Pathogen-associated Molecular Pattern Receptors Research Articles

Ca2+-responsive phospholipid-binding BONZAI genes confer a novel role for cotton resistance to Verticillium wilt.

Verticillium wilt which produced by the soil-borne fungus Verticillium dahliae is an important biotic threat that limits cotton (Gossypium hirsutum) growth and agricultural productivity. It is very essential to explore new genes for the generation of V. dahliae resistance or tolerance cotton varieties. Ca2+ signaling as a secondary messenger is involved in pathogen stress response. Despite Ca2+-responsive phospholipid-binding BONZAI (BON) genes have intensively been investigated in Arabidopsis, their function has not still been characterized in cotton. Here, we showed that three copies of GhBON1, two copies of GhBON2 and GhBON3 were found from the genome sequences of upland cotton. The expression of GhBON1 was inducible to V. dahliae. Knocking down of GhBON1, GhBON2 and GhBON3 using virus induced gene silencing (VIGS) each increased up-regulation of defense responses in cotton. These GhBON1, GhBON2 and GhBON3-silenced plants enhanced resistance to V. dahliae accompanied by higher burst of hydrogen peroxide and decreased cell death and had more effect on the up-regulation of defense response genes. Further analysis revealed that GhBON1 could interacts with BAK1-interacting receptor-like kinase 1 (GhBIR1) and pathogen-associated molecular pattern (PAMP) receptor regulator BAK1 (GhBAK1) at plasma membrane. Our study further reveals that plant Ca2+ -responsive phospholipid-binding BONZAI genes negatively regulate Verticillium wilt with the conserved function in response to disease resistance or plant immunity.

TLR4 is one of the receptors for Chikungunya virus envelope protein E2 and regulates virus induced pro-inflammatory responses in host macrophages.

Toll like receptor 4 (TLR4), a pathogen-associated molecular pattern (PAMP) receptor, is known to exert inflammation in various cases of microbial infection, cancer and autoimmune disorders. However, any such involvement of TLR4 in Chikungunya virus (CHIKV) infection is yet to be explored. Accordingly, the role of TLR4 was investigated towards CHIKV infection and modulation of host immune responses in the current study using mice macrophage cell line RAW264.7, primary macrophage cells of different origins and in vivo mice model. The findings suggest that TLR4 inhibition using TAK-242 (a specific pharmacological inhibitor) reduces viral copy number as well as reduces the CHIKV-E2 protein level significantly using p38 and JNK-MAPK pathways. Moreover, this led to reduced expression of macrophage activation markers like CD14, CD86, MHC-II and pro-inflammatory cytokines (TNF, IL-6, MCP-1) significantly in both the mouse primary macrophages and RAW264.7 cell line, in vitro. Additionally, TAK-242-directed TLR4 inhibition demonstrated a significant reduction of percent E2-positive cells, viral titre and TNF expression in hPBMC-derived macrophages, in vitro. These observations were further validated in TLR4-knockout (KO) RAW cells. Furthermore, the interaction between CHIKV-E2 and TLR4 was demonstrated by immuno-precipitation studies, in vitro and supported by molecular docking analysis, in silico. TLR4-dependent viral entry was further validated by an anti-TLR4 antibody-mediated blocking experiment. It was noticed that TLR4 is necessary for the early events of viral infection, especially during the attachment and entry stages. Interestingly, it was also observed that TLR4 is not involved in the post-entry stages of CHIKV infection in host macrophages. The administration of TAK-242 decreased CHIKV infection significantly by reducing disease manifestations, improving survivability (around 75%) and reducing inflammation in mice model. Collectively, for the first time, this study reports TLR4 as one of the novel receptors to facilitate the attachment and entry of CHIKV in host macrophages, the TLR4-CHIKV-E2 interactions are essential for efficient viral entry and modulation of infection-induced pro-inflammatory responses in host macrophages, which might have translational implication for designing future therapeutics to regulate the CHIKV infection.

TLR7 Activation in M-CSF-Dependent Monocyte-Derived Human Macrophages Potentiates Inflammatory Responses and Prompts Neutrophil Recruitment

Toll-like receptor 7 (TLR7) is an endosomal pathogen-associated molecular pattern (PAMP) receptor that senses single-stranded RNA (ssRNA) and whose engagement results in the production of type I IFN and pro-inflammatory cytokines upon viral exposure. Recent genetic studies have established that a dysfunctional TLR7-initiated signaling is directly linked to the development of inflammatory responses. We present evidence that TLR7 is preferentially expressed by monocyte-derived macrophages generated in the presence of M-CSF (M-MØ). We now show that TLR7 activation in M-MØ triggers a weak MAPK, NFκB, and STAT1 activation and results in low production of type I IFN. Of note, TLR7 engagement reprograms MAFB+ M-MØ towards a pro-inflammatory transcriptional profile characterized by the expression of neutrophil-attracting chemokines (CXCL1-3, CXCL5, CXCL8), whose expression is dependent on the transcription factors MAFB and AhR. Moreover, TLR7-activated M-MØ display enhanced pro-inflammatory responses and a stronger production of neutrophil-attracting chemokines upon secondary stimulation. As aberrant TLR7 signaling and enhanced pulmonary neutrophil/lymphocyte ratio associate with impaired resolution of virus-induced inflammatory responses, these results suggest that targeting macrophage TLR7 might be a therapeutic strategy for viral infections where monocyte-derived macrophages exhibit a pathogenic role.

Anti-inflammatory and antibacterial potential of Ajwa date (Phoenix dactylifera L.) extract in burn infection.

Thermal burns produce tissue damage, which eliminates the protective role of tissue. Due to the extensive tissue damage from severe burns, an overactive immune response occurs. Furthermore, this raises the possibility of getting sepsis, a condition in which a bacterial infection spreads throughout the body rather than only in the area of the injury or localized infection. To determine the compounds of Ajwa dates have the potential as an anti-inflammatory and antibacterial agent in infectious thermal burns. The research method used the Preferred Reporting Items for Systematic Review and Meta-Analyses guideline. Various references were collected from the online database Google Scholar and PubMed including reports, journals, and all references mostly published no more than the past 10 years. This systematic review revealed 16 research articles that were pertinent. Polyphenolic substances such as flavonoids, glycosides, and phenolic acids were found in ajwa dates. Specified polyphenol chemicals have the ability to interact with one or more immune cell receptors, moving intracellular messages and influencing the host's immunological response. Ajwa dates' polyphenol acts as an anti-inflammatory agent in severe burns by inhibiting the expression of pathogen-associated molecular pattern receptors, controlling transcription factors, and changing the phenotype of macrophage cells, among other ways. The bacterial activity and immune response regulation of Ajwa dates, on the other hand, also serve as an antibacterial agent directly. The polyphenol compounds in Ajwa dates have the potential to operate as an anti-inflammatory and antibacterial agent in infected thermal burns.

Alterations in innate immune responses of patients with chronic rhinosinusitis related to cystic fibrosis.

The role of phagocytes of children with cystic fibrosis (CF) associated with different phenotypes of chronic rhinosinusitis (CRS) is unclear. The aim of this study was to evaluate the phagocytic capacity of blood neutrophils and monocytes and production of superoxide anion by phagocytes in patients with CF with or without chronic rhinosinusitis and with or without nasal polyps (NP). This cross-sectional study was established in 2015-2017 in a tertiary reference center to the CF treatment, Brasilia, Brazil. Sample included 30 children volunteers with CRS related to CF (n = 16) and control subjects (n = 14). Epidemiological and clinical data were compared. Collection of 15 mL of peripheral blood and nasal endoscopy to identify the presence or absence of nasal polyps (NP) were performed. Phagocytosis of Saccharomyces cerevisiae by pathogen-associated molecular pattern receptors and opsonin receptors was assessed. Superoxide anion production was evaluated. The control group showed a higher phagocytic index to monocytes and neutrophils than to the CF or CF+CRS with NP groups [Kruskal-Wallis p = 0.0025] when phagocytosis were evaluated by pathogen-associated molecular pattern receptors (5 yeasts/cell). The phagocytic index of the CF+CRS without NP group was higher than in the CF+CRS with NP group (Kruskal-Wallis p = 0.0168). In the control group, the percentage of phagocytes involved in phagocytosis and superoxide anion production (74.0 ± 9.6%) were higher in all CF groups (p < 0,0001). The innate immune response, represented by phagocytic activity and superoxide anion production by monocytes and neutrophils was more impaired in patients with CF related or not related to CRS than in the control group. However, the phagocytic function of patients without NP showed less impairment.

A conserved module regulates receptor kinase signalling in immunity and development.

Ligand recognition by cell-surface receptors underlies development and immunity in both animals and plants. Modulating receptor signalling is critical for appropriate cellular responses but the mechanisms ensuring this are poorly understood. Here, we show that signalling by plant receptors for pathogen-associated molecular patterns (PAMPs) in immunity and CLAVATA3/EMBRYO SURROUNDING REGION-RELATED peptides (CLEp) in development uses a similar regulatory module. In the absence of ligand, signalling is dampened through association with specific type-2C protein phosphatases. Upon activation, PAMP and CLEp receptors phosphorylate divergent cytosolic kinases, which, in turn, phosphorylate the phosphatases, thereby promoting receptor signalling. Our work reveals a regulatory circuit shared between immune and developmental receptor signalling, which may have broader important implications for plant receptor kinase-mediated signalling in general.

Membrane Active Immunomodulator As a Novel Therapy for an Infectious Bacterial Disease, Buruli Ulcer.

Mycobacterium ulcerans causes the necrotizing skin disease Buruli ulcer (BU), characterized by the formation of subcutaneous lesions and immunosuppression thought to be mediated by the virulence factor mycolactone. Since early BU lesions are typically painless, patients often seek standard oral antibiotic therapy at the advanced stages when the treatment is less effective. Given that currently there is no curative topical treatment for BU, our objective was to evaluate a plasma membrane fluidizer, diethyl azelate (DEA), as a potential novel topical therapy for BU. We evaluated the effects of DEA against bacterial extracts and live strains of M. ulcerans ATCC 35840 (mycolactone positive; M+) and ATCC 19423 (mycolactone negative; M-) by measuring cytokine levels in cultured cells and tissue extracts using multiplexed immunoassays and numbers of skin lesions as the endpoints. In vitro, DEA counteracted immunosuppression induced by extract from the M+ strain in the 3-D human skin model (EpiDerm) and in human dendritic cells. In vivo, topical DEA reduced immunosuppressive activities of M+ and M- strains at all stages of BU, including advanced ulcers. DEA also diminished lesion formation and ulceration, accelerated healing of skin lesions and preserved normal immune responsiveness to pathogen-associated molecular pattern receptor agonists in blood of infected animals. The efficacy of DEA in BU models is linked to overcoming the immunosuppressive activity of virulence factors produced by M. ulcerans. Thanks to its pluripotent activity, DEA is a promising novel treatment for BU and possibly other pathogenic mycobacteria.

Src family kinases (SFKs): critical regulators of microglial homeostatic functions and neurodegeneration in Parkinson's and Alzheimer's diseases.

c-Src was the first protein kinase to be described as capable of phosphorylating tyrosine residues. Subsequent identification of other tyrosine-phosphorylating protein kinases with a similar structure to c-Src gave rise to the concept of Src family kinases (SFKs). Microglia are the resident innate immune cell population of the CNS. Under physiological conditions, microglia actively participate in brain tissue homeostasis, continuously patrolling the neuronal parenchyma and exerting neuroprotective actions. Activation of pathogen-associated molecular pattern (PAMP) and damage-associated molecular pattern (DAMP) receptors induces microglial proliferation, migration toward pathological foci, phagocytosis, and changes in gene expression, concurrent with the secretion of cytokines, chemokines, and growth factors. A significant body of literature shows that SFK stimulation positively associates with microglial activation and neuropathological conditions, including Alzheimer's and Parkinson's diseases. Here, we review essential microglial homeostatic functions regulated by SFKs, including phagocytosis, environmental sensing, and secretion of inflammatory mediators. In addition, we discuss the potential of SFK modulation for microglial homeostasis in Parkinson's and Alzheimer's diseases.

Extracellular Mitochondrial Components and Effects on Cardiovascular Disease.

Besides being powerhouses of the cell, mitochondria released into extracellular space act as intercellular signaling. Mitochondria and their components mediate cell-to-cell communication in free form or embedded in a carrier. The pathogenesis of cardiovascular disease is complex, which shows close relationship with inflammation and metabolic abnormalities. Since mitochondria sustain optimal function of the heart, extracellular mitochondria are emerging as a key regulator in the development of cardiovascular disease. In this review, we provide recent findings in the presence and forms of mitochondria transfer between cells, as well as the effects of these mitochondria on vascular inflammation and ischemic myocardium. Mitochondrial transplantation is a novel treatment paradigm for patients suffering from acute cardiovascular accident and challenges the traditional methods of mitochondria isolation.

Platelet activation by charged ligands and nanoparticles: platelet glycoprotein receptors as pattern recognition receptors

Charge interactions play a critical role in the activation of the innate immune system by damage- and pathogen-associated molecular pattern receptors. The ability of these receptors to recognize a wide spectrum of ligands through a common mechanism is critical in host defense. In this article, we argue that platelet glycoprotein receptors that signal through conserved tyrosine-based motifs function as pattern recognition receptors (PRRs) for charged endogenous and exogenous ligands, including sulfated polysaccharides, charged proteins and nanoparticles. This is exemplified by GPVI, CLEC-2 and PEAR1 which are activated by a wide spectrum of endogenous and exogenous ligands, including diesel exhaust particles, sulfated polysaccharides and charged surfaces. We propose that this mechanism has evolved to drive rapid activation of platelets at sites of injury, but that under some conditions it can drive occlusive thrombosis, for example, when blood comes into contact with infectious agents or toxins. In this Opinion Article, we discuss mechanisms behind charge-mediated platelet activation and opportunities for designing nanoparticles and related agents such as dendrimers as novel antithrombotics.

Differential expression of viral pathogen-associated molecular pattern receptors mRNA in Egyptian chronic hepatitis C virus patients

BackgroundOne possible mechanism utilized by hepatitis C virus (HCV) to escape from the host’s innate immune surveillance is modification of its pathogen-associated molecular patterns (PAMPs) by altering or hiding its RNA which interfering with toll-like receptors (TLRs) signaling and ultimately hindering the production of proinflammatory cytokines, chemokines, and interferons (IFNs). This study aimed to examine the expression levels of TLR3, TLR7, and IFN-α to investigate the correlated expression pattern among them in chronic HCV patients. Patients included in this study were categorized into two different groups, non-treated chronic HCV patients and treated chronic HCV patients, in addition to healthy volunteers as a control group. The blood samples were assessed for HCVAb, HCVRNA, HCV genotypes, and different biochemical analyses. The mRNA levels of TLR3, TLR7, and IFN-α in peripheral blood of chronic HCV patients were quantitatively measured in comparison to healthy controls.ResultsThe expression levels of TLR3, TLR7, and IFN-α were significantly downregulated in non-treated chronic HCV patients compared to both treated HCV patients and control subjects. On the other hand, treated HCV patients showed non-significant downregulation of the same three sensing receptors (TLR3, TLR7, and IFN-α) compared to control group. Obviously, the expression levels of IFN-α were positively correlated with the levels of both TLR3 and TLR7.ConclusionThe exhausted innate immunity against HCV may correlate to HCV downregulation of TLR3 and TLR7 expression on innate immune cells with a subsequent decrease in INF-α production and the possibility of targeting these receptors to enhance the immune response and clear the infection needs further studies.

Long-Term Liver Expression of an Apolipoprotein A-I Mimetic Peptide Attenuates Interferon-Alpha-Induced Inflammation and Promotes Antiviral Activity.

Apolipoprotein A-I mimetic peptides are amphipathic alpha-helix peptides that display similar functions to apolipoprotein A-I. Preclinical and clinical studies have demonstrated the safety and efficacy of apolipoprotein A-I mimetic peptides in multiple indications associated with inflammatory processes. In this study, we evaluated the effect of the long-term expression of L37pA in the liver by an adeno-associated virus (AAV-L37pA) on the expression of an adeno-associated virus encoding interferon-alpha (AAV-IFNα). Long-term IFNα expression in the liver leads to lethal hematological toxicity one month after AAV administration. Concomitant administration of AAV-L37pA prevented the lethal toxicity since the IFNα expression was reduced one month after AAV administration. To identify the mechanism of action of L37pA, a genomic and proteomic analysis was performed 15 days after AAV administration when a similar level of IFNα and interferon-stimulated genes were observed in mice treated with AAV-IFNα alone and in mice treated with AAV-IFNα and AAV-L37pA. The coexpression of the apolipoprotein A-I mimetic peptide L37pA with IFNα modulated the gene expression program of IFNα, inducing a significant reduction in inflammatory pathways affecting pathogen-associated molecular patterns receptor, dendritic cells, NK cells and Th1 immune response. The proteomic analysis confirmed the impact of the L37pA activity on several inflammatory pathways and indicated an activation of LXR/RXR and PPPARα/γ nuclear receptors. Thus, long-term expression of L37pA induces an anti-inflammatory effect in the liver that allows silencing of IFNα expression mediated by an adeno-associated virus.

A phosphoinositide 5-phosphatase from Solanum tuberosum is activated by PAMP-treatment and may antagonize phosphatidylinositol 4,5-bisphosphate at Phytophthora infestans infection sites.

Potato (Solanum tuberosum) plants susceptible to late blight disease caused by the oomycete Phytophthora infestans display enhanced resistance upon infiltration with the pathogen-associated molecular pattern (PAMP), Pep-13. Here, we characterize a potato gene similar to Arabidopsis 5-phosphatases which was identified in transcript arrays performed to identify Pep-13 regulated genes, and termed StIPP. Recombinant StIPP protein specifically dephosphorylated the D5-position of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2 ) in vitro. Other phosphoinositides or soluble inositolpolyphosphates were not converted. When transiently expressed in tobacco (Nicotiana tabacum) pollen tubes, a StIPP-YFP fusion localized to the subapical plasma membrane and antagonized PtdIns(4,5)P2 -dependent effects on cell morphology, indicating in vivo functionality. Phytophthora infestans-infection of N.benthamiana leaf epidermis cells resulted in relocalization of StIPP-GFP from the plasma membrane to the extra-haustorial membrane (EHM). Colocalizion with the effector protein RFP-AvrBlb2 at infection sites is consistent with a role of StIPP in the plant-oomycete interaction. Correlation analysis of fluorescence distributions of StIPP-GFP and biosensors for PtdIns(4,5)P2 or phosphatidylinositol 4-phosphate (PtdIns4P) indicate StIPP activity predominantly at the EHM. In Arabidopsis protoplasts, expression of StIPP resulted in the stabilization of the PAMP receptor, FLAGELLIN-SENSITIVE 2, indicating that StIPP may act as a PAMP-induced and localized antagonist of PtdIns(4,5)P2 -dependent processes during plant immunity.

Host-Pathogen Interactions between Xanthomonas fragariae and Its Host Fragaria × ananassa Investigated with a Dual RNA-Seq Analysis.

Strawberry is economically important and widely grown, but susceptible to a large variety of phytopathogenic organisms. Among them, Xanthomonas fragariae is a quarantine bacterial pathogen threatening strawberry productions by causing angular leaf spots. Using whole transcriptome sequencing, the gene expression of both plant and bacteria in planta was analyzed at two time points, 12 and 29 days post inoculation, in order to compare the pathogen and host response between the stages of early visible and of well-developed symptoms. Among 28,588 known genes in strawberry and 4046 known genes in X. fragariae expressed at both time points, a total of 361 plant and 144 bacterial genes were significantly differentially expressed, respectively. The identified higher expressed genes in the plants were pathogen-associated molecular pattern receptors and pathogenesis-related thaumatin encoding genes, whereas the more expressed early genes were related to chloroplast metabolism as well as photosynthesis related coding genes. Most X. fragariae genes involved in host interaction, recognition, and pathogenesis were lower expressed at late-phase infection. This study gives a first insight into the interaction of X. fragariae with its host. The strawberry plant changed gene expression in order to consistently adapt its metabolism with the progression of infection.

Codelivery of antigens with TLR7/8 agonists leads to an improved immune response to influenza vaccination

Abstract When designing an effective and safe vaccine, inducing a protective immune response to a pathogen without also inducing unacceptable levels of immunopathology is a major challenge. One promising strategy is the use of purified or recombinant antigens along with adjuvants that specifically engage pathogen-associated molecular pattern (PAMP) receptors. This targeted approach aims to minimize immune-mediated reactogenicity. Our group has developed libraries of novel toll-like receptor (TLR)7 and/or TLR8 ligands which show a range in receptor activity. Previous studies have shown that the high potency of TLR7/8 adjuvants leads to unacceptable toxicity in human clinical trials. One strategy to overcome this toxicity is direct adjuvant-antigen conjugation, which serves to limit systemic distribution of the adjuvant through the codelivery of the antigen and adjuvant to APCs. We have demonstrated that covalent conjugation of a TLR7/8 agonist to an antigen results in improved humoral and cell-mediated responses, with decreased systemic and local inflammation. This approach allows for the use of a reduced adjuvant dose by preventing the engagement of PAMPs in the absence of antigen. We hypothesize that antigen/adjuvant codelivery boosts the engagement of CD4+ T cells and elicits the necessary cytokines to promote a Th1-related switch to antigen-specific IgG2a antibodies. In addition, engagement of TLR7/8 appears to improve cross-presentation, thereby boosting the CD8+ T cell response, which is desirable for improved immunity to influenza and other viruses. We find this approach has great potential to enhance vaccine efficacy, while reducing the immunopathology often associated with highly active TLR7/8 adjuvants.

Role of IRF8 in immune cells functions, protection against infections, and susceptibility to inflammatory diseases.

The transcription factor IRF8 (ICSBP) is required for the development and maturation of myeloid cells (dendritic cells, monocytes, macrophages), and for expression of intrinsic anti-microbial function such as antigen capture, processing and presentation to lymphoid cells, and for activation of these cells in response to cytokines and pro-inflammatory stimuli (IFN-γ, IFN-β, LPS). IRF8 deficiency in humans causes a severe primary immunodeficiency presenting as susceptibility to infections, complete or severe depletion of blood dendritic cells (DC) subsets, depletion of CD14+ and CD16+ monocytes and reduced numbers and impaired activity of NK cells. In genome-wide association studies (GWAS), sequence variants near IRF8 are significant risk factors for multiple chronic inflammatory diseases in humans including inflammatory bowel disease, lupus, rheumatoid arthritis, multiple sclerosis, and several others. Recent studies have cataloged all the genes bound by and transcriptionally activated by IRF8 in myeloid cells, either alone or in combination with other transcription factors (PU.1, IRF1, STAT1) at steady state and in response to pro-inflammatory stimuli. This IRF1/IRF8 regulome comprises immune pathways such as antigen processing and presentation pathways, expression of costimulatory molecules, cytokines and chemokines, response to stimuli such as cytokine receptors, pathogen-associated molecular pattern receptors, TLRs and nucleotide-binding oligomerization domain-like receptor signaling pathways, and small antiviral GTPases. Members of the IRF8/IRF1 regulome are over-represented amongst genes in which mutations cause primary immunodeficiencies, and are specifically enriched at GWAS loci associated with chronic inflammatory diseases in humans. These recent studies highlight a critical role of IRF8 in the activity of several immune cell types for protection against infections, but also in pathological inflammation associated with common human inflammatory conditions.

RRGPredictor, a set-theory-based tool for predicting pathogen-associated molecular pattern receptors (PRRs) and resistance (R) proteins from plants

In plant–pathogen interactions, plant immunity through pathogen-associated molecular pattern receptors (PAMPs) and R proteins, also called pattern recognition receptors (PRRs), occurs in different ways depending on both plant and pathogen species. The use and search for a structural pattern based on the presence and absence of characteristic domains, regardless of their disposition within a sequence, could be efficient in identifying PRRs proteins. Here, we develop a method mainly based on text mining and set theory to identify PRR and R genes that classify them into 13 categories based on the presence and absence of the main domains. Analyzing 24 plant and algae genomes, we showed that the RRGPredictor was more efficient, specific and sensitive than other tools already available, and identified PRR proteins with variations in size and in domain distribution throughout the sequence. Besides an easy identification of new plant PRRs proteins, RRGPredictor provided a low computational cost.

Exogenous Treatment with Glutamate Induces Immune Responses in Arabidopsis.

Plant resistance inducers (PRIs) are compounds that protect plants from diseases by activating immunity responses. Exogenous treatment with glutamate (Glu), an important amino acid for all living organisms, induces resistance against fungal pathogens in rice and tomato. To understand the molecular mechanisms of Glu-induced immunity, we used the Arabidopsis model system. We found that exogenous treatment with Glu induces resistance against pathogens in Arabidopsis. Consistent with this, transcriptome analyses of Arabidopsis seedlings showed that Glu significantly induces the expression of wound-, defense-, and stress-related genes. Interestingly, Glu activates the expression of genes induced by pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns at much later time points than the flg22 peptide, which is a bacterial-derived PAMP. The Glu receptor-like (GLR) proteins GLR3.3 and GLR3.6 are involved in the early expression of Glu-inducible genes; however, the sustained expression of these genes does not require the GLR proteins. Glu-inducible gene expression is also not affected by mutations in genes that encode PAMP receptors (EFR, FLS2, and CERK1), regulators of pattern-triggered immunity (BAK1, BKK1, BIK1, and PBL1), or a salicylic acid biosynthesis enzyme (SID2). The treatment of roots with Glu activates the expression of PAMP-, salicylic acid-, and jasmonic acid-inducible genes in leaves. Moreover, the treatment of roots with Glu primes chitin-induced responses in leaves, possibly through transcriptional activation of LYSIN-MOTIF RECEPTOR-LIKE KINASE 5 (LYK5), which encodes a chitin receptor. Because Glu treatment does not cause discernible growth retardation, Glu can be used as an effective PRI.

The maize heterotrimeric G protein β subunit controls shoot meristem development and immune responses

Heterotrimeric G proteins are important transducers of receptor signaling, functioning in plants with CLAVATA receptors in controlling shoot meristem size and with pathogen-associated molecular pattern receptors in basal immunity. However, whether specific members of the heterotrimeric complex potentiate cross-talk between development and defense, and the extent to which these functions are conserved across species, have not yet been addressed. Here we used CRISPR/Cas9 to knock out the maize G protein β subunit gene (Gβ) and found that the mutants are lethal, differing from those in Arabidopsis, in which homologous mutants have normal growth and fertility. We show that lethality is caused not by a specific developmental arrest, but by autoimmunity. We used a genetic diversity screen to suppress the lethal Gβ phenotype and also identified a maize Gβ allele with weak autoimmune responses but strong development phenotypes. Using these tools, we show that Gβ controls meristem size in maize, acting epistatically with G protein α subunit gene (Gα), suggesting that Gβ and Gα function in a common signaling complex. Furthermore, we used an association study to show that natural variation in Gβ influences maize kernel row number, an important agronomic trait. Our results demonstrate the dual role of Gβ in immunity and development in a cereal crop and suggest that it functions in cross-talk between these competing signaling networks. Therefore, modification of Gβ has the potential to optimize the trade-off between growth and defense signaling to improve agronomic production.

The transcriptome analysis of the Arabidopsis thaliana in response to the Vibrio vulnificus by RNA-sequencing.

Because of the recent increase in the demand for fresh produce, contamination of raw food products has become an issue. Foodborne diseases are frequently caused by the infection of leguminous plants by human bacterial pathogens. Moreover, contamination by Vibrio cholerae, closely related with Vibrio vulnificus, has been reported in plants and vegetables. Here, we investigated the possibility of Vibrio vulnificus 96-11-17M, an opportunistic human pathogen, to infect and colonize Arabidopsis thaliana plants, resulting in typical disease symptoms at 5 and 7 days post-inoculation in vitro and in planta under artificial and favorable conditions, respectively. RNA-Seq analysis revealed 5,360, 4,204, 4,916 and 3,741 differentially expressed genes (DEGs) at 12, 24, 48 and 72 h post-inoculation, respectively, compared with the 0 h time point. Gene Ontology analysis revealed that these DEGs act in pathways responsive to chemical and hormone stimuli and plant defense. The expression of genes involved in salicylic acid (SA)-, jasmonic acid (JA)- and ethylene (ET)-dependent pathways was altered following V. vulnificus inoculation. Genetic analyses of Arabidopsis mutant lines verified that common pathogen-associated molecular pattern (PAMP) receptors perceive the V. vulnificus infection, thus activating JA and ET signaling pathways. Our data indicate that the human bacterial pathogen V. vulnificus 96-11-17M modulates defense-related genes and host defense machinery in Arabidopsis thaliana under favorable conditions.