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Rescooped by Rui Jiang from Plants and Microbes
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Annu Rev Phytopathology: Plant Pathogen Effectors: Cellular Probes Interfering with Plant Defenses in Spatial and Temporal Manners (2016)

Annu Rev Phytopathology: Plant Pathogen Effectors: Cellular Probes Interfering with Plant Defenses in Spatial and Temporal Manners (2016) | Pathology | Scoop.it

Plants possess large arsenals of immune receptors capable of recognizing all pathogen classes. To cause disease, pathogenic organisms must be able to overcome physical barriers, suppress or evade immune perception, and derive nutrients from host tissues. Consequently, to facilitate some of these processes, pathogens secrete effector proteins that promote colonization. This review covers recent advances in the field of effector biology, focusing on conserved cellular processes targeted by effectors from diverse pathogens. The ability of effectors to facilitate pathogen entry into the host interior, suppress plant immune perception, and alter host physiology for pathogen benefit is discussed. Pathogens also deploy effectors in a spatial and temporal manner, depending on infection stage. Recent advances have also enhanced our understanding of effectors acting in specific plant organs and tissues. Effectors are excellent cellular probes that facilitate insight into biological processes as well as key points of vulnerability in plant immune signaling networks.


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Rescooped by Rui Jiang from Plants and Microbes
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Current Biology: Pathogen Tactics to Manipulate Plant Cell Death (2016)

Current Biology: Pathogen Tactics to Manipulate Plant Cell Death (2016) | Pathology | Scoop.it

Programmed cell death (PCD) is a conserved process among eukaryotes that serves a multitude of functional roles during an organism’s natural life cycle. PCD involves the tightly regulated process of cell death cued by specific spatiotemporal stimuli, which confer survival benefits. In eukaryotes, PCD is an essential process involved in senescence, aging, embryo development, cell differentiation, and immunity. In animal systems, morphologically distinct forms of PCD have been described (Figure 1) [1, 2]. Type I, or apoptotic cell death, is the best understood form of PCD and is defined by cell shrinkage, nuclear condensation and fragmentation, and eventual disintegration of the cell into apoptotic bodies that are digested by phagocytes. Type II cell death is an autophagic process that is induced during nutrient deprivation and chronic stress. Autophagic cell death is characterized by the rupture of the lysosome and subsequent release of toxic chemicals that degrade the cell contents. Unlike type I and type II, type III PCD is distinguished by the swelling of organelles and subsequent rupture of the plasma membrane. A programmed necrosis or necroptosis was initially believed to be an uncontrolled process of necrosis, but has been recently reclassified as type III form of cell death. Finally, pyroptosis is another recently categorized form of cell death that is mediated by caspase-1 activity. Morphologically, pyroptotic cells share characteristics of both apoptosis and necrosis [1]. Noteworthy, necroptosis and pyroptosis are pro-inflammatory forms of PCD activated by microbial infections and diverse environmental stimuli.

In plants, PCD is less rigorously classified (Figure 1). One difficulty in distinguishing the forms of PCD in plants and animals comes as a result of the different cellular morphology in plant cells — most notably the presence of the cell wall and chloroplasts. Unlike the plasma membrane, the degradation of the cell wall is not a universal feature of PCD in plants. Additionally, the formation of apoptotic bodies is not observed in plant cells, as there are no circulating phagocytes to engulf them [3]. Instead, plant cells committed to PCD release autolytic compounds stored in the vacuole that degrade cell contents. In these cases, the cell wall may develop perforations for the absorption and recycling of cellular components by neighboring cells. Although not as well characterized as the mitochondria, the chloroplasts have been shown to induce light-dependent PCD through singlet oxygen species (1O2) that may function in parallel to mitochondrial-mediated PCD at an early step in initiating the rupture of the vacuole [3].

A specialized form of plant cell death called hypersensitive response (HR) is initiated as a defense response to pathogen infection. HR shares morphological features and molecular mechanisms reminiscent of both pyroptosis and necroptosis [4]. Moreover, HR is unique in that it induces a signaling cascade to propagate immunity in neighboring cells as well as priming distal tissues for potential pathogen challenge, a phenomenon known as systemic acquired resistance [5]. Here we will briefly describe diverse plant disease resistance pathways, early molecular events during pathogen perception, and downstream signaling components. We will thoroughly discuss how pathogens have evolved strategies to circumvent and/or suppress diverse immune responses, in particular plant cell death. While many of these mechanisms involve indirect disabling of upstream immune responses to avoid cell death, direct manipulation of PCD regulators by pathogen effectors has not been extensively explored in the literature, and will be the focal point of this article.


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Rakesh Yashroy's curator insight, July 27, 10:06 PM
Good description of APOPTOSIS in animal and plant cells. Gram negative pathogens like Salmonella use their outer membrane vesicles to signal hijacking and apoptosis in defense macrophages in animal body @ http://s3.amazonaws.com/academia.edu.documents/33932139/1211.pdf?AWSAccessKeyId=AKIAJ56TQJRTWSMTNPEA&Expires=1469674971&Signature=0HXlHa3eNfInsWTE0YqGOgD6HTA%3D&response-content-disposition=inline%3B%20filename%3DYashRoy_R_C_2007_Mechanism_of_infection.pdf
Rescooped by Rui Jiang from Plant Immunity And Microbial Effectors
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Salicylic acid biosynthesis is enhanced and contributes to increased biotrophic pathogen resistance in Arabidopsis hybrids

Salicylic acid biosynthesis is enhanced and contributes to increased biotrophic pathogen resistance in Arabidopsis hybrids | Pathology | Scoop.it
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The molecular basis for heterosis, the phenomenon whereby hybrid plants show phenotypic superiority to their parents, remains poorly understood. Here, Yang et al .

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Rescooped by Rui Jiang from Plants and Microbes
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Cell Host & Microbe: The Calcium-Dependent Protein Kinase CPK28 Buffers Plant Immunity and Regulates BIK1 Turnover (2014)

Cell Host & Microbe: The Calcium-Dependent Protein Kinase CPK28 Buffers Plant Immunity and Regulates BIK1 Turnover (2014) | Pathology | Scoop.it

• A forward-genetic screen identifies loci regulating Arabidopsis immune signaling
• MOB1/CPK28 negatively regulates immune signaling triggered by infection and PAMPs
• CPK28 interacts with and phosphorylates the central immune regulator BIK1
• CPK28 buffers immune responses and contributes to BIK1 turnover

 

Plant perception of pathogen-associated molecular patterns (PAMPs) triggers a phosphorylation relay leading to PAMP-triggered immunity (PTI). Despite increasing knowledge of PTI signaling, how immune homeostasis is maintained remains largely unknown. Here we describe a forward-genetic screen to identify loci involved in PTI and characterize the Arabidopsis calcium-dependent protein kinase CPK28 as a negative regulator of immune signaling. Genetic analyses demonstrate that CPK28 attenuates PAMP-triggered immune responses and antibacterial immunity. CPK28 interacts with and phosphorylates the plasma-membrane-associated cytoplasmic kinase BIK1, an important convergent substrate of multiple pattern recognition receptor (PRR) complexes. We find that BIK1 is rate limiting in PTI signaling and that it is continuously turned over to maintain cellular homeostasis. We further show that CPK28 contributes to BIK1 turnover. Our results suggest a negative regulatory mechanism that continually buffers immune signaling by controlling the turnover of this key signaling kinase.


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The Power Of The Mind

The Power Of The Mind | Pathology | Scoop.it
“Many apparently identical movements can be executed with different muscular combinations. This is why a horse can be crippled or rehabilitated by the same movement”
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Rescooped by Rui Jiang from Phytophthora biology
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PLOS Pathogens: Functionally Redundant RXLR Effectors from Phytophthora infestans Act at Different Steps to Suppress Early flg22-Triggered Immunity (2014)

PLOS Pathogens: Functionally Redundant RXLR Effectors from Phytophthora infestans Act at Different Steps to Suppress Early flg22-Triggered Immunity (2014) | Pathology | Scoop.it

Genome sequences of several economically important phytopathogenic oomycetes have revealed the presence of large families of so-called RXLR effectors. Functional screens have identified RXLR effector repertoires that either compromise or induce plant defense responses. However, limited information is available about the molecular mechanisms underlying the modes of action of these effectors in planta. The perception of highly conserved pathogen- or microbe-associated molecular patterns (PAMPs/MAMPs), such as flg22, triggers converging signaling pathways recruiting MAP kinase cascades and inducing transcriptional re-programming, yielding a generic anti-microbial response. We used a highly synchronizable, pathogen-free protoplast-based assay to identify a set of RXLR effectors from Phytophthora infestans (PiRXLRs), the causal agent of potato and tomato light blight that manipulate early stages of flg22-triggered signaling. Of thirty-three tested PiRXLR effector candidates, eight, called Suppressor of early Flg22-induced Immune response (SFI), significantly suppressed flg22-dependent activation of a reporter gene under control of a typical MAMP-inducible promoter (pFRK1-Luc) in tomato protoplasts. We extended our analysis to Arabidopsis thaliana, a non-host plant species of P. infestans. From the aforementioned eight SFI effectors, three appeared to share similar functions in both Arabidopsis and tomato by suppressing transcriptional activation of flg22-induced marker genes downstream of post-translational MAP kinase activation. A further three effectors interfere with MAMP signaling at, or upstream of, the MAP kinase cascade in tomato, but not in Arabidopsis. Transient expression of the SFI effectors in Nicotiana benthamianaenhances susceptibility to P. infestans and, for the most potent effector, SFI1, nuclear localization is required for both suppression of MAMP signaling and virulence function. The present study provides a framework to decipher the molecular mechanisms underlying the manipulation of host MAMP-triggered immunity (MTI) by P. infestans and to understand the basis of host versus non-host resistance in plants towards P. infestans.


Via Kamoun Lab @ TSL, Niklaus Grunwald
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Rescooped by Rui Jiang from Fungal|Oomycete Biology
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Nature Genetics: Oomycete pathogens encode RNA silencing suppressors (2013)

Nature Genetics: Oomycete pathogens encode RNA silencing suppressors (2013) | Pathology | Scoop.it

Effectors are essential virulence proteins produced by a broad range of parasites, including viruses, bacteria, fungi, oomycetes, protozoa, insects and nematodes. Upon entry into host cells, pathogen effectors manipulate specific physiological processes or signaling pathways to subvert host immunity. Most effectors, especially those of eukaryotic pathogens, remain functionally uncharacterized. Here, we show that two effectors from the oomycete plant pathogen Phytophthora sojae suppress RNA silencing in plants by inhibiting the biogenesis of small RNAs. Ectopic expression of thesePhytophthora suppressors of RNA silencing enhances plant susceptibility to both a virus and Phytophthora, showing that some eukaryotic pathogens have evolved virulence proteins that target host RNA silencing processes to promote infection. These findings identify RNA silencing suppression as a common strategy used by pathogens across kingdoms to cause disease and are consistent with RNA silencing having key roles in host defense.


Via Kamoun Lab @ TSL, Alejandro Rojas
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Rescooped by Rui Jiang from Phytophthora biology
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European Journal of Plant Pathology: Phylogeny and evolution of plant pathogenic oomycetes - a global overview (2014)

European Journal of Plant Pathology: Phylogeny and evolution of plant pathogenic oomycetes - a global overview (2014) | Pathology | Scoop.it

Oomycetes have colonised all continents and oceans in a great variety of habitats and are arguably one of the most successful eukaryotic lineages. This is contrasted by the limited knowledge available for this group in various fields in comparison to other ubiquitous eukaryotes, such as unikont fungi, animals or plants. In this review an overview is given on the evolution and diversification of the oomycetes, with focus on the plant parasitic lineages and aspects of wild pathosystems.


Via Kamoun Lab @ TSL, Niklaus Grunwald
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Rescooped by Rui Jiang from Phytophthora biology
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PLOS Pathogens: Functionally Redundant RXLR Effectors from Phytophthora infestans Act at Different Steps to Suppress Early flg22-Triggered Immunity (2014)

PLOS Pathogens: Functionally Redundant RXLR Effectors from Phytophthora infestans Act at Different Steps to Suppress Early flg22-Triggered Immunity (2014) | Pathology | Scoop.it

Genome sequences of several economically important phytopathogenic oomycetes have revealed the presence of large families of so-called RXLR effectors. Functional screens have identified RXLR effector repertoires that either compromise or induce plant defense responses. However, limited information is available about the molecular mechanisms underlying the modes of action of these effectors in planta. The perception of highly conserved pathogen- or microbe-associated molecular patterns (PAMPs/MAMPs), such as flg22, triggers converging signaling pathways recruiting MAP kinase cascades and inducing transcriptional re-programming, yielding a generic anti-microbial response. We used a highly synchronizable, pathogen-free protoplast-based assay to identify a set of RXLR effectors from Phytophthora infestans (PiRXLRs), the causal agent of potato and tomato light blight that manipulate early stages of flg22-triggered signaling. Of thirty-three tested PiRXLR effector candidates, eight, called Suppressor of early Flg22-induced Immune response (SFI), significantly suppressed flg22-dependent activation of a reporter gene under control of a typical MAMP-inducible promoter (pFRK1-Luc) in tomato protoplasts. We extended our analysis to Arabidopsis thaliana, a non-host plant species of P. infestans. From the aforementioned eight SFI effectors, three appeared to share similar functions in both Arabidopsis and tomato by suppressing transcriptional activation of flg22-induced marker genes downstream of post-translational MAP kinase activation. A further three effectors interfere with MAMP signaling at, or upstream of, the MAP kinase cascade in tomato, but not in Arabidopsis. Transient expression of the SFI effectors in Nicotiana benthamianaenhances susceptibility to P. infestans and, for the most potent effector, SFI1, nuclear localization is required for both suppression of MAMP signaling and virulence function. The present study provides a framework to decipher the molecular mechanisms underlying the manipulation of host MAMP-triggered immunity (MTI) by P. infestans and to understand the basis of host versus non-host resistance in plants towards P. infestans.


Via Kamoun Lab @ TSL, Niklaus Grunwald
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Rescooped by Rui Jiang from neutrophil extracellular traps
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Book: Plant-Pathogen Interactions: Methods and Protocols (2014)

Book: Plant-Pathogen Interactions: Methods and Protocols (2014) | Pathology | Scoop.it

Plant-Pathogen Interactions: Methods and Protocols, Second Edition by Paul Birch, John Jones, Jorunn Bos (Editors) expands upon the first edition with current, detailed protocols for the study of plant pathogen genome sequences. It contains new chapters on techniques to help identify and characterize effectors and to study their impacts on host immunity and their roles in pathogen biology. Additional chapters focus on protocols to identify avirulence and resistance genes, investigate the roles of effector targets and other defence-associated proteins in plant immunity. Written in the highly successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols and tips on troubleshooting and avoiding known pitfalls.


Via Kamoun Lab @ TSL, Gigy Varghese
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Rescooped by Rui Jiang from Plants and Microbes
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Cell Host & Microbe: Mechanisms Underlying Robustness and Tunability in a Plant Immune Signaling Network (2016)

Cell Host & Microbe: Mechanisms Underlying Robustness and Tunability in a Plant Immune Signaling Network (2016) | Pathology | Scoop.it
- A predictive, dynamic PTI signaling network model with four major sectors was built - Inhibition of the jasmonate sector by the ethylene sector was central to robustness - MAMP-specific patterns of multiple inputs can tune the network response - The symmetrically placed jasmonate and PAD4 sectors may form a tetrastable switch

The plant immune signaling network needs to be robust against attack from fast-evolving pathogens and tunable to optimize immune responses. We investigated the basis of robustness and tunability in the signaling network controlling pattern-triggered immunity (PTI) in Arabidopsis. A dynamic network model containing four major signaling sectors, the jasmonate, ethylene, phytoalexin-deficient 4, and salicylate sectors, which together govern up to 80% of the PTI levels, was built using data for dynamic sector activities and PTI levels under exhaustive combinatorial sector perturbations. Our regularized multiple regression model had a high level of predictive power and captured known and unexpected signal flows in the network. The sole inhibitory sector in the model, the ethylene sector, contributed centrally to network robustness via its inhibition of the jasmonate sector. The model’s multiple input sites linked specific signal input patterns varying in strength and timing to different network response patterns, indicating a mechanism enabling tunability.


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Rescooped by Rui Jiang from Publications
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Slides: Plant pathology in the post-genomics era (2015)

Presented at BASF Science Symposium: sustainable food chain - from field to table, Jun 23-24, 2015, Chicago.

 

Notes and acknowledgements at http://kamounlab.tumblr.com/post/122151022390/plant-pathology-in-the-post-genomics-era


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PNAS: Nep1-like proteins from three kingdoms of life act as a microbe-associated molecular pattern in Arabidopsis (2014)

PNAS: Nep1-like proteins from three kingdoms of life act as a microbe-associated molecular pattern in Arabidopsis (2014) | Pathology | Scoop.it

Necrosis and ethylene-inducing peptide 1 (Nep1)-like proteins (NLPs) are secreted by a wide range of plant-associated microorganisms. They are best known for their cytotoxicity in dicot plants that leads to the induction of rapid tissue necrosis and plant immune responses. The biotrophic downy mildew pathogen Hyaloperonospora arabidopsidis encodes 10 different noncytotoxic NLPs (HaNLPs) that do not cause necrosis. We discovered that these noncytotoxic NLPs, however, act as potent activators of the plant immune system in Arabidopsis thaliana. Ectopic expression of HaNLP3 in Arabidopsis triggered resistance to H. arabidopsidis, activated the expression of a large set of defense-related genes, and caused a reduction of plant growth that is typically associated with strongly enhanced immunity. N- and C-terminal deletions of HaNLP3, as well as amino acid substitutions, pinpointed to a small central region of the protein that is required to trigger immunity, indicating the protein acts as a microbe-associated molecular pattern (MAMP). This was confirmed in experiments with a synthetic peptide of 24 aa, derived from the central part of HaNLP3 and corresponding to a conserved region in type 1 NLPs that induces ethylene production, a well-known MAMP response. Strikingly, corresponding 24-aa peptides of fungal and bacterial type 1 NLPs were also able to trigger immunity in Arabidopsis. The widespread phylogenetic distribution of type 1 NLPs makes this protein family (to our knowledge) the first proteinaceous MAMP identified in three different kingdoms of life.


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Wageningen: PhD position: Deducing a physical interaction network between the late blight pathogen and tomato - Dutch Techcentre for Life Sciences

Wageningen: PhD position: Deducing a physical interaction network between the late blight pathogen and tomato - Dutch Techcentre for Life Sciences | Pathology | Scoop.it
In the Plant Sciences Group of Wageningen University, there is an exciting opportunity for an enthusiastic PhD student to develop integrative models of interactions between infectants and plant hosts, in particular the late blight pathogen...
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The Independent: Potatoes could be off the menu as crop pests threaten UK (2014)

The Independent: Potatoes could be off the menu as crop pests threaten UK (2014) | Pathology | Scoop.it

Britain has “significantly underestimated” the risk that crop pests pose to its food supply. Fungi and viruses present so great a danger to staples such as wheat and potatoes that they may force the nation to change its diet, an academic has warned. The rise of deadly pests poses a threat to the world’s entire food system, but the UK is among the most vulnerable countries, according to a new study from the University of Exeter. It forecasts that food-growing nations, including the UK, will be “overwhelmed” by pests within the next 30 years as climate change, inadequate biosecurity measures and new variants help them spread. “The UK has significantly underestimated the scale of the threat. This is a huge problem that is lacking in public and political awareness. People are absolutely paralysed with fear of diseases like Ebola, but while they are extremely dangerous, the need to tackle crop diseases is just as pressing,” said Professor Sarah Gurr, of the University of Exeter and Rothamsted Research. “We are not spending enough on research, on training, on surveillance and on biosecurity. Unless we significantly step up our efforts we could be forced to change our diets in the future as crops come and go,” she added. Crop pests include fungi, bacteria, viruses, insects, nematodes (worms) and viroids (plant viruses).

Fungi pose the biggest threat globally and in the UK, where they threaten the country’s wheat and potato harvests. Zymoseptoria tritici – or Septoria leaf blotch – and Blumeria graminis, a powdery mildew, are a danger to wheat, while the potato cyst nematode and new variants of Phytophthora infestans threaten the potato. The report warns that if crop pests continue to spread at their current rate a significant portion of the world’s biggest food-producing countries will be “saturated” with pests – the crops simply wouldn’t be able to accommodate any more.


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Rescooped by Rui Jiang from Oomycete Review Papers
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[2012 Annu Rev Phytopathol.] Mechanisms and evolution of virulence in oomycetes

Many destructive diseases of plants and animals are caused by oomycetes, a group of eukaryotic pathogens important to agricultural, ornamental, and natural ecosystems. Understanding the mechanisms underlying oomycete virulence and the genomic processes by which those mechanisms rapidly evolve is essential to developing effective long-term control measures for oomycete diseases. Several common mechanisms underlying oomycete virulence, including protein toxins and cell-entering effectors, have emerged from comparing oomycetes with different genome characteristics, parasitic lifestyles, and host ranges. Oomycete genomes display a strongly bipartite organization in which conserved housekeeping genes are concentrated in syntenic gene-rich blocks, whereas virulence genes are dispersed into highly dynamic, repeat-rich regions. There is also evidence that key virulence genes have been acquired by horizontal transfer from other eukaryotic and prokaryotic species.


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Oomycetes: Attacking the mediator : Nature Reviews Microbiology : Nature Publishing Group

Oomycetes: Attacking the mediator : Nature Reviews Microbiology : Nature Publishing Group | Pathology | Scoop.it

Plants use a range of mechanisms to respond to challenge by plant pathogens and, in turn, plant pathogens use a range of mechanisms to interfere with and evade these responses. Plant defence responses include those that are mediated by salicylic acid and jasmonic acid–ethylene but, so far, few phytopathogen effectors that interfere with these hormone-based systems have been identified. A study in PLoS Biology now shows that an effector from the biotrophic oomycete pathogen Hyaloperonospora arabidopsidis attenuates the salicylic acid response, thus enhancing biotrophy.

 

Many oomycete effectors contain an amino-terminal RXLR (where X is any amino acid) motif that correlates with entry into host cells. Previous characterization of the RXLR effector repertoire of H. arabidopsidis identified a subset of effectors that localize to the plant cell nucleus and interact with components of the Mediator complex — a multisubunit transcriptional regulation complex that is present in all eukaryotes. In plants, Mediator has been shown to influence key processes, including plant development and, recently, plant immunity.

 

Caillaud and colleagues present an in-depth characterization of one of the H. arabidopsidis RXLR nuclear effectors, HaRxL44, which interacts with the MED19a subunit of the Mediator complex. Analysis of transgenic Arabidopsis thaliana lines showed that those in which MED19a was non-functional were more susceptible than the wild type to infection with H. arabidopsidsis. By contrast, transgenic lines in which MED19a was overproduced were more resistant to infection than the wild type. This indicates that MED19a is a positive regulator of A. thaliana immunity to H. arabidopsidsisinfection. Confocal microscopy to monitor the subcellular localization of MED19a-containing and HaRxL44-containing fusion proteins showed that both localize to the plant nucleolus and nucleoplasm. However, colocalization analysis showed that when HaRxL44 was present in the nucleoplasm MED19a could not be detected. Further investigations revealed that HaRxL44 degrades MED19a in a proteasome-dependent manner.

 

To pinpoint the mechanism by which HaRxL44-mediated MED19a degradation affects the immune response to H. arabidopsidsis infection, the authors used quantitative reverse transcription (qRT)-PCR analysis and gene expression profiling. They found that, in the presence of HaRxL44, marker genes that were consistent with jasmonic acid–ethylene signalling were upregulated, whereas marker genes that were consistent with salicylic acid signalling — which has a key role in the response to biotrophic pathogens — were downregulated. Finally, the authors investigated the cell-specific expression patterns of marker genes that are associated with the salicylic acid response and found that H. arabidopsidsis infection only suppresses the salicylic acid response in those cells that have been parasitized by oomycete haustoria.

 

These data show that the H. arabidopsidsis HaRxL44 effector targets MED19a to modulate the balance between jasmonic acid–ethylene and salicylic acid signalling, such that the salicylic acid response is attenuated and biotrophic infection is favoured. It will be interesting to follow future studies that characterize the functions of the other H. arabidopsidsis RXLR nuclear effectors.

 

References

 

Caillaud, M.-C. et al. A downy mildew effector attenuates salicylic acid-triggered immunity inArabidopsis by interacting with the host mediator complex. PLoS Biol. 11, e1001732 (2013)

PubMed 

 


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Jumping Hosts: Mechanisms of speciation in Phytophthora infestans vs. P. mirabilis | The Scientist Magazine®

Jumping Hosts: Mechanisms of speciation in Phytophthora infestans vs. P. mirabilis | The Scientist Magazine® | Pathology | Scoop.it
A single amino acid change helps a plant pathogen related to the causative agent of the Irish potato famine infect a new host.

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MPMI: Single amino acid mutations in the potato immune receptor R3a expand response to Phytophthora effectors (2014)

MPMI: Single amino acid mutations in the potato immune receptor R3a expand response to Phytophthora effectors (2014) | Pathology | Scoop.it

Both plants and animals rely on nucleotide-binding domain and leucine-rich repeat-containing proteins (NB-LRRs or NLRs) to respond to invading pathogens and activate immune responses. How plant NB-LRR proteins respond to pathogens is poorly understood. We undertook a gain-of-function random mutagenesis screen of the potato NB-LRR immune receptor R3a to study how this protein responds to the effector protein AVR3a from the oomycete pathogen Phytophthora infestans. R3a response can be extended to the stealthy AVR3aEM isoform of the effector while retaining recognition of AVR3aKI. Each one of 8 single amino acid mutations is sufficient to expand the R3a response to AVR3aEM and other AVR3a variants. These mutations occur across the R3a protein, from the N-terminus to different regions of the LRR domain. Further characterization of these R3a mutants revealed that at least one of them was sensitized, exhibiting a stronger response than the wild-type R3a protein to AVR3aKI. Remarkably, the N336Y mutation, near the R3a nucleotide-binding pocket, conferred response to the effector protein PcAVR3a4 from the vegetable pathogen Phytophthora capsici. This work contributes to understanding how NB-LRR receptor specificity can be modulated. Together with knowledge of pathogen effector diversity, this strategy can be exploited to develop synthetic immune receptors.


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Stephen Bolus's curator insight, March 30, 2014 2:09 AM

I just really love the idea of synthetic immune receptors!

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The late blight pathogen in a plant leaf

This is a microscopic 3D image of Phytophthora infestans (red) infecting a leaf. The leaf cells are puzzle shaped. The pairwise bean shape cells are guard ce...
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