title: Analysis of Mesorhizobium loti glycogen operon: effect of phosphoglucomutase (pgm) and glycogen synthase (g/gA) null mutants on nodulation of Lotus tenuis.
abstract: The phosphoglucomutase (pgm) gene codes for a key enzyme required for the formation of UDP-glucose and ADP-glucose, the sugar donors for the biosynthesis of glucose containing polysaccharides. A Mesorhizobium loti pgm null mutant obtained in this study contains an altered form of lipopolysaccharide (LPS), lacks exopolysaccharide (EPS), beta cyclic glucan, and glycogen and is unable to nodulate Lotus tenuis. The nonnodulating phenotype of the pgm mutant was not due to the absence of glycogen, since a glycogen synthase (glgA) null mutant effectively nodulates this legume. In M. loti, pgm is part of the glycogen metabolism gene cluster formed by GlgP (glycogen phosphorylase), glgB (glycogen branching), glgC (ADP-glucose pyrophosphorylase), glgA, pgm, and glgX (glycogen debranching). The genes are transcribed as a single transcript from glgP to at least pgm under the control of a strong promoter (promoter I) upstream of glgP. An alternative promoter (promoter II), mapping in a 154-bp DNA fragment spanning 85 bp upstream of the glgA start codon and the first 69 bp of the glgA coding region, controls the expression of glgA and pgm, independently of the rest of the upstream genes. Primer extension experiments showed that transcription starts 19 bp upstream of the glgA start codon.
authors.affiliation: Instituto de Investigaciones Biotecnológicas, INTECH, Universidad Nacional de General San Martín, CONICET, Buenos Aires, Argentina.
authors.forename: Viviana C
authors.initials: VC
authors.lastname: Lepek
authors.forename: Alejandra L
authors.initials: AL
authors.lastname: D'Antuono
authors.forename: Pablo E
authors.initials: PE
authors.lastname: Tomatis
authors.forename: Juan E
authors.initials: JE
authors.lastname: Ugalde
authors.forename: Susana
authors.initials: S
authors.lastname: Giambiagi
authors.forename: Rodolfo A
authors.initials: RA
authors.lastname: Ugalde
mesh_terms: D015061:1,4-alpha-Glucan Branching Enzyme / Q000235:genetics; D016960:Agrobacterium tumefaciens / Q000201:enzymology / Q000235:genetics; D001483:Base Sequence; D005798:Genes, Bacterial / Q000235:genetics; D005816:Genetic Complementation Test; D051599:Glucose-1-Phosphate Adenylyltransferase; D006003:Glycogen / Q000378:metabolism*; D006004:Glycogen Debranching Enzyme System / Q000235:genetics; D024981:Glycogen Phosphorylase / Q000235:genetics; D006006:Glycogen Synthase / Q000235:genetics*; D007763:Lac Operon / Q000235:genetics; D000070116:Lotus / Q000382:microbiology*; D008969:Molecular Sequence Data; D009154:Mutation; D009713:Nucleotidyltransferases / Q000235:genetics; D009876:Operon / Q000235:genetics; D010733:Phosphoglucomutase / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012230:Rhizobiaceae / Q000201:enzymology / Q000235:genetics*; D013559:Symbiosis / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D006004:Glycogen Debranching Enzyme System; D011993:Recombinant Fusion Proteins; D006003:Glycogen; D024981:Glycogen Phosphorylase; D006006:Glycogen Synthase; D015061:1,4-alpha-Glucan Branching Enzyme; D009713:Nucleotidyltransferases; D051599:Glucose-1-Phosphate Adenylyltransferase; D010733:Phosphoglucomutase