Exopolysaccharides of Pantoea agglomerans have different priming and eliciting activities in suspension-cultured cells of monocots and dicots (original) (raw)
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Journal of Endotoxin Research, 2007
Plants in nature are involved in a variety of interactions with Gram-negative bacteria that may be of benefit or detriment to the host. In symbiotic interactions between leguminous plants and Gram-negative bacteria of the Rhizobiaceae, atmospheric nitrogen fixed by the bacteria within specialized plant-elaborated structures is made available to the host. Beneficial interactions of plants with Pseudomonas spp. in the rhizosphere (the zone of the soil directly influenced by the roots and characterized by increased microbiological activity) can lead to enhanced plant growth, increased plant disease resistance and increased resistance to environmental stresses. Conversely, pathogens belonging to the Gram-negative genera Agrobacterium, Erwinia, Pseudomonas, Ralstonia, Xanthomonas, and Xylella are responsible for some of the most serious diseases in cultivated crops. As ubiquitous and vital components of the cell surface of Gram-negative bacteria, lipopolysaccharides (LPSs) have multiple roles in these various plant-microbe interactions. LPS contributes to the reduced permeability of the Gram-negative outer membrane. This barrier function allows growth of bacteria in unfavourable conditions that
The Plant Journal, 2002
Lipopolysaccharide (LPS) is a ubiquitous component of Gram-negative bacteria which has a number of diverse biological effects on eukaryotic cells. In contrast to the large body of work in mammalian and insect cells, the effects of LPS on plant cells have received little attention. LPS can induce defenserelated responses in plants, but in many cases these direct effects are weak. Here we have examined the effects of prior inoculation of LPS on the induction of plant defense-related responses by phytopathogenic xanthomonads in leaves of pepper (Capsicum annuum). The resistance of pepper to incompatible strains of Xanthomonas axonopodis pv. vesicatoria or to X. campestris pv. campestris is associated with increased synthesis of the hydroxycinnamoyl-tyramine conjugates, feruloyl-tyramine (FT) and coumaroyl-tyramine (CT). FT and CT are produced only in trace amounts in response to compatible strains of X. axonopodis pv. vesicatoria. Treatment of leaves with LPS from a number of bacteria did not induce the synthesis of FT and CT but altered the kinetics of induction upon subsequent bacterial inoculation. In incompatible interactions FT and CT synthesis was accelerated, whereas in compatible interactions synthesis was also considerably enhanced. The ability of the tissue to respond more rapidly was induced within 4 h of LPS treatment and the potentiated state was maintained for at least 38 h. Earlier treatment with LPS also potentiated the expression of other defense responses such as transcription of genes encoding acidic b-1,3-glucanase. Our ®ndings indicate a wider role for LPS in plant±bacterial interactions beyond its limited activity as a direct inducer of plant defenses.
Priming, induction and modulation of plant defence responses by bacterial lipopolysaccharides
Journal of Endotoxin Research, 2007
Plants in nature are involved in a variety of interactions with Gram-negative bacteria that may be of benefit or detriment to the host. In symbiotic interactions between leguminous plants and Gram-negative bacteria of the Rhizobiaceae, atmospheric nitrogen fixed by the bacteria within specialized plant-elaborated structures is made available to the host. Beneficial interactions of plants with Pseudomonas spp. in the rhizosphere (the zone of the soil directly influenced by the roots and characterized by increased microbiological activity) can lead to enhanced plant growth, increased plant disease resistance and increased resistance to environmental stresses. Conversely, pathogens belonging to the Gram-negative genera Agrobacterium, Erwinia, Pseudomonas, Ralstonia, Xanthomonas, and Xylella are responsible for some of the most serious diseases in cultivated crops. As ubiquitous and vital components of the cell surface of Gram-negative bacteria, lipopolysaccharides (LPSs) have multiple roles in these various plant-microbe interactions. LPS contributes to the reduced permeability of the Gram-negative outer membrane. This barrier function allows growth of bacteria in unfavourable conditions that
The role of lipopolysaccharides in induction of plant defence responses
Molecular Plant Pathology, 2003
Lipopolysaccharides (LPS) are ubiquitous, indispensable components of the cell surface of Gram-negative bacteria that apparently have diverse roles in bacterial pathogenesis of plants. As an outer membrane component, LPS may contribute to the exclusion of plant-derived antimicrobial compounds promoting the ability of a bacterial plant pathogen to infect plants. In contrast, LPS can be recognized by plants to directly trigger some plant defencerelated responses. LPS also sensitize plant tissue to respond more rapidly or to a greater extent to subsequently inoculated phytopathogenic bacteria. Sensitization is manifested by an accelerated synthesis of antimicrobial hydroxycinnamoyl-tyramine conjugates, in the expression patterns of genes coding for some pathogenesis-related (PR) proteins, and prevention of the hypersensitive reaction caused by avirulent bacteria. The description at the molecular level of the various effects of LPS on plants is a necessary step towards an understanding of the signal transduction mechanisms through which LPS triggers these responses. A definition of these signal transduction pathways should allow an assessment of the contribution that LPS signalling makes to plant disease resistance in both natural infections and biocontrol.
Lipopolysaccharides and plant responses to phytopathogenic bacteria
Molecular Plant Pathology, 2000
Treatment of the leaves of pepper (Capsicum annuum) cv. ECW10R with lipopolysaccharides (LPS) from both plant pathogenic and enteric bacteria alters several aspects of the plant response to subsequent inoculation with phytopathogenic xanthomonads. LPS pre-treatment prevents the hypersensitive reaction caused by strains of Xanthomonas campestris pv. vesicatoria carrying the avirulence gene avrBs1 (a gene-for-gene interaction) and by X. campestris pv. campestris (a non-host interaction). Associated with this effect are the earlier synthesis of feruloyl-and coumaroyltyramine, phenolic conjugates that are potentially antimicrobial, and alterations in the expression patterns of genes for some pathogenesis-related (PR) proteins. Similar effects on the timing of phenolic conjugate synthesis are also seen in the compatible interaction with X. campestris pv. vesicatoria , although the level of the response is lower. Recognition of LPS by plants may allow expression of resistance in the absence of catastrophic tissue damage. However phytopathogenic bacteria may have evolved mechanisms to suppress the effects of LPS (and of other non-specific bacterial elicitors) on plant cells.
The Effects of Plant-Associated Bacterial Exopolysaccharides on Plant Abiotic Stress Tolerance
Metabolites
Plant growth-promoting rhizobacteria (PGPR) are beneficial soil microorganisms that can stimulate plant growth and increase tolerance to biotic and abiotic stresses. Some PGPR are capable of secreting exopolysaccharides (EPS) to protect themselves and, consequently, their plant hosts against environmental fluctuations and other abiotic stresses such as drought, salinity, or heavy metal pollution. This review focuses on the enhancement of plant abiotic stress tolerance by bacterial EPS. We provide a comprehensive summary of the mechanisms through EPS to alleviate plant abiotic stress tolerance, including salinity, drought, temperature, and heavy metal toxicity. Finally, we discuss how these abiotic stresses may affect bacterial EPS production and its role during plant-microbe interactions.
Molecular Plant-microbe Interactions, 2007
plant's natural defense response against pathogen attack. The PRms gene encodes a fungal-inducible PR protein from maize. Here, we demonstrate that expression of PRms in transgenic rice confers broad-spectrum protection against pathogens, including fungal (Magnaporthe oryzae, Fusarium verticillioides, and Helminthosporium oryzae) and bacterial (Erwinia chrysanthemi) pathogens. The PRms-mediated disease resistance in rice plants is associated with an enhanced capacity to express and activate the natural plant defense mechanisms. Thus, PRms rice plants display a basal level of expression of endogenous defense genes in the absence of the pathogen. PRms plants also exhibit stronger and quicker defense responses during pathogen infection. We also have found that sucrose accumulates at higher levels in leaves of PRms plants. Sucrose responsiveness of rice defense genes correlates with the pathogen-responsive priming of their expression in PRms rice plants. Moreover, pretreatment of rice plants with sucrose enhances resistance to M. oryzae infection. Together, these results support a sucrose-mediated priming of defense responses in PRms rice plants which results in broad-spectrum disease resistance.
Bacterial Exopolysaccharides: Insight into Their Role in Plant Abiotic Stress Tolerance
Journal of microbiology and biotechnology, 2021
Various abiotic stressors like drought, salinity, temperature, and heavy metal are the major environmental stresses that affects agricultural productivity and crop yields all over the world. Continuous changes in climatic conditions put a selective pressure on the microbial ecosystem to produces exopolysaccharides. Apart from soil aggregation, EPS production also helps in increasing water permeability, nutrient uptake by roots, soil stability, soil fertility, plant biomass, chlorophyll content, root and shoot length, and surface area of leaves and helps maintain metabolic and physiological activities under drought stress during drought stress. EPS-producing microbes can impart salt-tolerance to plants by binding to sodium ions in the soil and preventing these ions from reaching the stem thereby decreasing sodium absorption from the soil and increasing nutrient uptake by the roots. Biofilm formation in high salinity soils increases cell viability, enhances soil fertility, and promote...