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FEMS Microbiol Letters: Ramularia collo-cygni: the biology of an emerging pathogen of barley (2007)

FEMS Microbiol Letters: Ramularia collo-cygni: the biology of an emerging pathogen of barley (2007) | Plants and Microbes | Scoop.it

Ramularia collo-cygni is now recognized as an important pathogen of barley in Northern Europe and New Zealand. It induces necrotic spotting and premature leaf senescence, leading to loss of green leaf area in crops, and can result in substantial yield losses. The fungus produces a number of anthraquinone toxins called rubellins, which act as host nonspecific toxins with photodynamic activity. These toxins induce lipid peroxidation and are possibly the cause of the chlorosis and necrosis observed in leaves infected with R. collo-cygni. The fact that the fungus can remain latent in barley plants until flowering, coupled with its very slow growth in vitro, makes it difficult to detect in crops. As a result, the epidemiology of this pathogen remains poorly understood. However, the recent development of rapid and reliable PCR methods for specific detection of R. collo-cygni offers the prospect of increased understanding of its epidemiology and improved disease control.

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Euro J. Biochem: Structure and activity of proteins from pathogenic fungi Phytophthora eliciting necrosis and acquired resistance in tobacco (1989)

Euro J. Biochem: Structure and activity of proteins from pathogenic fungi Phytophthora eliciting necrosis and acquired resistance in tobacco (1989) | Plants and Microbes | Scoop.it

The phytopathogenic fungi Phytophthora cryptogea and Phytophthora capsici cause systemic leaf necrosis on their non-host tobacco; in culture they release proteins, called cryptogein and capsicein, which elicit similar necrosis. In addition, both proteins protect tobacco against invasion by the pathogen Phytophthora nicotianae, the agent of the tobacco black shank, that is unable to produce such an elicitor. Cryptogein causes visible leaf necrosis starting at about 1 μg/plant, whereas 50-fold as much capsicein is required for the same reaction. Capsicein induces protection even in near absence of leaf necrosis. The activities of both elicitors are eliminated upon pronase digestion. They are proteins of similar Mr (respectively 10323 and 10155) and their complete amino acid sequences were determined. They consist of 98 residues, with some internal repetitions of hexapeptides and heptapeptides. 85% identity was observed between both sequences: only two short terminal regions are heterologous, while the central core is entirely conserved. Secondary structure predictions, hydropathy and flexibility profiles differ only around position 15 and at the C-terminus; these modifications could play a role in the modulation of their biological activities. After a search of the sequence data bases, they appear to be novel proteins.

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#JGI2015 Day 3 of 10th Annual DOE Joint Genome Institute Genomics of Energy & Environment Meeting (with images, tweets)

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#JGI2015 Days 1/2 of 10th Annual DOE Joint Genome Institute Genomics of Energy & Environment Meeting, March 2015 (with images, tweets)

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Frontiers: Silver linings: a personal memoir about Hurricane Katrina and fungal volatiles (2015)

Frontiers: Silver linings: a personal memoir about Hurricane Katrina and fungal volatiles (2015) | Plants and Microbes | Scoop.it

In the aftermath of Hurricane Katrina, the levees protecting New Orleans, Louisiana failed. Because approximately 80% of the city was under sea level, widespread flooding ensued. As a resident of New Orleans who had evacuated before the storm and a life-long researcher on filamentous fungi, I had known what to expect. After the hurricane I traveled home with a suitcase full of Petri dishes and sampling equipment so as to study the fungi that were “eating my house.” Not only were surfaces covered with fungal growth, the air itself was full of concentrated mold odor, a smell that was orders of magnitude more funky than any damp, musty basement I had ever encountered. The smell made me feel bad and I had to take regular breaks as I sampled. Being a mycotoxin expert, I knew a fair amount about “sick building syndrome” but believed that it was difficult to get enough respiratory exposure to toxins to cause the array of symptoms associated with the syndrome. So why was I feeling sick? Some Scandinavian experts had hypothesized that mold volatile organic compounds (VOCs) might be the fungal metabolites to blame for sick building syndrome and the time in my smelly, mold infested home made me think they might be right. After securing a new job and establishing a new laboratory, I endeavored to test the hypothesis that some volatile mold metabolites might be toxic. My laboratory at Rutgers University has interrogated the role of VOCs in possible interkingdom toxicity by developing controlled microcosms for exposing simple genetic model organisms to the vapor phase of growing fungi. Both Arabidopsis thaliana and Drosophila melanogaster exhibit a range of toxic symptoms that vary with the species of fungus, the duration of exposure, and other experimental parameters. Moreover, low concentrations of chemical standards of individual fungal VOCs such as 1-octen-3-ol also exhibit varying toxicity and cause neurotoxicity in a Drosophila model. Collectively, these data suggest that fungal VOCs may contribute to some of the adverse health effects reported by people exposed to damp indoor environments and that biogenic gas phase molecules deserve increased attention by the research community.

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New Phytologist: Plants, fungi and oomycetes: a 400-million year affair that shapes the biosphere (2015)

New Phytologist: Plants, fungi and oomycetes: a 400-million year affair that shapes the biosphere (2015) | Plants and Microbes | Scoop.it

In a rare gathering, genomics met palaeontology at the 10th New Phytologist Workshop on the ‘Origin and evolution of plants and their interactions with fungi’. An eclectic group of 17 experts met at The Natural History Museum (London, UK) on 9–10 September 2014 to discuss the latest findings on plant interactions with fungi (Eumycota) and oomycetes (Oomycota = Peronosporomycota), with topics ranging from the fossil record and comparative genomics to symbiosis and phytopathology. The discussions were largely disseminated via social media (Box 1). Highly diverse plant–fungal interactions have formed the backbone of land ecosystems and biogeochemical cycles since the Palaeozoic (see Fig. 1 for geological timeframe). As summarized by Christine Strullu-Derrien and Paul Kenrick (The Natural History Museum, London, UK) the first land plants arose c. 470 million years (Myr) ago (Kenrick et al., 2012; Edwards et al., 2014), at which time fungi and oomycetes had already colonized terrestrial ecosystems. Following their terrestrialization, these microbes began to abound within plant fossils (Taylor et al., 2014, and references therein). Ultimately, biological interactions sculpted the genomes of plants, fungi and oomycetes (e.g. Schmidt & Panstruga, 2011; Kohler et al., 2015). Here we illustrate the picture that has emerged from the discussions at the 10th New Phytologist Workshop, and point to some pending questions.


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Pierre-Marc Delaux's curator insight, March 23, 5:54 AM

It was a great workshop indeed!

Peter Buckland's curator insight, March 23, 9:01 AM

The importance of plant-fungal interactions

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#Fungal15 28th Fungal Genetics Conference, Asilomar, California, 2015 (with images, tweets)

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#OMGN15 Day 3 - Oomycete Molecular Genetics Network Annual Meeting (with images, tweets)

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Harri Kokko's curator insight, March 18, 9:36 AM

Yes and  I can't live  without the  OMG-network.

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Plant Cell: Differential Recognition of Highly Divergent Downy Mildew Avirulence Gene Alleles by RPP1 Resistance Genes from Two Arabidopsis Lines (2005)

Plant Cell: Differential Recognition of Highly Divergent Downy Mildew Avirulence Gene Alleles by RPP1 Resistance Genes from Two Arabidopsis Lines (2005) | Plants and Microbes | Scoop.it

The perception of downy mildew avirulence (Arabidopsis thaliana Recognized[ATR]) gene products by matching Arabidopsis thaliana resistance (Recognition of Peronospora parasitica [RPP]) gene products triggers localized cell death (a hypersensitive response) in the host plant, and this inhibits pathogen development. The oomycete pathogen, therefore, is under selection pressure to alter the form of these gene products to prevent detection. That the pathogen maintains these genes indicates that they play a positive role in pathogen survival. Despite significant progress in cloning plant RPP genes and characterizing essential plant components of resistance signaling pathways, little progress has been made in identifying the oomycete molecules that trigger them. Concluding a map-based cloning effort, we have identified an avirulence gene, ATR1NdWsB, that is detected by RPP1 from the Arabidopsis accession Niederzenz in the cytoplasm of host plant cells. We report the cloning of six highly divergent alleles of ATR1NdWsB from eight downy mildew isolates and demonstrate that the ATR1NdWsB alleles are differentially recognized by RPP1 genes from two Arabidopsis accessions (Niederzenz and Wassilewskija). RPP1-Nd recognizes a single allele of ATR1NdWsBRPP1-WsB also detects this allele plus three additional alleles with divergent sequences. The Emco5 isolate expresses an allele ofATR1NdWsB that is recognized by RPP1-WsB, but the isolate evades detection in planta. Although the Cala2 isolate is recognized by RPP1-WsA, the ATR1NdWsBallele from Cala2 is not, demonstrating that RPP1-WsA detects a novel ATR gene product. Cloning of ATR1NdWsB has highlighted the presence of a highly conserved novel amino acid motif in avirulence proteins from three different oomycetes. The presence of the motif in additional secreted proteins from plant pathogenic oomycetes and its similarity to a host-targeting signal from malaria parasites suggest a conserved role in pathogenicity.

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PLOS ONE: xopAC -triggered Immunity against Xanthomonas Depends on Arabidopsis Receptor-Like Cytoplasmic Kinase Genes PBL2 and RIPK (2013)

PLOS ONE: xopAC -triggered Immunity against  Xanthomonas  Depends on  Arabidopsis  Receptor-Like Cytoplasmic Kinase Genes  PBL2  and  RIPK (2013) | Plants and Microbes | Scoop.it

Xanthomonas campestris pv. campestris (Xcc) colonizes the vascular system of Brassicaceaeand ultimately causes black rot. In susceptible Arabidopsis plants, XopAC type III effector inhibits by uridylylation positive regulators of the PAMP-triggered immunity such as the receptor-like cytoplasmic kinases (RLCK) BIK1 and PBL1. In the resistant ecotype Col-0, xopAC is a major avirulence gene of Xcc. In this study, we show that both the RLCK interaction domain and the uridylyl transferase domain of XopAC are required for avirulence. Furthermore, xopAC can also confer avirulence to both the vascular pathogen Ralstonia solanacearum and the mesophyll-colonizing pathogen Pseudomonas syringae indicating that xopAC-specified effector-triggered immunity is not specific to the vascular system. In planta, XopAC-YFP fusions are localized at the plasma membrane suggesting that XopAC might interact with membrane-localized proteins. Eight RLCK of subfamily VII predicted to be localized at the plasma membrane and interacting with XopAC in yeast two-hybrid assays have been isolated. Within this subfamily, PBL2 and RIPK RLCK genes but not BIK1 are important for xopAC-specified effector-triggered immunity and Arabidopsis resistance to Xcc.

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New Phytologist: Arabidopsis EF-Tu receptor enhances bacterial disease resistance in transgenic wheat (2015)

New Phytologist: Arabidopsis EF-Tu receptor enhances bacterial disease resistance in transgenic wheat (2015) | Plants and Microbes | Scoop.it

Perception of pathogen (or microbe)-associated molecular patterns (PAMPs/MAMPs) by pattern recognition receptors (PRRs) is a key component of plant innate immunity. The Arabidopsis PRR EF-Tu receptor (EFR) recognizes the bacterial PAMP elongation factor Tu (EF-Tu) and its derived peptide elf18. Previous work revealed that transgenic expression of AtEFR in Solanaceae confers elf18 responsiveness and broad-spectrum bacterial disease resistance.In this study, we developed a set of bioassays to study the activation of PAMP-triggered immunity (PTI) in wheat. We generated transgenic wheat (Triticum aestivum) plants expressing AtEFR driven by the constitutive rice actin promoter and tested their response to elf18.We show that transgenic expression of AtEFR in wheat confers recognition of elf18, as measured by the induction of immune marker genes and callose deposition. When challenged with the cereal bacterial pathogen Pseudomonas syringae pv. oryzae, transgenic EFR wheat lines had reduced lesion size and bacterial multiplication.These results demonstrate that AtEFR can be transferred successfully from dicot to monocot species, further revealing that immune signalling pathways are conserved across these distant phyla. As novel PRRs are identified, their transfer between plant families represents a useful strategy for enhancing resistance to pathogens in crops.


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The Sainsbury Lab's curator insight, March 12, 5:48 AM
Perception of pathogen (or microbe)-associated molecular patterns (PAMPs/MAMPs) by pattern recognition receptors (PRRs) is a key component of plant innate immunity. The Arabidopsis PRR EF-Tu receptor (EFR) recognizes the bacterial PAMP elongation factor Tu (EF-Tu) and its derived peptide elf18. Previous work revealed that transgenic expression of AtEFR in Solanaceae confers elf18 responsiveness and broad-spectrum bacterial disease resistance.In this study, we developed a set of bioassays to study the activation of PAMP-triggered immunity (PTI) in wheat. We generated transgenic wheat (Triticum aestivum) plants expressing AtEFR driven by the constitutive rice actin promoter and tested their response to elf18.We show that transgenic expression of AtEFR in wheat confers recognition of elf18, as measured by the induction of immune marker genes and callose deposition. When challenged with the cereal bacterial pathogen Pseudomonas syringae pv. oryzae, transgenic EFR wheat lines had reduced lesion size and bacterial multiplication.These results demonstrate that AtEFR can be transferred successfully from dicot to monocot species, further revealing that immune signalling pathways are conserved across these distant phyla. As novel PRRs are identified, their transfer between plant families represents a useful strategy for enhancing resistance to pathogens in crops.
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MPMI: Focus on The Good, the Bad and the Unknown: Genomics-Enabled Discovery of Plant-Associated Microbial Processes and Diversity (2015)

MPMI: Focus on The Good, the Bad and the Unknown: Genomics-Enabled Discovery of Plant-Associated Microbial Processes and Diversity (2015) | Plants and Microbes | Scoop.it

MPMI has played a leading role in disseminating new insights into plant-microbe interactions and promoting new approaches. Articles in this Focus Issue highlight the power of genomic studies in uncovering novel determinants of plant interactions with microbial symbionts (good), pathogens (bad), and complex microbial communities (unknown). Many articles also illustrate how genomics can support translational research by quickly advancing our knowledge of important microbes that have not been widely studied.


Click on Next Article or Table of Contents above to view the articles in this Focus Issue. (From the mobile site, go to the MPMI March 2015 issue.)

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Nature Communications: Two linked pairs of Arabidopsis TNL resistance genes independently confer recognition of bacterial effector ​AvrRps4 (2015)

Nature Communications: Two linked pairs of Arabidopsis TNL resistance genes independently confer recognition of bacterial effector ​AvrRps4 (2015) | Plants and Microbes | Scoop.it

Plant immunity requires recognition of pathogen effectors by intracellular NB-LRR immune receptors encoded by Resistance (R) genes. Most R proteins recognize a specific effector, but some function in pairs that recognize multiple effectors. Arabidopsis thaliana TIR-NB-LRR proteins RRS1-R and RPS4together recognize two bacterial effectors, AvrRps4 from Pseudomonas syringae and PopP2 from Ralstonia solanacearum. However, AvrRps4, but not PopP2, is recognized in rrs1/rps4 mutants. We reveal an R gene pair that resembles and is linked to RRS1/RPS4, designated as RRS1B/RPS4B, which confers recognition of AvrRps4 but not PopP2. Like RRS1/RPS4, RRS1B/RPS4B proteins associate and activate defence genes upon AvrRps4 recognition. Inappropriate combinations (RRS1/RPS4B or RRS1B/RPS4) are non-functional and this specificity is not TIR domain dependent. Distinct putative orthologues of both pairs are maintained in the genomes of Arabidopsis thalianarelatives and are likely derived from a common ancestor pair. Our results provide novel insights into paired R gene function and evolution.


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Plant immunity requires recognition of pathogen effectors by intracellular NB-LRR immune receptors encoded by Resistance (R) genes. Most R proteins recognize a specific effector, but some function in pairs that recognize multiple effectors. Arabidopsis thaliana TIR-NB-LRR proteins RRS1-R and RPS4together recognize two bacterial effectors, AvrRps4 from Pseudomonas syringae and PopP2 from Ralstonia solanacearum. However, AvrRps4, but not PopP2, is recognized in rrs1/rps4 mutants. We reveal an R gene pair that resembles and is linked to RRS1/RPS4, designated as RRS1B/RPS4B, which confers recognition of AvrRps4 but not PopP2. Like RRS1/RPS4, RRS1B/RPS4B proteins associate and activate defence genes upon AvrRps4 recognition. Inappropriate combinations (RRS1/RPS4B or RRS1B/RPS4) are non-functional and this specificity is not TIR domain dependent. Distinct putative orthologues of both pairs are maintained in the genomes of Arabidopsis thalianarelatives and are likely derived from a common ancestor pair. Our results provide novel insights into paired R gene function and evolution.

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PLOS Pathogens: Phytomonas : Trypanosomatids Adapted to Plant Environments (2015)

PLOS Pathogens: Phytomonas : Trypanosomatids Adapted to Plant Environments (2015) | Plants and Microbes | Scoop.it

Over 100 years after trypanosomatids were first discovered in plant tissues, Phytomonasparasites have now been isolated across the globe from members of 24 different plant families. Most identified species have not been associated with any plant pathology and to date only two species are definitively known to cause plant disease. These diseases (wilt of palm and coffee phloem necrosis) are problematic in areas of South America where they threaten the economies of developing countries. In contrast to their mammalian infective relatives, our knowledge of the biology of Phytomonas parasites and how they interact with their plant hosts is limited. This review draws together a century of research into plant trypanosomatids, from the first isolations and experimental infections to the recent publication of the first Phytomonas genomes. The availability of genomic data for these plant parasites opens a new avenue for comparative investigations into trypanosomatid biology and provides fresh insight into how this important group of parasites have adapted to survive in a spectrum of hosts from crocodiles to coconuts.

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Nature Plants: Elicitin recognition confers enhanced resistance to Phytophthora infestans in potato (2015)

Nature Plants: Elicitin recognition confers enhanced resistance to Phytophthora infestans in potato (2015) | Plants and Microbes | Scoop.it

Potato late blight, caused by the destructive Irish famine pathogen Phytophthora infestans, is a major threat to global food security1,2. All late blight resistance genes identified to date belong to the coiled-coil, nucleotide-binding, leucine-rich repeat class of intracellular immune receptors3. However, virulent races of the pathogen quickly evolved to evade recognition by these cytoplasmic immune receptors4. Here we demonstrate that the receptor-like protein ELR (elicitin response) from the wild potato Solanum microdontum mediates extracellular recognition of the elicitin domain, a molecular pattern that is conserved in Phytophthora species. ELR associates with the immune co-receptor BAK1/SERK3 and mediates broad-spectrum recognition of elicitin proteins from several Phytophthora species, including four diverse elicitins from P. infestans. Transfer of ELR into cultivated potato resulted in enhanced resistance to P. infestans. Pyramiding cell surface pattern recognition receptors with intracellular immune receptors could maximize the potential of generating a broader and potentially more durable resistance to this devastating plant pathogen.

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Phytobiomes 2015: Designing a New Paradigm for Crop Improvement​​​​​​​​​​​​​​​​​​​​​​, June 30–J​uly 2, 2015, Washington, DC, U.S.A.​

Phytobiomes 2015: Designing a New Paradigm for Crop Improvement​​​​​​​​​​​​​​​​​​​​​​, June 30–J​uly 2, 2015, Washington, DC, U.S.A.​ | Plants and Microbes | Scoop.it

Phytobiomes 2015: Designing a New Paradigm for Crop Improvement brings together renowned experts in diverse fields related to phytobiomes with sessions ranging from the lessons that can be learned from other microbiome efforts to designing a path forward for a phytobiomes systems approach. Plan now to attend these 2 ½ days encompassing plenary speakers, discussions, and posters presentations.

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PLOS Genetics: The Evolution of Fungal Metabolic Pathways (2014)

PLOS Genetics: The Evolution of Fungal Metabolic Pathways (2014) | Plants and Microbes | Scoop.it

Fungi contain a remarkable range of metabolic pathways, sometimes encoded by gene clusters, enabling them to digest most organic matter and synthesize an array of potent small molecules. Although metabolism is fundamental to the fungal lifestyle, we still know little about how major evolutionary processes, such as gene duplication (GD) and horizontal gene transfer (HGT), have interacted with clustered and non-clustered fungal metabolic pathways to give rise to this metabolic versatility. We examined the synteny and evolutionary history of 247,202 fungal genes encoding enzymes that catalyze 875 distinct metabolic reactions from 130 pathways in 208 diverse genomes. We found that gene clustering varied greatly with respect to metabolic category and lineage; for example, clustered genes in Saccharomycotina yeasts were overrepresented in nucleotide metabolism, whereas clustered genes in Pezizomycotina were more common in lipid and amino acid metabolism. The effects of both GD and HGT were more pronounced in clustered genes than in their non-clustered counterparts and were differentially distributed across fungal lineages; specifically, GD, which was an order of magnitude more abundant than HGT, was most frequently observed in Agaricomycetes, whereas HGT was much more prevalent in Pezizomycotina. The effect of HGT in some Pezizomycotina was particularly strong; for example, we identified 111 HGT events associated with the 15 Aspergillus genomes, which sharply contrasts with the 60 HGT events detected for the 48 genomes from the entire Saccharomycotina subphylum. Finally, the impact of GD within a metabolic category was typically consistent across all fungal lineages, whereas the impact of HGT was variable. These results indicate that GD is the dominant process underlying fungal metabolic diversity, whereas HGT is episodic and acts in a category- or lineage-specific manner. Both processes have a greater impact on clustered genes, suggesting that metabolic gene clusters represent hotspots for the generation of fungal metabolic diversity.

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JGI News: Retracing the Roots of Plant-Fungal Symbiosis (2015)

JGI News: Retracing the Roots of Plant-Fungal Symbiosis (2015) | Plants and Microbes | Scoop.it

Understanding how plants and fungi developed symbiotic relationships.


With apologies to the poet John Donne, and based on recent work from the U.S. Department of Energy Joint Genome Institute (DOE JGI), a DOE Office of Science user facility, it can be said that no plant is an island, entire of itself. Unseen by the human eye, plants interact with many species of fungi and other microbes in the surrounding environment, and these exchanges can impact the plant’s health and tolerance to stressors such as drought or disease, as well as the global carbon cycle.


To understand the basis for fungal symbiotic relationships with plants, a team of DOE JGI researchers led by Igor Grigoriev and longtime collaborators at the French National Institute for Agricultural Research (INRA) and Clark University conducted the first broad, comparative phylogenomic analysis of mycorrhizal fungi, drawing on 49 fungal genomes, 18 of which were sequenced for this study. The 18 new fungal sequences included 13 mycorrhizal genomes, from ectomycorrhizal fungi that penetrate the host roots, and including species that comingle with orchid and heathland (which include blueberry, heather, and heath) plant roots. Published ahead online February 23, 2015 in Nature Genetics, these researchers describe how the comparative analyses of these genomes allowed them to track the evolution of mycorrhizal fungi. The results help researchers understand how plants and fungi developed symbiotic relationships, and how the mutualistic association provides host plants with beneficial traits for environmental adaptation.

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#Fungal15 [Last Day] 28th Fungal Genetics Conference, Asilomar, California, 2015 (with images, tweets)

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Boyce Thompson Institute News: Karl Maramorosch, turns 100 (2015)

Boyce Thompson Institute News: Karl Maramorosch, turns 100 (2015) | Plants and Microbes | Scoop.it

Karl Maramorosch, a former BTI scientist, pioneer in insect cell culture and winner of the Wolf Prize in Agriculture, became a centenarian this past month.


The pioneering invertebrate pathologist is known not just for his work on the transmission of plant diseases, but for his knack for recruiting and nurturing talented researchers. He remains a beloved colleague and friend to the many scientists with whom he collaborated, mentored, edited or simply entertained at conferences with his wit and his accordion.


“He was gifted,” said BTI Professor Emeritus Bob Granados, who spent five years working as a junior faculty researcher in his laboratory. Unlike some scientists who become famous for a single “eureka paper,” Maramorosch made a more lasting contribution to his field. “It was his ability and his success in hiring young men and women who became extremely well-known and in some cases superstars in the fields of invertebrate pathology and vector transmission,” said Granados.


Maramorosch began his work with plant viruses at the Brooklyn Botanic Garden in New York in 1946. Though he had completed a master’s degree and most of a doctorate in Europe, he worked as a technician for famed insect pathologist Lindsay Black, studying plant viruses transmitted by leafhoppers. Black encouraged him to finish his PhD at Columbia University and even helped him secure a predoctoral fellowship. The award provided enough income for Maramorosch and his wife to have their first and only child, Lydia Ann. While working with Black, he developed techniques to infect leafhoppers with wound tumor virus using a needle, and to measure the number of viral particles as the pathogen incubated inside the insect.


After graduating from Columbia, Maramorosch accepted a position working independently under plant pathologist Louis Otto Kunkel at Rockefeller University. Kunkel, also a former employee of BTI, was the first scientist hired by the Institute in 1923. At Rockefeller University, Maramorosch demonstrated that aster yellows “virus,” which was later discovered to be a specialized type of bacteria called a phytoplasma, could multiply inside the leafhopper. He also made his first attempts at growing the pathogen in cultured insect cells.

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J Bacteriology: AvrACXcc8004, a Type III Effector with a Leucine-Rich Repeat Domain from Xanthomonas campestris campestris Confers Avirulence in Vascular Tissues of Arabidopsis thaliana (2008)

J Bacteriology: AvrACXcc8004, a Type III Effector with a Leucine-Rich Repeat Domain from Xanthomonas campestris campestris Confers Avirulence in Vascular Tissues of Arabidopsis thaliana (2008) | Plants and Microbes | Scoop.it

Xanthomonas campestris pathovar campestris causes black rot, a vascular disease on cruciferous plants, including Arabidopsis thaliana. The gene XC1553 from X. campestris pv. campestris strain 8004 encodes a protein containing leucine-rich repeats (LRRs) and appears to be restricted to strains of X. campestris pv. campestris. LRRs are found in a number of type III-secreted effectors in plant and animal pathogens. These prompted us to investigate the role of the XC1553 gene in the interaction between X. campestris pv. campestris and A. thaliana. Translocation assays using the hypersensitive-reaction-inducing domain of X. campestris pv. campestris AvrBs1 as a reporter revealed that XC1553 is a type III effector. Infiltration of Arabidopsis leaf mesophyll with bacterial suspensions showed no differences between the wild-type strain and an XC1553 gene mutant; both strains induced disease symptoms on Kashmir and Col-0 ecotypes. However, a clear difference was observed when bacteria were introduced into the vascular system by piercing the central vein of leaves. In this case, the wild-type strain 8004 caused disease on the Kashmir ecotype, but not on ecotype Col-0; the XC1553 gene mutant became virulent on the Col-0 ecotype and still induced disease on the Kashmir ecotype. Altogether, these data show that the XC1553 gene, which was renamed avrACXcc8004, functions as an avirulence gene whose product seems to be recognized in vascular tissues.


AvrXccAC also known as XopAC in further studies from @matthieu_arlat lab /via @NicoDnce

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NLR Biology in Plants and Animals - Interactions, Bavaria, Germany from May 3–6, 2015

NLR Biology in Plants and Animals - Interactions, Bavaria, Germany from May 3–6, 2015 | Plants and Microbes | Scoop.it

This workshop aims to draw together researchers in plant and animal NLR biology to discuss recent conceptual advances and future directions for the field. The workshop will take place at Schloss Ringberg in Bavaria, Germany from May 3–6, 2015. View the workshop poster for more information on how to register and submit an abstract.

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Nature Biotechnology: Engineering insect-free cereals (2015)

Nature Biotechnology: Engineering insect-free cereals (2015) | Plants and Microbes | Scoop.it

A cluster of three rice lectin receptor kinases confers resistance to planthopper insects.


Insect pests reduce yields of crops worldwide through direct damage and because they spread devastating viral diseases. In Asia, the brown planthopper (BPH) decimates rice (Oryza sativa) crops, causing the loss of billions of dollars annually1. In this issue, Liu et al.2 report the cloning of a rice genetic locus that confers broad-spectrum resistance to BPH and at least one other planthopper species (white back planthopper). Introducing this locus into plant genomes is likely to provide an effective means of combating insect pests of rice and of other cereals such as maize.


In modern rice agriculture, BPH damage is controlled through breeding and the application of vast amounts of chemical pesticides1. Pesticides are not a sustainable approach, however, owing to high costs, harmful environmental effects and rapid development of resistant insects. Breeding programs have identified more than 20 genetic loci in cultivated or wild rice species that confer BPH resistance1. However, these Bph loci are usually only effective against specific BPH biotypes, and newly evolved BPH populations have rapidly overcome several Bph resistance loci deployed in the field..


Of the >20 identified Bph loci, only Bph14 and Bph26 have been cloned. Both of these loci encode coiled-coil, nucleotide-binding and leucine-rich repeat proteins3, 4, the main class of plant intracellular immune receptors5. Bph3 is a resistance locus that was first pinpointed genetically in the Sri Lankan rice indica cultivar Rathu Heenati. Notably, unlike most other Bph loci, including Bph14 and Bph26, Bph3 confers broad-spectrum resistance to many BPH biotypes as well as to the white back planthopper1, 2. The success of Bph3 as a resistance locus might be linked to the fact that it acts against BPH at an early stage of the feeding cycle, before the insect can deploy its arsenal of virulence proteins that circumvent plant defenses.


Despite the huge potential of Bph3 for rice agriculture, its molecular identity has been unknown. Liu et al.2 now identify Bph3 through map-based cloning in a cross between the resistant indica cultivar Rathu Heenati and the susceptible japonica cultivar 02428. Bph3 maps to a 79-kb genomic region that contains a cluster of three lectin receptor kinases, OsLecRK1–3 (ref. 2) (Fig. 1). The authors find that single-nucleotide polymorphisms in these genes are associated with BPH resistance in different cultivated rice accessions. They also show that ectopic expression of the OsLecRK1–3 gene cluster in the susceptible japonica Kitaake cultivar confers BPH resistance.


See Liu et al. Nature Biotechnology http://www.nature.com/nbt/journal/v33/n3/full/nbt.3069.html

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Nature: Pathogen-secreted proteases activate a novel plant immune pathway (2015)

Nature: Pathogen-secreted proteases activate a novel plant immune pathway (2015) | Plants and Microbes | Scoop.it
Mitogen-activated protein kinase (MAPK) cascades play central roles in innate immune signalling networks in plants and animals1, 2. In plants, however, the molecular mechanisms of how signal perception is transduced to MAPK activation remain elusive1. Here we report that pathogen-secreted proteases activate a previously unknown signalling pathway in Arabidopsis thaliana involving the Gα, Gβ, and Gγ subunits of heterotrimeric G-protein complexes, which function upstream of an MAPK cascade. In this pathway, receptor for activated C kinase 1 (RACK1) functions as a novel scaffold that binds to the Gβ subunit as well as to all three tiers of the MAPK cascade, thereby linking upstream G-protein signalling to downstream activation of an MAPK cascade. The protease–G-protein–RACK1–MAPK cascade modules identified in these studies are distinct from previously described plant immune signalling pathways such as that elicited by bacterial flagellin, in which G proteins function downstream of or in parallel to an MAPK cascade without the involvement of the RACK1 scaffolding protein. The discovery of the new protease-mediated immune signalling pathway described here was facilitated by the use of the broad host range, opportunistic bacterial pathogen Pseudomonas aeruginosa. The ability of P. aeruginosa to infect both plants and animals makes it an excellent model to identify novel immunoregulatory strategies that account for its niche adaptation to diverse host tissues and immune systems.

Via Christophe Jacquet, Giannis Stringlis, Jim Alfano
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