunken, with the epidermal cells of the seed coat irregularly shaped. Moreover, gwd2 seeds contain a lower lipid to protein ratio and are impaired in germination. Similar seed phenotypes were observed in pwd and gwd1 mutants, except for the normal morphology of epidermal cells in gwd1 seed coats. The gwd1, pwd and gwd2 mutants were also very similar in growth and flowering time when grown under continuous light and all three behaved differently from wild-type plants. Besides pinpointing a novel role of GWD2 and PWD in seed development, this analysis suggests that the phenotypic features of the dikinase mutants in A. thaliana cannot be explained solely in terms of defects in leaf starch degradation at night.
authors.affiliation: Department of Pharmacy and Biotechnology FaBiT, University of Bologna, Bologna, 40126, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Pirone
authors.affiliation: Department of Pharmacy and Biotechnology FaBiT, University of Bologna, Bologna, 40126, Italy.
authors.forename: Libero
authors.initials: L
authors.lastname: Gurrieri
authors.affiliation: Department of Pharmacy and Biotechnology FaBiT, University of Bologna, Bologna, 40126, Italy.
authors.forename: Ivan
authors.initials: I
authors.lastname: Gaiba
authors.affiliation: Department of Chemistry "G. Ciamician", University of Bologna, Bologna, 40126, Italy.|Institute of Science and Technology for Ceramics (ISTEC), National Research Council (CNR), Faenza, 48018, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Adamiano
authors.affiliation: Institute for the Study of Nanostructured Materials (ISNM), National Research Council (CNR), Bologna, 40129, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Valle
authors.affiliation: Department of Pharmacy and Biotechnology FaBiT, University of Bologna, Bologna, 40126, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Trost
authors.affiliation: Department of Pharmacy and Biotechnology FaBiT, University of Bologna, Bologna, 40126, Italy.
authors.forename: Francesca
authors.identifier: http://orcid.org/0000-0002-2103-4870
authors.initials: F
authors.lastname: Sparla
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D002736:Chloroplasts / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D008027:Light; D009154:Mutation; D010766:Phosphorylation; D017866:Phosphotransferases (Paired Acceptors) / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D020033:Protein Isoforms; D013213:Starch / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins
chemical_list: D029681:Arabidopsis Proteins; D017866:Phosphotransferases (Paired Acceptors); D020033:Protein Isoforms; D013213:Starch; C000625517:GWD2 protein, Arabidopsis; C500578:OK1 protein, Arabidopsis; C435922:At1g10760 protein, Arabidopsis; D009004:Monosaccharide Transport Proteins