Further Studies of the Role of Cyclic β-Glucans in Symbiosis. An <i>ndvC</i> Mutant of <i>Bradyrhizobium japonicum</i>Synthesizes Cyclodecakis-(1→3)-β-Glucosyl1

Bhagwat, Arvind A.; Mithöfer, Axel; Pfeffer, Philip E.; Kraus, Christine; Spickers, Nicole; Hotchkiss, Arland T.; Ebel, Jürgen; Keister, Donald L.

doi:10.1104/pp.119.3.1057

Cited by 81 publications

(69 citation statements)

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“…In fact, soybean defence responses provoked by the β-heptaglucoside elicitor from the plant pathogen Phytophthora sojae can be suppressed by cyclic-β-glucans produced by the soybean symbiont Bradyrhizobium japonicum 138 . As B. japonicum cyclic-β-glucans are effective antagonists of the soybean β-heptaglucoside receptor, the most likely mechanism for this suppression is competition for the same binding sites 139 .…”

Section: Rhizobial Evasion Of Plant Innate Immunitymentioning

confidence: 99%

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

et al. 2007

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Nitrogen-fixing rhizobial bacteria and leguminous plants have evolved complex signal exchange mechanisms that allow a specific bacterial species to induce its host plant to form invasion structures through which the bacteria can enter the plant root. Once the bacteria have been endocytosed within a host-membrane-bound compartment by root cells, the bacteria differentiate into a new form that can convert atmospheric nitrogen into ammonia. Bacterial differentiation and nitrogen fixation are dependent on the microaerobic environment and other support factors provided by the plant. In return, the plant receives nitrogen from the bacteria, which allows it to grow in the absence of an external nitrogen source. Here, we review recent discoveries about the mutual recognition process that allows the model rhizobial symbiont Sinorhizobium meliloti to invade and differentiate inside its host plant alfalfa (Medicago sativa) and the model host plant barrel medic (Medicago truncatula).The recent completion of the Sinorhizobium meliloti genome sequence, and the progress towards the completion of the Medicago truncatula genome sequence, have led to a surge in the molecular characterization of the determinants that are involved in the development of the symbiosis between rhizobial bacteria and leguminous plants. Aromatic compounds from legumes called flavonoids first signal the rhizobial bacteria to produce lipochitooligosaccharide compounds called Nod factors 1 . Nod factors that are secreted by the bacteria activate multiple responses in the host plant that prepare the plant to receive the invading bacteria. Nod factors and symbiotic exopolysaccharides induce the plant to form infection threads, which are thin tubules filled with bacteria that penetrate into the plant cortical tissue and deliver the bacteria to their target cells. Plant cells in the inner cortex internalize the invading bacteria in host-membrane-bound compartments that mature into structures known Correspondence to G.C.W. gwalker@mit.edu. Competing interests statementThe authors declare no competing financial interests. DATABASES Invasion of plant rootsAlthough plant roots are exposed to various micro-organisms in the soil, their cell walls form a strong protective barrier against most harmful species. The early steps in the invasion of barrel medic (M. truncatula) and alfalfa (Medicago sativa) roots by S. meliloti are characterized by the reciprocal exchange of signals that allow the bacteria to use the plant root hair cells as a means of entry. Initial signal exchangeFlavonoid compounds (2-phenyl-1,4-benzopyrone derivatives) produced by leguminous plants are the first signals to be exchanged by host-rhizobial symbiont pairs 1 (FIG. 1). Flavonoids bind bacterial NodD proteins, which are members of the LysR family of transcriptional regulators, and activate these proteins to induce the transcription of rhizobial genes 1,2 . For example, the M. sativa-derived flavonoid luteolin stimulates binding of an active form of NodD1 to an S. meliloti 'nod-box' p...

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Section: Rhizobial Evasion Of Plant Innate Immunitymentioning

confidence: 99%

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

et al. 2007

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“…Bacterial cultures for analysis of LPS were grown overnight in LB at 37 uC, diluted 1 : 100 in the same medium and grown at 37 uC for 3 h to late-exponential phase. A 10 ml sample was collected and centrifuged as described previously (Bhagwat et al, 1999;Johnson & Perry, 1976). The cell pellet was resuspended in PBS to an OD 600 of 0.5-0.6.…”

Section: Methodsmentioning

confidence: 99%

Osmoregulated periplasmic glucans of Salmonella enterica serovar Typhimurium are required for optimal virulence in mice

et al. 2009

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We purified osmoregulated periplasmic glucans (OPGs) from Salmonella enterica serovar Typhimurium and found them to be composed of 100 % glucose with 2-linked glucose as the most abundant residue, with terminal glucose, 2,3-linked and 2,6-linked glucose also present in high quantities. The two structural genes for OPG biosynthesis, opgG and opgH, form a bicistronic operon, and insertion of a kanamycin resistance gene cassette into this operon resulted in a strain devoid of OPGs. The opgGH mutant strain was impaired in motility and growth under low osmolarity conditions. The opgGH mutation also resulted in a 2 log increase in the LD 50 in mice compared to the wild-type strain SL1344. Inability to synthesize OPGs had no significant impact on the organism's lipopolysaccharide pattern or its ability to survive antimicrobial peptides-, detergent-, pH-and nutrient-stress conditions. We observed that the opgGH-defective strain respired at a reduced rate under acidic growth conditions (pH 5.0) and had lower ATP levels compared to the wild-type strain. These data indicate that OPGs of S. Typhimurium contribute towards mouse virulence as well as growth and motility under low osmolarity growth conditions.

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“…36. Additional glucan polymers used were 1,3-␤-glucooligosaccharides (MoBiTec), cyclic 1,3-1,6-␤-glucan from Bradyrhizobium japonicum (37), and ␤-glucan preparations derived from P. sojae cell walls as described (38). Briefly, mycelial cell wall-derived ␤-glucans were size-fractionated by use of gel-permeation chromatography on a calibrated Bio-Gel P-4 column.…”

Section: Methodsmentioning

confidence: 99%

An Ancient Enzyme Domain Hidden in the Putative β-Glucan Elicitor Receptor of Soybean May Play an Active Part in the Perception of Pathogen-associated Molecular Patterns during Broad Host Resistance

Fliegmann

Mithöfer

Wanner

et al. 2004

Journal of Biological Chemistry

146

115

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A successful defense against potential pathogens requires that a host organism is able to discriminate between self and nonself structures. Soybean (Glycine max L.) exploits a specific molecular pattern, a 1,6-␤-linked and 1,3-␤-branched heptaglucoside (HG), present in cell walls of the oomycetal pathogen Phytophthora sojae, as a signal compound eliciting the onset of defense reactions. The specific and high affinity HG-binding site is contained in the ␤-glucan-binding protein (GBP), which in turn is part of a proposed receptor complex. The ability to perceive and respond to Phytophthora cell wall-derived ␤-glucan elicitors is exclusive to plants that belong to the Fabaceae. However, we propose that the presence of the GBP is essential, but not sufficient for ␤-glucan elicitor-dependent disease resistance because genes encoding GBP-related proteins can be retrieved from many plant species. Furthermore, we show that the GBP is composed of two different carbohydrateactive protein domains, one containing the ␤-glucanbinding site, and the other related to glucan endoglucosidases of fungal origin. The glucan hydrolase displays most likely an endo-specific mode of action, cleaving only 1,3-␤-D-glucosidic linkages of oligoglucosides consisting of at least four moieties. Thus, the intrinsic endo-1,3-␤-glucanase activity of the GBP is perfectly suited during initial contact with Phytophthora to release oligoglucoside fragments enriched in motifs that constitute ligands for the high affinity binding site present in the same protein. The concept of innate immunity in plants receives substantial support by this highly sophisticated system using ancient enzyme modules as an active part of the recognition mechanism.

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Further Studies of the Role of Cyclic β-Glucans in Symbiosis. An ndvC Mutant of Bradyrhizobium japonicumSynthesizes Cyclodecakis-(1→3)-β-Glucosyl1

Cited by 81 publications

References 50 publications

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

Osmoregulated periplasmic glucans of Salmonella enterica serovar Typhimurium are required for optimal virulence in mice

An Ancient Enzyme Domain Hidden in the Putative β-Glucan Elicitor Receptor of Soybean May Play an Active Part in the Perception of Pathogen-associated Molecular Patterns during Broad Host Resistance

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