Plant-Microbe Interaction
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The Botrytis cinerea cerato-platanin BcSpl1 is a potent inducer of systemic acquired resistance (SAR) in tobacco and generates a wave of salicylic acid expanding from the site of application - Fría...

The Botrytis cinerea cerato-platanin BcSpl1 is a potent inducer of systemic acquired resistance (SAR) in tobacco and generates a wave of salicylic acid expanding from the site of application - Fría... | Plant-Microbe Interaction | Scoop.it

Systemic acquired resistance (SAR) is a potent plant defence system that, in response to a first contact with a plant pathogen, prepares the whole plant for subsequent attacks, so that it becomes more resistant to the same and to other pathogens. BcSpl1, a cerato-platanin family protein abundantly secreted by Botrytis cinerea, is required for full virulence and elicits the hypersensitive response in the host. Here, we report that BcSpl1 is also able to induce in tobacco systemic resistance to two plant pathogens, Pseudomonas syringae and B. cinerea, which correlates with the induction of two pathogenesis-related genes, PR-1a and PR-5. Levels of salicylic acid were quantified in situ on BcSpl1 infiltration, and a wave of salicylic acid departing from the point of infiltration and running through the leaf was observed, as well as the appearance of this plant hormone in the neighbouring leaves as early as 3 days after infiltration.

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Nature Biotech: Accelerated cloning of a potato late blight–resistance gene using RenSeq and SMRT sequencing (2016)

Nature Biotech: Accelerated cloning of a potato late blight–resistance gene using RenSeq and SMRT sequencing (2016) | Plant-Microbe Interaction | Scoop.it

Global yields of potato and tomato crops have fallen owing to potato late blight disease, which is caused by Phytophthora infestans. Although most commercial potato varieties are susceptible to blight, many wild potato relatives show variation for resistance and are therefore a potential source of Resistance to P. infestans (Rpi) genes. Resistance breeding has exploited Rpi genes from closely related tuber-bearing potato relatives, but is laborious and slow1, 2, 3. Here we report that the wild, diploid non-tuber-bearing Solanum americanum harbors multiple Rpi genes. We combine resistance (R) gene sequence capture (RenSeq)4 with single-molecule real-time (SMRT) sequencing (SMRT RenSeq) to clone Rpi-amr3i. This technology should enable de novo assembly of complete nucleotide-binding, leucine-rich repeat receptor (NLR) genes, their regulatory elements and complex multi-NLR loci from uncharacterized germplasm. SMRT RenSeq can be applied to rapidly clone multiple R genes for engineering pathogen-resistant crops.


Via The Sainsbury Lab, Kamoun Lab @ TSL
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The Sainsbury Lab's curator insight, April 26, 4:21 AM
Global yields of potato and tomato crops have fallen owing to potato late blight disease, which is caused by Phytophthora infestans. Although most commercial potato varieties are susceptible to blight, many wild potato relatives show variation for resistance and are therefore a potential source of Resistance to P. infestans (Rpi) genes. Resistance breeding has exploited Rpi genes from closely related tuber-bearing potato relatives, but is laborious and slow1, 2, 3. Here we report that the wild, diploid non-tuber-bearing Solanum americanum harbors multiple Rpi genes. We combine resistance (R) gene sequence capture (RenSeq)4 with single-molecule real-time (SMRT) sequencing (SMRT RenSeq) to clone Rpi-amr3i. This technology should enable de novo assembly of complete nucleotide-binding, leucine-rich repeat receptor (NLR) genes, their regulatory elements and complex multi-NLR loci from uncharacterized germplasm. SMRT RenSeq can be applied to rapidly clone multiple R genes for engineering pathogen-resistant crops.
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Arabidopsis PROTEASOME REGULATOR1 is required for auxin-mediated suppression of proteasome activity and regulates auxin signalling : Nature Communications : Nature Publishing Group

Arabidopsis PROTEASOME REGULATOR1 is required for auxin-mediated suppression of proteasome activity and regulates auxin signalling : Nature Communications : Nature Publishing Group | Plant-Microbe Interaction | Scoop.it
The plant hormone auxin is perceived by the nuclear F-box protein TIR1 receptor family and regulates gene expression through degradation of Aux/IAA transcriptional repressors. Several studies have revealed the importance of the proteasome in auxin signalling, but details on how the proteolytic machinery is regulated and how this relates to degradation of Aux/IAA proteins remains unclear. Here we show that an Arabidopsis homologue of the proteasome inhibitor PI31, which we name PROTEASOME REGULATOR1 (PTRE1), is a positive regulator of the 26S proteasome. Loss-of-function ptre1 mutants are insensitive to auxin-mediated suppression of proteasome activity, show diminished auxin-induced degradation of Aux/IAA proteins and display auxin-related phenotypes. We found that auxin alters the subcellular localization of PTRE1, suggesting this may be part of the mechanism by which it reduces proteasome activity. Based on these results, we propose that auxin regulates proteasome activity via PTRE1 to fine-tune the homoeostasis of Aux/IAA repressor proteins thus modifying auxin activity.

Via Suayib Üstün
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NADPH-dependent thioredoxin reductase C plays a role in nonhost disease resistance against Pseudomonas syringae pathogens by regulating chloroplast-generated reactive oxygen species

NADPH-dependent thioredoxin reductase C plays a role in nonhost disease resistance against Pseudomonas syringae pathogens by regulating chloroplast-generated reactive oxygen species | Plant-Microbe Interaction | Scoop.it
Chloroplasts are cytoplasmic organelles for photosynthesis in eukaryotic cells. In addition, recent studies have shown that chloroplasts have a critical role in plant innate immunity against invading pathogens. Hydrogen peroxide is a toxic by-product from photosynthesis, which also functions as a signaling compound in plant innate immunity. Therefore, it is important to regulate the level of hydrogen peroxide in response to pathogens. Chloroplasts maintain components of the redox detoxification system including enzymes such as 2-Cys peroxiredoxins (2-Cys Prxs), and NADPH-dependent thioredoxin reductase C (NTRC). However, the significance of 2-Cys Prxs and NTRC in the molecular basis of nonhost disease resistance is largely unknown. We evaluated the roles of Prxs and NTRC using knock-out mutants of Arabidopsis in response to nonhost Pseudomonas syringae pathogens. Plants lacking functional NTRC showed localized cell death (LCD) accompanied by the elevated accumulation of hydrogen peroxide in response to nonhost pathogens. Interestingly, the Arabidopsis ntrc mutant showed enhanced bacterial growth and disease susceptibility of nonhost pathogens. Furthermore, the expression profiles of the salicylic acid (SA) and jasmonic acid (JA)-mediated signaling pathways and phytohormone analyses including SA and JA revealed that the Arabidopsis ntrc mutant shows elevated JA-mediated signaling pathways in response to nonhost pathogen. These results suggest the critical role of NTRC in plant innate immunity against nonhost P. syringae pathogens.

Via Christophe Jacquet
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Endocytosis and Endosomal Trafficking in Plants - Annual Review of Plant Biology, 67(1):309

Endocytosis and Endosomal Trafficking in Plants - Annual Review of Plant Biology, 67(1):309 | Plant-Microbe Interaction | Scoop.it
Endocytosis and endosomal trafficking are essential processes in cells that control the dynamics and turnover of plasma membrane proteins, such as receptors, transporters, and cell wall biosynthetic enzymes. Plasma membrane proteins (cargo) are internalized by endocytosis through clathrin-dependent or clathrin-independent mechanism and delivered to early endosomes. From the endosomes, cargo proteins are recycled back to the plasma membrane via different pathways, which rely on small GTPases and the retromer complex. Proteins that are targeted for degradation through ubiquitination are sorted into endosomal vesicles by the ESCRT (endosomal sorting complex required for transport) machinery for degradation in the vacuole. Endocytic and endosomal trafficking regulates many cellular, developmental, and physiological processes, including cellular polarization, hormone transport, metal ion homeostasis, cytokinesis, pathogen responses, and development. In this review, we discuss the mechanisms that mediate the recognition and sorting of endocytic and endosomal cargos, the vesiculation processes that mediate their trafficking, and their connection to cellular and physiological responses in plants.

Via Christophe Jacquet
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miRNA863-3p sequentially targets negative immune regulator ARLPKs and positive regulator SERRATE upon bacterial infection : Nature Communications : Nature Publishing Group

miRNA863-3p sequentially targets negative immune regulator ARLPKs and positive regulator SERRATE upon bacterial infection : Nature Communications : Nature Publishing Group | Plant-Microbe Interaction | Scoop.it
Plant small RNAs play important roles in gene regulation during pathogen infection. Here we show that miR863-3p is induced by the bacterial pathogen Pseudomonas syringae carrying various effectors. Early during infection, miR863-3p silences two negative regulators of plant defence, atypical receptor-like pseudokinase1 (ARLPK1) and ARLPK2, both lacking extracellular domains and kinase activity, through mRNA degradation to promote immunity. ARLPK1 associates with, and may function through another negative immune regulator ARLPK1-interacting receptor-like kinase 1 (AKIK1), an active kinase with an extracellular domain. Later during infection, miR863-3p silences SERRATE, which is essential for miRNA accumulation and positively regulates defence, through translational inhibition. This results in decreased miR863-3p levels, thus forming a negative feedback loop to attenuate immune responses after successful defence. This is an example of a miRNA that sequentially targets both negative and positive regulators of immunity through two modes of action to fine-tune the timing and amplitude of defence responses.

Via Christophe Jacquet
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Gatekeeper Tyrosine Phosphorylation of SYMRK Is Essential for Synchronizing the Epidermal and Cortical Responses in Root Nodule Symbiosis

Gatekeeper Tyrosine Phosphorylation of SYMRK Is Essential for Synchronizing the Epidermal and Cortical Responses in Root Nodule Symbiosis | Plant-Microbe Interaction | Scoop.it
Symbiosis receptor kinase (SYMRK) is indispensable for activation of root nodule symbiosis (RNS) at both epidermal and cortical levels and is functionally conserved in legumes. Previously, we reported SYMRK to be phosphorylated on “gatekeeper” Tyr both in vitro as well as in planta. Since gatekeeper phosphorylation was not necessary for activity, the significance remained elusive. Herein, we show that substituting gatekeeper with nonphosphorylatable residues like Phe or Ala significantly affected autophosphorylation on selected targets on activation segment/αEF and β3-αC loop of SYMRK. In addition, the same gatekeeper mutants failed to restore proper symbiotic features in a symrk null mutant where rhizobial invasion of the epidermis and nodule organogenesis was unaffected but rhizobia remain restricted to the epidermis in infection threads migrating parallel to the longitudinal axis of the root, resulting in extensive infection patches at the nodule apex. Thus, gatekeeper phosphorylation is critical for synchronizing epidermal/cortical responses in RNS.

Via Christophe Jacquet
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Magnaporthe oryzae Effector AVR-Pii Helps to Establish Compatibility by Inhibition of the Rice NADP-Malic Enzyme Resulting in Disruption of Oxidative Burst and Host Innate Immunity

Magnaporthe oryzae Effector AVR-Pii Helps to Establish Compatibility by Inhibition of the Rice NADP-Malic Enzyme Resulting in Disruption of Oxidative Burst and Host Innate Immunity | Plant-Microbe Interaction | Scoop.it
Plant disease resistance occurs as a hypersensitive response (HR) at the site of attempted pathogen invasion. This specific event is initiated in response to recognition of pathogen-associated molecular pattern (PAMP) and subsequent PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI). Both PTI and ETI mechanisms are tightly connected with reactive oxygen species (ROS) production and disease resistance that involves distinct biphasic ROS production as one of its pivotal plant immune responses. This unique oxidative burst is strongly dependent on the resistant cultivars because a monophasic ROS burst is a hallmark of the susceptible cultivars. However, the cause of the differential ROS burst remains unknown. In the study here, we revealed the plausible underlying mechanism of the differential ROS burst through functional understanding of the Magnaporthe oryzae (M. oryzae) AVR effector, AVR-Pii. We performed yeast two-hybrid (Y2H) screening using AVRPii as bait and isolated rice NADP-malic enzyme2 (Os-NADP-ME2) as the rice target protein. To our surprise, deletion of the rice Os-NADP-ME2 gene in a resistant rice cultivar disrupted innate immunity against the rice blast fungus. Malic enzyme activity and inhibition studies demonstrated that AVR-Pii proteins specifically inhibit in vitro NADP-ME activity. Overall, we demonstrate that rice blast fungus, M. oryzae attenuates the host ROS burst via AVR-Pii-mediated inhibition of Os-NADP-ME2, which is indispensable in ROS metabolism for the innate immunity of rice. This characterization of the regulation of the host oxidative burst will help to elucidate how the products of AVR genes function associated with virulence of the pathogen.

Via Elsa Ballini
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Rescooped by Guogen Yang from Host Cell & Pathogen Interactions
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Designing A Faster, Better, Stronger Immune Response

Designing A Faster, Better, Stronger Immune Response | Plant-Microbe Interaction | Scoop.it
It is the antibodies that detect pathogens in order to fight infections and prevent disease, but there is an entire team of immune cells that work together
Via Krishan Maggon , Gilbert C FAURE, Kenzibit
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The crystal structure of Cpf1 in complex with CRISPR RNA 

The crystal structure of Cpf1 in complex with CRISPR RNA  | Plant-Microbe Interaction | Scoop.it
The CRISPR–Cas systems, as exemplified by CRISPR–Cas9, are RNA-guided adaptive immune systems used by bacteria and archaea to defend against viral infection1, 2, 3, 4, 5, 6, 7. The CRISPR–Cpf1 system, a new class 2 CRISPR–Cas system, mediates robust DNA interference in human cells1, 8, 9, 10. Although functionally conserved, Cpf1 and Cas9 differ in many aspects including their guide RNAs and substrate specificity. Here we report the 2.38 Å crystal structure of the CRISPR RNA (crRNA)-bound Lachnospiraceae bacterium ND2006 Cpf1 (LbCpf1). LbCpf1 has a triangle-shaped architecture with a large positively charged channel at the centre. Recognized by the oligonucleotide-binding domain of LbCpf1, the crRNA adopts a highly distorted conformation stabilized by extensive intramolecular interactions and the (Mg(H2O)6)2+ ion. The oligonucleotide-binding domain also harbours a looped-out helical domain that is important for LbCpf1 substrate binding. Binding of crRNA or crRNA lacking the guide sequence induces marked conformational changes but no oligomerization of LbCpf1. Our study reveals the crRNA recognition mechanism and provides insight into crRNA-guided substrate binding of LbCpf1, establishing a framework for engineering LbCpf1 to improve its efficiency and specificity for genome editing.

Via Gerd Moe-Behrens, SRB
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PEPRs spice up plant immunity -  EMBO J

PEPRs spice up plant immunity -  EMBO J | Plant-Microbe Interaction | Scoop.it
Some pattern recognition receptors (PRRs) in plants, such as PEPRs, sense endogenous, damage‐associated molecular patterns (DAMPs) that are released during pathogen infection. In this issue of The EMBO Journal, Yamada and colleagues show that genetic or pathogen‐induced depletion of Arabidopsis BAK1, a co‐receptor for multiple PRRs, primes immune activation through PEPRs. The work illustrates a link between pathogen‐induced perturbation of BAK1 and DAMP signaling.

Via Christophe Jacquet
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Zhenchuan Ma's comment, May 10, 8:55 PM
The work about PEPRs is wonderful in sensing of DAMPs.
Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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Press release: When foes become friends

Because of their sedentary life, plants have to make the most of their surroundings. To do so, they take advantage of hitherto unknown molecular mechanisms to determine what benefits them and what harms them. They also grant microorganisms access to their roots in exchange for essential nutrients in the soil. The soil fungus Colletotrichum tofieldiae serves the model plant Arabidopsis as such a subtenant when required. The plant accepts the fungus as a phosphate supplier in situations where it has no access to those minerals itself, but rejects the fungus if it is able to tap phosphate supplies on its own. Thus, the plant very accurately weighs the demands of its environment to which it must respond. In the process, the plant’s immune system plays a key role. Stéphane Hacquard, Paul Schulze-Lefert and Richard O'Connell of the Max Planck Institute for Plant Breeding Research in Cologne are addressing the question of what changes are responsible for ensuring that Colletotrichum tofieldiae no longer has to contend with the full brunt of the plant’s immune system under certain conditions. They have found that just a few changes in the genome are sufficient to turn a pathogen into a partner.

Via Stéphane Hacquard, Francis Martin
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PEPRs spice up plant immunity -  EMBO J

PEPRs spice up plant immunity -  EMBO J | Plant-Microbe Interaction | Scoop.it
Some pattern recognition receptors (PRRs) in plants, such as PEPRs, sense endogenous, damage‐associated molecular patterns (DAMPs) that are released during pathogen infection. In this issue of The EMBO Journal, Yamada and colleagues show that genetic or pathogen‐induced depletion of Arabidopsis BAK1, a co‐receptor for multiple PRRs, primes immune activation through PEPRs. The work illustrates a link between pathogen‐induced perturbation of BAK1 and DAMP signaling.

Via Christophe Jacquet
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Zhenchuan Ma's comment, May 10, 8:55 PM
The work about PEPRs is wonderful in sensing of DAMPs.
Rescooped by Guogen Yang from Plant-Microbe Symbiosis
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A high-quality carrot genome assembly provides new insights into carotenoid accumulation and asterid genome evolution

A high-quality carrot genome assembly provides new insights into carotenoid accumulation and asterid genome evolution | Plant-Microbe Interaction | Scoop.it
We report a high-quality chromosome-scale assembly and analysis of the carrot (Daucus carota) genome, the first sequenced genome to include a comparative evolutionary analysis among members of the euasterid II clade. We characterized two new polyploidization events, both occurring after the divergence of carrot from members of the Asterales order, clarifying the evolutionary scenario before and after radiation of the two main asterid clades. Large- and small-scale lineage-specific duplications have contributed to the expansion of gene families, including those with roles in flowering time, defense response, flavor, and pigment accumulation. We identified a candidate gene, DCAR_032551, that conditions carotenoid accumulation (Y) in carrot taproot and is coexpressed with several isoprenoid biosynthetic genes. The primary mechanism regulating carotenoid accumulation in carrot taproot is not at the biosynthetic level. We hypothesize that DCAR_032551 regulates upstream photosystem development and functional processes, including photomorphogenesis and root de-etiolation.

Via Jean-Michel Ané
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Nature Biotech: A pigeonpea gene confers resistance to Asian soybean rust in soybean (2016)

Nature Biotech: A pigeonpea gene confers resistance to Asian soybean rust in soybean (2016) | Plant-Microbe Interaction | Scoop.it

Asian soybean rust (ASR), caused by the fungus Phakopsora pachyrhizi, is one of the most economically important crop diseases, but is only treatable with fungicides, which are becoming less effective owing to the emergence of fungicide resistance. There are no commercial soybean cultivars with durable resistance to P. pachyrhizi, and although soybean resistance loci have been mapped, no resistance genes have been cloned. We report the cloning of a P. pachyrhizi resistance gene CcRpp1 (Cajanus cajan Resistance against Phakopsora pachyrhizi 1) from pigeonpea (Cajanus cajan) and show that CcRpp1 confers full resistance to P. pachyrhizi in soybean. Our findings show that legume species related to soybean such as pigeonpea, cowpea, common bean and others could provide a valuable and diverse pool of resistance traits for crop improvement.


Via The Sainsbury Lab, Kamoun Lab @ TSL
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The Sainsbury Lab's curator insight, April 26, 4:45 AM
Asian soybean rust (ASR), caused by the fungus Phakopsora pachyrhizi, is one of the most economically important crop diseases, but is only treatable with fungicides, which are becoming less effective owing to the emergence of fungicide resistance. There are no commercial soybean cultivars with durable resistance to P. pachyrhizi, and although soybean resistance loci have been mapped, no resistance genes have been cloned. We report the cloning of a P. pachyrhizi resistance gene CcRpp1 (Cajanus cajan Resistance against Phakopsora pachyrhizi 1) from pigeonpea (Cajanus cajan) and show that CcRpp1 confers full resistance to P. pachyrhizi in soybean. Our findings show that legume species related to soybean such as pigeonpea, cowpea, common bean and others could provide a valuable and diverse pool of resistance traits for crop improvement.
Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Nature Biotech: Rapid cloning of disease-resistance genes in plants using mutagenesis and sequence capture (2016)

Nature Biotech: Rapid cloning of disease-resistance genes in plants using mutagenesis and sequence capture (2016) | Plant-Microbe Interaction | Scoop.it

Wild relatives of domesticated crop species harbor multiple, diverse, disease resistance (R) genes that could be used to engineer sustainable disease control. However, breeding R genes into crop lines often requires long breeding timelines of 5–15 years to break linkage between R genes and deleterious alleles (linkage drag). Further, when R genes are bred one at a time into crop lines, the protection that they confer is often overcome within a few seasons by pathogen evolution1. If several cloned R genes were available, it would be possible to pyramid R genes2 in a crop, which might provide more durable resistance1. We describe a three-step method (MutRenSeq)-that combines chemical mutagenesis with exome capture and sequencing for rapid R gene cloning. We applied MutRenSeq to clone stem rust resistance genes Sr22 and Sr45 from hexaploid bread wheat. MutRenSeq can be applied to other commercially relevant crops and their relatives, including, for example, pea, bean, barley, oat, rye, rice and maize.


Via The Sainsbury Lab, Kamoun Lab @ TSL, Christophe Jacquet
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The Sainsbury Lab's curator insight, April 26, 4:14 AM
Wild relatives of domesticated crop species harbor multiple, diverse, disease resistance (R) genes that could be used to engineer sustainable disease control. However, breeding R genes into crop lines often requires long breeding timelines of 5–15 years to break linkage between R genes and deleterious alleles (linkage drag). Further, when R genes are bred one at a time into crop lines, the protection that they confer is often overcome within a few seasons by pathogen evolution1. If several cloned R genes were available, it would be possible to pyramid R genes2 in a crop, which might provide more durable resistance1. We describe a three-step method (MutRenSeq)-that combines chemical mutagenesis with exome capture and sequencing for rapid R gene cloning. We applied MutRenSeq to clone stem rust resistance genes Sr22 and Sr45 from hexaploid bread wheat. MutRenSeq can be applied to other commercially relevant crops and their relatives, including, for example, pea, bean, barley, oat, rye, rice and maize.
Neelam Redekar's curator insight, April 29, 8:19 AM
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Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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The two-speed genomes of filamentous pathogens: waltz with plants

The two-speed genomes of filamentous pathogens: waltz with plants | Plant-Microbe Interaction | Scoop.it
Fungi and oomycetes include deep and diverse lineages of eukaryotic plant pathogens. The last 10 years have seen the sequencing of the genomes of a multitude of species of these so-called filamentous plant pathogens. Already, fundamental concepts have emerged. Filamentous plant pathogen genomes tend to harbor large repertoires of genes encoding virulence effectors that modulate host plant processes. Effector genes are not randomly distributed across the genomes but tend to be associated with compartments enriched in repetitive sequences and transposable elements. These findings have led to the ‘two-speed genome’ model in which filamentous pathogen genomes have a bipartite architecture with gene sparse, repeat rich compartments serving as a cradle for adaptive evolution. Here, we review this concept and discuss how plant pathogens are great model systems to study evolutionary adaptations at multiple time scales. We will also introduce the next phase of research on this topic.

Via Christophe Jacquet, Francis Martin
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Immune responses induced by oligogalacturonides are differentially affected by AvrPto and loss of BAK1/BKK1 and PEPR1/PEPR2 - Gravino - Molecular Plant Pathology -

Immune responses induced by oligogalacturonides are differentially affected by AvrPto and loss of BAK1/BKK1 and PEPR1/PEPR2 - Gravino - Molecular Plant Pathology - | Plant-Microbe Interaction | Scoop.it
Plants possess an innate immune system capable of restricting invasion by most potential pathogens. At the cell surface, recognition of microbe-associated molecular patterns (MAMPs) and/or damage-associated molecular patterns (DAMPs) by pattern recognition receptors (PRRs) represents the first event for promptly mounting an effective immune response. Pathogens have evolved effectors that block MAMP-triggered immunity. The Pseudomonas syringae effector AvrPto abolishes immunity triggered by the peptide MAMPs flg22 and elf18, derived from the bacterial flagellin and Elongation factor Tu, respectively, by inhibiting the kinase function of the corresponding receptors FLS2 and EFR, as well as of their co-receptors BAK1 and BKK1. Oligogalacturonides (OGs), a well-known class of DAMPs, are oligomers of alpha-1,4-linked galacturonosyl residues released upon partial degradation of the plant cell wall homogalacturonan. We show here that AvrPto affects only a subset of the OG-triggered immune responses and that, among these responses, only a subset is affected by the concomitant loss of BAK1 and BKK1. On the other hand, the antagonistic effect on auxin-related responses is not affected by either AvrPto or the loss of BAK1/BKK1. These observations reveal an unprecedented complexity among the MAMP/DAMP response cascades. We also show that the signaling system mediated by Peps, another class of DAMPs, and their receptors PEPRs, contributes to OG-activated immunity. We hypothesize that OGs are sensed through multiple and partially redundant perception/transduction complexes, some targeted by AvrPto but not necessarily comprise BAK1 and BKK1. This article is protected by copyright. All rights reserved.

Via Christophe Jacquet
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Aquaporin-mediated long-distance polyphosphate translocation directed towards the host in arbuscular mycorrhizal symbiosis: application of virus-induced gene silencing

Aquaporin-mediated long-distance polyphosphate translocation directed towards the host in arbuscular mycorrhizal symbiosis: application of virus-induced gene silencing | Plant-Microbe Interaction | Scoop.it
Arbuscular mycorrhizal fungi translocate polyphosphate through hyphae over a long distance to deliver to the host. More than three decades ago, suppression of host transpiration was found to decelerate phosphate delivery of the fungal symbiont, leading us to hypothesize that transpiration provides a primary driving force for polyphosphate translocation, probably via creating hyphal water flow in which fungal aquaporin(s) may be involved. The impact of transpiration suppression on polyphosphate translocation through hyphae of Rhizophagus clarus was evaluated. An aquaporin gene expressed in intraradical mycelia was characterized and knocked down by virus-induced gene silencing to investigate the involvement of the gene in polyphosphate translocation. Rhizophagus clarus aquaporin 3 (RcAQP3) that was most highly expressed in intraradical mycelia encodes an aquaglyceroporin responsible for water transport across the plasma membrane. Knockdown of RcAQP3 as well as the suppression of host transpiration decelerated polyphosphate translocation in proportion to the levels of knockdown and suppression, respectively. These results provide the first insight into the mechanism underlying long-distance polyphosphate translocation in mycorrhizal associations at the molecular level, in which host transpiration and the fungal aquaporin play key roles. A hypothetical model of the translocation is proposed for further elucidation of the mechanism.

Via Pierre-Marc Delaux, Francis Martin
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Jessie Uehling's curator insight, May 3, 12:56 PM
 Long-distance polyphosphate translocation in mycorrhizal symbioses mediated by fungal host transpiration and aquaporins 
Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Potato NPH3/RPT2-Like Protein StNRL1, Targeted by a Phytophthora infestans RXLR Effector, Is a Susceptibility Factor

Potato NPH3/RPT2-Like Protein StNRL1, Targeted by a Phytophthora infestans RXLR Effector, Is a Susceptibility Factor | Plant-Microbe Interaction | Scoop.it
Plant pathogens deliver effectors to manipulate host processes. We know little about how fungal and oomycete effectors target host proteins to promote susceptibility, yet such knowledge is vital to understand crop disease. We show that either transient expression in Nicotiana benthamiana, or stable transgenic expression in potato (Solanum tuberosum), of the Phytophthora infestans RXLR effector Pi02860 enhances leaf colonization by the pathogen. Expression of Pi02860 also attenuates cell death triggered by the P. infestans microbe-associated molecular pattern INF1, indicating that the effector suppresses pattern-triggered immunity. However, the effector does not attenuate cell death triggered by Cf4/Avr4 coexpression, showing that it does not suppress all cell death activated by cell surface receptors. Pi02860 interacts in yeast two-hybrid assays with potato NPH3/RPT2-LIKE1 (NRL1), a predicted CULLIN3-associated ubiquitin E3 ligase. Interaction of Pi02860 in planta was confirmed by coimmunoprecipitation and bimolecular fluorescence complementation assays. Virus-induced gene silencing of NRL1 in N. benthamiana resulted in reduced P. infestans colonization and accelerated INF1-mediated cell death, indicating that this host protein acts as a negative regulator of immunity. Moreover, whereas NRL1 virus-induced gene silencing had no effect on the ability of the P. infestans effector Avr3a to suppress INF1-mediated cell death, such suppression by Pi02860 was significantly attenuated, indicating that this activity of Pi02860 is mediated by NRL1. Transient overexpression of NRL1 resulted in the suppression of INF1-mediated cell death and enhanced P. infestans leaf colonization, demonstrating that NRL1 acts as a susceptibility factor to promote late blight disease.

Via Christophe Jacquet
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The SnRK1 Energy Sensor in Plant Biotic Interactions: Trends in Plant Science

The SnRK1 Energy Sensor in Plant Biotic Interactions: Trends in Plant Science | Plant-Microbe Interaction | Scoop.it
Our understanding of plant biotic interactions has grown significantly in recent years with the identification of the mechanisms involved in innate immunity, hormone signaling, and secondary metabolism. The impact of such interactions on primary metabolism and the role of metabolic signals in the response of the plants, however, remain far less explored. The SnRK1 (SNF1-related kinase 1) kinases act as metabolic sensors, integrating very diverse stress conditions, and are key in maintaining energy homeostasis for growth and survival. Consistently, an important role is emerging for these kinases as regulators of biotic stress responses triggered by viral, bacterial, fungal, and oomycete infections as well as by herbivory. While this identifies SnRK1 as a promising target for directed modification or selection for more quantitative and sustainable resistance, its central function also increases the chances of unwanted side effects on growth and fitness, stressing the need for identification and in-depth characterization of the mechanisms and target processes involved.

Via Suayib Üstün, Christophe Jacquet
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Zhenchuan Ma's comment, May 5, 8:39 PM
Nice paper!
Rescooped by Guogen Yang from Plant Pathogenomics
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BMC Genomics: The compact genome of the plant pathogen Plasmodiophora brassicae is adapted to intracellular interactions with host Brassica spp (2016)

BMC Genomics: The compact genome of the plant pathogen Plasmodiophora brassicae is adapted to intracellular interactions with host Brassica spp (2016) | Plant-Microbe Interaction | Scoop.it

Background - The protist Plasmodiophora brassicae is a soil-borne pathogen of cruciferous species and the causal agent of clubroot disease of Brassicas including agriculturally important crops such as canola/rapeseed (Brassica napus). P. brassicae has remained an enigmatic plant pathogen and is a rare example of an obligate biotroph that resides entirely inside the host plant cell. The pathogen is the cause of severe yield losses and can render infested fields unsuitable for Brassica crop growth due to the persistence of resting spores in the soil for up to 20 years.


Results - To provide insight into the biology of the pathogen and its interaction with its primary host B. napus, we produced a draft genome of P. brassicae pathotypes 3 and 6 (Pb3 and Pb6) that differ in their host range. Pb3 is highly virulent on B. napus (but also infects other Brassica species) while Pb6 infects only vegetable Brassica crops. Both the Pb3 and Pb6 genomes are highly compact, each with a total size of 24.2 Mb, and contain less than 2 % repetitive DNA. Clustering of genome-wide single nucleotide polymorphisms (SNP) of Pb3, Pb6 and three additional re-sequenced pathotypes (Pb2, Pb5 and Pb8) shows a high degree of correlation of cluster grouping with host range. The Pb3 genome features significant reduction of intergenic space with multiple examples of overlapping untranslated regions (UTRs). Dependency on the host for essential nutrients is evident from the loss of genes for the biosynthesis of thiamine and some amino acids and the presence of a wide range of transport proteins, including some unique to P. brassicae. The annotated genes of Pb3 include those with a potential role in the regulation of the plant growth hormones cytokinin and auxin. The expression profile of Pb3 genes, including putative effectors, during infection and their potential role in manipulation of host defence is discussed.


Conclusion - The P. brassicae genome sequence reveals a compact genome, a dependency of the pathogen on its host for some essential nutrients and a potential role in the regulation of host plant cytokinin and auxin. Genome annotation supported by RNA sequencing reveals significant reduction in intergenic space which, in addition to low repeat content, has likely contributed to the P. brassicae compact genome.

 


Via Kamoun Lab @ TSL
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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The Chloroplastic Protein THF1 Interacts with the Coiled-Coil Domain of the Disease Resistance Protein N′ and Regulates Light-Dependent Cell Death

The Chloroplastic Protein THF1 Interacts with the Coiled-Coil Domain of the Disease Resistance Protein N′ and Regulates Light-Dependent Cell Death | Plant-Microbe Interaction | Scoop.it
One branch of plant immunity is mediated through nucleotide-binding/Leu-rich repeat (NB-LRR) family proteins that recognize specific effectors encoded by pathogens. Members of the I2-like family constitute a well-conserved subgroup of NB-LRRs from Solanaceae possessing a coiled-coil (CC) domain at their N termini. We show here that the CC domains of several I2-like proteins are able to induce a hypersensitive response (HR), a form of programmed cell death associated with disease resistance. Using yeast two-hybrid screens, we identified the chloroplastic protein Thylakoid Formation1 (THF1) as an interacting partner for several I2-like CC domains. Co-immunoprecipitations and bimolecular fluorescence complementation assays confirmed that THF1 and I2-like CC domains interact in planta and that these interactions take place in the cytosol. Several HR-inducing I2-like CC domains have a negative effect on the accumulation of THF1, suggesting that the latter is destabilized by active CC domains. To confirm this model, we investigated N′, which recognizes the coat protein of most Tobamoviruses, as a prototypical member of the I2-like family. Transient expression and gene silencing data indicated that THF1 functions as a negative regulator of cell death and that activation of full-length N′ results in the destabilization of THF1. Consistent with the known function of THF1 in maintaining chloroplast homeostasis, we show that the HR induced by N′ is light-dependent. Together, our results define, to our knowledge, novel molecular mechanisms linking light and chloroplasts to the induction of cell death by a subgroup of NB-LRR proteins.

Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant-Microbe Symbiosis
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Survival trade-offs in plant roots during colonization by closely related beneficial and pathogenic fungi

Survival trade-offs in plant roots during colonization by closely related beneficial and pathogenic fungi | Plant-Microbe Interaction | Scoop.it
The sessile nature of plants forced them to evolve mechanisms to prioritize their responses to simultaneous stresses, including colonization by microbes or nutrient starvation. Here, we compare the genomes of a beneficial root endophyte, Colletotrichum tofieldiae and its pathogenic relative C. incanum, and examine the transcriptomes of both fungi and their plant host Arabidopsis during phosphate starvation. Although the two species diverged only 8.8 million years ago and have similar gene arsenals, we identify genomic signatures indicative of an evolutionary transition from pathogenic to beneficial lifestyles, including a narrowed repertoire of secreted effector proteins, expanded families of chitin-binding and secondary metabolism-related proteins, and limited activation of pathogenicity-related genes in planta. We show that beneficial responses are prioritized in C. tofieldiae-colonized roots under phosphate-deficient conditions, whereas defense responses are activated under phosphate-sufficient conditions. These immune responses are retained in phosphate-starved roots colonized by pathogenic C. incanum, illustrating the ability of plants to maximize survival in response to conflicting stresses.

Via Stéphane Hacquard, Jean-Michel Ané
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Danger peptide receptor signaling in plants ensures basal immunity upon pathogen-induced depletion of BAK1 - Yamada - 2015 - The EMBO Journal -

Danger peptide receptor signaling in plants ensures basal immunity upon pathogen-induced depletion of BAK1 - Yamada - 2015 - The EMBO Journal - | Plant-Microbe Interaction | Scoop.it
Pathogens infect a host by suppressing defense responses induced upon recognition of microbe-associated molecular patterns (MAMPs). Despite this suppression, MAMP receptors mediate basal resistance to limit host susceptibility, via a process that is poorly understood. The Arabidopsis leucine-rich repeat (LRR) receptor kinase BAK1 associates and functions with different cell surface LRR receptors for a wide range of ligands, including MAMPs. We report that BAK1 depletion is linked to defense activation through the endogenous PROPEP peptides (Pep epitopes) and their LRR receptor kinases PEPR1/PEPR2, despite critical defects in MAMP signaling. In bak1-knockout plants, PEPR elicitation results in extensive cell death and the prioritization of salicylate-based defenses over jasmonate-based defenses, in addition to elevated proligand and receptor accumulation. BAK1 disruption stimulates the release of PROPEP3, produced in response to Pep application and during pathogen challenge, and renders PEPRs necessary for basal resistance. These findings are biologically relevant, since specific BAK1 depletion coincides with PEPR-dependent resistance to the fungal pathogen Colletotrichum higginsianum. Thus, the PEPR pathway ensures basal resistance when MAMP-triggered defenses are compromised by BAK1 depletion.

Via Christophe Jacquet
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Rescooped by Guogen Yang from WU_Phyto-Publications
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Frontiers in Plant Sciences (2016): Analysis of Cryptic, Systemic Botrytis Infections in Symptomless Hosts

Frontiers in Plant Sciences (2016): Analysis of Cryptic, Systemic Botrytis Infections in Symptomless Hosts | Plant-Microbe Interaction | Scoop.it
Botrytis species are generally considered to be aggressive, necrotrophic plant pathogens. By contrast to this general perception, however, Botrytis species could frequently be isolated from the interior of multiple tissues in apparently healthy hosts of many species. Infection frequencies reached 50% of samples or more, but were commonly less, and cryptic infections were rare or absent in some plant species. Prevalence varied substantially from year to year and from tissue to tissue, but some host species routinely had high prevalence. The same genotype was found to occur throughout a host, representing mycelial spread. B. cinerea and B. pseudocinerea are the species that most commonly occur as cryptic infections, but phylogenetically distant isolates of Botrytis were also detected, one of which does not correspond to previously described species. Sporulation and visible damage occurred only when infected tissues were stressed, or became mature or senescent. There was no evidence of cryptic infection having a deleterious effect on growth of the host, and prevalence was probably greater in plants grown in high light conditions. Isolates from cryptic infections were often capable of causing disease (to varying extents) when spore suspensions were inoculated onto their own host as well as on distinct host species, arguing against co-adaptation between cryptic isolates and their hosts. These data collectively suggest that several Botrytis species, including the most notorious pathogenic species, exist frequently in cryptic form to an extent that has thus far largely been neglected, and do not need to cause disease on healthy hosts in order to complete their life-cycles.

Via WU_Phyto
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