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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) | My MPMI | 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.


Via Kamoun Lab @ TSL
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I just really love the idea of synthetic immune receptors!

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Rescooped by Stephen Bolus from Plant Pathogenomics
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bioRxiv: Comparative analysis highlights variable genome content of wheat rusts and divergence of the mating loci (2016)

bioRxiv: Comparative analysis highlights variable genome content of wheat rusts and divergence of the mating loci (2016) | My MPMI | Scoop.it

Three members of the Puccini genus, P. triticina (Pt), P. striiformis f.sp. tritici (Pst), and P. graminis f.sp. tritici (Pgt), cause the most common and often most significant foliar diseases of wheat. While similar in biology and life cycle, each species is uniquely adapted and specialized. The genomes of Pt and Pst were sequenced and compared to that of Pgt to identify common and distinguishing gene content, to determine gene variation among wheat rust pathogens, other rust fungi and basidiomycetes, and to identify genes of significance for infection. Pt had the largest genome of the three, estimated at 135 Mb with expansion due to mobile elements and repeats encompassing 50.9% of contig bases; by comparison repeats occupy 31.5% for Pst and 36.5% for Pgt. We find all three genomes are highly heterozygous, with Pst (5.97 SNPs/kb) nearly twice the level detected in Pt (2.57 SNPs/kb) and that previously reported for Pgt. Of 1,358 predicted effectors in Pt, 784 were found expressed across diverse life cycle stages including the sexual stage. Comparison to related fungi highlighted the expansion of gene families involved in transcriptional regulation and nucleotide binding, protein modification, and carbohydrate enzyme degradation. Two allelic homeodomain, HD1 and HD2, pairs and three pheromone receptor (STE3) mating-type genes were identified in each dikaryotic Pucciniaspecies. The HD proteins were active in a heterologous Ustilago maydis mating assay and host induced gene silencing of the HD and STE3 alleles reduced wheat host infection.


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Hybridization of powdery mildew strains gives rise to pathogens on novel agricultural crop species : Nature Genetics : Nature Publishing Group

Hybridization of powdery mildew strains gives rise to pathogens on novel agricultural crop species : Nature Genetics : Nature Publishing Group | My MPMI | Scoop.it
Beat Keller, Thomas Wicker and colleagues compare the genomes of 46 isolates of powdery mildew, Blumeria graminis. They find that B. graminis f. sp. triticale, a pathogen growing on triticale (a wheat [times] rye hybrid plant), is a hybrid of B. graminis f. sp. tritici and B. graminis f. sp. secalis, which grow on wheat and rye, respectively.
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Amazing!

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Rescooped by Stephen Bolus from Publications from The Sainsbury Laboratory
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Frontiers in Plant Sci: Strategies for transferring resistance into wheat: from wide crosses to GM cassettes (2014)

Frontiers in Plant Sci: Strategies for transferring resistance into wheat: from wide crosses to GM cassettes (2014) | My MPMI | Scoop.it
The domestication of wheat in the Fertile Crescent 10,000 years ago led to a genetic bottleneck. Modern agriculture has further narrowed the genetic base by introducing extreme levels of uniformity...

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The Sainsbury Lab's curator insight, December 8, 2014 5:30 AM

The domestication of wheat in the Fertile Crescent 10,000 years ago led to a genetic bottleneck. Modern agriculture has further narrowed the genetic base by introducing extreme levels of uniformity on a vast spatial and temporal scale. This reduction in genetic complexity renders the crop vulnerable to new and emerging pests and pathogens. The wild relatives of wheat represent an important source of genetic variation for disease resistance. For nearly a century farmers, breeders, and cytogeneticists have sought to access this variation for crop improvement. Several barriers restricting interspecies hybridization and introgression have been overcome, providing the opportunity to tap an extensive reservoir of genetic diversity. Resistance has been introgressed into wheat from at least 52 species from 13 genera, demonstrating the remarkable plasticity of the wheat genome and the importance of such natural variation in wheat breeding. Two main problems hinder the effective deployment of introgressed resistance genes for crop improvement: (1) the simultaneous introduction of genetically linked deleterious traits and (2) the rapid breakdown of resistance when deployed individually. In this review, we discuss how recent advances in molecular genomics are providing new opportunities to overcome these problems.

Bharat Employment's curator insight, January 20, 2015 11:42 PM

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Rescooped by Stephen Bolus from Pest Alerts
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Yellow bud: a new bacterial disease of onion in Georgia (US)

Yellow bud: a new bacterial disease of onion in Georgia (US) | My MPMI | Scoop.it

Since 2007, a new disease of onion (Allium cepa) called yellow bud has been causing problems in Georgia (US). Emerging leaves display intense chlorosis and older leaves exhibit extensive leaf blight. Yield reductions can be severe due to stand loss and reduced bulb size. The causal agent was identified as Pseudomonas syringae (but the pathovar could not be determined).

 

Gitaitis R, Mullis S, Lewis K, Langston D, Watson AK, Sanders H, Torrance R, Jones, JB, Nischwitz C (2012) First report of a new disease of onion in Georgia caused by a nonfluorescent Pseudomonas species. Plant Disease 96(2), 285-286.


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Rescooped by Stephen Bolus from Plants and Microbes
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PLOS Biology: Unsolved Mystery - How Do Filamentous Pathogens Deliver Effector Proteins into Plant Cells? (2014)

PLOS Biology: Unsolved Mystery - How Do Filamentous Pathogens Deliver Effector Proteins into Plant Cells? (2014) | My MPMI | Scoop.it

Fungal and oomycete plant parasites are among the most devastating pathogens of food crops. These microbes secrete effector proteins inside plant cells to manipulate host processes and facilitate colonization. How these effectors reach the host cytoplasm remains an unclear and debated area of plant research. In this article, we examine recent conflicting findings that have generated discussion in the field. We also highlight promising approaches based on studies of both parasite and host during infection. Ultimately, this knowledge may inform future broad spectrum strategies for protecting crops from such pathogens.


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MPMI: Substitutions of two amino acids in the nucleotide-binding site domain of a resistance protein enhance the hypersensitive response and enlarge the PM3F resistance spectrum in wheat (2013)

MPMI: Substitutions of two amino acids in the nucleotide-binding site domain of a resistance protein enhance the hypersensitive response and enlarge the PM3F resistance spectrum in wheat (2013) | My MPMI | Scoop.it

Proteins with nucleotide-binding-site (NBS) and leucine-rich-repeat (LRR) domains are major components of the plant immune system. They usually mediate resistance against a subgroup of races of a specific pathogen. For the allelic series of the wheat powdery mildew resistance gene Pm3, alleles with a broad and a narrow resistance spectrum have been described. Here we show that a broad Pm3-spectrum range correlates with a fast and intense hypersensitive response (HR) in a Nicotiana transient-expression system and this activity can be attributed to two particular amino acids in the ARC2 subdomain of the NBS. The combined substitution of these amino acids in narrow-spectrum PM3 proteins enhances their capacity to induce an HR in Nicotiana and we demonstrate that these substitutions also enlarge the resistance spectrum of the Pm3f allele in wheat. UsingBph14 we finally show that the region carrying the relevant amino acids also plays a role in the HR regulation of another coiled-coil-NBS-LRR resistance protein. These results highlight the importance of an optimized NBS-"molecular switch” for the conversion of initial pathogen perception by the LRR into resistance-protein activation and we describe a possible approach to extend the effectiveness of resistance genes via minimal targeted modifications in the NBS domain.


Via Kamoun Lab @ TSL
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Engineering better R genes - yes!

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GMOAnswers - Your Questions on Health and Safety of GM Food and Crops

GMOAnswers - Your Questions on Health and Safety of GM Food and Crops | My MPMI | Scoop.it
GMO Answers is dedicated to creating an open dialogue on the topics of biotechnology and GMOs in food and modern agriculture
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Rescooped by Stephen Bolus from Plants and Microbes
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3D Animation: Moving Forward from Ash Dieback (2013)


Via Kamoun Lab @ TSL
Stephen Bolus's insight:

I am still sticking with my prediction that Chalara fraxinea is an endophytic fungus on exotic ash trees, but it forms an inappropriate, toxic relationship with Fraxinus excelsior.

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Rescooped by Stephen Bolus from Plant Pathogenomics
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Nature Communications: The evolution and pathogenic mechanisms of the rice sheath blight pathogen (2013)

Nature Communications: The evolution and pathogenic mechanisms of the rice sheath blight pathogen (2013) | My MPMI | Scoop.it

Rhizoctonia solani is a major fungal pathogen of rice (Oryza sativa L.) that causes great yield losses in all rice-growing regions of the world. Here we report the draft genome sequence of the rice sheath blight disease pathogen, R. solani AG1 IA, assembled using next-generation Illumina Genome Analyser sequencing technologies. The genome encodes a large and diverse set of secreted proteins, enzymes of primary and secondary metabolism, carbohydrate-active enzymes, and transporters, which probably reflect an exclusive necrotrophic lifestyle. We find few repetitive elements, a closer relationship to Agaricomycotina among Basidiomycetes, and expand protein domains and families. Among the 25 candidate pathogen effectors identified according to their functionality and evolution, we validate 3 that trigger crop defence responses; hence we reveal the exclusive expression patterns of the pathogenic determinants during host infection.


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The Genomes of the Fungal Plant Pathogens Cladosporium fulvum and Dothistroma septosporum Reveal Adaptation to Different Hosts and Lifestyles But Also Signatures of Common Ancestry

The Genomes of the Fungal Plant Pathogens Cladosporium fulvum and Dothistroma septosporum Reveal Adaptation to Different Hosts and Lifestyles But Also Signatures of Common Ancestry | My MPMI | Scoop.it

Cladosporium fulvum and Dothistroma septosporum infect tomato and pine, yet share a common fungal ancestor.

 

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Rescooped by Stephen Bolus from Plants and Microbes
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Science: Using decoys to expand the recognition specificity of a plant disease resistance protein (2016)

Science: Using decoys to expand the recognition specificity of a plant disease resistance protein (2016) | My MPMI | Scoop.it

Maintaining high crop yields in an environmentally sustainable manner requires the development of disease-resistant crop varieties. We describe a method to engineer disease resistance in plants by means of an endogenous disease resistance gene from Arabidopsis thaliana named RPS5, which encodes a nucleotide-binding leucine-rich repeat (NLR) protein. RPS5 is normally activated when a second host protein, PBS1, is cleaved by the pathogen-secreted protease AvrPphB. We show that the AvrPphB cleavage site within PBS1 can be substituted with cleavage sites for other pathogen proteases, which then enables RPS5 to be activated by these proteases, thereby conferring resistance to new pathogens. This “decoy” approach may be applicable to other NLR proteins and should enable engineering of resistance in plants to diseases for which we currently lack robust genetic resistance.


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eLife: Structural basis of pathogen recognition by an integrated HMA domain in a plant NLR immune receptor (2015)

eLife: Structural basis of pathogen recognition by an integrated HMA domain in a plant NLR immune receptor (2015) | My MPMI | Scoop.it

Plants have evolved intracellular immune receptors to detect pathogen proteins known as effectors. How these immune receptors detect effectors remains poorly understood. Here we describe the structural basis for direct recognition of AVR-Pik, an effector from the rice blast pathogen, by the rice intracellular NLR immune receptor Pik. AVR-PikD binds a dimer of the Pikp-1 HMA integrated domain with nanomolar affinity. The crystal structure of the Pikp-HMA/AVR-PikD complex enabled design of mutations to alter protein interaction in yeast and in vitro, and perturb effector-mediated response both in a rice cultivar containing Pikp and upon expression of AVR-PikD and Pikp in the model plant Nicotiana benthamiana. These data reveal the molecular details of a recognition event, mediated by a novel integrated domain in an NLR, which initiates a plant immune response and resistance to rice blast disease. Such studies underpin novel opportunities for engineering disease resistance to plant pathogens in staple food crops.


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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) | My MPMI | 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.


Via Kamoun Lab @ TSL
Stephen Bolus's insight:

I just really love the idea of synthetic immune receptors!

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Rescooped by Stephen Bolus from Plants and Microbes
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MPMI: Mycosphaerella graminicola LysM effector-mediated stealth pathogenesis subverts recognition through both CERK1 and CEBiP homologues in wheat (2013)

MPMI: Mycosphaerella graminicola LysM effector-mediated stealth pathogenesis subverts recognition through both CERK1 and CEBiP homologues in wheat (2013) | My MPMI | Scoop.it

Fungal cell wall chitin is a well-recognized pathogen-associated molecular pattern. Recognition of chitin in plants by pattern recognition receptors activates pathogen triggered immunity (PTI). In Arabidopsis this process is mediated by a plasma membrane receptor kinase CERK1, whereas in rice a receptor-like protein CEBiP in addition to CERK1 is required. Secreted chitin-binding lysin motif (LysM) containing fungal effector proteins such as Ecp6 from the biotrophic fungusCladosporium fulvum have been reported to interfere with PTI. Here we identified wheat homologues of CERK1 and CEBiP and investigated their role in the interaction with the non-biotrophic pathogen of wheatMycosphaerella graminicola (synonym Zymoseptoria tritici). We show that silencing of either CERK1 or CEBiP in wheat using Barley stripe mosaic virus-mediated Virus-induced gene silencing (BSMV-VIGS) is sufficient in allowing leaf colonization by the normally nonpathogenic M. graminicola Mg3LysM (homologue of Ecp6) deletion mutant, while theMg1LysM deletion mutant was fully pathogenic toward both silenced and wild type wheat leaves. These data indicate that Mg3LysM is important for fungal evasion of PTI in wheat leaf tissue and that both CERK1 and CEBiP are required for activation of chitin-induced defenses, a feature conserved between rice and wheat, and also perhaps in other cereal species.


Via Kamoun Lab @ TSL
Stephen Bolus's insight:

I want to do VIGS on wheat!

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Rescooped by Stephen Bolus from Plants and Microbes
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MPMI: A Bacterial Type III Secretion Assay for Delivery of Fungal Effector Proteins into Wheat (2013)

MPMI: A Bacterial Type III Secretion Assay for Delivery of Fungal Effector Proteins into Wheat (2013) | My MPMI | Scoop.it

Large numbers of candidate effectors from fungal pathogens are being identified through whole genome sequencing and in planta expression studies. AlthoughAgrobacterium-mediated transient expression has enabled high-throughput functional analysis of effectors in dicot plants, this assay is not effective in cereal leaves. Here we show that a non-pathogenic Pseudomonas fluorescens(Pf) engineered to express the T3SS of Pseudomonas syringae and the wheat pathogen Xanthomonas translucens (Xt) deliver fusion proteins containing T3SS signals from P. syringae (AvrRpm1) and X. campestris (AvrBs2) Avr proteins, respectively, into wheat leaf cells. A calmodulin-dependent adenylate cyclase (Cya) reporter protein was delivered effectively into wheat and barley by both bacteria. Absence of any disease symptoms with Pf, makes it more suitable than Xt) for detecting hypersensitive cell death (HR) induced by effector protein with avirulence activity. We further modified the delivery system by removal of the myristoylation site from the AvrRpm1 fusion to prevent its localisation to the PM which could inhibit recognition of an Avr protein. Delivery of the flax rust AvrM protein by the modified delivery system into transgenic tobacco leaves expressing the corresponding M resistance protein induced a strong HR indicating that the system is capable of delivering a functional rust Avr protein. In a preliminary screen of effectors from the stem rust fungus Puccinia graminisf. sp. tritici, we identified one effector that induced a host genotype-specific HR in wheat. Thus the modified AvrRpm1:effector/Pf system is an effective tool for large scale screening of pathogen effectors for recognition in wheat.


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245732's curator insight, November 19, 2013 11:53 AM

Another cool article I think. I find all walks of life interesting, even microbial plant diseases. I believe that studying these and how they work is always cool.

Rescooped by Stephen Bolus from Plants and Microbes
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New Phytologist: Apoplastic immunity and its suppression by filamentous plant pathogens (2013)

New Phytologist: Apoplastic immunity and its suppression by filamentous plant pathogens (2013) | My MPMI | Scoop.it

Microbial plant pathogens have evolved a variety of strategies to enter plant hosts and cause disease. In particular, biotrophic pathogens, which parasitize living plant tissue, establish sophisticated interactions in which they modulate the plant's metabolism to their own good. The prime decision, whether or not a pathogen can accommodate itself in its host tissue, is made during the initial phase of infection. At this stage, the plant immune system recognizes conserved molecular patterns of the invading microbe, which initiate a set of basal immune responses. Induced plant defense proteins, toxic compounds and antimicrobial proteins encounter a broad arsenal of pathogen-derived virulence factors that aim to disarm host immunity. Crucial regulatory processes and protein–protein interactions take place in the apoplast, that is, intercellular spaces, plant cell walls and defined host–pathogen interfaces which are formed between the plant cytoplasm and the specialized infection structures of many biotrophic pathogens. This article aims to provide an insight into the most important principles and components of apoplastic plant immunity and its modulation by filamentous microbial pathogens.


Via Kamoun Lab @ TSL
Stephen Bolus's insight:

Now, this is the review article that I have been talking about!

 

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Leading Environmental Activist’s Blunt Confession: I Was Completely Wrong To Oppose GMOs

Leading Environmental Activist’s Blunt Confession: I Was Completely Wrong To Oppose GMOs | My MPMI | Scoop.it
If you fear genetically modified food, you may have Mark Lynas to thank.
Stephen Bolus's insight:

Although victory for science comes in small battles, this one was particularly noteworthy. 

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