Plants and Microbes
314.4K views | +61 today
Follow
 
Scooped by Kamoun Lab @ TSL
onto Plants and Microbes
Scoop.it!

NY Times: The Worldwide Vulnerability of Forests (2012)

NY Times: The Worldwide Vulnerability of Forests (2012) | Plants and Microbes | Scoop.it

Many trees operate with only a narrow margin of safety when it comes to their water supply, so many of the world's important forest species are vulnerable to hydraulic failure.

 

A warming climate creates summertime water stress for trees like these mountain pines in Montana, making them more vulnerable to attack by beetles. The gray trees above died several years ago.

more...
No comment yet.
Plants and Microbes
Everything related to the science of plant-microbe interactions
Your new post is loading...
Your new post is loading...
Rescooped by Kamoun Lab @ TSL from Plants & Evolution
Scoop.it!

bioRxiv: Phytophthora palmivora establishes tissue-specific intracellular infection structures in the earliest divergent land plant lineage (2017)

bioRxiv: Phytophthora palmivora establishes tissue-specific intracellular infection structures in the earliest divergent land plant lineage (2017) | Plants and Microbes | Scoop.it

The expansion of plants onto land was a formative event that brought forth profound changes to the Earth's geochemistry and biota. Filamentous eukaryotic microbes developed the ability to colonize plant tissues early during the evolution of land plants, as demonstrated by intimate symbiosis-like associations in >400 million-year-old fossils. However, the degree to which filamentous microbes establish pathogenic interactions with early divergent land plants is unclear. Here, we demonstrate that the broad host-range oomycete pathogen Phytophthora palmivora colonizes liverworts, the earliest divergent land plant lineage. We show that P. palmivora establishes a complex tissue-specific interaction with Marchantia polymorpha, where it completes a full infection cycle within air chambers of the dorsal photosynthetic layer. Remarkably, P. palmivora invaginates M. polymorpha cells with haustoria-like structures that accumulate host cellular trafficking machinery and the membrane-syntaxin MpSYP13B but not the related MpSYP13A. Our results indicate that the intracellular accommodation of filamentous microbes is an ancient plant trait that is successfully exploited by pathogens like P. palmivora.


Via Pierre-Marc Delaux
more...
Philip Carella's curator insight, September 15, 1:28 PM

Our new pre-print! Happy to receive any feedback. 

Philip Carella's curator insight, September 15, 1:29 PM

Our new pre-print! Happy to receive any feedback

Scooped by Kamoun Lab @ TSL
Scoop.it!

Molecular Plant Pathology: Rmg8 and Rmg7, wheat genes for resistance to the wheat blast fungus, recognize the same avirulence gene AVR‐Rmg8 (2017)

Molecular Plant Pathology: Rmg8 and Rmg7, wheat genes for resistance to the wheat blast fungus, recognize the same avirulence gene AVR‐Rmg8 (2017) | Plants and Microbes | Scoop.it

Rmg8 and Rmg7 are genes for resistance to the wheat blast fungus (Pyricularia oryzae) located on 2B chromosome in hexaploid wheat and 2A chromosome in tetraploid wheat, respectively. AVR-Rmg8, an avirulence gene corresponding to Rmg8, was isolated from a wheat blast isolate through map-based strategy. The cloned fragment encoded a small protein containing a putative signal peptide. AVR-Rmg8 was recognized not only by Rmg8 but also by Rmg7, suggesting that these two resistance genes are equivalent to a single gene from the viewpoint of resistance breeding. This article is protected by copyright. All rights reserved.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

bioRxiv: MicroRNAs from the parasitic plant Cuscuta campestris target host messenger RNAs (2017)

bioRxiv: MicroRNAs from the parasitic plant Cuscuta campestris target host messenger RNAs (2017) | Plants and Microbes | Scoop.it

Dodders (Cuscuta spp.) are obligate parasitic plants that obtain water and nutrients from the stems of host plants via specialized feeding structures called haustoria. Dodder haustoria facilitate bi-directional movement of viruses, proteins, and mRNAs between host and parasite, but the functional effects of these movements are not clear. Here we show that C. campestris haustoria accumulate high levels of many novel microRNAs (miRNAs) while parasitizing Arabidopsis thaliana hosts. Many of these miRNAs are 22 nts long, a usually rare size of plant miRNA associated with amplification of target silencing through secondary small interfering RNA (siRNA) production. Several A. thaliana mRNAs are targeted by C. campestris 22 nt miRNAs during parasitism, resulting in mRNA cleavage, high levels of secondary siRNA production, and decreased mRNA accumulation levels. Hosts with a mutation in the target SIEVE ELEMENT OCCLUSION RELATED 1 (SEOR1) supported significantly higher growth of C. campestris. Homologs of target mRNAs from diverse plants also have predicted target sites to induced C. campestris miRNAs, and several of the same miRNAs are expressed when C. campestris parasitizes a second host, Nicotiana benthamiana. These data show that C. campestris miRNAs act as trans-species regulators of host gene expression, and suggest that they may act as virulence factors during parasitism.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

bioRxiv: A plant receptor-like kinase promotes cell-to-cell spread of RNAi and is targeted by a virus (2017)

bioRxiv: A plant receptor-like kinase promotes cell-to-cell spread of RNAi and is targeted by a virus (2017) | Plants and Microbes | Scoop.it

RNA interference (RNAi) in plants can move from cell to cell, allowing for systemic spread of an anti-viral immune response. How this cell-to-cell spread of silencing is regulated is currently unknown. Here, we describe that the C4 protein from Tomato yellow leaf curl virus has the ability to inhibit the intercellular spread of RNAi. Using this viral protein as a probe, we have identified the receptor-like kinase (RLK) BARELY ANY MERISTEM 1 (BAM1) as a positive regulator of the cell-to-cell movement of RNAi, and determined that BAM1 and its closest homologue, BAM2, play a redundant role in this process. C4 interacts with the intracellular domain of BAM1 and BAM2 at the plasma membrane and plasmodesmata, the cytoplasmic connections between plant cells, interfering with the function of these RLKs in the cell-to-cell spread of RNAi. Our results identify BAM1 as an element required for the cell-to-cell spread of RNAi and highlight that signalling components have been co-opted to play multiple functions in plants.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

Genome Biology: MAPK-triggered chromatin reprogramming by histone deacetylase in plant innate immunity (2017)

Genome Biology: MAPK-triggered chromatin reprogramming by histone deacetylase in plant innate immunity (2017) | Plants and Microbes | Scoop.it

Background. Microbial-associated molecular patterns activate several MAP kinases, which are major regulators of the innate immune response in Arabidopsis thaliana that induce large-scale changes in gene expression. Here, we determine whether microbial-associated molecular pattern-triggered gene expression involves modifications at the chromatin level.

 

Results. Histone acetylation and deacetylation are major regulators of microbial-associated molecular pattern-triggered gene expression and implicate the histone deacetylase HD2B in the reprogramming of defence gene expression and innate immunity. The MAP kinase MPK3 directly interacts with and phosphorylates HD2B, thereby regulating the intra-nuclear compartmentalization and function of the histone deacetylase.

 

Conclusions. By studying a number of gene loci that undergo microbial-associated molecular pattern-dependent activation or repression, our data reveal a mechanistic model for how protein kinase signaling directly impacts chromatin reprogramming in plant defense.

 

more...
No comment yet.
Rescooped by Kamoun Lab @ TSL from Host Translocation of Plant Pathogen Effectors
Scoop.it!

New Phytologist: Delivery of cytoplasmic and apoplastic effectors from Phytophthora infestans haustoria by distinct secretion pathways (2017)

New Phytologist: Delivery of cytoplasmic and apoplastic effectors from Phytophthora infestans haustoria by distinct secretion pathways (2017) | Plants and Microbes | Scoop.it
  • The potato blight pathogen Phytophthora infestans secretes effector proteins that are delivered inside (cytoplasmic) or can act outside (apoplastic) plant cells to neutralize host immunity. Little is known about how and where effectors are secreted during infection, yet such knowledge is essential to understand and combat crop disease.
  • We used transient Agrobacterium tumefaciens-mediated in planta expression, transformation of P. infestans with fluorescent protein fusions and confocal microscopy to investigate delivery of effectors to plant cells during infection.
  • The cytoplasmic effector Pi04314, expressed as a monomeric red fluorescent protein (mRFP) fusion protein with a signal peptide to secrete it from plant cells, did not passively re-enter the cells upon secretion. However, Pi04314-mRFP expressed in P. infestans was translocated from haustoria, which form intimate interactions with plant cells, to accumulate at its sites of action in the host nucleus. The well-characterized apoplastic effector EPIC1, a cysteine protease inhibitor, was also secreted from haustoria. EPIC1 secretion was inhibited by brefeldin A (BFA), demonstrating that it is delivered by conventional Golgi-mediated secretion. By contrast, Pi04314 secretion was insensitive to BFA treatment, indicating that the cytoplasmic effector follows an alternative route for delivery into plant cells.
  • Phytophthora infestans haustoria are thus sites for delivery of both apoplastic and cytoplasmic effectors during infection, following distinct secretion pathways.
more...
No comment yet.
Rescooped by Kamoun Lab @ TSL from Publications
Scoop.it!

bioRxiv: Lessons in effector and NLR biology of plant-microbe systems (2017)

bioRxiv: Lessons in effector and NLR biology of plant-microbe systems (2017) | Plants and Microbes | Scoop.it

A diversity of plant-associated organisms secrete effectors: proteins and metabolites that modulate plant physiology to favor host infection and colonization. However, effectors can also activate plant immune receptors, notably nucleotide-binding domain and leucine-rich repeat-containing (NLR) proteins, enabling plants to fight off invading organisms. This interplay between effectors, their host targets, and the matching immune receptors is shaped by intricate molecular mechanisms and exceptionally dynamic coevolution. In this article, we focus on three effectors, AVR-Pik, AVR-Pia, and AVR-Pii, from the rice blast fungus Magnaporthe oryzae (syn. Pyricularia oryzae), and their corresponding rice NLR immune receptors, Pik, Pia, and Pii, to highlight general concepts of plant-microbe interactions. We draw 12 lessons in effector and NLR biology that have emerged from studying these three little effectors and are broadly applicable to other plant-microbe systems.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

Nature Communications: A TAL effector repeat architecture for frameshift binding (2014)

Nature Communications: A TAL effector repeat architecture for frameshift binding (2014) | Plants and Microbes | Scoop.it

Transcription activator-like effectors (TALEs) are important Xanthomonas virulence factors that bind DNA via a unique tandem 34-amino-acid repeat domain to induce expression of plant genes. So far, TALE repeats are described to bind as a consecutive array to a consecutive DNA sequence, in which each repeat independently recognizes a single DNA base. This modular protein architecture enables the design of any desired DNA-binding specificity for biotechnology applications. Here we report that natural TALE repeats of unusual amino-acid sequence length break the strict one repeat-to-one base pair binding mode and introduce a local flexibility to TALE–DNA binding. This flexibility allows TALEs and TALE nucleases to recognize target sequence variants with single nucleotide deletions. The flexibility also allows TALEs to activate transcription at allelic promoters that otherwise confer resistance to the host plant.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

MailOnline: Two children are cancer-free after receiving TALEN gene-editing therapy (2017)

MailOnline: Two children are cancer-free after receiving TALEN gene-editing therapy (2017) | Plants and Microbes | Scoop.it

Cancer-free for up to 18 months

 

Researchers from Great Ormond Street Hospital in London investigated a new cancer treatment in two infants with an aggressive form of leukaemia.

 

The youngsters had previously been treated with chemotherapy and received stem cell transplants.

 

The researchers made four DNA alterations on immune cells from donors and infused the cells into the patients.

 

Results revealed that both youngsters have been cancer-free for 16 and 18 months, respectively.

 

The findings were published in the journal Science Translational Medicine.

 

How does the new treatment work?

 

The researchers combined a immune-boosting treatment with a gene-editing technique, known as TALENS.

 

Gene-editing technology, such as CRISPR, can precisely 'cut and paste' sections of DNA to either remove unwanted genes or insert desirable ones.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

YouTube: Engineering resistance in banana against Fusarium Wilt disease (2017)

Bananas are more than delicious fruits, bananas are the fourth most important food crop in the world. Currently, the biggest threat to worldwide banana production is Fusarium Wilt. I am a scientist working to engineer resistance in banana against this devastating disease. If you want to know more about bananas, check out my blog, write me a mail, follow me on Twitter or stay tuned to this channel.

more...
No comment yet.
Rescooped by Kamoun Lab @ TSL from Plant Pathogenomics
Scoop.it!

bioRxiv: Gene flow between divergent cereal- and grass-specific lineages of the rice blast fungus Magnaporthe oryzae (2017)

bioRxiv: Gene flow between divergent cereal- and grass-specific lineages of the rice blast fungus Magnaporthe oryzae (2017) | Plants and Microbes | Scoop.it

Delineating species and epidemic lineages in fungal plant pathogens is critical to our understanding of disease emergence and the structure of fungal biodiversity, and also informs international regulatory decisions. Pyricularia oryzae (syn. Magnaporthe oryzae) is a multi-host pathogen that infects multiple grasses and cereals, is responsible for the most damaging rice disease (rice blast), and of growing concern due to the recent introduction of wheat blast to Bangladesh from South America. However, the genetic structure and evolutionary history of M. oryzae, including the possible existence of cryptic phylogenetic species, remain poorly defined. Here, we use whole-genome sequence information for 76 M. oryzae isolates sampled from 12 grass and cereal genera to infer the population structure of M. oryzae, and to reassess the species status of wheat-infecting populations of the fungus. Species recognition based on genealogical concordance, using published data or extracting previously-used loci from genome assemblies, failed to confirm a prior assignment of wheat blast isolates to a new species (Pyricularia graminis tritici). Inference of population subdivisions revealed multiple divergent lineages within M. oryzae, each preferentially associated with one host genus, suggesting incipient speciation following host shift or host range expansion. Analyses of gene flow, taking into account the possibility of incomplete lineage sorting, revealed that genetic exchanges have contributed to the makeup of multiple lineages within M. oryzae. These findings provide greater understanding of the eco-evolutionary factors that underlie the diversification of M. oryzae and highlight the practicality of genomic data for epidemiological surveillance in this important multi-host pathogen.

more...
No comment yet.
Rescooped by Kamoun Lab @ TSL from Plant pathogenic fungi
Scoop.it!

Scientific Reports: Fungal infestation boosts fruit aroma and fruit removal by mammals and birds (2017)

Scientific Reports: Fungal infestation boosts fruit aroma and fruit removal by mammals and birds (2017) | Plants and Microbes | Scoop.it

For four decades, an influential hypothesis has posited that competition for food resources between microbes and vertebrates selects for microbes to alter these resources in ways that make them unpalatable to vertebrates. We chose an understudied cross kingdom interaction to experimentally evaluate the effect of fruit infection by fungi on both vertebrate (mammals and birds) fruit preferences and on ecologically relevant fruit traits (volatile compounds, toughness, etc). Our well-replicated field experiments revealed that, in contrast to previous studies, frugivorous mammals and birds consistently preferred infested over intact fruits. This was concordant with the higher level of attractive volatiles (esters, ethanol) in infested fruits. This investigation suggests that vertebrate frugivores, fleshy-fruited plants, and microbes form a tripartite interaction in which each part could interact positively with the other two (e.g. both orange seeds and fungal spores are likely dispersed by mammals). Such a mutualistic view of these complex interactions is opposed to the generalized idea of competition between frugivorous vertebrates and microorganisms. Thus, this research provides a new perspective on the widely accepted plant evolutionary dilemma to make fruits attractive to mutualistic frugivores while unattractive to presumed antagonistic microbes that constrain seed dispersal.


Via Steve Marek
more...
No comment yet.
Rescooped by Kamoun Lab @ TSL from Publications
Scoop.it!

PNAS: NLR network mediates immunity to diverse plant pathogens (2017)

PNAS: NLR network mediates immunity to diverse plant pathogens (2017) | Plants and Microbes | Scoop.it

Both plants and animals rely on nucleotide-binding domain and leucine-rich repeat-containing (NLR) proteins to respond to invading pathogens and activate immune responses. An emerging concept of NLR function is that “sensor” NLR proteins are paired with “helper” NLRs to mediate immune signaling. However, our fundamental knowledge of sensor/helper NLRs in plants remains limited. In this study, we discovered a complex NLR immune network in which helper NLRs in the NRC (NLR required for cell death) family are functionally redundant but display distinct specificities toward different sensor NLRs that confer immunity to oomycetes, bacteria, viruses, nematodes, and insects. The helper NLR NRC4 is required for the function of several sensor NLRs, including Rpi-blb2, Mi-1.2, and R1, whereas NRC2 and NRC3 are required for the function of the sensor NLR Prf. Interestingly, NRC2, NRC3, and NRC4 redundantly contribute to the immunity mediated by other sensor NLRs, including Rx, Bs2, R8, and Sw5. NRC family and NRC-dependent NLRs are phylogenetically related and cluster into a well-supported superclade. Using extensive phylogenetic analysis, we discovered that the NRC superclade probably emerged over 100 Mya from an NLR pair that diversified to constitute up to one-half of the NLRs of asterids. These findings reveal a complex genetic network of NLRs and point to a link between evolutionary history and the mechanism of immune signaling. We propose that this NLR network increases the robustness of immune signaling to counteract rapidly evolving plant pathogens.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

Molecular Plant Pathology: Plum pox virus capsid protein suppresses plant pathogen-associated molecular pattern (PAMP)-triggered immunity (2016)

Molecular Plant Pathology: Plum pox virus capsid protein suppresses plant pathogen-associated molecular pattern (PAMP)-triggered immunity (2016) | Plants and Microbes | Scoop.it

The perception of pathogen-associated molecular patterns (PAMPs) by immune receptors launches defence mechanisms referred to as PAMP-triggered immunity (PTI). Successful pathogens must suppress PTI pathways via the action of effectors to efficiently colonize their hosts. So far, plant PTI has been reported to be active against most classes of pathogens, except viruses, although this defence layer has been hypothesized recently as an active part of antiviral immunity which needs to be suppressed by viruses for infection success. Here, we report that Arabidopsis PTI genes are regulated upon infection by viruses and contribute to plant resistance to Plum pox virus (PPV). Our experiments further show that PPV suppresses two early PTI responses, the oxidative burst and marker gene expression, during Arabidopsis infection. In planta expression of PPV capsid protein (CP) was found to strongly impair these responses in Nicotiana benthamiana and Arabidopsis, revealing its PTI suppressor activity. In summary, we provide the first clear evidence that plant viruses acquired the ability to suppress PTI mechanisms via the action of effectors, highlighting a novel strategy employed by viruses to escape plant defences.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

bioRxiv: Chemosensory proteins in the CSP4 clade evolved as plant immunity suppressors before two suborders of plant-feeding hemipteran insects diverged (2017)

bioRxiv: Chemosensory proteins in the CSP4 clade evolved as plant immunity suppressors before two suborders of plant-feeding hemipteran insects diverged (2017) | Plants and Microbes | Scoop.it

Chemosensory proteins (CSPs) are small globular proteins with hydrophobic binding pockets that have a role in detection of chemicals, regulation of development and growth and host seeking behaviour and feeding of arthropods. Here, we show that a CSP has evolved to modulate plant immune responses. Firstly, we found that the green peach aphid Myzus persicae CSP Mp10, which is delivered into the cytoplasm of plant cells, suppresses the reactive oxygen species (ROS) bursts to both aphid and bacterial elicitors in Arabidopsis thaliana and Nicotiana benthamiana. In contrast, other CSPs, including MpOS-D1, do not have this ROS suppression activity. Aphid RNA interference studies demonstrated that Mp10 modulates the first layer of the plant defence response, specifically the BAK1 pathway. Alignment of CSPs from multiple aphid species showed that Mp10 homologues uniquely have tyrosine (Y40) and tryptophan (W120) flanking the central binding region. Exchange of aromatic residues between Mp10 and MpOS-D1 showed a gain of ROS activity of MpOS-D1 and loss of this activity of Mp10. We identified Mp10 homologs in diverse plant-sucking insect species, including aphids, whiteflies, psyllids and leafhoppers, but not in other insect species, including blood-feeding hemipteran insects. Moreover, the positions of Y and W residues are conserved among these Mp10 homologs, which we found also suppress plant ROS. Together, these data and phylogenetic analyses provides evidence that an ancestral Mp10-like sequence acquired plant ROS suppression activity via gain-of-function mutations before the divergence of plant-sucking insect species over 250 million years ago.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

bioRxiv: Plant genes influence microbial hubs that shape beneficial leaf communities (2017)

bioRxiv: Plant genes influence microbial hubs that shape beneficial leaf communities (2017) | Plants and Microbes | Scoop.it

Although the complex interactions between hosts and microbial associates are increasingly well documented, we still know little about how and why hosts shape microbial communities in nature. We characterized the leaf microbiota within 200 clonal accessions in eight field experiments and detected effects of both local environment and host genotype on community structure. Within environments, hosts′ genetics preferentially associate with a core of ubiquitous microbial hubs that, in turn, structure the community. These microbial hubs correlate with host performance, and a GWAS revealed strong candidate genes for the host factors impacting heritable hubs. Our results reveal how selection may act to enhance fitness through microbial associations and bolster the possibility of enhancing crop performance through these host factors.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

Nature Plants: The pattern-recognition receptor CORE of Solanaceae detects bacterial cold-shock protein (2017)

Nature Plants: The pattern-recognition receptor CORE of Solanaceae detects bacterial cold-shock protein (2017) | Plants and Microbes | Scoop.it

Plants and animals recognize microbial invaders by detecting microbe-associated molecular patterns (MAMPs) by cell surface receptors. Many plant species of the Solanaceae family detect the highly conserved nucleic acid binding motif RNP-1 of bacterial cold-shock proteins (CSPs), represented by the peptide csp22, as a MAMP. Here, we exploited the natural variation in csp22 perception observed between cultivated tomato (Solanum lycopersicum) and Solanum pennellii to map and identify the leucine-rich repeat (LRR) receptor kinase CORE (cold shock protein receptor) of tomato as the specific, high-affinity receptor site for csp22. Corroborating its function as a genuine receptor, heterologous expression of CORE in Arabidopsis thaliana conferred full sensitivity to csp22 and, importantly, it also rendered these plants more resistant to infection by the bacterial pathogen Pseudomonas syringaepv. tomato DC3000. Our study also confirms the biotechnological potential of enhancing plant immunity by interspecies transfer of highly effective pattern-recognition receptors such as CORE to different plant families.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

PNAS: Disease resistance through impairment of α-SNAP–NSF interaction and vesicular trafficking by soybean Rhg1 (2017)

PNAS: Disease resistance through impairment of α-SNAP–NSF interaction and vesicular trafficking by soybean Rhg1 (2017) | Plants and Microbes | Scoop.it

The Rhg1 resistance locus of soybean helps control one of the most damaging diseases in world agriculture. We found that Rhg1 (resistance to Heterodera glycines 1)-mediated resistance utilizes an unusual mechanism. Resistant soybeans carry a dysfunctional variant of the housekeeping protein α-SNAP [soluble NSF (N-ethylmaleimide–sensitive factor) attachment protein]. Rhg1 resistance-type α-SNAPs interact poorly with NSF and disrupt vesicle trafficking. High levels of resistance-type α-SNAPs interfere with wild-type α-SNAP activities, yet are functionally balanced in most tissues by sufficient wild-type α-SNAP levels. However, the biotrophic plant–pathogen interface is disabled by localized hyperaccumulation of resistance-type α-SNAPs. This study suggests a paradigm of resistance conferred by a dysfunctional version of a core cellular housekeeping protein.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

bioRxiv: Heterologous expression of the immune receptor EFR in Medicago truncatula reduces pathogenic infection, but not rhizobia symbiosis (2017)

bioRxiv: Heterologous expression of the immune receptor EFR in Medicago truncatula reduces pathogenic infection, but not rhizobia symbiosis (2017) | Plants and Microbes | Scoop.it

Interfamily transfer of plant pattern recognition receptors (PRRs) represents a promising biotechnological approach to engineer broad-spectrum, and potentially durable, disease resistance in crops. It is however unclear whether new recognition specificities to given pathogen-associated molecular patterns (PAMPs) affect the interaction of the recipient plant with beneficial microbes. To test this in a direct reductionist approach, we transferred the Brassicaceae-specific PRR ELONGATION FACTOR-THERMO UNSTABLE RECEPTOR (EFR) from Arabidopsis thaliana to the legume Medicago truncatula, conferring recognition of the bacterial EF-Tu protein. Constitutive EFR expression led to EFR accumulation and activation of immune responses upon treatment with the EF-Tu-derived elf18 peptide in leaves and roots. The interaction of M. truncatula with the bacterial symbiont Sinorhizobium meliloti is characterized by the formation of root nodules that fix atmospheric nitrogen. Although nodule numbers were slightly reduced at an early stage of the infection in EFR-Medicago when compared to control lines, nodulation was similar in all lines at later stages. Furthermore, nodule colonization by rhizobia, and nitrogen fixation were not compromised by EFR expression. Importantly, the M. truncatula lines expressing EFR were substantially more resistant to the root bacterial pathogen Ralstonia solanacearum. Our data suggest that the transfer of EFR to M. truncatula does not impede root nodule symbiosis, but has a positive impact on disease resistance against a bacterial pathogen. In addition, our results indicate that Rhizobium can either avoid PAMP recognition during the infection process, or is able to actively suppress immune signaling.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

Frontiers Plant Science:| Suppression of Xo1-Mediated Disease Resistance in Rice by a Truncated, Non-DNA-Binding TAL Effector of Xanthomonas oryzae | Plant Science (2016)

Frontiers Plant Science:| Suppression of Xo1-Mediated Disease Resistance in Rice by a Truncated, Non-DNA-Binding TAL Effector of Xanthomonas oryzae | Plant Science (2016) | Plants and Microbes | Scoop.it

Delivered into plant cells by type III secretion from pathogenic Xanthomonas species, TAL (transcription activator-like) effectors are nuclear-localized, DNA-binding proteins that directly activate specific host genes. Targets include genes important for disease, genes that confer resistance, and genes inconsequential to the host-pathogen interaction. TAL effector specificity is encoded by polymorphic repeats of 33–35 amino acids that interact one-to-one with nucleotides in the recognition site. Activity depends also on N-terminal sequences important for DNA binding and C-terminal nuclear localization signals (NLS) and an acidic activation domain (AD). Coding sequences missing much of the N- and C-terminal regions due to conserved, in-frame deletions are present and annotated as pseudogenes in sequenced strains of Xanthomonas oryzae pv. oryzicola (Xoc) and pv. oryzae (Xoo), which cause bacterial leaf streak and bacterial blight of rice, respectively. Here we provide evidence that these sequences encode proteins we call “truncTALEs,” for “truncated TAL effectors.” We show that truncTALE Tal2h of Xoc strain BLS256, and by correlation truncTALEs in other strains, specifically suppress resistance mediated by the Xo1 locus recently described in the heirloom rice variety Carolina Gold. Xo1-mediated resistance is triggered by different TAL effectors from diverse X. oryzae strains, irrespective of their DNA binding specificity, and does not require the AD. This implies a direct protein-protein rather than protein-DNA interaction. Similarly, truncTALEs exhibit diverse predicted DNA recognition specificities. And, in vitro, Tal2h did not bind any of several potential recognition sites. Further, a single candidate NLS sequence in Tal2h was dispensable for resistance suppression. Many truncTALEs have one 28 aa repeat, a length not observed previously. Tested in an engineered TAL effector, this repeat required a single base pair deletion in the DNA, suggesting that it or a neighbor disengages. The presence of the 28 aa repeat, however, was not required for resistance suppression. TruncTALEs expand the paradigm for TAL effector-mediated effects on plants. We propose that Tal2h and other truncTALEs act as dominant negative ligands for an immune receptor encoded by the Xo1 locus, likely a nucleotide binding, leucine-rich repeat protein. Understanding truncTALE function and distribution will inform strategies for disease control.

more...
No comment yet.
Rescooped by Kamoun Lab @ TSL from Plant Pathogenomics
Scoop.it!

bioRxiv: Parallel loss of symbiosis genes in relatives of nitrogen-fixing non-legume Parasponia (2017)

bioRxiv: Parallel loss of symbiosis genes in relatives of nitrogen-fixing non-legume Parasponia (2017) | Plants and Microbes | Scoop.it

Rhizobium nitrogen-fixing nodules are a well-known trait of legumes, but nodules also occur in other plant lineages either with rhizobium or the actinomycete Frankia as microsymbiont. The widely accepted hypothesis is that nodulation evolved independently multiple times, with only a few losses. However, insight in the evolutionary trajectory of nodulation is lacking. We conducted comparative studies using Parasponia (Cannabaceae), the only non-legume able to establish nitrogen fixing nodules with rhizobium. This revealed that Parasponia and legumes utilize a large set of orthologous symbiosis genes. Comparing genomes of Parasponia and its non-nodulating relative Trema did not reveal specific gene duplications that could explain a recent gain of nodulation in Parasponia. Rather, Trema and other non-nodulating species in the order Rosales show evidence of pseudogenization or loss of key symbiosis genes. This demonstrates that these species have lost the potential to nodulate. This finding challenges a long-standing hypothesis on evolution of nitrogen-fixing symbioses, and has profound implications for translational approaches aimed at engineering nitrogen-fixing nodules in crop plants.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

Plant Physiology: Sequence exchange between R genes converts virus resistance into nematode resistance, and vice versa (2017)

Plant Physiology: Sequence exchange between R genes converts virus resistance into nematode resistance, and vice versa (2017) | Plants and Microbes | Scoop.it

Plants have evolved a limited repertoire of NB-LRR disease resistance (R) genes to protect themselves against a myriad of pathogens. This limitation is thought to be counterbalanced by the rapid evolution of NB-LRR proteins, as only few sequence changes have been shown to be sufficient to alter resistance specificities towards novel strains of a pathogen. However, little is known about the flexibility of NB-LRR genes to switch resistance specificities between phylogenetically unrelated pathogens. To investigate this, we created domain swaps between the close homologs Gpa2 and Rx1, which confer resistance in potato to the cyst nematode Globodera pallida and Potato virus X (PVX), respectively. The genetic fusion of the CC-NB-ARC of Gpa2 with the LRR of Rx1 (Gpa2CN/Rx1L) resulted in autoactivity, but lowering the protein levels restored its specific activation response including extreme resistance to PVX in potato shoots. The reciprocal construct (Rx1CN/Gpa2L) showed a loss-of-function phenotype, but exchange of the first 3 LRR repeats of Rx1 was sufficient to regain a wild type resistance response to G. pallida in the roots. These data demonstrate that exchanging the recognition moiety in the LRR is sufficient to convert extreme virus resistance in the leaves into mild nematode resistance in the roots, and vice versa. In addition, we show that the CC-NB-ARC can operate independently of the recognition specificities defined by the LRR domain, either above or belowground. These data show the versatility of NB-LRR genes to generate resistances to unrelated pathogens with completely different lifestyles and routes of invasion.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

Nature Microbiology: Stop neglecting fungi (2017)

Nature Microbiology: Stop neglecting fungi (2017) | Plants and Microbes | Scoop.it

Fungal pathogens are virtually ignored by the press, the public and funding bodies, despite posing a significant threat to public health, food biosecurity and biodiversity.

 

Fungal infections will probably not have made major news today, perhaps not even this week or month. Indeed, in comparison to the threat from drug-resistant bacterial infections or viral outbreaks, diseases caused by fungi, fungal drug resistance and the development of new antifungal therapeutics gets little coverage. Yet in this case, no news is certainly not good news, and the disparity relative to other infectious disease agents unjustified. The word fungus usually evokes images of athlete's foot, unseemly looking nails, or scrumptious cheese and mouth-watering mushrooms. However, few realize that over 300 million people suffer from serious fungal-related diseases, or that fungi collectively kill over 1.6 million people annually1, which is more than malaria and similar to the tuberculosis death toll. Fungi and oomycetes destroy a third of all food crops each year, which would be sufficient to feed 600 million people. Furthermore, fungal infestation of amphibians has led to the largest disease-caused loss of biodiversity ever recorded, while fungi also cause mass mortality of bats, bees and other animals, and decimate fruit orchards, pine, elm and chestnut forests2. Headline-grabbing statistics, one would imagine.

 

There are an estimated 1.5 million fungal species3, of which over 8,000 are known to cause disease in plants and 300 to be pathogenic to humans. Candida, Aspergillus, Pneumocystis and Cryptococcus spp. are the most common cause of serious disease in humans, and five fungal diseases — wheat stem rust, rice blast, corn smut, soybean fungi and potato late blight — are the most devastating for crop production. Infections primarily occur in immunocompromised patients, such as those undergoing chemotherapy or infected with HIV, and many are acquired in hospitals. However, infections of otherwise healthy people are on the rise. Global warming is inducing rapid poleward movement of crop fungal pathogens, and may also increase the prevalence of fungal disease in humans as fungi adapt to survival in warmer temperatures4. In this scenario, increasing resistance to the limited arsenal of antifungal drugs is a serious concern5, especially for Candida and Aspergillus infections, for which the therapeutic options have become limited. The emergence of multi-drug resistant Candida glabrata and Candida auris is a global health threat6, and azole-resistant Aspergillushas up to 30% prevalence in some European hospitals, which report higher than 90% mortality rates7.

Experts agree that fungal pathogens are a serious threat to human health, food biosecurity and ecosystem resilience, yet lack of funding translates into inadequate surveillance systems to monitor fungal disease incidence and antifungal drug resistance, which often rely on not-for-profit initiatives, such as the Global Action Fund for Fungal Infections (GAFFI; http://www.gaffi.org/). As highlighted in the World Health Organization (WHO) Global Report on Antimicrobial Resistance Surveillance8, which devotes fewer than 10% of its pages to fungi, resources allocated for monitoring and reducing antifungal drug resistance are limited. Indeed, the WHO has no funded programmes specifically targeting fungal diseases, fewer than 10 countries have national surveillance programs for fungal infections, and fewer than 20 have fungal reference diagnostic laboratories. Many of the diagnostic tests that do exist are not available in developing countries, and well-established antifungal drugs — such as amphotericin B, flucytosine and cotrim — that would cure disease do not reach people that need them, a large fraction of which are in sub-Saharan Africa9. In an attempt to tackle this silent humanitarian crisis, organizations such as GAFFI, the US Centres for Disease Control, Médecins Sans Frontières and Clinton Health Access lobbied to include amphotericin B and flucytosine on the WHO Essential Medicines List9. Beyond this, GAFFI has put forth a roadmap to achieve diagnosis and access to antifungals for 95% of infected people by 2025, which aims to improve the availability/affordability of diagnostics, train clinicians in fungal disease diagnosis and treatment, and ensure that antifungals are available globally10. Funding is also urgently needed to advance our understanding of fungal pathogenesis and drug resistance, develop new diagnostics and antifungal strategies, and improve monitoring of infection and antifungal resistance, as this will ultimately inform new strategies to tackle fungal infections.

 

Why then do fungi remain stubbornly off the mainstream radar? A possible reason is that most people think of fungi as causing infections that are uncomfortable but relatively easy to address, as invasive, life-threatening disease impacts few people in developed countries. In addition, our human-centric view of the world limits the amount of attention devoted to plant health, even if this directly impacts food availability. Bacteria and viruses have historically received more attention, in part because of the simple (yet not always correct) narrative to portray them as harmful, whereas fungi and their products can be edible, or useful drugs, and they are used as model organisms for understanding higher eukaryotes. Nevertheless, bringing emerging fungal threats into better focus for the broader research community, funders, media organizations and the general public should be a priority and will catalyse support and progress for this important and neglected group of pathogens.

 

Something that should make headlines this month, but may not, is the opening in South Africa of the AFGrica Unit in Medical Mycology, the first international research centre for tackling fungal infections (http://go.nature.com/2sN8x0z). This centre is an initiative of the University of Aberdeen Fungal Group (now the MRC Centre for Medical Mycology), in conjunction with the University of Cape Town. It will benefit from a Wellcome Trust Strategic Award that funds PhD students from developing nations to train in Aberdeen and other medical mycology centres and return home to help address fungal research and training needs. International collaborative efforts such as this one will be essential to give fungal diseases the prominence they require, and as such they should be encouraged. It is time to stop the neglect and put fungal diseases firmly in the spotlight.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

European conference on Xylella fastidiosa: finding answers to a global problem: Palma de Mallorca, 13-15 November 2017

European conference on Xylella fastidiosa: finding answers to a global problem: Palma de Mallorca, 13-15 November 2017 | Plants and Microbes | Scoop.it

A major scientific conference on European research into Xylella fastidiosa is to be held in Palma de Mallorca, Spain, from 13-15 November 2017. The conference is being organised jointly by EFSA, the University of the Balearic Islands, the Euphresconetwork for phytosanitary research coordination and funding, the EU Horizon 2020 projects POnTE and XF-ACTORS, and the European Commission’s Directorate-Generalfor Research and Innovation (DG RTD).

 

The event will provide a platform for in-depth discussion on the results of research into X. fastidiosa and its vectors, in support of on-going efforts to control the European outbreaks. As well as speakers and participants from Europe, the conference will be attended by scientific experts from other parts of the world – such as Brazil and the United States – where X. fastidiosa has been present for many years.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

International SPS Conference 2018: Plant Sciences for the Future, Paris July 4-6, 2018

International SPS Conference 2018: Plant Sciences for the Future, Paris July 4-6, 2018 | Plants and Microbes | Scoop.it
more...
No comment yet.