Plant defense mechanisms against pathogens
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Plant defense mechanisms against pathogens
Plant defense mechanisms against phytopahtogens
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Rescooped by Hamed Soren Seifi from Plants and Microbes
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Nature Genetics: Oomycete pathogens encode RNA silencing suppressors (2013)

Nature Genetics: Oomycete pathogens encode RNA silencing suppressors (2013) | Plant defense mechanisms against pathogens | 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
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Rescooped by Hamed Soren Seifi from Plants and Microbes
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PLOS Biology: A Downy Mildew Effector Attenuates Salicylic Acid–Triggered Immunity in Arabidopsis by Interacting with the Host Mediator Complex (2013)

PLOS Biology: A Downy Mildew Effector Attenuates Salicylic Acid–Triggered Immunity in Arabidopsis by Interacting with the Host Mediator Complex (2013) | Plant defense mechanisms against pathogens | Scoop.it

Plants are continually exposed to pathogen attack but usually remain healthy because they can activate defences upon perception of microbes. However, pathogens have evolved to overcome plant immunity by delivering effectors into the plant cell to attenuate defence, resulting in disease. Recent studies suggest that some effectors may manipulate host transcription, but the specific mechanisms by which such effectors promote susceptibility remain unclear. We study the oomycete downy mildew pathogen of Arabidopsis,Hyaloperonospora arabidopsidis (Hpa), and show here that the nuclear-localized effector HaRxL44 interacts with Mediator subunit 19a (MED19a), resulting in the degradation of MED19a in a proteasome-dependent manner. The Mediator complex of ~25 proteins is broadly conserved in eukaryotes and mediates the interaction between transcriptional regulators and RNA polymerase II. We found MED19a to be a positive regulator of immunity against Hpa. Expression profiling experiments reveal transcriptional changes resembling jasmonic acid/ethylene (JA/ET) signalling in the presence of HaRxL44, and also 3 d after infection withHpa. Elevated JA/ET signalling is associated with a decrease in salicylic acid (SA)–triggered immunity (SATI) in Arabidopsis plants expressing HaRxL44 and in med19a loss-of-function mutants, whereas SATI is elevated in plants overexpressing MED19a. Using a PR1::GUS reporter, we discovered that Hpa suppresses PR1 expression specifically in cells containing haustoria, into which RxLR effectors are delivered, but not in nonhaustoriated adjacent cells, which show high PR1::GUS expression levels. Thus, HaRxL44 interferes with Mediator function by degrading MED19, shifting the balance of defence transcription from SA-responsive defence to JA/ET-signalling, and enhancing susceptibility to biotrophs by attenuating SA-dependent gene expression.


Via Kamoun Lab @ TSL
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Pietro Spanu's curator insight, December 17, 2013 2:39 AM

This looks very much like the "green island" effect that powdery mildews induce in stressed plants

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Rice blast research reveals details on how a fungus invades plants

Rice blast research reveals details on how a fungus invades plants | Plant defense mechanisms against pathogens | Scoop.it
Like a stealthy enemy, blast disease invades rice crops around the world, killing plants and cutting production of one of the most important global food sources.
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Rescooped by Hamed Soren Seifi from Plants and Microbes
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Database: Plant Resistance Gene Wiki (2013)

Database: Plant Resistance Gene Wiki (2013) | Plant defense mechanisms against pathogens | Scoop.it

PRG-Wiki is an open and daily update space about plant resistance gene, in which all information about this family is stored, curated and discussed. The purpose of our work is creating a worldwide community working on plant resistance genes with a constant update on all aspects of this research field and to encourage scientists to be actors of the discussion and of the data exchange. PRG-Wiki actually stores more than 112 reference resistance gene and 104335 putative disease resistance gene. Through the wiki pages any contributor can suggest changes to the PRG database and directly update it with new data, new information and with corrections of wrong information.

 
Via Kamoun Lab @ TSL
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Glutamate metabolism in plant disease and defense: friend or foe?

Glutamate metabolism in plant disease and defense: friend or foe? | Plant defense mechanisms against pathogens | Scoop.it

The plant glutamate metabolism (GM) plays a pivotal role in amino acid metabolism and orchestrates crucial metabolic functions with key roles in plant defense against pathogens. These functions concern three major areas: nitrogen transportation via the GS/GOGAT cycle, cellular redox regulation, and TCA cycle-dependent energy reprogramming. During interactions with pathogens the host GM is markedly altered leading to either a metabolic state, termed ‘endurance’, in which cell viability is maintained; or to an opposite metabolic state, termed ‘evasion’, in which the process of cell death is facilitated. It seems that endurance-natured modulations result in resistance to necrotrophic pathogens and susceptibility to biotrophs, whereas evasion-related reconfigurations lead to resistance to biotrophic pathogens, but stimulate the infection by necrotrophs. Pathogens, however, have evolved strategies, such as toxin secretion, hemibiotrophy and selective amino acid utilization, to exploit the plant GM to their own benefit. Collectively, alterations in the host GM in response to different pathogenic scenarios appear to function in two opposing ways, either backing the ongoing defense strategy to ultimately shape an efficient resistance response, or being exploited by the pathogen to promote and facilitate infection.


Hamed Soren Seifi, Jonas Van Bockhaven, Geert Angenon, Monica Höfte


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Michael Pollan: How Smart Are Plants?

Michael Pollan: How Smart Are Plants? | Plant defense mechanisms against pathogens | Scoop.it
Depending on whom you talk to, the field of plant neurobiology represents either a radical new paradigm in our understanding of life or a slide down into murky scientific waters. Its proponents believe that we must stop regarding plants as passive objects and begin to treat them as protagonists in their own dramas. It is only human arrogance, and the fact that the lives of plants unfold in what amounts to a much slower dimension of time, that keep us from appreciating their intelligence and consequent success.
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Science: Pivoting the Plant Immune System from Dissection to Deployment (2013)

Science: Pivoting the Plant Immune System from Dissection to Deployment (2013) | Plant defense mechanisms against pathogens | Scoop.it

Diverse and rapidly evolving pathogens cause plant diseases and epidemics that threaten crop yield and food security around the world. Research over the last 25 years has led to an increasingly clear conceptual understanding of the molecular components of the plant immune system. Combined with ever-cheaper DNA-sequencing technology and the rich diversity of germ plasm manipulated for over a century by plant breeders, we now have the means to begin development of durable (long-lasting) disease resistance beyond the limits imposed by conventional breeding and in a manner that will replace costly and unsustainable chemical controls.


Via Suayib Üstün, Nicolas Denancé
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Jennifer Mach's curator insight, August 27, 2013 9:59 AM

Part of the Pesticides special issue...

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Concurrent overactivation of the cytosolic glutamine synthetase and the GABA shunt in the ABA-deficient sitiens mutant of tomato leads to resistance against Botrytis cinerea - Seifi - 2013 - New Ph...

Concurrent overactivation of the cytosolic glutamine synthetase and the GABA shunt in the ABA-deficient sitiens mutant of tomato leads to resistance against Botrytis cinerea - Seifi - 2013 - New Ph... | Plant defense mechanisms against pathogens | Scoop.it
Hamed Soren Seifi's insight:
SummaryDeficiency of abscisic acid (ABA) in the sitiens mutant of tomato (Solanum lycopersicum) culminates in increased resistance toBotrytis cinerea through a rapid epidermal hypersensitive response (HR) and associated phenylpropanoid pathway-derived cell wall fortifications. This study focused on understanding the role of primary carbon : nitrogen (C : N) metabolism in the resistance response of sitiens to B. cinerea. How alterations in C : N metabolism are linked with the HR-mediated epidermal arrest of the pathogen has been also investigated.Temporal alterations in the γ-aminobutyric acid (GABA) shunt, glutamine synthetase/glutamate synthase (GS/GOGAT) cycle and phenylpropanoid pathway were transcriptionally, enzymatically and metabolically monitored in both wild-type and sitiens plants. Virus-induced gene silencing, microscopic analyses and pharmacological assays were used to further confirm the data.Our results on the sitiens–B. cinerea interaction favor a model in which cell viability in the cells surrounding the invaded tissue is maintained by a constant replenishment of the tricarboxylic acid (TCA) cycle through overactivation of the GS/GOGAT cycle and the GABA shunt, resulting in resistance through both tightly controlling the defense-associated HR and slowing down the pathogen-induced senescence.Collectively, this study shows that maintaining cell viability via alterations in host C : N metabolism plays a vital role in the resistance response against necrotrophic pathogens.
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Scientists identify genetic mechanism that contributed to Irish Famine

Scientists identify genetic mechanism that contributed to Irish Famine | Plant defense mechanisms against pathogens | Scoop.it
When a pathogen attacks a plant, infection usually follows after the plant's immune system is compromised.
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