Plant pathogens and pests
43.7K views | +3 today
Follow
Plant pathogens and pests
Mainly dedicated to plant pathogens , mechanisms of pathogenicity, life cycles, epidemiology and plant breeding methods and results helping to prevent their propagation.  This site is complementary to the Plant immunity and legume symbiosis Scoop-It site :      https://www.scoop.it/t/plant-pathogen-interactions-by-christophe-jacquet
Your new post is loading...
Your new post is loading...
Scooped by Christophe Jacquet
Scoop.it!

The biotroph Agrobacterium tumefaciens thrives in tumors by exploiting a wide spectrum of plant host metabolites - Gonzalez‐Mula - 2019 - New Phytologist -

The biotroph Agrobacterium tumefaciens thrives in tumors by exploiting a wide spectrum of plant host metabolites - Gonzalez‐Mula - 2019 - New Phytologist - | Plant pathogens and pests | Scoop.it
Agrobacterium tumefaciens is a niche‐constructing biotroph that exploits host plant metabolites.
We combined metabolomics, transposon‐sequencing (Tn‐seq), transcriptomics, and reverse genetics to characterize A. tumefaciens pathways involved in the exploitation of resources from the Solanum lycopersicum host plant.
Metabolomics of healthy stems and plant tumors revealed the common (e.g. sucrose, glutamate) and enriched (e.g. opines, γ‐aminobutyric acid (GABA), γ‐hydroxybutyric acid (GHB), pyruvate) metabolites that A. tumefaciens could use as nutrients. Tn‐seq and transcriptomics pinpointed the genes that are crucial and/or upregulated when the pathogen grew on either sucrose (pgi, kdgA, pycA, cisY) or GHB (blcAB, pckA, eno, gpsA) as a carbon source. While sucrose assimilation involved the Entner–Doudoroff and tricarboxylic acid (TCA) pathways, GHB degradation required the blc genes, TCA cycle, and gluconeogenesis. The tumor‐enriched metabolite pyruvate is at the node connecting these pathways. Using reverse genetics, we showed that the blc, pckA, and pycA loci were important for aggressiveness (tumor weight), proliferation (bacterial charge), and/or fitness (competition between the constructed mutants and wild‐type) of A. tumefaciens in plant tumors.
This work highlighted how a biotroph mobilizes its central metabolism for exploiting a wide diversity of resources in a plant host. It further shows the complementarity of functional genome‐wide scans by transcriptomics and Tn‐seq to decipher the lifestyle of a plant pathogen.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

The Phytophthora sojae RXLR effector Avh238 destabilizes soybean Type2 GmACSs to suppress ethylene biosynthesis and promote infection - Yang - 2019 - New Phytologist - Wiley Online Library

The Phytophthora sojae RXLR effector Avh238 destabilizes soybean Type2 GmACSs to suppress ethylene biosynthesis and promote infection - Yang - 2019 - New Phytologist - Wiley Online Library | Plant pathogens and pests | Scoop.it
Phytophthora pathogens secrete many effector proteins to manipulate host innate immunity. PsAvh238 is a Phytophthora sojae N‐terminal Arg‐X‐Leu‐Arg (RXLR) effector, which evolved to escape host recognition by mutating one nucleotide while retaining plant immunity‐suppressing activity to enhance infection. However, the molecular basis of the PsAvh238 virulence function remains largely enigmatic.
By using coimmunoprecipitation and liquid chromatography‐tandem mass spectrometry analysis, we identified the 1‐aminocyclopropane‐1‐carboxylate synthase (ACS) isoforms, the key enzymes in ethylene (ET) biosynthesis, as a host target of PsAvh238.
We show that PsAvh238 interacts with soybean ACSs (GmACSs) in vivo and in vitro. By destabilizing Type2 GmACSs, PsAvh238 suppresses Type2 ACS‐catalyzed ET biosynthesis and facilitates Phytophthora infection. Silencing of Type2 GmACSs, and inhibition of ET biosynthesis or signaling, increase soybean susceptibility to P. sojae infection, supporting a role for Type2 GmACSs and ET in plant immunity against P. sojae. Moreover, wild‐type P. sojae but not the PsAvh238‐disrupted mutants, inhibits ET induction and promotes P. sojae infection in soybean.
Our results highlight the ET biosynthesis pathway as an essential part in plant immunity against P. sojae and a direct effector target.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Appressoria - ScienceDirect

Appressoria - ScienceDirect | Plant pathogens and pests | Scoop.it
What are appressoria? Appressoria are specialised infection structures used by many disease-causing microorganisms to breach the outer surface of a host plant or animal, and thereby gain entry to internal tissues. Appressoria are made by a wide range of disease-causing microbes — and even by parasitic plants — and they come in many different shapes and sizes. They are, however, best known in plant pathogenic fungi, in which appressoria have been most intensively studied because of their importance to some of the most devastating diseases affecting world agriculture. Appressoria are necessary for rusts, powdery mildews and blast diseases, which affect the major cereal crops of the world, as well as devastating oomycete diseases like potato late blight.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Transcriptional profiling identifies critical steps of cell cycle reprogramming necessary for Plasmodiophora brassicae‐driven gall formation in Arabidopsis - Olszak - 2019 - The Plant Journal -

Transcriptional profiling identifies critical steps of cell cycle reprogramming necessary for Plasmodiophora brassicae‐driven gall formation in Arabidopsis - Olszak - 2019 - The Plant Journal - | Plant pathogens and pests | Scoop.it
Plasmodiophora brassicae is a soil‐borne biotroph whose life cycle involves reprogramming host developmental processes leading to the formation of galls on its underground parts. Formation of such structures involves modification of the host cell cycle leading initially to hyperplasia, increasing the number of cells to be invaded, followed by overgrowth of cells colonised by the pathogen. Here we show that P. brassicae infection stimulates formation of the E2Fa/RBR1 complex and upregulation of MYB3R1, MYB3R4 and A‐ and B‐type cyclin expression. These factors were previously described as important regulators of the G2−M cell cycle checkpoint. As a consequence of this manipulation, a large population of host hypocotyl cells are delayed in cell cycle exit and maintained in the proliferative state. We also report that, during further maturation of galls, enlargement of host cells invaded by the pathogen involves endoreduplication leading to increased ploidy levels. This study characterises two aspects of the cell cycle reprogramming efforts of P. brassicae: systemic, related to the disturbance of host hypocotyl developmental programs by preventing cell cycle exit; and local, related to the stimulation of cell enlargement via increased endocycle activity.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Plant begomoviruses subvert ubiquitination to suppress plant defenses against insect vectors

Plant begomoviruses subvert ubiquitination to suppress plant defenses against insect vectors | Plant pathogens and pests | Scoop.it
Most plant viruses are vectored by insects and the interactions of virus-plant-vector have important ecological and evolutionary implications. Insect vectors often perform better on virus-infected plants. This indirect mutualism between plant viruses and insect vectors promotes the spread of virus and has significant agronomical effects. However, few studies have investigated how plant viruses manipulate plant defenses and promote vector performance. Begomoviruses are a prominent group of plant viruses in tropical and sub-tropical agro-ecosystems and are transmitted by whiteflies. Working with the whitefly Bemisia tabaci, begomoviruses and tobacco, we revealed that C2 protein of begomoviruses lacking DNA satellites was responsible for the suppression of plant defenses against whitefly vectors. We found that infection of plants by tomato yellow leaf curl virus (TYLCV), one of the most devastating begomoviruses worldwide, promoted the survival and reproduction of whitefly vectors. TYLCV C2 protein suppressed plant defenses by interacting with plant ubiquitin. This interaction compromised the degradation of JAZ1 protein, thus inhibiting jasmonic acid defense and the expression of MYC2-regulated terpene synthase genes. We further demonstrated that function of C2 protein among begomoviruses not associated with satellites is well conserved and ubiquitination is an evolutionarily conserved target of begomoviruses for the suppression of plant resistance to whitefly vectors. Taken together, these results demonstrate that ubiquitination inhibition by begomovirus C2 protein might be a general mechanism in begomovirus, whitefly and plant interactions.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Conserved fungal effector suppresses PAMP-triggered immunity by targeting plant immune kinases

Conserved fungal effector suppresses PAMP-triggered immunity by targeting plant immune kinases | Plant pathogens and pests | Scoop.it
Plant pathogens have optimized their own effector sets to adapt to their hosts. However, certain effectors, regarded as core effectors, are conserved among various pathogens, and may therefore play an important and common role in pathogen virulence. We report here that the widely distributed fungal effector NIS1 targets host immune components that transmit signaling from pattern recognition receptors (PRRs) in plants. NIS1 from two Colletotrichum spp. suppressed the hypersensitive response and oxidative burst, both of which are induced by pathogen-derived molecules, in Nicotiana benthamiana. Magnaporthe oryzae NIS1 also suppressed the two defense responses, although this pathogen likely acquired the NIS1 gene via horizontal transfer from Basidiomycota. Interestingly, the root endophyte Colletotrichum tofieldiae also possesses a NIS1 homolog that can suppress the oxidative burst in N. benthamiana. We show that NIS1 of multiple pathogens commonly interacts with the PRR-associated kinases BAK1 and BIK1, thereby inhibiting their kinase activities and the BIK1-NADPH oxidase interaction. Furthermore, mutations in the NIS1-targeting proteins, i.e., BAK1 and BIK1, in Arabidopsis thaliana also resulted in reduced immunity to Colletotrichum fungi. Finally, M. oryzae lacking NIS1 displayed significantly reduced virulence on rice and barley, its hosts. Our study therefore reveals that a broad range of filamentous fungi maintain and utilize the core effector NIS1 to establish infection in their host plants and perhaps also beneficial interactions, by targeting conserved and central PRR-associated kinases that are also known to be targeted by bacterial effectors.
No comment yet.
Rescooped by Christophe Jacquet from Plants and Microbes
Scoop.it!

PNAS: Intercellular cooperation in a fungal plant pathogen facilitates host colonization (2019)

PNAS: Intercellular cooperation in a fungal plant pathogen facilitates host colonization (2019) | Plant pathogens and pests | Scoop.it

Cooperation between specialized cells and organisms supports complex biological functions, from the colonization of unfavorable environments to the formation of organs and sociality. Some bacterial pathogens are known to rely on cooperation between individuals and species for efficient colonization of their host and the onset of disease. We examined the regulation of genes in cells from different parts of a fungal plant pathogen and found evidence for cooperation between these fungal cells. We further show that cooperation between fungal cells is particularly important for the efficient colonization of resistant plants. These findings establish cooperation as a mechanism supporting disease caused by fungal pathogens that should be taken into account in the design of disease management strategies.

Cooperation is associated with major transitions in evolution such as the emergence of multicellularity. It is central to the evolution of many complex traits in nature, including growth and virulence in pathogenic bacteria. Whether cells of multicellular parasites function cooperatively during infection remains, however, largely unknown. Here, we show that hyphal cells of the fungal pathogen Sclerotinia sclerotiorum reprogram toward division of labor to facilitate the colonization of host plants. Using global transcriptome sequencing, we reveal that gene expression patterns diverge markedly in cells at the center and apex of hyphae during Arabidopsis thaliana colonization compared with in vitro growth. We reconstructed a genome-scale metabolic model for S. sclerotiorum and used flux balance analysis to demonstrate metabolic heterogeneity supporting division of labor between hyphal cells. Accordingly, continuity between the central and apical compartments of invasive hyphae was required for optimal growth in planta . Using a multicell model of fungal hyphae, we show that this cooperative functioning enhances fungal growth predominantly during host colonization. Our work identifies cooperation in fungal hyphae as a mechanism emerging at the multicellular level to support host colonization and virulence.


Via Rey Thomas, Kamoun Lab @ TSL
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Conserved fungal effector suppresses PAMP-triggered immunity by targeting plant immune kinases

Conserved fungal effector suppresses PAMP-triggered immunity by targeting plant immune kinases | Plant pathogens and pests | Scoop.it
Plant pathogens have optimized their own effector sets to adapt to their hosts. However, certain effectors, regarded as core effectors, are conserved among various pathogens, and may therefore play an important and common role in pathogen virulence. We report here that the widely distributed fungal effector NIS1 targets host immune components that transmit signaling from pattern recognition receptors (PRRs) in plants. NIS1 from two Colletotrichum spp. suppressed the hypersensitive response and oxidative burst, both of which are induced by pathogen-derived molecules, in Nicotiana benthamiana. Magnaporthe oryzae NIS1 also suppressed the two defense responses, although this pathogen likely acquired the NIS1 gene via horizontal transfer from Basidiomycota. Interestingly, the root endophyte Colletotrichum tofieldiae also possesses a NIS1 homolog that can suppress the oxidative burst in N. benthamiana. We show that NIS1 of multiple pathogens commonly interacts with the PRR-associated kinases BAK1 and BIK1, thereby inhibiting their kinase activities and the BIK1-NADPH oxidase interaction. Furthermore, mutations in the NIS1-targeting proteins, i.e., BAK1 and BIK1, in Arabidopsis thaliana also resulted in reduced immunity to Colletotrichum fungi. Finally, M. oryzae lacking NIS1 displayed significantly reduced virulence on rice and barley, its hosts. Our study therefore reveals that a broad range of filamentous fungi maintain and utilize the core effector NIS1 to establish infection in their host plants and perhaps also beneficial interactions, by targeting conserved and central PRR-associated kinases that are also known to be targeted by bacterial effectors.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Two Basidiomycete Fungi in the Cortex of Wolf Lichens - ScienceDirect

Two Basidiomycete Fungi in the Cortex of Wolf Lichens - ScienceDirect | Plant pathogens and pests | Scoop.it
Since the late 1800s, mycologists have been detecting fungi above and beyond the assumed single fungus in lichen thalli [1, 2, 3, 4, 5, 6]. Over the last century, these fungi have been accorded roles ranging from commensalists to pathogens. Recently, Cyphobasidiales yeasts were shown to be ubiquitous in the cortex layer of many macrolichens [7], but for most species, little is known of their cellular distribution and constancy beyond visible fruiting structures. Here, we demonstrate the occurrence of an additional and distantly related basidiomycete, Tremella, in 95% of studied thalli in a global sample of one of the most intensively studied groups of lichens, the wolf lichens (genus Letharia). Tremella species are reported from a wide range of lichen genera [8], but until now, their biology was deduced from fruiting bodies (basidiomata) formed on lichen thalli. Based on this, they have been thought to be uncommon to rare, to occur exclusively in a hyphal form, and to be parasitic on the dominant fungal partner [9, 10]. We show that, in wolf lichens, Tremella occurs as yeast cells also in thalli that lack basidiomata and infer that this is its dominant stage in nature. We further show that the hyphal stage, when present in Letharia, is in close contact with algal cells, challenging the assumption that lichen-associated Tremella species are uniformly mycoparasites. Our results suggest that extent of occurrence and cellular interactions of known fungi within lichens have historically been underestimated and raise new questions about their function in specific lichen symbioses.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Natural allelic variations provide insights into host adaptation of Phytophthora avirulence effector PsAvr3c - Huang - 2019 - New Phytologist -

Natural allelic variations provide insights into host adaptation of Phytophthora avirulence effector PsAvr3c - Huang - 2019 - New Phytologist - | Plant pathogens and pests | Scoop.it
Filamentous pathogens, such as fungi and oomycetes, secrete avirulence (AVR) effectors that trigger plant immune responses and provide striking examples of host adaptations. Avr effector genes display different types of allelic variations, including deletions, epigenetic silencing and sequence polymorphisms, to avoid detection. However, how effector sequence polymorphisms enable pathogens to dodge host immune surveillance remains largely unknown.
PsAvr3c is a Phytophthora AVR gene that is recognized by soybean carrying Rps3c. PsAvr3c natural alleles display a rich diversity of single nucleotide polymorphisms in field isolates. We combined both site‐directed mutagenesis and population sequence surveys to identify a serine substitution of glycine at position 174 in PsAvr3c that resulted in evasion of Rps3c‐mediated soybean immunity.
The S174G substitution did not affect the nuclear localization of PsAvr3c in planta, which is required to activate Rps3c, but it significantly impaired the binding affinity of PsAvr3c with a previously identified spliceosome‐associated protein GmSKRPs. Silencing GmSKRPs specifically impaired PsAvr3c‐triggered cell death in Rps3c soybean.
This study uncovered a plant Phytophthora pathogen that adapted to a resistant plant through a key amino acid mutation and subsequently reduced the binding affinity with a plant immune regulator to evade host resistance.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Redox signalling from NADPH oxidase targets metabolic enzymes and developmental proteins in Fusarium graminearum - Fernando - 2019 - Molecular Plant Pathology -

Redox signalling from NADPH oxidase targets metabolic enzymes and developmental proteins in Fusarium graminearum - Fernando - 2019 - Molecular Plant Pathology - | Plant pathogens and pests | Scoop.it
NADPH oxidase (NOX) is one of the sources of reactive oxygen species (ROS) that modulates the activity of proteins through modifications of their cysteine residues. In a previous study, we demonstrated the importance of NOX in both the development and pathogenicity of the phytopathogen Fusarium graminearum. In this article, comparative proteomics between the wild‐type and a Nox mutant of F. graminearum was used to identify active cysteine residues on candidate redox‐sensing proteins. A two‐dimensional gel approach based on labelling with monobromobimane (mBBR) identified 19 candidate proteins, and was complemented with a gel‐free shotgun approach based on a biotin switch method, which yielded 99 candidates. The results indicated that, in addition to temporal regulation, a large number of primary metabolic enzymes are potentially targeted by NoxAB‐generated ROS. Targeted disruption of these metabolic genes showed that, although some are dispensable, others are essential. In addition to metabolic enzymes, developmental proteins, such as the Woronin body major protein (FGSG_08737) and a glycosylphosphatidylinositol (GPI)‐anchored protein (FGSG_10089), were also identified. Deletion of either of these genes reduced the virulence of F. graminearum. Furthermore, changing the redox‐modified cysteine (Cys325) residue in FGSG_10089 to either serine or phenylalanine resulted in a similar phenotype to the FGSG_10089 knockout strain, which displayed reduced virulence and altered cell wall morphology; this underscores the importance of Cys325 to the function of the protein. Our results indicate that NOX‐generated ROS act as intracellular signals in F. graminearum and modulate the activity of proteins affecting development and virulence in planta.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Teratosphaeria stem canker of Eucalyptus: two pathogens, one devastating disease - Aylward - 2019 - Molecular Plant Pathology -

Teratosphaeria stem canker of Eucalyptus: two pathogens, one devastating disease - Aylward - 2019 - Molecular Plant Pathology - | Plant pathogens and pests | Scoop.it
Background

Teratosphaeria gauchensis and T. zuluensis are closely related fungi that cause Teratosphaeria (previously Coniothyrium) stem canker disease on Eucalyptus species propagated in plantations for commercial purposes. This disease is present in many countries in which Eucalyptus trees are planted, and continues to spread with the international trade of infected plant germplasm.
Taxonomy

Fungi, Ascomycota, Pezizomycotina, Dothideomycetes, Dothideomycetidae, Capnodiales, Teratosphaeriaceae, Teratosphaeria.
Identification

The causal agents form dark masses of pycnidia that are visible on the surface of distinct stem cankers that typically form on young green stem tissues. Accurate diagnosis of the causal agents requires DNA sequence data.
Host range

Nine species of Eucalyptus are known to be affected. Of these, E. grandis and its hybrids, which include some of the most important planting stock globally, appear to be particularly vulnerable.
Disease symptoms

Small necrotic lesions develop on young green stem tissue. These lesions coalesce to form large cankers that exude gum. Epicormic shoots develop below the girdling canker and, in severe cases, trees die.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Type III secretion inhibitors for the management of bacterial plant diseases - Puigvert - 2019 - Molecular Plant Pathology -

Type III secretion inhibitors for the management of bacterial plant diseases - Puigvert - 2019 - Molecular Plant Pathology - | Plant pathogens and pests | Scoop.it
The identification of chemical compounds that prevent and combat bacterial diseases is fundamental for crop production. Bacterial virulence inhibitors are a promising alternative to classical control treatments, because they have a low environmental impact and are less likely to generate bacterial resistance. The major virulence determinant of most animal and plant bacterial pathogens is the type III secretion system (T3SS). In this work, we screened nine plant extracts and 12 isolated compounds—including molecules effective against human pathogens—for their capacity to inhibit the T3SS of plant pathogens and for their applicability as virulence inhibitors for crop protection. The screen was performed using a luminescent reporter system developed in the model pathogenic bacterium Ralstonia solanacearum. Five synthetic molecules, one natural product and two plant extracts were found to down‐regulate T3SS transcription, most through the inhibition of the regulator hrpB. In addition, for three of the molecules, corresponding to salicylidene acylhydrazide derivatives, the inhibitory effect caused a dramatic decrease in the secretion capacity, which was translated into impaired plant responses. These candidate virulence inhibitors were then tested for their ability to protect plants. We demonstrated that salicylidene acylhydrazides can limit R. solanacearum multiplication in planta and protect tomato plants from bacterial speck caused by Pseudomonas syringae pv. tomato. Our work validates the efficiency of transcription reporters to discover compounds or natural product extracts that can be potentially applied to prevent bacterial plant diseases.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Phytophthora infestans effector SFI3 targets potato UBK to suppress early immune transcriptional responses - He - 2019 - New Phytologist -

Phytophthora infestans effector SFI3 targets potato UBK to suppress early immune transcriptional responses - He - 2019 - New Phytologist - | Plant pathogens and pests | Scoop.it
The potato blight agent Phytophthora infestans secretes a range of RXLR effectors to promote disease. Recent evidence indicates that some effectors suppress early pattern‐triggered immunity (PTI) following perception of microbe‐associated molecular patterns (MAMPs). Phytophthora infestans effector PiSFI3/Pi06087/PexRD16 has been previously shown to suppress MAMP‐triggered pFRK1‐Luciferase reporter gene activity. How PiSFI3 suppresses immunity is unknown.
We employed yeast‐two‐hybrid (Y2H) assays, co‐immunoprecipitation, transcriptional silencing by RNA interference and virus‐induced gene silencing (VIGS), and X‐ray crystallography for structure‐guided mutagenesis, to investigate the function of PiSFI3 in targeting a plant U‐box‐kinase protein (StUBK) to suppress immunity.
We discovered that PiSFI3 is active in the host nucleus and interacts in yeast and in planta with StUBK. UBK is a positive regulator of specific PTI pathways in both potato and Nicotiana benthamiana. Importantly, it contributes to early transcriptional responses that are suppressed by PiSFI3. PiSFI3 forms an unusual trans‐homodimer. Mutation to disrupt dimerization prevents nucleolar localisation of PiSFI3 and attenuates both its interaction with StUBK and its ability to enhance P. infestans leaf colonisation.
PiSFI3 is a ‘WY‐domain’ RXLR effector that forms a novel trans‐homodimer which is required for its ability to suppress PTI via interaction with the U‐box‐kinase protein StUBK.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

From pathogen to endophyte: an endophytic population of Verticillium dahliae evolved from a sympatric pathogenic population - Wheeler - 2019 - New Phytologist -

From pathogen to endophyte: an endophytic population of Verticillium dahliae evolved from a sympatric pathogenic population - Wheeler - 2019 - New Phytologist - | Plant pathogens and pests | Scoop.it
The fungus Verticillium dahliae causes wilts of several hundred plant species, including potato and mint. Verticillium spp. also colonize sympatric hosts such as mustards and grasses as endophytes. The evolutionary history of and interactions between pathogenic and endophytic of this fungus are unknown.
Verticillium dahliae isolates recovered from sympatric potato, mint, mustard and grasses were characterized genotypically with microsatellite markers and phenotypically for pathogenicity. The evolutionary history of pathogenic and endophytic populations was reconstructed and gene flow between populations quantified.
Verticillium dahliae was recovered from all hosts. Endophytic populations were genetically and genotypically similar to but marginally differentiated from the potato population, from which they evolved. Bidirectional migration was detected between these populations and endophytic isolates were pathogenic to potato and behaved as endophytes in mustard and barley.
Verticillium dahliae colonizes plants as both endophytes and pathogens. A historical host‐range expansion together with endophytic and pathogenic capabilities are likely to have enabled infection of and gene flow between asymptomatic and symptomatic host populations despite minor differentiation. The ability of hosts to harbor asymptomatic infections and the stability of asymptomatic infections over time warrants investigation to elucidate the mechanisms involved in the maintenance of endophytism and pathogenesis.
Xun Sun's curator insight, March 5, 2019 9:04 PM
Share your insight
Scooped by Christophe Jacquet
Scoop.it!

Sunflower resistance to multiple downy mildew pathotypes revealed by recognition of conserved effectors of the oomycete Plasmopara halstedii - Pecrix - 2019 - The Plant Journal -

Sunflower resistance to multiple downy mildew pathotypes revealed by recognition of conserved effectors of the oomycete Plasmopara halstedii - Pecrix - 2019 - The Plant Journal - | Plant pathogens and pests | Scoop.it
Over the last 40 years, new sunflower downy mildew isolates (Plasmopara halstedii) have overcome major gene resistances in sunflower, requiring the identification of additional and possibly more durable broad‐spectrum resistances. Here, 354 RXLR effectors defined in silico from our new genomic data were classified in a network of 40 connected components sharing conserved protein domains. Among 205 RXLR effector genes encoding conserved proteins in 17 P. halstedii pathotypes of varying virulence, we selected 30 effectors that were expressed during plant infection as potentially essential genes to target broad‐spectrum resistance in sunflower. The transient expression of the 30 core effectors in sunflower and in Nicotiana benthamiana leaves revealed a wide diversity of targeted subcellular compartments, including organelles not so far shown to be targeted by oomycete effectors such as chloroplasts and processing bodies. More than half of the 30 core effectors were able to suppress pattern‐triggered immunity in N. benthamiana, and five of these induced hypersensitive responses (HR) in sunflower broad‐spectrum resistant lines. HR triggered by PhRXLRC01 co‐segregated with Pl22 resistance in F3 populations and both traits localized in 1.7 Mb on chromosome 13 of the sunflower genome. Pl22 resistance was physically mapped on the sunflower genome recently sequenced, unlike all the other downy mildew resistances published so far. PhRXLRC01 and Pl22 are proposed as an avirulence/resistance gene couple not previously described in sunflower. Core effector recognition is a successful strategy to accelerate broad‐spectrum resistance gene identification in complex crop genomes such as sunflower.
Xun Sun's curator insight, March 5, 2019 9:19 PM
Share your insight
Scooped by Christophe Jacquet
Scoop.it!

Engineering Plant Secondary Metabolism in Microbial Systems

Engineering Plant Secondary Metabolism in Microbial Systems | Plant pathogens and pests | Scoop.it
Secondary metabolites are broadly defined as natural products synthesized by an organism that are not essential to support growth and life. The plant kingdom manufactures over 200,000 distinct chemical compounds, most of which arise from specialized metabolism. While these compounds play important roles in interspecies competition and defense, many plant natural products have been exploited for use as medicines, fragrances, flavors, nutrients, repellants, and colorants.

Despite this vast chemical diversity, many secondary metabolites are present at very low concentrations in planta, eliminating crop-based manufacturing as a means of attaining these important products. The structural and stereochemical complexity of specialized metabolites hinders most attempts to access these compounds using chemical synthesis.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

A Phytophthora Effector Suppresses Trans-Kingdom RNAi to Promote Disease Susceptibility - ScienceDirect

A Phytophthora Effector Suppresses Trans-Kingdom RNAi to Promote Disease Susceptibility - ScienceDirect | Plant pathogens and pests | Scoop.it
RNA silencing (RNAi) has a well-established role in anti-viral immunity in plants. The destructive eukaryotic pathogen Phytophthora encodes suppressors of RNAi (PSRs), which enhance plant susceptibility. However, the role of small RNAs in defense against eukaryotic pathogens is unclear. Here, we show that Phytophthora infection of Arabidopsis leads to increased production of a diverse pool of secondary small interfering RNAs (siRNAs). Instead of regulating endogenous plant genes, these siRNAs are found in extracellular vesicles and likely silence target genes in Phytophthora during natural infection. Introduction of a plant siRNA in Phytophthora leads to developmental deficiency and abolishes virulence, while Arabidopsis mutants defective in secondary siRNA biogenesis are hypersusceptible. Notably, Phytophthora effector PSR2 specifically inhibits secondary siRNA biogenesis in Arabidopsis and promotes infection. These findings uncover the role of siRNAs as antimicrobial agents against eukaryotic pathogens and highlight a defense/counter-defense arms race centered on trans-kingdom gene silencing between hosts and pathogens.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Frontiers | Infestation by Myzus persicae Increases Susceptibility of Brassica napus cv. “Canard” to Rhizoctonia solani AG 2-1 | Plant Science

Frontiers | Infestation by Myzus persicae Increases Susceptibility of Brassica napus cv. “Canard” to Rhizoctonia solani AG 2-1 | Plant Science | Plant pathogens and pests | Scoop.it
Activation of plant defense pathways can be influenced by the presence of different species of attacking organisms. Understanding the complicated interactions triggering plant defense mechanisms is of great interest as it may allow the development of more effective and sustainable disease control methods. Myzus persicae and Rhizoctonia solani anastomosis group (AG) 2-1 are two important organisms attacking oilseed rape (OSR), causing disease and reduced yields. At present, is unclear how these two interact with each other and with OSR defenses and therefore the aim of the present study was to gain a better insight into the indirect interaction between aphids and pathogen. In separate experiments, we assessed the effect of AG 2-1 infection on aphid performance, measured as growth rate and population increase and then the effect of aphid infestation on AG 2-1 by quantifying disease and the amount of fungal DNA in plant stems and compost for two OSR varieties, “Canard” and “Temple.” Additionally, we examined the expression of genes related to jasmonic acid (JA) and salicylic acid (SA) defense pathways. There was no significant effect of AG 2-1 infection on M. persicae performance. However, aphid infestation in one of the varieties, “Canard,” resulted in significantly increased disease symptoms caused by AG 2-1, although, the amount of fungal DNA was not significantly different between treatments. This meant that “Canard” plants had become more susceptible to the disease. Expression of LOX3 and MYC2 was elevated under AG 2-1 treatment but downregulated in plants with both aphids and pathogen. Therefore it seems plausible that alterations in the JA signaling due to aphid infestation resulted in the increased susceptibility to AG 2-1.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Plant-parasitic nematodes respond to root exudate signals with host-specific gene expression patterns

Plant-parasitic nematodes respond to root exudate signals with host-specific gene expression patterns | Plant pathogens and pests | Scoop.it
Plant parasitic nematodes must be able to locate and feed from their host in order to survive. Here we show that Pratylenchus coffeae regulates the expression of selected cell-wall degrading enzyme genes relative to the abundance of substrate in root exudates, thereby tailoring gene expression for root entry of the immediate host. The concentration of cellulose or xylan within the exudate determined the level of β-1,4-endoglucanase (Pc-eng-1) and β-1,4-endoxylanase (Pc-xyl) upregulation respectively. Treatment of P. coffeae with cellulose or xylan or with root exudates deficient in cellulose or xylan conferred a specific gene expression response of Pc-eng-1 or Pc-xyl respectively with no effect on expression of another cell wall degrading enzyme gene, a pectate lyase (Pc-pel). RNA interference confirmed the importance of regulating these genes as lowered transcript levels reduced root penetration by the nematode. Gene expression in this plant parasitic nematode is therefore influenced, in a host-specific manner, by cell wall components that are either secreted by the plant or released by degradation of root tissue. Transcriptional plasticity may have evolved as an adaptation for host recognition and increased root invasion by this polyphagous species.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Clubroot Disease Stimulates Early Steps of Phloem Differentiation and Recruits SWEET Sucrose Transporters within Developing Galls

Clubroot Disease Stimulates Early Steps of Phloem Differentiation and Recruits SWEET Sucrose Transporters within Developing Galls | Plant pathogens and pests | Scoop.it
Successful biotrophic plant pathogens can divert host nutrition toward infection sites. Here we describe how the protist Plasmodiophora brassicae establishes a long-term feeding relationship with its host by stimulating phloem differentiation and phloem-specific expression of sugar transporters within developing galls. Development of galls in infected Arabidopsis ( Arabidopsis thaliana ) plants is accompanied by stimulation of host BREVIS RADIX , COTYLEDON VASCULAR PATTERN , and OCTOPUS gene expression leading to an increase in phloem complexity. We characterized how the arrest of this developmental reprogramming influences both the host and the invading pathogen. Furthermore, we found that infection leads to phloem-specific accumulation of SUGARS WILL EVENTUALLY BE EXPORTED TRANSPORTERS11 and 12 facilitating local distribution of sugars toward the pathogen. Utilizing Fourier-transform infrared microspectroscopy to monitor spatial distribution of carbohydrates, we found that infection leads to the formation of a strong physiological sink at the site of infection. High resolution metabolic and structural imaging of sucrose distributions revealed that sweet11 sweet12 double mutants are impaired in sugar transport toward the pathogen, delaying disease progression. This work highlights the importance of precise regulation of sugar partitioning for plant–pathogen interactions and the dependence of P . brassicae ’s performance on its capacity to induce a phloem sink at the feeding site.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Defensive symbionts - ScienceDirect

Defensive symbionts - ScienceDirect | Plant pathogens and pests | Scoop.it
What is a defensive symbiont? Generally, symbiotic relationships are those between species that live closely together. The nature of a given symbiosis can vary along a continuum from harmful (host–parasite interaction) to helpful (mutualism). A defensive symbiont is one that benefits its host by fighting off the host’s natural enemies, including viruses, pathogens and parasitoids
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Hijacking a host scaffold protein, RACK1, for replication of a plant RNA virus - Hyodo - 2019 - New Phytologist -

Hijacking a host scaffold protein, RACK1, for replication of a plant RNA virus - Hyodo - 2019 - New Phytologist - | Plant pathogens and pests | Scoop.it
Receptor for activated C kinase 1 (RACK1) is strictly conserved across eukaryotes and acts as a versatile scaffold protein involved in various signaling pathways. Plant RACK1 is known to exert important functions in innate immunity against fungal and bacterial pathogens. However, the role of the RACK1 in plant–virus interactions remains unknown.
Here, we addressed the role of RACK1 of Nicotiana benthamiana during infection by red clover necrotic mosaic virus (RCNMV), a plant positive‐stranded RNA virus. NbRACK1 was shown to be recruited by the p27 viral replication protein into endoplasmic reticulum‐derived aggregated structures (possible replication sites). Downregulation of NbRACK1 by virus‐induced gene silencing inhibited viral cap‐independent translation and p27‐mediated reactive oxygen species (ROS) accumulation, which are prerequisite for RCNMV replication.
We also found that NbRACK1 interacted with a host calcium‐dependent protein kinase (NbCDPKiso2) that activated a ROS‐generating enzyme. Interestingly, NbRACK1 was required for the interaction of p27 with NbCDPKiso2, suggesting that NbRACK1 acts as a bridge between the p27 viral replication protein and NbCDPKiso2.
Collectively, our findings provide an example of a viral strategy in which a host multifaceted scaffold protein RACK1 is highjacked for promoting viral protein‐triggered ROS production necessary for robust viral replication.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Sporisorium reilianum possesses a pool of effector proteins that modulate virulence on maize - Ghareeb - 2019 - Molecular Plant Pathology -

Sporisorium reilianum possesses a pool of effector proteins that modulate virulence on maize - Ghareeb - 2019 - Molecular Plant Pathology - | Plant pathogens and pests | Scoop.it
The biotrophic maize head smut fungus Sporisorium reilianum is a close relative of the tumour‐inducing maize smut fungus Ustilago maydis with a distinct disease aetiology. Maize infection with S. reilianum occurs at the seedling stage, but spores first form in inflorescences after a long endophytic growth phase. To identify S. reilianum‐specific virulence effectors, we defined two gene sets by genome comparison with U. maydis and with the barley smut fungus Ustilago hordei. We tested virulence function by individual and cluster deletion analysis of 66 genes and by using a sensitive assay for virulence evaluation that considers both disease incidence (number of plants with a particular symptom) and disease severity (number and strength of symptoms displayed on any individual plant). Multiple deletion strains of S. reilianum lacking genes of either of the two sets (sr10057, sr10059, sr10079, sr10703, sr11815, sr14797 and clusters uni5‐1, uni6‐1, A1A2, A1, A2) were affected in virulence on the maize cultivar ‘Gaspe Flint’, but each of the individual gene deletions had only a modest impact on virulence. This indicates that the virulence of S. reilianum is determined by a complex repertoire of different effectors which each contribute incrementally to the aggressiveness of the pathogen.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Tomato yellow leaf curl virus intergenic siRNAs target a host long noncoding RNA to modulate disease symptoms

Tomato yellow leaf curl virus intergenic siRNAs target a host long noncoding RNA to modulate disease symptoms | Plant pathogens and pests | Scoop.it
Tomato yellow leaf curl virus (TYLCV) and its related begomoviruses cause fast-spreading diseases in tomato worldwide. How this virus induces diseases remains largely unclear. Here we report a noncoding RNA-mediated model to elucidate the molecular mechanisms of TYLCV-tomato interaction and disease development. The circular ssDNA genome of TYLCV contains a noncoding intergenic region (IR), which is known to mediate viral DNA replication and transcription in host cells, but has not been reported to contribute directly to viral disease development. We demonstrate that the IR is transcribed in dual orientations during plant infection and confers abnormal phenotypes in tomato independently of protein-coding regions of the viral genome. We show that the IR sequence has a 25-nt segment that is almost perfectly complementary to a long noncoding RNA (lncRNA, designated as SlLNR1) in TYLCV-susceptible tomato cultivars but not in resistant cultivars which contains a 14-nt deletion in the 25-nt region. Consequently, we show that viral small-interfering RNAs (vsRNAs) derived from the 25-nt IR sequence induces silencing of SlLNR1 in susceptible tomato plants but not resistant plants, and this SlLNR1 downregulation is associated with stunted and curled leaf phenotypes reminiscent of TYLCV symptoms. These results suggest that the lncRNA interacts with the IR-derived vsRNAs to control disease development during TYLCV infection. Consistent with its possible function in virus disease development, over-expression of SlLNR1 in tomato reduces the accumulation of TYLCV. Furthermore, gene silencing of the SlLNR1 in the tomato plants induced TYLCV-like leaf phenotypes without viral infection. Our results uncover a previously unknown interaction between vsRNAs and host lncRNA, and provide a plausible model for TYLCV-induced diseases and host antiviral immunity, which would help to develop effective strategies for the control of this important viral pathogen.
No comment yet.