Lipopolysaccharides and plant responses to phytopathogenic bacteria (original) (raw)
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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.
Molecular Plant-Microbe Interactions, 2004
The nonpathogenic hrcC mutant of Xanthomonas campestris pv. vesicatoria 85-10∷hrpA22 multiplied in pepper leaves if it was mixed with pathogenic strains of X. campestris pv. vesicatoria. Reactions to the mutant alone included localized deposition of phenolics and callose in papillae, and alterations to the plant cell wall leading to increased electron density. Electron microscopy showed that the localized responses were suppressed in the presence of wild-type bacteria but other wall changes occurred at some sites, involving cellulose-rich ingrowth of the wall. Multiplication of the hrp mutant in mixed inocula was confirmed by tagging 85-10∷hrpA22 using immunocytochemical location of AvrBs3 expressed from the plasmid pD36. Elicitors of callose deposition and other wall changes were isolated from the hrcC mutant. Activity in extracts of bacteria was attributed to the presence of high molecular weight lipopolysaccharides (LPS). Wild-type X. campestris pv. vesicatoria suppressed inducti...
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.
Bacterial lipopolysaccharides and plant-pathogen interactions
European Journal of Plant Pathology, 2001
Lipopolysaccharides are amphipathic molecules forming the outermost layer of the cell surface of Gram-negative bacteria. They are essential for protecting the cell from hostile environments and, in the case of pathogens, they play a direct role in interactions with eukaryotic host cells. Mutants with altered lipopolysaccharide structure have been obtained with several plant pathogenic bacteria; such mutants generally show reduced virulence. Purified lipopolysaccharide has several effects on plants, notably suppression of the hypersensitive response to subsequently inoculated avirulent pathogens. The suppression is strictly localized and is observed within a time 'window' of, typically, 10-30 h. Although infiltration of lipopolysaccharide into leaves produces no macroscopic symptoms, characteristic changes in plant gene expression can be observed. One effect is to sensitize the plant tissue to subsequent bacterial inoculation so that the sensitized tissue responds more rapidly and intensely, giving partial inhibition of bacterial growth. The synthesis of antimicrobial hydroxycinnamoyl tyramine conjugates is one facet of the process which provides an excellent biochemical model for analysing the phenomenon. Lipopolysaccharide induces the synthesis of two enzymes involved in conjugate production (tyrosine decarboxylase and tyraminehydroxycinnamoyl transferase), but the conjugates themselves are not produced until bacteria are subsequently inoculated. Using this and other examples we discuss the mechanisms of lipopolysaccharide action on plants in the context of plant disease.
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
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 Elicitation of Plant Innate Immunity by Lipooligosaccharide of Xanthomonas campestris
Journal of Biological Chemistry, 2005
(LPSs) and lipooligosaccharides (LOSs) are major components of the cell surface of Gram negative bacteria with diverse roles in bacterial pathogenesis of animals and plants that include elicitation of host defenses. Little is known about the mechanisms of perception of these molecules by plants and about the associated signal transduction pathways that trigger plant immunity. Here we address the issue of the molecular basis of elicitation of plant defenses through the structural determination of the LOS of the plant pathogen Xanthomonas campestris pv. campestris strain 8004 and examination of the effects of LOS and fragments obtained by chemical treatments on the immune response in Arabidopsis thaliana.
Plants
Pepper (Capsicum annuum L.) carrying the gds (corresponding to bs5) gene can prevent the development of bacterial leaf spot disease without HR. However, little is known regarding the development of the resistance mechanism encoded by gds, especially its influence on the bacterium. Here, the effect of gds was compared with pattern-triggered immunity (PTI), another form of asymptomatic resistance, to reveal the interactions and differences between these two defense mechanisms. The level of resistance was examined by its effect on the bacterial growth and in planta expression of the stress and pathogenicity genes of Xanthomonas euvesicatoria. PTI, which was activated with a Pseudomonas syringae hrcC mutant pretreatment, inhibited the growth of Xanthomonas euvesicatoria to a greater extent than gds, and the effect was additive when PTI was activated in gds plants. The stronger influence of PTI was further supported by the expression pattern of the dpsA bacterial stress gene, which reach...
Plant Physiology and Biochemistry, 2014
Plants lack the adaptive immunity mechanisms of jawed vertebrates, so they rely on innate immune responses to defense themselves from pathogens. The plant immune system perceives the presence of pathogens by recognition of molecules known as pathogen-associated molecular patterns (PAMPs). PAMPs have several common characteristics, including highly conserved structures, essential for the microorganism but absent in host organisms. Plants can specifically recognize PAMPs using a large set of receptors and can respond with appropriate defenses by activating a multicomponent and multilayered response.
Plant-phytopathogen interactions: bacterial responses to environmental and plant stimuli
Environmental Microbiology, 2017
Plant pathogenic bacteria attack numerous agricultural crops, causing devastating effects on plant productivity and yield. They survive in diverse environments, both in plants, as pathogens, and also outside their hosts as saprophytes. Hence, they are confronted with numerous changing environmental parameters. During infection, plant pathogens have to deal with stressful conditions, such as acidic, oxidative and osmotic stresses; anaerobiosis; plant defenses; and contact with antimicrobial compounds. These adverse conditions can reduce bacterial survival and compromise disease initiation and propagation. Successful bacterial plant pathogens must detect potential hosts and also coordinate their possibly conflicting programs for survival and virulence. Consequently, these bacteria have a strong and finely tuned capacity for sensing and responding to environmental and plant stimuli. This review summarizes our current knowledge of the signals and genetic circuits that affect survival and virulence factor expression in three important and well-studied plant pathogenic bacteria with wide host ranges and the capacity for long-term environmental survival. These are: Ralstonia solanacerarum, a vascular pathogen that causes wilt disease; Agrobacterium tumefaciens, a biotrophic tumorigenic pathogen responsible for crown gall disease and Dickeya, a brute force apoplastic pathogen responsible for soft-rot disease.