title: A missense mutation in the glucosamine-6-phosphate N-acetyltransferase-encoding gene causes temperature-dependent growth defects and ectopic lignin deposition in Arabidopsis.
abstract: To study the regulatory mechanisms underlying lignin biosynthesis, we isolated and characterized lignescens (lig), a previously undescribed temperature-sensitive mutant of Arabidopsis thaliana that exhibits ectopic lignin deposition and growth defects under high-temperature conditions. The lig mutation was identified as a single base transition in GNA1 encoding glucosamine-6-phosphate N-acetyltransferase (GNA), a critical enzyme of UDP-N-acetylglucosamine (UDP-GlcNAc) biosynthesis. lig harbors a glycine-to-serine substitution at residue 68 (G68S) of GNA1. Enzyme activity assays of the mutant protein (GNA1(G68S)) showed its thermolability relative to the wild-type protein. The lig mutant exposed to the restrictive temperature contained a significantly smaller amount of UDP-GlcNAc than did the wild type. The growth defects and ectopic lignification of lig were suppressed by the addition of UDP-GlcNAc. Since UDP-GlcNAc is an initial sugar donor of N-glycan synthesis and impaired N-glycan synthesis is known to induce the unfolded protein response (UPR), we examined possible relationships between N-glycan synthesis, UPR, and the lig phenotype. N-glycans were reduced and LUMINAL BINDING PROTEIN3, a typical UPR gene, was expressed in lig at the restrictive temperature. Furthermore, treatment with UPR-inducing reagents phenocopied the lig mutant. Our data collectively suggest that impairment of N-glycan synthesis due to a shortage of UDP-GlcNAc leads to ectopic lignin accumulation, mostly through the UPR.
authors.affiliation: Biology and Environmental Science, Graduate School of Science and Engineering, Ehime University, Matsuyama, Ehime 790-8577, Japan.
authors.forename: Mamoru
authors.initials: M
authors.lastname: Nozaki
authors.forename: Munetaka
authors.initials: M
authors.lastname: Sugiyama
authors.forename: Jun
authors.initials: J
authors.lastname: Duan
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Uematsu
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Genda
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Sato
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D002874:Chromosome Mapping; D004789:Enzyme Activation; D057075:Enzyme Assays; D004795:Enzyme Stability; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005944:Glucosamine / Q000031:analogs & derivatives; D051081:Glucosamine 6-Phosphate N-Acetyltransferase / Q000235:genetics* / Q000378:metabolism; D019298:Glucose-6-Phosphate / Q000031:analogs & derivatives; D005998:Glycine / Q000378:metabolism; D006031:Glycosylation; D007178:Inbreeding; D008031:Lignin / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010641:Phenotype; D018517:Plant Roots / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D011134:Polysaccharides / Q000378:metabolism; D013696:Temperature; D056811:Unfolded Protein Response; D014537:Uridine Diphosphate N-Acetylglucosamine / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D011134:Polysaccharides; C077221:BIP protein, Arabidopsis; C001293:glucosamine 6-phosphate; D014537:Uridine Diphosphate N-Acetylglucosamine; D019298:Glucose-6-Phosphate; D008031:Lignin; D051081:Glucosamine 6-Phosphate N-Acetyltransferase; D005944:Glucosamine; D005998:Glycine