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MPMI: Foundational and translational research opportunities to improve plant health (2017)

MPMI: Foundational and translational research opportunities to improve plant health (2017) | Plants and Microbes | Scoop.it

This whitepaper reports the deliberations of a workshop focused on biotic challenges to plant health held in Washington, D.C. in September 2016. Ensuring health of food plants is critical to maintaining the quality and productivity of crops and for sustenance of the rapidly growing human population. There is a close linkage between food security and societal stability; however, global food security is threatened by the vulnerability of our agricultural systems to numerous pests, pathogens, weeds, and environmental stresses. These threats are aggravated by climate change, the globalization of agriculture, and an over-reliance on non-sustainable inputs. New analytical and computational technologies are providing unprecedented resolution at a variety of molecular, cellular, organismal, and population scales for crop plants as well as pathogens, pests, beneficial microbes, and weeds. It is now possible to both characterize useful or deleterious variation as well as precisely manipulate it. Data-driven, informed decisions based on knowledge of the variation of biotic challenges and of natural and synthetic variation in crop plants will enable deployment of durable interventions throughout the world. These should be integral, dynamic components of agricultural strategies for sustainable agriculture. Specific findings: ● Genetic improvement of crops is the most reliable, least expensive management strategy when suitable genetic variation is available. Nonetheless, some interventions have not proved durable due to the evolution and global dispersal of virulent pathogens and pests as well as herbicide-resistant weeds. ● Additional strategies are becoming essential as multiple fungicides, nematicides, and herbicides become ineffective due to the evolution of resistance and/or are phased out due to registration withdrawals. ● Strategies are needed that maximize the evolutionary hurdles for pathogens, pests, and weeds to overcome control measures. Interventions need to evolve as fast as the biotic challenges. Moreover, deployments of interventions must be driven by knowledge of the evolutionary capacity of the biotic challenge. ● Considerable knowledge exists but more research into the mechanisms of plant immunity and other forms of resistance is needed as the foundation for translational applications. ● Several new technologies are increasing foundational knowledge and providing numerous opportunities for generating crops with durable resistance to pests and diseases as well as control of weeds and reduction of the environmental impact of agriculture. ● There are multiple strategies for counteracting biotic challenges involving canonical and non-canonical disease resistance genes, genes encoding susceptibility factors, small RNAs, or immunomodulators. Simultaneous deployment of disease resistance strategies with different modes of action, as well as the judicious use of fungicides, will enhance durability of control measures. ● Pathogen effectors provide tools for discovering resistance genes and susceptibility factors as well as for dissecting/manipulating plant biology and breeding plants for durable disease resistance. ● There are several, as yet little exploited, opportunities for leveraging beneficial interactions among plants, microbes, insects and other organisms in the phytobiome to enhance plant health and productivity as well as breeding plants to promote beneficial phytobiome communities. ● Global monitoring of plant health is feasible and desirable in order to anticipate and counter threats. ● Climate change increases the need for continual global monitoring of pathogens, pests, and weeds and adjusting of control strategies. ● There are numerous current and future opportunities for knowledge exchange and partnerships between developed and developing countries to foster improved local and global food security. ● Both genetically modified (GM) and non-GM strategies are needed to maximize plant health and food security. ● Significant, sustained financial support is required if the beneficial impacts of foundational and translational research on global food security are to be realized. The needs, opportunities, approaches, and deliverables for addressing biotic challenges to plant health are detailed in Table 1. These can be broadly classified as assessing variation, characterizing it in detail at a variety of scales, and deploying beneficial interventions. Immediate investments in global monitoring of pathogens/pests and in situ and ex-situ determination of what natural variation exists in crop plants for countering challenges and threats should be a high priority. Detailed investigations of the molecular basis of the various types of plant resistance and of the basis of pathogen/pest virulence are critical for providing the foundation for novel intervention strategies; these will be facilitated by development of high resolution structural and functional analytical techniques. Optimization of protocols for delivery of reagents for allele replacement and gene insertions into diverse major and minor crop plants should be a high priority. Monitoring and deployment should be a global endeavor involving multinational partnerships and knowledge exchanges in order to ensure that interventions are locally relevant and globally durable.

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BMC Biology: Albugo-imposed changes to tryptophan-derived antimicrobial metabolite biosynthesis may contribute to suppression of non-host resistance to Phytophthora infestans in Arabidopsis thalian...

BMC Biology: Albugo-imposed changes to tryptophan-derived antimicrobial metabolite biosynthesis may contribute to suppression of non-host resistance to Phytophthora infestans in Arabidopsis thalian... | Plants and Microbes | Scoop.it

Plants are exposed to diverse pathogens and pests, yet most plants are resistant to most plant pathogens. Non-host resistance describes the ability of all members of a plant species to successfully prevent colonization by any given member of a pathogen species. White blister rust caused by Albugo species can overcome non-host resistance and enable secondary infection and reproduction of usually non-virulent pathogens, including the potato late blight pathogen Phytophthora infestans on Arabidopsis thaliana. However, the molecular basis of host defense suppression in this complex plant–microbe interaction is unclear. Here, we investigate specific defense mechanisms in Arabidopsis that are suppressed by Albugo infection.

 


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The Sainsbury Lab's curator insight, March 22, 8:01 AM
Plants are exposed to diverse pathogens and pests, yet most plants are resistant to most plant pathogens. Non-host resistance describes the ability of all members of a plant species to successfully prevent colonization by any given member of a pathogen species. White blister rust caused by Albugo species can overcome non-host resistance and enable secondary infection and reproduction of usually non-virulent pathogens, including the potato late blight pathogen Phytophthora infestans on Arabidopsis thaliana. However, the molecular basis of host defense suppression in this complex plant–microbe interaction is unclear. Here, we investigate specific defense mechanisms in Arabidopsis that are suppressed by Albugo infection.
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Moscou Group at The Sainsbury Laboratory (2017)

Moscou Group at The Sainsbury Laboratory (2017) | Plants and Microbes | Scoop.it

The Moscou group focuses on understanding immunity in the grasses. Current themes in our research include dissecting the genetic architecture of nonhost resistance, tradeoffs between biotrophs and necrotrophs, seedling versus adult plant resistance, and suppression of resistance in polyploid genomes. The group uses genetics and bioinformatics to explore biology and solve long-standing puzzles.

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Scientific Reports: Rapid generation of a transgene-free powdery mildew resistant tomato by genome deletion (2017)

Scientific Reports: Rapid generation of a transgene-free powdery mildew resistant tomato by genome deletion (2017) | Plants and Microbes | Scoop.it

Genome editing has emerged as a technology with a potential to revolutionize plant breeding. In this study, we report on generating, in less than ten months, Tomelo, a non-transgenic tomato variety resistant to the powdery mildew fungal pathogen using the CRISPR/Cas9 technology. We used whole-genome sequencing to show that Tomelo does not carry any foreign DNA sequences but only carries a deletion that is indistinguishable from naturally occurring mutations. We also present evidence for CRISPR/Cas9 being a highly precise tool, as we did not detect off-target mutations in Tomelo. Using our pipeline, mutations can be readily introduced into elite or locally adapted tomato varieties in less than a year with relatively minimal effort and investment.

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New Phytologist: AvrPm2 encodes an RNase‐like avirulence effector which is conserved in the two different specialized forms of wheat and rye powdery mildew fungus (2017)

New Phytologist: AvrPm2 encodes an RNase‐like avirulence effector which is conserved in the two different specialized forms of wheat and rye powdery mildew fungus (2017) | Plants and Microbes | Scoop.it
  • There is a large diversity of genetically defined resistance genes in bread wheat against the powdery mildew pathogen Blumeria graminis (B. g.) f. sp. tritici. Many confer race-specific resistance to this pathogen, but until now only the mildew avirulence gene AvrPm3a2/f2 that is recognized by Pm3a/f was known molecularly.
  • We performed map-based cloning and genome-wide association studies to isolate a candidate for the mildew avirulence gene AvrPm2. We then used transient expression assays in Nicotiana benthamiana to demonstrate specific and strong recognition of AvrPm2 by Pm2.
  • The virulent AvrPm2 allele arose from a conserved 12 kb deletion, while there is no protein sequence diversity in the gene pool of avirulent B. g. tritici isolates. We found one polymorphic AvrPm2 allele in B. g. triticale and one orthologue in B. g. secalis and both are recognized by Pm2AvrPm2 belongs to a small gene family encoding structurally conserved RNase-like effectors, including Avra13 from B. g. hordei, the cognate Avr of the barley resistance gene Mla13.
  • These results demonstrate the conservation of functional avirulence genes in two cereal powdery mildews specialized on different hosts, thus providing a possible explanation for successful introgression of resistance genes from rye or other grass relatives to wheat.

 

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Tweet from @PlantoPhagy: Three recent papers demonstrate antiviral role of autophagy in plants (2017)

Selective autophagy limits cauliflower mosaic virus infection by NBR1-mediated targeting of viral capsid protein and particles.
Hafrén A, Macia JL, Love AJ, Milner JJ, Drucker M, Hofius D.
http://www.pnas.org/content/early/2017/02/17/1610687114.abstract

 

A calmodulin-like protein suppresses RNA silencing and promotes geminivirus infection by degrading SGS3 via the autophagy pathway in Nicotiana benthamiana.
Li F, Zhao N, Li Z, Xu X, Wang Y, Yang X, Liu SS, Wang A, Zhou X.
http://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1006213#ppat-1006213-g003

 

Autophagy functions as an antiviral mechanism against geminiviruses in plants.
Haxim Y, Ismayil A, Jia Q, Wang Y, Zheng X, Chen T, Qian L, Liu N, Wang Y, Shaojie H, Cheng J, Yijun Q, Hong Y, Liu Y.
https://elifesciences.org/content/6/e23897

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MPMI Call for Papers - FOCUS Issue: Effector-triggered Susceptibility

MPMI Call for Papers - FOCUS Issue: Effector-triggered Susceptibility | Plants and Microbes | Scoop.it

Ground-breaking research over recent decades has established that secreted proteins and small molecules, termed effectors, serve important functions to support the interactions of diverse organisms with their plant hosts. Studies focused on effectors have revealed key virulence and avirulence mechanisms, and have provided new insights into the functions of plant regulatory networks, and have informed long-standing questions about host-microbe co-evolution. This fundamental understanding also holds clear implications for management of disease in crops. However, much remains to be learned, and effector biology is one of the most vibrant areas of research in the molecular plant-microbe field.


We invite research and perspective articles that explore all aspects of effector structure, function, and evolution, encompassing the full breadth of plant-associated organisms. Articles highlighting translational research as well as fundamental understanding are welcome. We look forward to assembling an issue that highlights some of the best current research in this rapidly advancing area!

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Nature Plants: Resistance: Double gain with one gene (2017)

Nature Plants: Resistance: Double gain with one gene (2017) | Plants and Microbes | Scoop.it

The rice gene Xa4 encodes a wall-associated kinase and controls disease resistance and mechanical strength, possibly through a common mechanism.


Crop plants experience a wide range of stresses that negatively affect their performance. Rice, one of the most important global crops, is the main calorie source for more than half of the global population. Two of the major constraints in rice cultivation are bacterial diseases and lodging (Fig. 1). In this issue of Nature Plants, Hu and colleagues unravel the identity and molecular function of the Xa4 gene1. This important diseaseresistance gene codes for a wall-associated kinase (WAK). The presence of Xa4 confers resistance to bacterial blight and was found to strengthen the cell wall, which is a primary entry point for pathogens. Interestingly, cell wall reinforcement also led to reduced height of Xa4-expressing plants, thereby increasing lodging resistance. Hence, this gene has a beneficial effect on multiple agronomic traits, which can explain its importance and widespread use in rice breeding.

 

Original paper by Hu et al. is here http://www.nature.com/articles/nplants20179

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TSL Summer School PLANT MICROBE INTERACTIONS, 31st July - 11th August 2017,  Norwich, UK

TSL Summer School PLANT MICROBE INTERACTIONS, 31st July - 11th August 2017,  Norwich, UK | Plants and Microbes | Scoop.it

The last 20 years have provided a sophisticated understanding of how plants recognise relatively conserved microbial patterns to activate defence. In recent years DNA sequencing allowed genomes and transcriptomes of eukaryotic rusts and mildew pathogens to be studied and high-throughput imaging permit the study and visualisation of intracellular interactions during pathogenesis and defence.


We will present many aspects of plant microbe interactions including:

 

  • gene discovery
  • genome analysis
  • intra-cellular interactions with high-throughput imaging technology
  • mechanistic understanding of cellular and molecular processes to translational activities


The focus on the dynamic and interactive practical sessions will naturally promote strong interactions between lecturers and participants.

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YouTube: Gene regulation the secret to aphid’s wide-ranging crop diet (2017)

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PNAS: Multiple functional self-association interfaces in plant TIR domains (2017)

PNAS: Multiple functional self-association interfaces in plant TIR domains (2017) | Plants and Microbes | Scoop.it

The self-association of Toll/interleukin-1 receptor/resistance protein (TIR) domains has been implicated in signaling in plant and animal immunity receptors. Structure-based studies identified different TIR-domain dimerization interfaces required for signaling of the plant nucleotide-binding oligomerization domain-like receptors (NLRs) L6 from flax and disease resistance protein RPS4 from Arabidopsis. Here we show that the crystal structure of the TIR domain from the Arabidopsis NLR suppressor of npr1-1, constitutive 1 (SNC1) contains both an L6-like interface involving helices αD and αE (DE interface) and an RPS4-like interface involving helices αA and αE (AE interface). Mutations in either the AE- or DE-interface region disrupt cell-death signaling activity of SNC1, L6, and RPS4 TIR domains and full-length L6 and RPS4. Self-association of L6 and RPS4 TIR domains is affected by mutations in either region, whereas only AE-interface mutations affect SNC1 TIR-domain self-association. We further show two similar interfaces in the crystal structure of the TIR domain from the Arabidopsis NLR recognition of Peronospora parasitica 1 (RPP1). These data demonstrate that both the AE and DE self-association interfaces are simultaneously required for self-association and cell-death signaling in diverse plant NLRs.

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PLOS ONE: Floral Scent Mimicry and Vector-Pathogen Associations in a Pseudoflower-Inducing Plant Pathogen System (2016)

PLOS ONE: Floral Scent Mimicry and Vector-Pathogen Associations in a Pseudoflower-Inducing Plant Pathogen System (2016) | Plants and Microbes | Scoop.it

Several fungal plant pathogens induce ‘pseudoflowers’ on their hosts to facilitate insect-mediated transmission of gametes and spores. When spores must be transmitted to host flowers to complete the fungal life cycle, we predict that pseudoflowers should evolve traits that mimic flowers and attract the most effective vectors in the flower-visiting community. We quantified insect visitation to flowers, healthy leaves and leaves infected with Monilinia vaccinii-corymbosi(Mvc), the causative agent of mummy berry disease of blueberry. We developed a nested PCR assay for detecting Mvc spores on bees, flies and other potential insect vectors. We also collected volatiles from blueberry flowers, healthy leaves and leaves infected with Mvc, and experimentally manipulated specific pathogen-induced volatiles to assess attractiveness to potential vectors. Bees and flies accounted for the majority of contacts with flowers, leaves infected with Mvc and healthy leaves. Flowers were contacted most often, while there was no difference between bee or fly contacts with healthy and infected leaves. While bees contacted flowers more often than flies, flies contacted infected leaves more often than bees. Bees were more likely to have Mvc spores on their bodies than flies, suggesting that bees may be more effective vectors than flies for transmitting Mvc spores to flowers. Leaves infected with Mvc had volatile profiles distinct from healthy leaves but similar to flowers. Two volatiles produced by flowers and infected leaves, cinnamyl alcohol and cinnamic aldehyde, were attractive to bees, while no volatiles manipulated were attractive to flies or any other insects. These results suggest that Mvc infection of leaves induces mimicry of floral volatiles, and that transmission occurs primarily via bees, which had the highest likelihood of carrying Mvc spores and visited flowers most frequently.

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Bridget Barker's curator insight, February 2, 11:15 AM
Those darn fungi!
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PLOS Pathogens: The Rice Dynamin-Related Protein OsDRP1E Negatively Regulates Programmed Cell Death by Controlling the Release of Cytochrome c from Mitochondria (2017)

PLOS Pathogens: The Rice Dynamin-Related Protein OsDRP1E Negatively Regulates Programmed Cell Death by Controlling the Release of Cytochrome c from Mitochondria (2017) | Plants and Microbes | Scoop.it

Programmed cell death (PCD) mediated by mitochondrial processes has emerged as an important mechanism for plant development and responses to abiotic and biotic stress. However, the role of translocation of cytochrome c from the mitochondria to the cytosol during PCD remains unclear. Here, we demonstrate that the rice dynamin-related protein 1E (OsDRP1E) negatively regulates PCD by controlling mitochondrial structure and cytochrome c release. We used a map-based cloning strategy to isolate OsDRP1E from the lesion mimic mutant dj-lm and confirmed that the E409V mutation in OsDRP1E causes spontaneous cell death in rice. Pathogen inoculation showed that dj-lm significantly enhances resistance to fungal and bacterial pathogens. Functional analysis of the E409V mutation showed that the mutant protein impairs OsDRP1E self-association and formation of a higher-order complex; this in turn reduces the GTPase activity of OsDRP1E. Furthermore, confocal microscopy showed that the E409V mutation impairs localization of OsDRP1E to the mitochondria. The E409V mutation significantly affects the morphogenesis of cristae in the mitochondria and causes the abnormal release of cytochrome c from the mitochondria into the cytoplasm. Taken together, our results demonstrate that the mitochondria-localized protein OsDRP1E functions as a negative regulator of cytochrome c release and PCD in plants.

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Trends in Plant Sciences: Strigolactones in Plant Interactions with Beneficial and Detrimental Organisms: The Yin and Yang (2017)

Trends in Plant Sciences: Strigolactones in Plant Interactions with Beneficial and Detrimental Organisms: The Yin and Yang (2017) | Plants and Microbes | Scoop.it

Strigolactones (SLs) are plant hormones that have important roles as modulators of plant development. They were originally described as ex planta signaling molecules in the rhizosphere that induce the germination of parasitic plants, a role that was later linked to encouraging the beneficial symbiosis with arbuscular mycorrhizal (AM) fungi. Recently, the focus has shifted to examining the role of SLs in plant–microbe interactions, and has revealed roles for SLs in the association of legumes with nitrogen-fixing rhizobacteria and in interactions with disease-causing pathogens.


Via Pierre-Marc Delaux, Jean-Michel Ané, Jim Alfano
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PNAS: Live imaging of root–bacteria interactions in a microfluidics setup (2017)

PNAS: Live imaging of root–bacteria interactions in a microfluidics setup (2017) | Plants and Microbes | Scoop.it

Plant roots play a dominant role in shaping the rhizosphere, the environment in which interaction with diverse microorganisms occurs. Tracking the dynamics of root–microbe interactions at high spatial resolution is currently limited because of methodological intricacy. Here, we describe a microfluidics-based approach enabling direct imaging of root–bacteria interactions in real time. The microfluidic device, which we termed tracking root interactions system (TRIS), consists of nine independent chambers that can be monitored in parallel. The principal assay reported here monitors behavior of fluorescently labeled Bacillus subtilis as it colonizes the root of Arabidopsis thaliana within the TRIS device. Our results show a distinct chemotactic behavior of B. subtilis toward a particular root segment, which we identify as the root elongation zone, followed by rapid colonization of that same segment over the first 6 h of root–bacteria interaction. Using dual inoculation experiments, we further show active exclusion of Escherichia coli cells from the root surface after B. subtilis colonization, suggesting a possible protection mechanism against root pathogens. Furthermore, we assembled a double-channel TRIS device that allows simultaneous tracking of two root systems in one chamber and performed real-time monitoring of bacterial preference between WT and mutant root genotypes. Thus, the TRIS microfluidics device provides unique insights into the microscale microbial ecology of the complex root microenvironment and is, therefore, likely to enhance the current rate of discoveries in this momentous field of research.


Via Christophe Jacquet, IPM Lab
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Frontiers Plant Science: Effector Mimics and Integrated Decoys, the Never-Ending Arms Race between Rice and Xanthomonas oryzae (2017)

Frontiers Plant Science: Effector Mimics and Integrated Decoys, the Never-Ending Arms Race between Rice and Xanthomonas oryzae (2017) | Plants and Microbes | Scoop.it

Plants are constantly challenged by a wide range of pathogens and have therefore evolved an array of mechanisms to defend against them. In response to these defense systems, pathogens have evolved strategies to avoid recognition and suppress plant defenses (Brown & Tellier 2011). Three recent reports dealing with the resistance of rice to Xanthomonas oryzae have added a new twist to our understanding of this fascinating co-evolutionary arms race (Ji et al. 2016; Read et al. 2016 and Triplett et al. 2016). They show that pathogens also develop sophisticated effector mimics to trick recognition.


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Microbiology Molecular Biology Reviews: Effectors of Filamentous Plant Pathogens: Commonalities amid Diversity (2017)

Microbiology Molecular Biology Reviews: Effectors of Filamentous Plant Pathogens: Commonalities amid Diversity (2017) | Plants and Microbes | Scoop.it

Fungi and oomycetes are filamentous microorganisms that include a diversity of highly developed pathogens of plants. These are sophisticated modulators of plant processes that secrete an arsenal of effector proteins to target multiple host cell compartments and enable parasitic infection. Genome sequencing revealed complex catalogues of effectors of filamentous pathogens, with some species harboring hundreds of effector genes. Although a large fraction of these effector genes encode secreted proteins with weak or no sequence similarity to known proteins, structural studies have revealed unexpected similarities amid the diversity. This article reviews progress in our understanding of effector structure and function in light of these new insights. We conclude that there is emerging evidence for multiple pathways of evolution of effectors of filamentous plant pathogens but that some families have probably expanded from a common ancestor by duplication and diversification. Conserved folds, such as the oomycete WY and the fungal MAX domains, are not predictive of the precise function of the effectors but serve as a chassis to support protein structural integrity while providing enough plasticity for the effectors to bind different host proteins and evolve unrelated activities inside host cells. Further effector evolution and diversification arise via short linear motifs, domain integration and duplications, and oligomerization.

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APS Feature: Tobacco Mosaic Virus: The Beginning of Plant Virology (2008)

For the past century, plant virology and the American Phytopathological Society have a deeply intertwined history. As the Society emerged as a distinct entity in the first decade of the 20th century, viruses were also making their mark as newly described and discovered agents of disease. Interestingly, Tobacco mosaic virus (TMV) and its economic hosts in the Solanaceae, such as tobacco and tomato, also find their origins in the Americas.


What follows is a brief review of the origins of our understanding of “the nature of the virus,” deciphering the basis of host-pathogen interaction, and vignettes of the early TMV workers who developed many of the tools and techniques that have become part of the definition of what it is “to be” a virologist or “to do” virology. As plant molecular virology has its origins in the early 20th century, first from the early descriptive work of viruses diseases (1900-1935), followed by the biochemical, the genetics, and biophysical work (1935-1960), the molecular biology (1960-1980), and our current era of transgenic technology, functional genetics of plant viruses, and using viruses as molecular tools, it is useful to develop a contextual understanding of how we came to work with TMV.

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PNAS: Cytosolic activation of cell death and stem rust resistance by cereal MLA-family CC–NLR proteins (2016)

PNAS: Cytosolic activation of cell death and stem rust resistance by cereal MLA-family CC–NLR proteins (2016) | Plants and Microbes | Scoop.it

Plants possess intracellular immune receptors designated “nucleotide-binding domain and leucine-rich repeat” (NLR) proteins that translate pathogen-specific recognition into disease-resistance signaling. The wheat immune receptors Sr33 and Sr50 belong to the class of coiled-coil (CC) NLRs. They confer resistance against a broad spectrum of field isolates of Puccinia graminis f. sp. tritici, including the Ug99 lineage, and are homologs of the barley powdery mildew-resistance protein MLA10. Here, we show that, similarly to MLA10, the Sr33 and Sr50 CC domains are sufficient to induce cell death in Nicotiana benthamiana. Autoactive CC domains and full-length Sr33 and Sr50 proteins self-associate in planta. In contrast, truncated CC domains equivalent in size to an MLA10 fragment for which a crystal structure was previously determined fail to induce cell death and do not self-associate. Mutations in the truncated region also abolish self-association and cell-death signaling. Analysis of Sr33 and Sr50 CC domains fused to YFP and either nuclear localization or nuclear export signals in N. benthamiana showed that cell-death induction occurs in the cytosol. In stable transgenic wheat plants, full-length Sr33 proteins targeted to the cytosol provided rust resistance, whereas nuclear-targeted Sr33 was not functional. These data are consistent with CC-mediated induction of both cell-death signaling and stem rust resistance in the cytosolic compartment, whereas previous research had suggested that MLA10-mediated cell-death and disease resistance signaling occur independently, in the cytosol and nucleus, respectively.

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Frontiers: A perspective on CRN proteins in the genomics age: Evolution, Classification, Delivery and Function revisited (2017)

Frontiers: A perspective on CRN proteins in the genomics age: Evolution, Classification, Delivery and Function revisited (2017) | Plants and Microbes | Scoop.it

Plant associated microbes rely on secreted virulence factors (effectors) to modulate host immunity and ensure progressive infection. Amongst the secreted protein repertoires defined and studied in pathogens to date, the CRNs (for CRinkling and Necrosis) have emerged as one of only a few highly conserved protein families, spread across several kingdoms. CRN proteins were first identified in plant pathogenic oomycetes where they were found to be modular factors that are secreted and translocated inside host cells by means of a conserved N-terminal domain. Subsequent localization and functional studies have led to the view that CRN C-termini execute their presumed effector function in the host nucleus, targeting processes required for immunity. These findings have led to great interest in this large protein family and driven the identification of additional CRN-like proteins in other organisms. The identification of CRN proteins and subsequent functional studies have markedly increased the number of candidate CRN protein sequences, expanded the range of phenotypes tentatively associated with function and revealed some of their molecular functions towards virulence. The increased number of characterised CRNs also has presented a set of challenges that may impede significant progress in the future. Here, we summarise our current understanding of the CRNs and re-assess some basic assumptions regarding this protein family. We will discuss the latest findings on CRN biology and highlight exciting new hypotheses that have emanated from the field. Finally, we will discuss new approaches to study CRN functions that would lead to a better understanding of CRN effector biology as well as the processes that lead to host susceptibility and immunity.


Via Christophe Jacquet
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International Molecular Mycorrhiza Meeting 2017, 26th – 28th July 2017, Toulouse, France

International Molecular Mycorrhiza Meeting 2017, 26th – 28th July 2017, Toulouse, France | Plants and Microbes | Scoop.it
iMMM2017 Research into the molecular basis of symbiosis between plant roots and fungi has achieved major breakthroughs in recent years. The international Molecular Mycorrhiza Meeting (iMMM) is a response to the perceived need for a specialized meeting series covering the molecular mechanistic aspects of mycorrhizal symbioses including yet non-categorised endophytic root fungus interactions. After the success of the two first editions in Munich (2012) and Cambridge (2015), the 3rd international Molecular Mycorrhiza Meeting will be held in Toulouse in 2017. To keep the meeting highly interactive, the participant number will be limited to 150 people.

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Genome Biology: Rapid transcriptional plasticity of duplicated gene clusters enables a clonally reproducing aphid to colonise diverse plant species (2017)

Genome Biology: Rapid transcriptional plasticity of duplicated gene clusters enables a clonally reproducing aphid to colonise diverse plant species (2017) | Plants and Microbes | Scoop.it

Background. The prevailing paradigm of host-parasite evolution is that arms races lead to increasing specialisation via genetic adaptation. Insect herbivores are no exception and the majority have evolved to colonise a small number of closely related host species. Remarkably, the green peach aphid, Myzus persicae, colonises plant species across 40 families and single M. persicae clonal lineages can colonise distantly related plants. This remarkable ability makes M. persicae a highly destructive pest of many important crop species.


Results. To investigate the exceptional phenotypic plasticity of M. persicae, we sequenced the M. persicae genome and assessed how one clonal lineage responds to host plant species of different families. We show that genetically identical individuals are able to colonise distantly related host species through the differential regulation of genes belonging to aphid-expanded gene families. Multigene clusters collectively upregulate in single aphids within two days upon host switch. Furthermore, we demonstrate the functional significance of this rapid transcriptional change using RNA interference (RNAi)-mediated knock-down of genes belonging to the cathepsin B gene family. Knock-down of cathepsin B genes reduced aphid fitness, but only on the host that induced upregulation of these genes.


Conclusions. Previous research has focused on the role of genetic adaptation of parasites to their hosts. Here we show that the generalist aphid pest M. persicae is able to colonise diverse host plant species in the absence of genetic specialisation. This is achieved through rapid transcriptional plasticity of genes that have duplicated during aphid evolution.

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PNAS: TIR-only protein RBA1 recognizes a pathogen effector to regulate cell death in Arabidopsis (2017)

PNAS: TIR-only protein RBA1 recognizes a pathogen effector to regulate cell death in Arabidopsis (2017) | Plants and Microbes | Scoop.it

Detection of pathogens by plants is mediated by intracellular nucleotide-binding site leucine-rich repeat (NLR) receptor proteins. NLR proteins are defined by their stereotypical multidomain structure: an N-terminal Toll–interleukin receptor (TIR) or coiled-coil (CC) domain, a central nucleotide-binding (NB) domain, and a C-terminal leucine-rich repeat (LRR). The plant innate immune system contains a limited NLR repertoire that functions to recognize all potential pathogens. We isolated Response to the bacterial type III effector protein HopBA1 (RBA1), a gene that encodes a TIR-only protein lacking all other canonical NLR domains. RBA1 is sufficient to trigger cell death in response to HopBA1. We generated a crystal structure for HopBA1 and found that it has similarity to a class of proteins that includes esterases, the heme-binding protein ChaN, and an uncharacterized domain of Pasteurella multocida toxin. Self-association, coimmunoprecipitation with HopBA1, and function of RBA1 require two previously identified TIR–TIR dimerization interfaces. Although previously described as distinct in other TIR proteins, in RBA1 neither of these interfaces is sufficient when the other is disrupted. These data suggest that oligomerization of RBA1 is required for function. Our identification of RBA1 demonstrates that “truncated” NLRs can function as pathogen sensors, expanding our understanding of both receptor architecture and the mechanism of activation in the plant immune system.

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16th International Conference on Pseudomonas, Liverpool, UK, 5-9 September 2017

16th International Conference on Pseudomonas, Liverpool, UK, 5-9 September 2017 | Plants and Microbes | Scoop.it

The 16th International Conference on Pseudomonas will take place at St George's Hall in Liverpool, UK.

 

The Pseudomonas International Conference is a biennial event that brings together researchers from all over the world who are working on the genus Pseudomonas, including not only the important human pathogen Pseudomonas aeruginosa, but also a range of other important species with relevance to plant pathogenicity, bioremediation and environmental microbiology. It is also a group of organisms used widely for the study of host–pathogen interactions; cell–cell communication systems; evolutionary biology; gene regulation and metabolic networks; secretion systems; antibiotics (and resistance); bioremediation; biofilms; bacterial genomics; and other topics of broader relevance to microbiology and molecular biology generally.

 

The meeting is aimed primarily at scientists (from postgraduate students to PIs) with an interest in Pseudomonas, but because of the widespread use of this genus as a model to study multiple systems, it will be of general interest to other researchers active in areas such as evolutionary biology, communication systems, genomics and biofilm research. In addition, because P. aeruginosa is a key pathogen associated with both acute and chronic infections, and particularly important in the context of cystic fibrosis and antimicrobial resistance, the meeting will be of interest to clinicians and clinical researchers.

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bioRxiv: Host autophagosomes are diverted to a plant-pathogen interface (2017)

bioRxiv: Host autophagosomes are diverted to a plant-pathogen interface (2017) | Plants and Microbes | Scoop.it

Filamentous plant pathogens and symbionts invade their host cells but remain enveloped by host-derived membranes. The mechanisms underlying the biogenesis and functions of these host-microbe interfaces are poorly understood. Recently, we showed that PexRD54, an effector from the Irish potato famine pathogen Phytophthora infestans, binds host protein ATG8CL to stimulate autophagosome formation and deplete the selective autophagy receptor Joka2 from ATG8CL complexes. Here, we show that during P. infestans infection, ATG8CL autophagosomes are diverted to the pathogen interface. Our findings are consistent with the view that the pathogen coopts host selective autophagy for its own benefit.

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