Analysis of Mesorhizobium loti Glycogen Operon: Effect of Phosphoglucomutase (pgm) and Glycogen Synthase (glgA) 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.

Glycogen phosphorylase is involved in stress endurance and biofilm formation inAzospirillum brasilense Sp7

“…Glycogen is a reserve glucose polysaccharide occurring in many bacteria, with properties similar to those of animal glycogen (Preiss, 1984(Preiss, , 2006. Its metabolism in bacteria has been extensively studied and involves enzymes such as ADPglucose pyrophosphorylase, ADP-glucose glycogen synthase, glycogen branching enzyme, glycogen phosphorylase and glycogen debranching enzyme (Lepek et al, 2002). In the present study, a glgP gene, encoding glycogen phosphorylase, was identified in A. brasilense Sp7.…”

Proteomic Analysis of Soybean Root Hairs After Infection by Bradyrhizobium japonicum

“…The activation of phospholipase D was previously correlated with microtubule reorganization in living plant cells (Dhonukshe et al 2003), and therefore, it may play this role during root-hair deformation induced by compatible rhizobia (den Hartog et al 2001). Phosphoglucomutase, a key enzyme required for the formation of UDPglucose and ADP-glucose, the sugar donors for the biosynthesis of glucose-containing polysaccharides, is known to be required by rhizobia for nodulation (Lepek et al 2002). In plants, phosphoglucomutase plays a significant role in the partitioning of stored carbon.…”

A comparative proteomic analysis of the early response to compatible symbiotic bacteria in the roots of a supernodulating soybean variety

“…The upregulation of ATPase beta subunit suggests that inoculation with rhizobia leads to enhanced ATP production in soybean cells. Another upregulated protein, phosphoglucomutase, catalyzes the formation of the glycolytic entry molecule glucose-6-phosphate from glucose-phosphate produced from glycogen through the action of phosphorylase [41]. Upregulation of ATPase beta subunit and phosphoglucomutase 2 days after inoculation indicates that the demand for energy increases substantially in the early stage of symbiosis, and that the cells need to maintain a high ATP concentration.…”