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Your input requested for Top 10 oomycete pathogens in molecular plant pathology

Your input requested for Top 10 oomycete pathogens in molecular plant pathology | Plant pathogenic fungi | Scoop.it

We are writing to seek your input to generate a list of the Top 10 oomycete pathogens in molecular plant pathology to use as the basis for an article in the Top 10 reviews series to be published in Molecular Plant Pathology.

 

Several of you must be familiar with the Top 10 reviews, which have covered so far fungi, viruses, bacteria and nematodes. These articles are available free to download from the journal website.

 

Yes, it is about time to cover our cherished oomycetes so please do vote and indicate your favourite by emailing the ballot to diane.hird@bristol.ac.uk. Each of you can vote for up to 5 species. The criteria we would like to cover are both the scientific and economic importance of the taxa. Feel free to draft a brief justification.

 

Please send your responses before October 20, 2013. The voting ballot is available at http://kamounlab.dreamhosters.com/Top10oomycetes_Ballot.docx

 

Also, feel free to forward this message to relevant colleagues.

 

Many thanks,

 

Sophien Kamoun and Diane Hird

 


Via Kamoun Lab @ TSL
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dromius's comment, September 30, 2013 4:21 AM
Phytophthora palmivora is the best ;)

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Rescooped by Steve Marek from Plant evolution
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Diversity and variability of NOD-like receptors in fungi

Diversity and variability of NOD-like receptors in fungi | Plant pathogenic fungi | Scoop.it

NOD-like receptors (NLRs) are intracellular receptors that control innate immunity and other biotic interactions in animals and plants. NLRs have been characterized in plant and animal lineages, but in fungi, this gene family has not been systematically described. There is however previous indications of the involvement of NLR-like genes in non-self recognition and programmed cell death in fungi. We have analyzed 198 fungal genomes for the presence of NLRs and have annotated a total of 5616 NLR candidates. We describe their phylogenetic distribution, domain organization and evolution. Fungal NLRs are characterized by a great diversity of domain organizations, suggesting frequently occurring combinatorial assortments of different effector, NOD and repeat domains. The repeat domains are of the WD, ANK and TPR type; no LRR motifs were found. As previously documented for WD-repeat domains of fungal NLRs, TPR and ANK repeats evolve under positive selection and show highly conserved repeats and repeat length polymorphism, suggesting the possibility of concerted evolution of these repeats. We identify novel effector domains not previously found associated with NLRs, while others are related to effector domains of plant or animals NLRs. In particular, we show that the HET domain found in fungal NLRs may be related to TIR domains found in animal and plant immune receptors. This description of fungal NLR repertoires reveals both similarities and differences with plant and animals NLR collections, highlights the importance of domain re-assortment and repeat evolution and provides a novel entry point to explore the evolution of NLRs in eukaryotes.


Via Pierre-Marc Delaux
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Pierre-Marc Delaux's curator insight, November 17, 4:15 AM

I am sure the title will be confusing for some of you ;)

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Population Structure of Geosmithia morbida, the Causal Agent of Thousand Cankers Disease of Walnut Trees in the United States

Population Structure of Geosmithia morbida, the Causal Agent of Thousand Cankers Disease of Walnut Trees in the United States | Plant pathogenic fungi | Scoop.it
The ascomycete Geosmithia morbida and the walnut twig beetle Pityophthorus juglandis are associated with thousand cankers disease of Juglans (walnut) and Pterocarya (wingnut). The disease was first reported in the western United States (USA) on several Juglans species, but has been found more recently in the eastern USA in the native range of the highly susceptibleJuglans nigra. We performed a comprehensive population genetic study of 209 G. morbidaisolates collected from Juglans and Pterocarya from 17 geographic regions distributed across 12 U.S. states. The study was based on sequence typing of 27 single nucleotide polymorphisms from three genomic regions and genotyping with ten microsatellite primer pairs. Using multilocus sequence-typing data, 197 G. morbida isolates were placed into one of 57 haplotypes. In some instances, multiple haplotypes were recovered from isolates collected on the same tree. Twenty-four of the haplotypes (42%) were recovered from more than one isolate; the two most frequently occurring haplotypes (H02 and H03) represented 36% of all isolates. These two haplotypes were abundant in California, but were not recovered from Arizona or New Mexico. G. morbida population structure was best explained by four genetically distinct groups that clustered into three geographic regions. Most of the haplotypes isolated from the native range of J. major (Arizona and New Mexico) were found in those states only or present in distinct genetic clusters. There was no evidence of sexual reproduction or genetic recombination in any population. The scattered distribution of the genetic clusters indicated that G. morbida was likely disseminated to different regions at several times and from several sources. The large number of haplotypes observed and the genetic complexity of G. morbidaindicate that it evolved in association with at least one Juglans spp. and the walnut twig beetle long before the first reports of the disease.
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BMC Biology | Full text | Reagent and laboratory contamination can critically impact sequence-based microbiome analyses

BMC Biology | Full text | Reagent and laboratory contamination can critically impact sequence-based microbiome analyses | Plant pathogenic fungi | Scoop.it
The study of microbial communities has been revolutionised in recent years by the widespread adoption of culture independent analytical techniques such as 16S rRNA gene sequencing and metagenomics. One potential confounder of these sequence-based approaches is the presence of contamination in DNA extraction kits and other laboratory reagents.
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Botrytis species: relentless necrotrophic thugs or endophytes gone rogue? - Kan - 2014 - Molecular Plant Pathology - Wiley Online Library

Botrytis species: relentless necrotrophic thugs or endophytes gone rogue? - Kan - 2014 - Molecular Plant Pathology - Wiley Online Library | Plant pathogenic fungi | Scoop.it

Plant pathology has a long-standing tradition of classifying microbes as pathogens, endophytes or saprophytes. Lifestyles of pathogens are categorized as biotrophic, necrotrophic or hemibiotrophic. Botrytis species are considered by many to be archetypal examples of necrotrophic fungi, with B. cinerea being the most extensively studied species because of its broad host range and economic impact. In this review, we discuss recent work which illustrates that B. cinerea is capable of colonizing plants internally, presumably as an endophyte, without causing any disease or stress symptoms. The extent of the facultative endophytic behaviour of B. cinerea and its relevance in the ecology and disease epidemiology may be vastly underestimated. Moreover, we discuss the recent discovery of a novel Botrytis species,B. deweyae, which normally grows as an endophyte in ornamental daylilies (Hemerocallis), but displays facultative pathogenic behaviour, and is increasingly causing economic damage. We propose that the emergence of endophytes ‘gone rogue’ as novel diseases may be related to increased inbreeding of hybrid lines and reduced genetic diversity. These observations lead us to argue that the sometimes inflexible classification of pathogenic microbes by their lifestyles requires serious reconsideration. There is much more variety to the interactions of Botrytis with its hosts than the eye (or the plant pathologist) can see, and this may be true for other microbes interacting with plants.

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Frontiers | Nonhost resistance to rust pathogens – a continuation of continua | Plant-Microbe Interaction

Frontiers | Nonhost resistance to rust pathogens – a continuation of continua | Plant-Microbe Interaction | Plant pathogenic fungi | Scoop.it
The rust fungi (order: Pucciniales) are a group of widely distributed fungal plant pathogens, which can infect representatives of all vascular plant groups. Rust diseases significantly impact several crop species and considerable research focuses on understanding the basis of host specificity and nonhost resistance. Like many pathogens, rust fungi vary considerably in the number of hosts they can infect, such as wheat leaf rust (Puccinia triticina), which can only infect species in the genera Triticum and Aegilops, whereas Asian soybean rust (Phakopsora pachyrhizi) is known to infect over 95 species from over 42 genera. A greater understanding of the genetic basis determining host range has the potential to identify sources of durable resistance for agronomically important crops. Delimiting the boundary between host and nonhost has been complicated by the quantitative nature of phenotypes in the transition between these two states. Plant-pathogen interactions in this intermediate state are characterized either by (1) the majority of accessions of a species being resistant to the rust or (2) the rust only being able to partially complete key components of its life cycle. This leads to a continuum of disease phenotypes in the interaction with different plant species, observed as a range from compatibility (host) to complete immunity within a species (nonhost). In this review we will highlight how the quantitative nature of disease resistance in these intermediate interactions is caused by a continuum of defense barriers, which a pathogen needs to overcome for successfully establishing itself in the host. To illustrate continua as this underlying principle, we will discuss the advances that have been made in studying nonhost resistance towards rust pathogens, particularly cereal rust pathogens.
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Rescooped by Steve Marek from Plants and Microbes
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Frontiers in Plant-Microbe Interaction | Research Topics: Plant Immunity: From model systems to crops species (2014)

Frontiers in Plant-Microbe Interaction | Research Topics: Plant Immunity: From model systems to crops species (2014) | Plant pathogenic fungi | Scoop.it

Plants posses an intricate innate immune system that enables them to fight off most invading pathogens. Around the world, agriculture relies on robust disease resistance to ensure adequate food and feed production. Researchers and breeders are constantly generating new resistant crop varieties mostly employing the lengthy process of conventional breeding. Nonetheless, crop losses due to plant pathogens are estimated to be over 15% every year - the main cause of such losses is rapid evolution of new virulent races. In order to keep up with emerging pathogens, we need to gain a deeper and more systematic understanding of the immune system of our crops. During the past two decades, molecular understanding of plant innate immune signaling has been greatly expanded using dicotyledonous model systems such as Arabidopsis thaliana. Now, it is time to connect this volume of knowledge with the immune system of the crop species.

 

In this Research Topic we aim to collect manuscripts covering the current knowledge of the immune systems of major crop species. Specifically, we encourage the submission of manuscripts (Original Research, Hypothesis & Theory, Methods, Reviews, Mini Reviews, Perspective and Opinion) covering the following topics:

 

a. Manuscripts describing our current understanding of the plant immune system with a focus on crop species or comparative analyses between model systems and crops.

b. Manuscripts exploring how to best exploit our insight into genomes of plant pathogens and molecular understanding of effector function.
c. Manuscripts debating (novel) strategies of how to generate more resistant crop varieties. These might include biotechnological, social and economical aspects of crop improvement.

 

We anticipate that this Research Topic will become an important resource for plant immunologists especially those interested in comparative studies of plant innate immune systems of model systems and crop species.

 

Topic Editors

 

Benjamin Schwessinger
UC Davis
Davis, USA

 

Rebecca Bart
Donald Danforth Plant Science Center
St. Louis, USA

 

Gitta Coaker
University of California, Davis
Davis, USA

 

Ksenia V Krasileva
University of California Davis
Davis, USA


Via Kamoun Lab @ TSL
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Phylogenomics resolves the timing and pattern of insect evolution

Phylogenomics resolves the timing and pattern of insect evolution | Plant pathogenic fungi | Scoop.it

Insects are the most speciose group of animals, but the phylogenetic relationships of many major lineages remain unresolved. We inferred the phylogeny of insects from 1478 protein-coding genes. Phylogenomic analyses of nucleotide and amino acid sequences, with site-specific nucleotide or domain-specific amino acid substitution models, produced statistically robust and congruent results resolving previously controversial phylogenetic relations hips. We dated the origin of insects to the Early Ordovician [~479 million years ago (Ma)], of insect flight to the Early Devonian (~406 Ma), of major extant lineages to the Mississippian (~345 Ma), and the major diversification of holometabolous insects to the Early Cretaceous. Our phylogenomic study provides a comprehensive reliable scaffold for future comparative analyses of evolutionary innovations among insects.

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The Colletotrichum destructivum species complex – hemibiotrophic pathogens of forage and field crops

The Colletotrichum destructivum species complex – hemibiotrophic pathogens of forage and field crops | Plant pathogenic fungi | Scoop.it

Colletotrichum destructivum is an important plant pathogen, mainly of forage and grain legumes including clover, alfalfa, cowpea and lentil, but has also been reported as an anthracnose pathogen of many other plants worldwide. Several Colletotrichum isolates, previously reported as closely related to C. destructivum, are known to establish hemibiotrophic infections in different hosts. The inconsistent application of names to those isolates based on outdated species concepts has caused much taxonomic confusion, particularly in the plant pathology literature. A multilocus DNA sequence analysis (ITS, GAPDH, CHS-1, HIS3, ACT, TUB2) of 83 isolates of C. destructivum and related species revealed 16 clades that are recognised as separate species in the C. destructivum complex, which includes C. destructivum, C. fuscum, C. higginsianum, C. lini and C. tabacum. Each of these species is lecto-, epi- or neotypified in this study. Additionally, eight species, namely C. americae-borealis, C. antirrhinicola, C. bryoniicola, C. lentis, C. ocimi, C. pisicola, C. utrechtense and C. vignae are newly described.


Via Serenella A Sukno
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Rescooped by Steve Marek from Plants and Microbes
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Science: Genomic-scale exchange of mRNA between a parasitic plant and its hosts (2014)

Science: Genomic-scale exchange of mRNA between a parasitic plant and its hosts (2014) | Plant pathogenic fungi | Scoop.it

Movement of RNAs between cells of a single plant is well documented, but cross-species RNA transfer is largely unexplored. Cuscuta pentagona (dodder) is a parasitic plant that forms symplastic connections with its hosts and takes up host messenger RNAs (mRNAs). We sequenced transcriptomes of Cuscuta growing on Arabidopsis and tomato hosts to characterize mRNA transfer between species and found that mRNAs move in high numbers and in a bidirectional manner. The mobile transcripts represented thousands of different genes, and nearly half the expressed transcriptome of Arabidopsis was identified in Cuscuta. These findings demonstrate that parasitic plants can exchange large proportions of their transcriptomes with hosts, providing potential mechanisms for RNA-based interactions between species and horizontal gene transfer.


Via Kamoun Lab @ TSL
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A new and reliable method for live imaging and quantification of reactive oxygen species in Botrytis cinerea: Technological advancement

A new and reliable method for live imaging and quantification of reactive oxygen species in Botrytis cinerea: Technological advancement | Plant pathogenic fungi | Scoop.it

Reactive oxygen species (ROS) are produced in conserved cellular processes either as by-products of the cellular respiration in mitochondria, or purposefully for defense mechanisms, signaling cascades or cell homeostasis. ROS have two diametrically opposed attributes due to their highly damaging potential for DNA, lipids and other molecules and due to their indispensability for signaling and developmental processes. In filamentous fungi, the role of ROS in growth and development has been studied in detail, but these analyses were often hampered by the lack of reliable and specific techniques to monitor different activities of ROS in living cells.

Here, we present a new method for live cell imaging of ROS in filamentous fungi. We demonstrate that by use of a mixture of two fluorescent dyes it is possible to monitor H2O2 and superoxide specifically and simultaneously in distinct cellular structures during various hyphal differentiation processes. In addition, the method allows for reliable fluorometric quantification of ROS. We demonstrate that this can be used to characterize different mutants with respect to their ROS production/scavenging potential.

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Rescooped by Steve Marek from Plant pathogens and pests
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Frontiers | Annotation of a hybrid partial genome of the coffee rust (Hemileia vastatrix) contributes to the gene repertoire catalog of the Pucciniales | Plant-Microbe Interaction

Frontiers | Annotation of a hybrid partial genome of the coffee rust (Hemileia vastatrix) contributes to the gene repertoire catalog of the Pucciniales | Plant-Microbe Interaction | Plant pathogenic fungi | Scoop.it
Coffee leaf rust caused by the fungus Hemileia vastatrix is the most damaging disease to coffee worldwide. The pathogen has recently appeared in multiple outbreaks in coffee producing countries resulting in significant yield losses and increases in costs related to its control. New races/isolates are constantly emerging as evidenced by the presence of the fungus in plants that were previously resistant. Genomic studies are opening new avenues for the study of the evolution of pathogens, the detailed description of plant-pathogen interactions and the development of molecular techniques for the identification of individual isolates. For this purpose we sequenced 8 different H. vastatrix isolates using NGS technologies and gathered partial genome assemblies due to the large repetitive content in the coffee rust hybrid genome; 74.4% of the assembled contigs harbor repetitive sequences. A hybrid assembly of 333 Mb was built based on the 8 isolates; this assembly was used for subsequent analyses. Analysis of the conserved gene space showed that the hybrid H. vastatrix genome, though highly fragmented, had a satisfactory level of completion with 91.94% of core protein-coding orthologous genes present. RNA-Seq from urediniospores was used to guide the de novo annotation of the H. vastatrix gene complement. In total, 14,445 genes organized in 3921 families were uncovered; a considerable proportion of the predicted proteins (73.8%) were homologous to other Pucciniales species genomes. Several gene families related to the fungal lifestyle were identified, particularly 483 predicted secreted proteins that represent candidate effector genes and will provide interesting hints to decipher virulence in the coffee rust fungus. The genome sequence of Hva will serve as a template to understand the molecular mechanisms used by this fungus to attack the coffee plant, to study the diversity of this species and for the development of molecular markers to distinguish races/isolates.

Via Christophe Jacquet
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Nutrient transfer in plant–fungal symbioses

Nutrient transfer in plant–fungal symbioses | Plant pathogenic fungi | Scoop.it
Almost all plant species form symbioses with soil fungi, and nutrient transfer to plants is largely mediated through this partnership. Studies of fungal nutrient transfer to plants have largely focused on the transfer of limiting soil nutrients, such as nitrogen and phosphorous, by mycorrhizal fungi. However, certain fungal endophytes, such as Metarhizium and Beauveria, are also able to transfer nitrogen to their plant hosts. Here, we review recent studies that have identified genes and their encoded transporters involved in the movement of nitrogen, phosphorous, and nonlimiting soil nutrients between symbionts. These recent advances in our understanding could lead to applications in agricultural and horticultural settings, and to the development of model fungal systems that could further elucidate the role of fungi in these symbioses.
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Frontiers: The past, present and future of breeding rust resistant wheat (2014)

Frontiers: The past, present and future of breeding rust resistant wheat (2014) | Plant pathogenic fungi | Scoop.it

Two classes of genes are used for breeding rust resistant wheat. The first class, called R (for resistance) genes, are pathogen race-specific in their action, effective at all plant growth stages and probably mostly encode immune receptors of the nucleotide binding leucine rich repeat (NB-LRR) class. The second class called Adult Plant Resistance genes (APR) because resistance is usually functional only in adult plants, and, in contrast to most R genes, the levels of resistance conferred by single APR genes are only partial and allow considerable disease development. Some but not all APR genes provide resistance to all isolates of a rust pathogen species and a subclass of these provides resistance to several fungal pathogen species. Initial indications are that APR genes encode a more heterogeneous range of proteins than R proteins. Two APR genes, Lr34 and Yr36, have been cloned from wheat and their products are an ABC transporter and a protein kinase, respectively. Lr34 and Sr2 have provided long lasting and widely used (durable) partial resistance and are mainly used in conjunction with other R and APR genes to obtain adequate rust resistance. We caution that some APR genes indeed include race-specific, weak R genes which may be of the NB-LRR class. A research priority to better inform rust resistance breeding is to characterize further APR genes in wheat and to understand how they function and how they interact when multiple APR and R genes are stacked in a single genotype by conventional and GM breeding. An important message is do not be complacent about the general durability of all APR genes.


Via Kamoun Lab @ TSL
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Mating-type switching by chromosomal inversion in methylotrophic yeasts suggests an origin for the three-locus Saccharomyces cerevisiae system

Mating-type switching by chromosomal inversion in methylotrophic yeasts suggests an origin for the three-locus Saccharomyces cerevisiae system | Plant pathogenic fungi | Scoop.it

Saccharomyces cerevisiae undergoes a programmed DNA rearrangement to switch between mating types a and alpha. The origins of this complex and multifaceted process, which requires three copies of the mating-type (MAT) locus (with two silenced), have remained unknown. In this study we present a mechanism for mating-type switching in methylotrophic yeasts that shares a common origin with the well-characterized system in S. cerevisiae but has simpler components. This system requires only two copies of the MAT locus, with one copy transcriptionally repressed by proximity to centromeric or telomeric chromatin. Switching between the mating types occurs by recombination between inverted-repeat sequences flanking the MAT loci. This system suggests an ancestral mechanism for mating-type switching in yeasts.

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PLOS Pathogens: The Plasmodesmal Protein PDLP1 Localises to Haustoria-Associated Membranes during Downy Mildew Infection and Regulates Callose Deposition (2014)

PLOS Pathogens: The Plasmodesmal Protein PDLP1 Localises to Haustoria-Associated Membranes during Downy Mildew Infection and Regulates Callose Deposition (2014) | Plant pathogenic fungi | Scoop.it

The downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa) is a filamentous oomycete that invades plant cells via sophisticated but poorly understood structures called haustoria. Haustoria are separated from the host cell cytoplasm and surrounded by an extrahaustorial membrane (EHM) of unknown origin. In some interactions, including Hpa-Arabidopsis, haustoria are progressively encased by host-derived, callose-rich materials but the molecular mechanisms by which callose accumulates around haustoria remain unclear. Here, we report that PLASMODESMATA-LOCATED PROTEIN 1 (PDLP1) is expressed at high levels in Hpainfected cells. Unlike other plasma membrane proteins, which are often excluded from the EHM, PDLP1 is located at the EHM in Hpa-infected cells prior to encasement. The transmembrane domain and cytoplasmic tail of PDLP1 are sufficient to convey this localization. PDLP1 also associates with the developing encasement but this association is lost when encasements are fully mature. We found that the pdlp1,2,3 triple mutant is more susceptible to Hpa while overexpression of PDLP1 enhances plant resistance, suggesting that PDLPs enhance basal immunity against Hpa. Haustorial encasements are depleted in callose in pdlp1,2,3 mutant plants whereas PDLP1 over-expression elevates callose deposition around haustoria and across the cell surface. These data indicate that PDLPs contribute to callose encasement of Hpa haustoria and suggests that the deposition of callose at haustoria may involve similar mechanisms to callose deposition at plasmodesmata.


Via Kamoun Lab @ TSL
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Chlorovirus ATCV-1 is part of the human oropharyngeal virome and is associated with changes in cognitive functions in humans and mice

Chlorovirus ATCV-1 is part of the human oropharyngeal virome and is associated with changes in cognitive functions in humans and mice | Plant pathogenic fungi | Scoop.it

Human mucosal surfaces contain a wide range of microorganisms. The biological effects of these organisms are largely unknown. Large-scale metagenomic sequencing is emerging as a method to identify novel microbes. Unexpectedly, we identified DNA sequences homologous to virus ATCV-1, an algal virus not previously known to infect humans, in oropharyngeal samples obtained from healthy adults. The presence of ATCV-1 was associated with a modest but measurable decrease in cognitive functioning. A relationship between ATCV-1 and cognitive functioning was confirmed in a mouse model, which also indicated that exposure to ATCV-1 resulted in changes in gene expression within the brain. Our study indicates that viruses in the environment not thought to infect humans can have biological effects.

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A 'plant' virus may be causing a human disease...

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Rescooped by Steve Marek from microbial pathogenesis and plant immunity
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Mol Plant Path: The zigzag model of plant–microbe interactions: is it time to move on?

Mol Plant Path: The zigzag model of plant–microbe interactions: is it time to move on? | Plant pathogenic fungi | Scoop.it
‘Remember that all models are wrong; the practical question is how wrong do they have to be to not be useful.’ (George E. P. Box)
Via Jim Alfano
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PLOS Pathogens: A Conserved Peptide Pattern from a Widespread Microbial Virulence Factor Triggers Pattern-Induced Immunity in Arabidopsis (2014)

PLOS Pathogens: A Conserved Peptide Pattern from a Widespread Microbial Virulence Factor Triggers Pattern-Induced Immunity in Arabidopsis (2014) | Plant pathogenic fungi | Scoop.it

Microbe- or host damage-derived patterns mediate activation of pattern-triggered immunity (PTI) in plants. Microbial virulence factor (effector)-triggered immunity (ETI) constitutes a second layer of plant protection against microbial attack. Various necrosis and ethylene-inducing peptide 1 (Nep1)-like proteins (NLPs) produced by bacterial, oomycete and fungal microbes are phytotoxic virulence factors that exert immunogenic activities through phytotoxin-induced host cell damage. We here show that multiple cytotoxic NLPs also carry a pattern of 20 amino acid residues (nlp20) that triggers immunity-associated plant defenses and immunity to microbial infection in Arabidopsis thaliana and related plant species with similar characteristics as the prototype pattern, bacterial flagellin. Characteristic differences in flagellin and nlp20 plant responses exist however, as nlp20s fail to trigger extracellular alkalinization in Arabidopsis cell suspensions and seedling growth inhibition. Immunogenic nlp20 peptide motifs are frequently found in bacterial, oomycete and fungal NLPs. Such an unusually broad taxonomic distribution within three phylogenetic kingdoms is unprecedented among microbe-derived triggers of immune responses in either metazoans or plants. Our findings suggest that cytotoxic NLPs carrying immunogenic nlp20 motifs trigger PTI in two ways as typical patterns and by inflicting host cell damage. We further propose that conserved structures within a microbial virulence factor might have driven the emergence of a plant pattern recognition system mediating PTI. As this is reminiscent of the evolution of immune receptors mediating ETI, our findings support the idea that there is a continuum between PTI and ETI.


Via IPM Lab, Kamoun Lab @ TSL
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Resolving the polyphyletic nature of Pyricularia (Pyriculariaceae)

Resolving the polyphyletic nature of Pyricularia (Pyriculariaceae) | Plant pathogenic fungi | Scoop.it

Species of Pyricularia (magnaporthe-like sexual morphs) are responsible for major diseases on grasses.Pyricularia oryzae (sexual morph Magnaporthe oryzae) is responsible for the major disease of rice called rice blast disease, and foliar diseases of wheat and millet, while Pyricularia grisea (sexual morphMagnaporthe grisea) is responsible for foliar diseases of Digitaria. Magnaporthe salvinii, M. poae andM. rhizophila produce asexual spores that differ from those of Pyricularia sensu stricto that has pyriform, 2-septate conidia produced on conidiophores with sympodial proliferation. Magnaporthe salvinii was recently allocated to Nakataea, while M. poae and M. rhizophila were placed in Magnaporthiopsis. To clarify the taxonomic relationships among species that are magnaporthe- or pyricularia-like in morphology, we analysed phylogenetic relationships among isolates representing a wide range of host plants by using partial DNA sequences of multiple genes such as LSU, ITS, RPB1, actin and calmodulin. Species ofPyricularia s. str. belong to a monophyletic clade that includes all P. oryzae/P. grisea isolates tested, defining the Pyriculariaceae, which is sister to the Ophioceraceae, representing two novel families. These clades are clearly distinct from species belonging to the Gaeumannomyces pro parte/Magnaporthiopsis/Nakataea generic complex that are monophyletic and define theMagnaporthaceae. A few magnaporthe- and pyricularia-like species are unrelated to Magnaporthaceaeand Pyriculariaceae. Pyricularia oryzae/P. grisea isolates cluster into two related clades. Host plants such as Eleusine, Oryza, Setaria or Triticum were exclusively infected by isolates from P. oryzae, while some host plant such as Cenchrus, Echinochloa, Lolium, Pennisetum or Zingiber were infected by differentPyricularia species. This demonstrates that host range cannot be used as taxonomic criterion without extensive pathotyping. Our results also show that the typical pyriform, 2-septate conidium morphology ofP. grisea/P. oryzae is restricted to Pyricularia and Neopyricularia, while most other genera have obclavate to more ellipsoid 2-septate conidia. Some related genera (Deightoniella, Macgarvieomyces) have evolved 1-septate conidia. Therefore, conidium morphology cannot be used as taxonomic criterion at generic level without phylogenetic data. We also identified 10 novel genera, and seven novel species. A re-evaluation of generic and species concepts within Pyriculariaceae is presented, and novelties are proposed based on morphological and phylogenetic data.

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Molecular tools for functional genomics in filamentous fungi: Recent advances and new strategies

Molecular tools for functional genomics in filamentous fungi: Recent advances and new strategies | Plant pathogenic fungi | Scoop.it

In this review, various molecular tools used in filamentous fungi are compared and discussed, including methods for genetic transformation (e.g., protoplast transformation, electroporation, and microinjection), the construction of random mutant libraries (e.g., restriction enzyme mediated integration, transposon arrayed gene knockout, and Agrobacterium tumefaciens mediated transformation), and the analysis of gene function (e.g., RNA interference and transcription activator-like effector nucleases). We also focused on practical strategies that could enhance the efficiency of genetic manipulation in filamentous fungi, such as choosing a proper screening system and marker genes, assembling target-cassettes or vectors effectively, and transforming into strains that are deficient in the nonhomologous end joining pathway.

 

 


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Frontiers: Epigenetic control of effectors in plant pathogens (2014)

Frontiers: Epigenetic control of effectors in plant pathogens (2014) | Plant pathogenic fungi | Scoop.it

Plant pathogens display impressive versatility in adapting to host immune systems. Pathogen effector proteins facilitate disease but can become avirulence (Avr) factors when the host acquires discrete recognition capabilities that trigger immunity. The mechanisms that lead to changes to pathogen Avr factors that enable escape from host immunity are diverse, and include epigenetic switches that allow for reuse or recycling of effectors. This perspective outlines possibilities of how epigenetic control of Avr effector gene expression may have arisen and persisted in plant pathogens, and how it presents special problems for diagnosis and detection of specific pathogen strains or pathotypes.


Via Kamoun Lab @ TSL
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Frontiers | Carbohydrates in plant immunity and plant protection: roles and potential application as foliar sprays | Crop Science and Horticulture

Frontiers | Carbohydrates in plant immunity and plant protection: roles and potential application as foliar sprays | Crop Science and Horticulture | Plant pathogenic fungi | Scoop.it
Increasing interest is devoted to carbohydrates for their roles in plant immunity. Some of them are elicitors of plant defenses whereas other ones act as signaling molecules in a manner similar to phytohormones. This review first describes the main classes of carbohydrates associated to plant immunity, their role and mode of action. More precisely, the state of the art about perception of “PAMP, MAMP and DAMP type” oligosaccharides is presented and examples of induced defense events are provided. A particular attention is paid to the structure / activity relationships of these compounds. The role of sugars as signaling molecules, especially in plant microbe interactions, is also presented. Secondly, the potentialities and limits of foliar sprays of carbohydrates to stimulate plant immunity for crop protection against diseases are discussed, with focus on the roles of the leaf cuticle and phyllosphere microflora.
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Fungal Genetics and Biology (2014): Functional analysis of hydrophobin genes in sexual development of Botrytis cinerea

Fungal Genetics and Biology (2014): Functional analysis of hydrophobin genes in sexual development of Botrytis cinerea | Plant pathogenic fungi | Scoop.it

Hydrophobins are small secreted fungal proteins that play roles in growth and development of filamentous fungi, i.e. in the formation of aerial structures and the attachment of hyphae to hydrophobic surfaces. In Botrytis cinerea, three hydrophobin genes have been identified. Studies by Mosbach et al. (2011) showed that hydrophobins are neither involved in conferring surface hydrophobicity to conidia and aerial hyphae of B. cinerea, nor are they required for virulence. The present study investigated the role of hydrophobins in sclerotium and apothecium development. Expression analysis revealed high expression of the Bhp1 gene during different stages of apothecium development. Two Bhp1 splice variants were detected that differ by an internal stretch of 13 amino acid residues. Seven different mutants in which either a single, two or three hydrophobin genes were knocked out, as well as two wild type strains of opposite mating types, were characterized for sclerotium and apothecium development. No aberrant morphology was observed in sclerotium development when single deletion mutants in hydrophobin genes were analyzed. Sclerotia of double knock out mutant ΔBhp1/ΔBhp3 and the triple knock out mutant, however, showed easily wettable phenotypes. For analyzing apothecium development, a reciprocal crossing scheme was setup. Morphological aberrations were observed in crosses with two hydrophobin mutants. When the double knock out mutant ΔBhp1/ΔBhp2 and the triple knock out mutant were used as the maternal parent (sclerotia), and fertilized with wild type microconidia, the resulting apothecia were swollen, dark brown in color and had a blotched surface. After initially growing upwards toward the light source, the apothecia in many cases collapsed due to loss of structural integrity. Aberrant apothecium development was not observed in the reciprocal cross, when these same mutants were used as the paternal parent (microconidia). These results indicate that the presence of hydrophobins in maternal tissue is important for normal development of apothecia of B. cinerea.


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Cloning of Insertion Site Flanking Sequence and Construction of Transfer DNA Insert Mutant Library in Stylosanthes Colletotrichum

Cloning of Insertion Site Flanking Sequence and Construction of Transfer DNA Insert Mutant Library in Stylosanthes Colletotrichum | Plant pathogenic fungi | Scoop.it

Stylosanthes sp. is the most important forage legume in tropical areas worldwide. Stylosanthes anthracnose, which is mainly caused by Colletotrichum gloeosporioides, is a globally severe disease in stylo production. Little progress has been made in anthracnose molecular pathogenesis research. In this study, Agrobacterium tumefaciens-mediated transformation was used to transform Stylosanthes colletotrichum strain CH008. The major factors of the genetic transformation system of S. colletotrichum were optimized as follows: A. tumefaciens’ AGL-1 concentration (OD600), 0.8; concentration of Colletotrichum conidium, 1×106 conidia/mL; acetosyringone concentration, 100 mmol/L; induction time, 6 h; co-culture temperature, 25°C; and co-culture time, 3 d. Thus, the transformation efficiency was increased to 300–400 transformants per 106 conidia. Based on the optimized system, a mutant library containing 4616 mutants was constructed, from which some mutants were randomly selected for analysis. Results show that the mutants were single copies that could be stably inherited. The growth rate, spore amount, spore germination rate, and appressorium formation rate in some mutants were significantly different from those in the wild-type strain. We then selected the most appropriate method for the preliminary screening and re-screening of each mutant’s pathogenic defects. We selected 1230 transformants, and obtained 23 strains with pathogenic defects, namely, 18 strains with reduced pathogenicity and five strains with lost pathogenicity. Thermal asymmetric interlaced PCR was used to identify the transfer DNA (T-DNA) integration site in the mutant that was coded 2430, and a sequence of 476 bp was obtained. The flanking sequence of T-DNA was compared with the Colletotrichum genome by BLAST, and a sequence of 401 bp was found in Contig464 of the Colletotrichum genome. By predicting the function of the flanking sequence, we discovered that T-DNA insertion in the promoter region of the putative gene had 79% homology with the aspartate aminotransferase gene in Magnaporthe oryzae (XP_003719674.1).


Via Christophe Jacquet
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Do chlorophyllous orchids heterotrophically use mycorrhizal fungal carbon?

Do chlorophyllous orchids heterotrophically use mycorrhizal fungal carbon? | Plant pathogenic fungi | Scoop.it

The roots of orchids associate with mycorrhizal fungi, the rhizoctonias, which are considered to exchange mineral nutrients against plant carbon. The recent discovery that rhizoctonias grow endophytically in non-orchid plants raises the possibility that they provide carbon to orchids, explaining why some orchids differ in isotopic abundances from autotrophic plants.

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