title: KONJAC1 and 2 Are Key Factors for GDP-Mannose Generation and Affect l-Ascorbic Acid and Glucomannan Biosynthesis in Arabidopsis.
abstract: Humans are unable to synthesize l-ascorbic acid (AsA), yet it is required as a cofactor in many critical biochemical reactions. The majority of human dietary AsA is obtained from plants. In Arabidopsis thaliana, a GDP-mannose pyrophosphorylase (GMPP), VITAMIN C DEFECTIVE1 (VTC1), catalyzes a rate-limiting step in AsA synthesis: the formation of GDP-Man. In this study, we identified two nucleotide sugar pyrophosphorylase-like proteins, KONJAC1 (KJC1) and KJC2, which stimulate the activity of VTC1. The kjc1kjc2 double mutant exhibited severe dwarfism, indicating that KJC proteins are important for growth and development. The kjc1 mutation reduced GMPP activity to 10% of wild-type levels, leading to a 60% reduction in AsA levels. On the contrary, overexpression of KJC1 significantly increased GMPP activity. The kjc1 and kjc1kjc2 mutants also exhibited significantly reduced levels of glucomannan, which is also synthesized from GDP-Man. Recombinant KJC1 and KJC2 enhanced the GMPP activity of recombinant VTC1 in vitro, while KJCs did not show GMPP activity. Yeast two-hybrid assays suggested that the stimulation of GMPP activity occurs via interaction of KJCs with VTC1. These results suggest that KJCs are key factors for the generation of GDP-Man and affect AsA level and glucomannan accumulation through the stimulation of VTC1 GMPP activity.
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Sawake
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan.
authors.forename: Noriaki
authors.initials: N
authors.lastname: Tajima
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom Biomass Engineering Program Cooperation Division, RIKEN Center for Sustainable Resource Science, Yokohama 230-0045, Japan Joint Bioenergy Institute, Emeryville, California 94608.
authors.forename: Jenny C
authors.identifier: http://orcid.org/0000-0001-6624-636X
authors.initials: JC
authors.lastname: Mortimer
authors.affiliation: Joint Bioenergy Institute, Emeryville, California 94608.
authors.forename: Jeemeng
authors.initials: J
authors.lastname: Lao
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Ishikawa
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom.
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Yu
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Yamanashi
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Yoshimi
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Kawai-Yamada
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom.
authors.forename: Paul
authors.identifier: http://orcid.org/0000-0001-9270-6286
authors.initials: P
authors.lastname: Dupree
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan.
authors.forename: Yoichi
authors.identifier: http://orcid.org/0000-0001-9835-383X
authors.initials: Y
authors.lastname: Tsumuraya
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom kotake@mail.saitama-u.ac.jp.
authors.forename: Toshihisa
authors.identifier: http://orcid.org/0000-0002-1110-5006
authors.initials: T
authors.lastname: Kotake
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006155:Guanosine Diphosphate Mannose / Q000378:metabolism*; D008351:Mannans / Q000378:metabolism*; D009154:Mutation; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D036226:Seedlings / Q000235:genetics / Q000378:metabolism; D014815:Vitamins / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D008351:Mannans; D014815:Vitamins; D006155:Guanosine Diphosphate Mannose; C022901:(1-6)-alpha-glucomannan; D009713:Nucleotidyltransferases; C026917:mannose 1-phosphate guanylyltransferase; D001205:Ascorbic Acid