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Results for “Plant Immunity”

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At least 163 records · Page 9Linked to original sources
PubMed2003

N-cyanomethyl-2-chloroisonicotinamide induces systemic acquired resistance in arabidopsis without salicylic acid accumulation.

Systemic acquired resistance (SAR) is a potent innate immunity system in plants that is induced through the salicylic acid-mediated pathway. N-cyanomethyl-2-chloroisonicotinamide (NCI) is able to induce a broad range of disease resistance in tobacco and rice and induces SAR marker gene expression without SA accumulation in tobacco. To clarify the detailed mode of action of NCI, we analyzed its ability to induce defense gene expression and resistance in Arabidopsis mutants that are defective in various defense signaling pathways. Wild-type Arabidopsis treated with NCI exhibited increased expression of several pathogenesis-related genes and enhanced resistance to the bacterial pathogen, Pseudomonas syringae pv. tomato DC3000. NCI induced disease resistance and PR gene expression in NahG transgenic plants, but not in the npr1 mutant. NCI could induce PR gene expression in the etr1-1, ein2-1 and jar1-1 mutants. Thus, NCI activates SAR, independently from ethylene and jasmonic acid, by stimulating the site between SA and NPR1.

Arabidopsis↗
PubMed2003

Passive immunization of mice pups through oral immunization of dams with a plant-derived vaccine.

Passive immunization plays an important role in protecting young mammals against pathogens before the maturation of their own immune systems. Although many reports have shown active immunization of animals and human through the use of plant-derived vaccines, only one report has given evidence of passive immunization of offspring through oral immunization of parents using plant-derived vaccines. In this case, a challenge alone provided the evidence of passive immunization and the mechanism through which this occurred was not investigated. This report describes the first step in elucidating the mechanism of passive immunization of offspring through actively immunizing the female parent through an orally delivered, plant-derived vaccine. The authors found passive immunization of offspring was caused by transfer of antigen-specific IgG through either transplacental transfer or ingesting colostrum. Future studies will investigate the roles of transplacental antibody transfer and ingesting colostrum in passive immunization and the possible involvement of IgA in this immunization route.

Administration, Oral↗
PubMed2006

Mucosal immunization using recombinant plant-based oral vaccines.

The induction of mucosal immunity is very important in conferring protection against pathogens that typically invade via mucosal surfaces. Delivery of a vaccine to a mucosal surface optimizes the induction of mucosal immunity. The apparent linked nature of the mucosal immune system allows delivery to any mucosal surface to potentially induce immunity at others. Oral administration is a very straightforward and inexpensive approach to deliver a vaccine to the mucosal lining of the gut. However, vaccines administered by this route are subject to proteolysis in the gastrointestinal tract. Thus, dose levels for protein subunit vaccines are likely to be very high and the antigen may need to be protected from proteolysis for oral delivery to be efficacious. Expression of candidate vaccine antigens in edible recombinant plant material offers an inexpensive means to deliver large doses of vaccines in encapsulated forms. Certain plant tissues can also stably store antigens for extensive periods of time at ambient temperatures, obviating the need for a cold-chain during vaccine storage and distribution, and so further limiting costs. Antigens can be expressed from transgenes stably incorporated into a host plant's nuclear or plastid genome, or from engineered plant viruses infected into plant tissues. Molecular approaches can serve to boost expression levels and target the expressed protein for appropriate post-translational modification. There is a wide range of options for processing plant tissues to allow for oral delivery of a palatable product. Alternatively, the expressed antigen can be enriched or purified prior to formulation in a tablet or capsule for oral delivery. Fusions to carrier molecules can stabilize the expressed antigen, aid in antigen enrichment or purification strategies, and facilitate delivery to effector sites in the gastrointestinal tract. Many antigens have been expressed in plants. In a few cases, vaccine candidates have entered into early phase clinical trials, and in the case of farmed animal vaccines into relevant animal trials.

Administration, Oral↗
PubMed2006

Plant stomata function in innate immunity against bacterial invasion.

Microbial entry into host tissue is a critical first step in causing infection in animals and plants. In plants, it has been assumed that microscopic surface openings, such as stomata, serve as passive ports of bacterial entry during infection. Surprisingly, we found that stomatal closure is part of a plant innate immune response to restrict bacterial invasion. Stomatal guard cells of Arabidopsis perceive bacterial surface molecules, which requires the FLS2 receptor, production of nitric oxide, and the guard-cell-specific OST1 kinase. To circumvent this innate immune response, plant pathogenic bacteria have evolved specific virulence factors to effectively cause stomatal reopening as an important pathogenesis strategy. We provide evidence that supports a model in which stomata, as part of an integral innate immune system, act as a barrier against bacterial infection.

Abscisic Acid↗
PubMed1982

Enzyme-assisted immune detection of plant virus proteins electroblotted onto nitrocellulose paper.

A technique for the detection of plant virus coat proteins in plant sap is described. The method entails the electroblotting of sodium dodecyl sulphate-polyacrylamide gel electrophoresis-fractionated plant extracts onto nitrocellulose paper, probing the paper with virus-specific rabbit antisera, and indirect detection of virus proteins with horseradish peroxidase-conjugated goat anti-rabbit globulins. The sensitivity and specificity of the technique were tested using brome mosaic and barley stripe mosaic viruses. As little as 1 ng per track of virus protein was detectable, either as pure virus or when mixed with plant sap. Distant serological relationships were detected amongst tobamoviruses, and amongst the bromoviruses, with single antisera. The uses of the technique in probing capsid configuration in a presumed aphid picornavirus, and in routine diagnostic practice, are described.

Antigens, Viral↗
PubMed2006

Effector-triggered immunity by the plant pathogen Phytophthora.

A new genetic locus mediating avirulence in the potato late blight pathogen Phytophthora infestans has been discovered. The Avr3b-Avr10-Avr11 locus is recognized by three different potato resistance genes, and is different from other Avr loci that have been identified thus far. This locus encodes a large protein with a WD40 domain and sequence similarities to transcription factors. Multiple, truncated copies of this gene have arisen by gene amplification and are characteristic of avirulent strains of P. infestans. Here, we describe the new avirulence locus and discuss the importance of this finding.

Models, Genetic↗
PubMed2026

A UG5 reverse transcriptase-nitrilase antiviral module confers phage immunity in the plant symbiont Sinorhizobium meliloti.

Bacteriophages exert strong selective pressure on soil- and rhizosphere-associated bacteria, including plant-associated symbionts. Reverse transcriptase-associated defense systems of the UG family are widespread across bacterial lineages, yet their ecological roles remain largely undefined. Within this family, UG5 systems are distinguished by reverse transcriptases fused to or associated with a nitrilase domain. Here, we combine phylogenetic, metagenomic, and functional analyses to investigate the evolutionary context and antiviral activity of UG5-associated systems. Phylogenetic analysis of 728 nitrilase domains places UG5-associated nitrilases within a well-supported UG-related radiation encompassing the UG1, UG5, and UG6 families, with UG1 nested within a broader UG5 lineage. Metagenomic analysis further revealed UG5-associated reverse transcriptases in soil- and rhizosphere-derived metagenomes. Based on this observation, we characterized a UG5-large reverse transcriptase (RT)-associated system, here designated DRT11, encoded on the pSymA megaplasmid of Sinorhizobium meliloti RMO17, a nitrogen-fixing symbiont of Medicago sativa. Despite lacking the transmembrane protein typical of canonical UG5-large architectures, DRT11 confers protection against naturally occurring M. sativa rhizosphere phages with podovirus-like morphology. Phage infection assays reveal protection at low multiplicities of infection, consistent with an abortive-infection-like mechanism. Moreover, mutational analyses demonstrate that antiviral activity requires only the RT and its fused C-terminal nitrilase domain, establishing DRT11 as a minimal UG5-associated antiviral system.IMPORTANCEIn this study, we report the functional characterization of a UG5-large reverse transcriptase-associated defense system (DRT11) encoded on the pSymA megaplasmid of the nitrogen-fixing plant symbiont Sinorhizobium meliloti. Using a combination of phylogenetic, metagenomic, genomic, and experimental approaches, we demonstrate that DRT11 functions as a bona fide antiviral defense module, providing protection against naturally occurring rhizosphere phages through a minimal reverse transcriptase-nitrilase architecture. This work establishes direct functional evidence for antiviral activity within the UG5 family and clarifies the evolutionary placement of UG5-associated systems within the broader UG radiation.

Phylogeny↗
PubMed2006

Differential polarization of immune responses by plant 2S seed albumins, Ber e 1, and SFA8.

The plant 2S seed albumins Ber e 1 and SFA8, although structurally very similar, vary with respect to their allergenic properties. Whereas the former represents a major allergen, the latter appears to promote only weak allergenic responses. The aim of this investigation was to determine whether the allergenic properties of Ber e 1 and SFA8 reflected differential polarization of dendritic cell (DC) and Th cell responses. We thus investigated the effect of recombinant forms of both allergens on DC and Th cell responses as indicated by cell surface phenotype and cytokine production. Exposure of murine DCs to SFA8, but not Ber e 1, resulted in production of the cytokines IL-12 p40 and TNF-alpha by a mechanism independent of recognition by TLRs. Furthermore, depending on the mouse strain used, increased expression of MHC class II and costimulatory molecules such as CD40, CD80, and CD86 was associated with exposure to SFA8, but not Ber e 1. In coculture experiments using the DO11.10 transgenic T cell that recognizes OVA peptide, DCs exposed to both allergens induced T cells to produce IFN-gamma, but only Ber e 1 could induce significant production of IL-4 and IL-5. Likewise, analysis of transcription factors shows increased T-bet with respect to both allergens, but also GATA-3 with respect to Ber e 1. Overall, our data are consistent with the idea that the ability of Ber e 1, but not SFA8, to act as a potent allergen may reflect differences in their ability to induce IL-12 production.

2S Albumins, Plant↗
PubMed1996

Transgenic Plants Created for Oral Immunization Against Diarrheal Diseases.

We have created transgenic plants that express subunit antigens of infectious bacteria and viruses. These proteins have been isolated and characterized to demonstrate that they retain immunogenic properties. When raw potatoes containing the recombinant immunogens were fed to mice, the animals were orally immunized. Research completed to date has demonstrated the feasibility of using a genetically-engineered food as an inexpensive oral vaccine production and delivery system for diarrheal disease. The system could be a convenient means to deliver vaccines to travelers. It also has great potential as an appropriate technology for producing vaccines "in country" in the developing world. This review focuses on work from our group on recombinant subunit vaccines in potato tubers against enterotoxigenic Escherichia coli and Norwalk virus.

Journal Article↗
PubMed2007

The use of protoplasts to study innate immune responses.

The use of plant protoplast transient expression system has facilitated the discovery and dissection of many signal transduction pathways in response to hormones, metabolites, and stresses. Recently, Arabidopsis protoplasts also have been used successfully to study plant innate immune responses triggered by pathogen-derived elicitors. Here, we describe the detailed protocols for studying innate immune responses, including cell death and early defense gene regulation activated by two types of elicitors, pathogen-associated molecular patterns and bacterial type III effectors in Arabidopsis protoplasts. This cell-based system simplifies the complex pathogen-plant interactions to pure individual signals and synchronized cell-autonomous responses. The application of this novel approach provides high temporal and spatial resolution to enhance our understanding of the distinct and overlapping signaling events in pathogen-associated molecular pattern- and bacterial type III effector-activated immune responses at the molecular and cellular level.

Arabidopsis↗
PubMed2004

Cysteine proteases in phytopathogenic bacteria: identification of plant targets and activation of innate immunity.

Phytopathogenic bacteria use the type-III secretion system (TTSS) to inject effector proteins into plant cells, presumably to colonize their hosts. The function of these proteins inside plant cells has remained a mystery for years. The recent discovery that the effectors XopD, AvrXv4, AvrPphB, and AvrRpt2 have cysteine protease functions reveals that the proteolysis of host substrates is an important strategy employed by pathogens to alter plant physiology. Moreover, the characterization of these proteases and their targets provides new insight to mechanisms of bacterial virulence and the activation of plant immunity.

Bacteria↗
PubMedDate not supplied

Alpha2-macroglobulin: an evolutionarily conserved arm of the innate immune system.

All animals and plants have immune systems that protect them from the diversity of pathogens that would otherwise threaten their survival. The different components of the immune system may inactivate the pathogens themselves or promote the inactivation and clearance of toxic products produced by the pathogens. An important category of virulence factors of bacterial and prokaryotic pathogens are the proteases, which act to facilitate the invasion of the pathogens and to promote their destructive growth in the host organism. The present review concentrates on the comparative biology of an evolutionarily conserved arm of the immune system, the protein, alpha2-macroglobulin. alpha2-Macroglobulin is an abundant protein of the plasma of vertebrates and members of several invertebrate phyla and functions as a broad-spectrum protease-binding protein. Protease-conjugated alpha2-macroglobulin is selectively bound by cells contacting the body fluids and alpha2-macroglobulin and its protease cargo are then internalized and degraded in secondary lysosomes of those cells. In addition to this function as an agent for protease clearance, alpha2-macroglobulin binds a variety of other ligands, including several peptide growth factors and modulates the activity of a lectin-dependent cytolytic pathway in arthropods.

Amino Acid Sequence↗