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Nature: A Xanthomonas uridine 5′-monophosphate transferase inhibits plant immune kinases (2012)

Nature: A Xanthomonas uridine 5′-monophosphate transferase inhibits plant immune kinases (2012) | Plants and Microbes | Scoop.it

Plant innate immunity is activated on the detection of pathogen-associated molecular patterns (PAMPs) at the cell surface, or of pathogen effector proteins inside the plant cell1, 2, 3, 4. Together, PAMP-triggered immunity and effector-triggered immunity constitute powerful defences against various phytopathogens. Pathogenic bacteria inject a variety of effector proteins into the host cell to assist infection or propagation. A number of effector proteins have been shown to inhibit plant immunity5, but the biochemical basis remains unknown for the vast majority of these effectors. Here we show that the Xanthomonas campestris pathovar campestris type III effector AvrAC enhances virulence and inhibits plant immunity by specifically targeting Arabidopsis BIK1 and RIPK, two receptor-like cytoplasmic kinases known to mediate immune signalling6, 7, 8. AvrAC is a uridylyl transferase that adds uridine 5′-monophosphate to and conceals conserved phosphorylation sites in the activation loop of BIK1 and RIPK, reducing their kinase activity and consequently inhibiting downstream signalling.

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PLOS One: Seed Transmission of Pseudoperonospora cubensis (2014)

PLOS One: Seed Transmission of Pseudoperonospora cubensis (2014) | Plants and Microbes | Scoop.it

Pseudoperonospora cubensis, an obligate biotrophic oomycete causing devastating foliar disease in species of the Cucurbitaceae family, was never reported in seeds or transmitted by seeds. We now show that P. cubensis occurs in fruits and seeds of downy mildew-infected plants but not in fruits or seeds of healthy plants. About 6.7% of the fruits collected during 2012–2014 have developed downy mildew when homogenized and inoculated onto detached leaves and 0.9% of the seeds collected developed downy mildew when grown to the seedling stage. This is the first report showing that P. cubensis has become seed-transmitted in cucurbits. Species-specific PCR assays showed that P. cubensis occurs in ovaries, fruit seed cavity and seed embryos of cucurbits. We propose that international trade of fruits or seeds of cucurbits might be associated with the recent global change in the population structure of P. cubensis.

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Workshop: Genomics Research on Plant-Parasite Interactions to Increase Food Production UK-Mexico, 3-6 February 2015

Workshop: Genomics Research on Plant-Parasite Interactions to Increase Food Production UK-Mexico, 3-6 February 2015 | Plants and Microbes | Scoop.it

The British Council and the Mexican National Council of Science and Technology (CONACyT) have launched the programme 'Researcher Links' to encourage international research collaboration between young researchers from the UK and Mexico.


We are now inviting Early Career Researchers from the UK and Mexico to apply to attend this binational workshop on Genomics Research on Plant-Parasite Interactions to Increase Food Production that will take place in the city of Leon in the state of Guanajuato, Mexico.


All travel and accommodation expenses will be covered by the Researcher Links programme.

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British Council: Researcher Links workshop in Thailand on plant pathology, - 16-19 February 2015

British Council: Researcher Links workshop in Thailand on plant pathology, - 16-19 February 2015 | Plants and Microbes | Scoop.it

ABOUT THIS OPPORTUNITY


We have grants for early career researchers to attend a workshop entitled 'Plant-microbe interactions: pathogen and host diversity, infection and defense mechanisms and disease protection'. All travel, accommodation and meals will be covered.

Under the Researcher Links scheme offered within the Newton Fund, the British Council and the Thailand Research Fund will be holding a workshop on the above theme in Bangkok, Thailand on 16 – 19 February 2015. The workshop is being coordinated by Drs. Chatchawan Jantasuriyarat and Sophien Kamoun, and will have contributions from other leading researchers. The theme of the workshop is plant-pathogen interactions with an emphasis on studies of pathogen and host diversity, infection and defense mechanisms, as well as disease protection.


KEY DATES


Dates of workshop - 16-19 February 2015

Deadline for applications - 31 October 2014


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Cell Host & Microbe: A Plant Phosphoswitch Platform Repeatedly Targeted by Type III Effector Proteins Regulates the Output of Both Tiers of Plant Immune Receptors (2014)

Cell Host & Microbe: A Plant Phosphoswitch Platform Repeatedly Targeted by Type III Effector Proteins Regulates the Output of Both Tiers of Plant Immune Receptors (2014) | Plants and Microbes | Scoop.it

Plants detect microbes via two functionally interconnected tiers of immune receptors. Immune detection is suppressed by equally complex pathogen mechanisms. The small plasma-membrane-tethered protein RIN4 negatively regulates microbe-associated molecular pattern (MAMP)-triggered responses, which are derepressed upon bacterial flagellin perception. We demonstrate that recognition of the flagellin peptide MAMP flg22 triggers accumulation of RIN4 phosphorylated at serine 141 (pS141) that mediates derepression of several immune outputs. RIN4 is targeted by four bacterial type III effector proteins, delivered temporally after flagellin perception. Of these, AvrB acts with a host kinase to increase levels of RIN4 phosphorylated at threonine 166 (pT166). RIN4 pT166 is epistatic to RIN4 pS141. Thus, AvrB contributes to virulence by enhancing “rerepression” of immune system outputs. Our results explain the evolution of independent effectors that antagonize accumulation of RIN4 pS141 and of a specific plant intracellular NLR protein, RPM1, which is activated by AvrB-mediated accumulation of RIN4 pT166.

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Fungal Genetics and Biology: The Podosphaera xanthii haustorium, the fungal Trojan horse of cucurbit-powdery mildew interactions (2014)

Fungal Genetics and Biology: The Podosphaera xanthii haustorium, the fungal Trojan horse of cucurbit-powdery mildew interactions (2014) | Plants and Microbes | Scoop.it

The powdery mildew fungi are obligate biotrophic plant pathogens that develop a specialized structure for parasitism termed haustorium, which is responsible for nutrient uptake and factor exchange with the plant. In this work, we present a detailed microscopy analysis of the haustoria of the cucurbit powdery mildew fungus Podosphaera xanthii, a major limiting factor for cucurbit production worldwide. Despite being located inside plant epidermal cells, transmission electron microscopy (TEM) analysis showed the characteristic highly irregular outline of the extrahaustorial membrane that separates the extrahaustorial matrix of haustoria from the cytoplasm of the plant cell. TEM analysis also revealed the presence of some vesicles and electron-dense plaques of material surrounding the haustoria. In confocal microscopy analysis and aniline blue staining we found a positive correlation between haustorial development and deposition of callose, which is distributed as plaques around haustorial complex. In this study, a method for the isolation of P. xanthii haustoria was also adapted, which permitted the analysis of the formation of haustorial lobes and the visualization of vacuoles and the pool of vesicles inside the haustorial complex. Our findings suggested that the haustorial lobes were responsible for vesicular trafficking and most likely act as the main mediators of the fungus-plant dialogue. All of these findings were integrated into a model of the P. xanthii-host cellular interactions.

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Plant Journal: Probing formation of cargo/importin-α transport complexes in plant cells using a pathogen effector (2014)

Plant Journal: Probing formation of cargo/importin-α transport complexes in plant cells using a pathogen effector (2014) | Plants and Microbes | Scoop.it

Importin-αs are essential adapter proteins that recruit cytoplasmic proteins destined for active nuclear import to the nuclear transport machinery. Cargo proteins interact with the importin-α armadillo repeat domain via nuclear localization sequences (NLSs), short amino acids motifs enriched in Lys and Arg residues. Plant genomes typically encode several importin-α paralogs that can have both specific and partially redundant functions. Although some cargos are preferentially imported by a distinct importin-α, it remains unknown how this specificity is generated and to what extent cargos compete for binding to nuclear transport receptors. Here we report that the effector protein HaRxL106 from the oomycete pathogen Hyaloperonospora arabidopsidis co-opts the host cell's nuclear import machinery. We use HaRxL106 as a probe to determine redundant and specific functions of importin-α paralogs from Arabidopsis thaliana. A crystal structure of the importin-α3/MOS6 armadillo repeat domain suggests that five of the six Arabidopsis importin-αs expressed in rosette leaves have an almost identical NLS binding site. Comparison of the importin-α binding affinities of HaRxL106 and other cargos in vitro and in plant cells suggests that relatively small affinity differences in vitro affect the rate of transport complex formation in vivo. Our results suggest that cargo affinity for importin-α, sequence variation at the importin-α NLS binding sites and tissue-specific expression levels of importin-αs determine formation of cargo/importin-α transport complexes in plant cells.


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Importin-αs are essential adapter proteins that recruit cytoplasmic proteins destined for active nuclear import to the nuclear transport machinery. Cargo proteins interact with the importin-α armadillo repeat domain via nuclear localization sequences (NLSs), short amino acids motifs enriched in Lys and Arg residues. Plant genomes typically encode several importin-α paralogs that can have both specific and partially redundant functions. Although some cargos are preferentially imported by a distinct importin-α, it remains unknown how this specificity is generated and to what extent cargos compete for binding to nuclear transport receptors. Here we report that the effector protein HaRxL106 from the oomycete pathogen Hyaloperonospora arabidopsidis co-opts the host cell's nuclear import machinery. We use HaRxL106 as a probe to determine redundant and specific functions of importin-α paralogs from Arabidopsis thaliana. A crystal structure of the importin-α3/MOS6 armadillo repeat domain suggests that five of the six Arabidopsis importin-αs expressed in rosette leaves have an almost identical NLS binding site. Comparison of the importin-α binding affinities of HaRxL106 and other cargos in vitro and in plant cells suggests that relatively small affinity differences in vitro affect the rate of transport complex formation in vivo. Our results suggest that cargo affinity for importin-α, sequence variation at the importin-α NLS binding sites and tissue-specific expression levels of importin-αs determine formation of cargo/importin-α transport complexes in plant cells.

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Plant J: Deep sequencing of the ancestral tobacco species Nicotiana tomentosiformis reveals multiple T-DNA inserts and a complex evolutionary history of natural transformation in the genus Nicotian...

Plant J: Deep sequencing of the ancestral tobacco species Nicotiana tomentosiformis reveals multiple T-DNA inserts and a complex evolutionary history of natural transformation in the genus Nicotian... | Plants and Microbes | Scoop.it

Nicotiana species carry cellular T-DNA sequences (cT-DNAs), acquired by Agrobacterium-mediated transformation. We characterized the cT-DNA sequences of the ancestral N. tabacum species N. tomentosiformis by deep sequencing. N. tomentosiformis contains four cT-DNA inserts derived from different Agrobacterium strains. Each has an incomplete inverted repeat structure. TA is similar to part of the A. rhizogenes 1724 mikimopine-type T-DNA, but has unusual orf14 and mis genes. TB carries a 1724 mikimopine-type orf14-mis fragment and a mannopine-agropine synthesis region (mas2’-mas1’-ags). The mas2’ gene codes for an active enzyme. TC is similar to the left part of the A. rhizogenes A4 T-DNA but also carries octopine synthase-like (ocl) and c-like genes normally found in A. tumefaciens. TD shows a complex rearrangement of T-DNA fragments similar to the right end of the A4 TL-DNA, and including an orf14-like gene and a gene with unknown function, orf511. The TA, TB, TC and TD insertion sites were identified by alignment to N. tabacum and N. sylvestris sequences. The divergence values for the TA, TB, TC and TD repeats provide an estimate for their relative introduction times. A large deletion has occurred in the central part of the N. tabacum cv. Basma/Xanthi TA region, another one removed the complete TC region in N. tabacum. N. otophora lacks TA, TB and TD, but contains TC and another cT-DNA, TE. This analysis, together with that of N. glauca and other Nicotiana species, indicates multiple sequential insertions of cT-DNAs during the evolution of the genus Nicotiana.

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The Scientist: Opinion: The Planet Needs More Plant Scientists (2014)

The Scientist: Opinion: The Planet Needs More Plant Scientists (2014) | Plants and Microbes | Scoop.it

Academia is not producing sufficient PhDs in the plant sciences to solve the crop production challenges facing a rapidly growing population.

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Peter Buckland's curator insight, October 2, 6:34 AM

Yet more evidence of the decline in plant sciences

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New Phytologist: Special Issue: Plants interacting with other organisms (October 2014)

New Phytologist: Special Issue: Plants interacting with other organisms (October 2014) | Plants and Microbes | Scoop.it

Editorial


Plant interactions with other organisms: molecules, ecology and evolution


Commentary


Different shades of JAZ during plant growth and defense


Nutrient supply differentially alters the dynamics of co-infecting phytoviruses


Letters


From shade avoidance responses to plant performance at vegetation level: using virtual plant modelling as a tool
F. J. Bongers, J. B. Evers, N. P. R. Anten & R. Pierik


Review


Magical mystery tour: MLO proteins in plant immunity and beyond
J. Acevedo-Garcia, S. Kusch & R. Panstruga


The squeeze cell hypothesis for the activation of jasmonate synthesis in response to wounding

E. E. Farmer, D. Gasperini & I. F. Acosta


Lipochitooligosaccharide recognition: an ancient story
Y. Liang, K. Tóth, Y. Cao, K. Tanaka, C. Espinoza & G. Stacey


Herbivore-induced plant volatiles: targets, perception and unanswered questions
M. Heil


There’s no place like home? An exploration of the mechanisms behind plant litter–decomposer affinity in terrestrial ecosystems
A. T. Austin, L. Vivanco, A. González-Arzac & L. I. Pérez


Insect herbivore-associated organisms affect plant responses to herbivory
F. Zhu, E. H. Poelman & M. Dicke


When mutualism goes bad: density- dependent impacts of introduced bees on plant reproduction
M. A. Aizen, C. L. Morales, D. P. Vázquez, L. A. Garibaldi, A. Sáez & L. D. Harder


Insect and pathogen attack and resistance in maize and its wild ancestors, the teosintes
E. S. de Lange, D. Balmer, B. Mauch-Mani & T. C. J. Turlings


Full papers


Linking phytochrome to plant immunity: low red : far-red ratios increase Arabidopsis susceptibility to Botrytis cinerea by reducing the biosynthesis of indolic glucosinolates and camalexin
M. D. Cargnel, P. V. Demkura & C. L. Ballaré


To grow or defend? Low red : far-red ratios reduce jasmonate sensitivity in Arabidopsis seedlings by promoting DELLA degradation and increasing JAZ10 stability
M. Leone, M. M. Keller, I. Cerrudo & C. L. Ballaré


β-Glucosidase BGLU42 is a MYB72-dependent key regulator of rhizobacteria-induced systemic resistance and modulates iron deficiency responses in Arabidopsis roots
C. Zamioudis, J. Hanson & C. M. J. Pieterse


Deciphering the language of plant communication: volatile chemotypes of sagebrush
R. Karban, W. C. Wetzel, K. Shiojiri, S. Ishizaki, S. R. Ramirez & J. D. Blande


The context dependence of beneficiary feedback effects on benefactors in plant facilitation
C. Schöb, R. M. Callaway, F. Anthelme, R. W. Brooker, L. A. Cavieres, Z. Kikvidze, C. J. Lortie, R. Michalet, F. I. Pugnaire, S. Xiao, B. H. Cranston, M-C. García, N. R. Hupp, L. D. Llambí, E. Lingua, A. M. Reid, L. Zhao & B. J. Butterfield


Herbivore-mediated material fluxes in a northern deciduous forest under elevated carbon dioxide and ozone concentrations
T. D. Meehan, J. J. Couture, A. E. Bennett & R. L. Lindroth


Are plant–soil feedback responses explained by plant traits?
C. Baxendale, K. H. Orwin, F. Poly, T. Pommier & R. D. Bardgett


Environmental nutrient supply alters prevalence and weakens competitive interactions among coinfecting viruses
C. Lacroix, E. W. Seabloom & E. T. Borer

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Scientific Reports: Secret lifestyles of Neurospora crassa: can it be a plant pathogen? (2014)

Scientific Reports: Secret lifestyles of Neurospora crassa: can it be a plant pathogen? (2014) | Plants and Microbes | Scoop.it

Neurospora crassa has a long history as an excellent model for genetic, cellular, and biochemical research. Although this fungus is known as a saprotroph, it normally appears on burned vegetations or trees after forest fires. However, due to a lack of experimental evidence, the nature of its association with living plants remains enigmatic. Here we report that Scots pine (Pinus sylvestris) is a host plant for N. crassa. The endophytic lifestyle of N. crassa was found in its interaction with Scots pine. Moreover, the fungus can switch to a pathogenic state when its balanced interaction with the host is disrupted. Our data reveal previously unknown lifestyles of N. crassa, which are likely controlled by both environmental and host factors. Switching among the endophytic, pathogenic, and saprotrophic lifestyles confers upon fungi phenotypic plasticity in adapting to changing environments and drives the evolution of fungi and associated plants.

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PLOS Pathogens: The Ins and Outs of Rust Haustoria (2014)

PLOS Pathogens: The Ins and Outs of Rust Haustoria (2014) | Plants and Microbes | Scoop.it

Rust diseases caused by fungi of the order Pucciniales afflict a wide range of plants, including cereals, legumes, ornamentals, and fruit trees, and pose a serious threat to cropping systems and global food security. The obligate parasitic lifestyle of these fungi and their complex life cycles, often involving alternate hosts for the sexual and asexual stages, also make this group of pathogens of great biological interest. One of the most remarkable adaptations of rust fungi is the specialized infection structure that underpins the sustained biotrophic association with hosts; the haustorium (Figure 1A and C). This organ forms after penetration of the wall of a live host cell, expanding on the inner side of the cell wall while invaginating the surrounding host plasma membrane (Figure 1C). Through haustoria, the pathogen derives nutrients from the host and secretes virulence proteins called effectors, which are believed to be the key players that manipulate the physiological and immune responses of host cells [1][4]. Analogous terminal feeding structures have independently evolved in other organisms such as the haustorium in powdery mildews (ascomycetes) and downy mildews (oomycetes, not true fungi), and the arbuscules in arbuscular mycorrhizae, suggesting that such architecture represents a successful adaptation of these organisms to interact with their respective host plants [5][6].

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PLOS ONE: Variation in Capsidiol Sensitivity between Phytophthora infestans and Phytophthora capsici Is Consistent with Their Host Range (2014)

PLOS ONE: Variation in Capsidiol Sensitivity between Phytophthora infestans and Phytophthora capsici Is Consistent with Their Host Range (2014) | Plants and Microbes | Scoop.it

Plants protect themselves against a variety of invading pathogenic organisms via sophisticated defence mechanisms. These responses include deployment of specialized antimicrobial compounds, such as phytoalexins, that rapidly accumulate at pathogen infection sites. However, the extent to which these compounds contribute to species-level resistance and their spectrum of action remain poorly understood. Capsidiol, a defense related phytoalexin, is produced by several solanaceous plants including pepper and tobacco during microbial attack. Interestingly, capsidiol differentially affects growth and germination of the oomycete pathogensPhytophthora infestans and Phytophthora capsici, although the underlying molecular mechanisms remain unknown. In this study we revisited the differential effect of capsidiol on P. infestans and P. capsici, using highly pure capsidiol preparations obtained from yeast engineered to express the capsidiol biosynthetic pathway. Taking advantage of transgenicPhytophthora strains expressing fluorescent markers, we developed a fluorescence-based method to determine the differential effect of capsidiol on Phytophtora growth. Using these assays, we confirm major differences in capsidiol sensitivity between P. infestans and P. capsiciand demonstrate that capsidiol alters the growth behaviour of both Phytophthora species. Finally, we report intraspecific variation within P. infestans isolates towards capsidiol tolerance pointing to an arms race between the plant and the pathogens in deployment of defence related phytoalexins.

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Steve Marek's curator insight, September 17, 3:04 PM

Pepper pathogen can handle the 'heat'

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PNAS: Four hundred-million-year-old vesicular arbuscular mycorrhizae (2004)

PNAS: Four hundred-million-year-old vesicular arbuscular mycorrhizae (2004) | Plants and Microbes | Scoop.it

The discovery of arbuscules in Aglaophyton major, an Early Devonian land plant, provides unequivocal evidence that mycorrhizae were established >400 million years ago. Nonseptate hyphac and arbuscules occur in a specialized meristematic region of the cortex that continually provided new cells for fungal infection. Arbuscules are morphologically identical to those of living arbuscular mycorrhizae in consisting of a basal trunk and repeatedly branched bush-like tuft within the plant cell. Although interpretations of the evolution of mycorrhizal mutualisms continue to be speculative, the existence of arbuscules in the Early Devonian indicates that nutrient transfer mutualism may have been in existence when plants invaded the land.

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Frontiers in Legume Biology - The second Adam Kondorosi Symposium, 11-12 December 2014, Gif-sur-Yvette (France)

Frontiers in Legume Biology - The second Adam Kondorosi Symposium, 11-12 December 2014, Gif-sur-Yvette (France) | Plants and Microbes | Scoop.it

The objective of this symposium is to create a scientific event that is at the forefront of fundamental research in diverse aspects of legume biology.


The meeting will be divided into 5 sessions:
1) Symbiosis; 2) Genomics; 3) Pathogenesis; 4) Physiology and stress responses; 5) Development


The symposium will bring together about 150 participants in a rather informal atmosphere, facilitating exchanges. We also aim at proposing a highly attractive program at a moderate inscription fee to give the opportunity to researchers - in particular those at the early stage of their career – to participate to an exciting top-level scientific event. Young researchers will have the opportunity to present their work with a poster.

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PLOS Pathogens: Expression Profiling during Arabidopsis/Downy Mildew Interaction Reveals a Highly-Expressed Effector That Attenuates Responses to Salicylic Acid (2014)

PLOS Pathogens: Expression Profiling during Arabidopsis/Downy Mildew Interaction Reveals a Highly-Expressed Effector That Attenuates Responses to Salicylic Acid (2014) | Plants and Microbes | Scoop.it

Plants have evolved strong innate immunity mechanisms, but successful pathogens evade or suppress plant immunity via effectors delivered into the plant cell. Hyaloperonospora arabidopsidis (Hpa) causes downy mildew on Arabidopsis thaliana, and a genome sequence is available for isolate Emoy2. Here, we exploit the availability of genome sequences for Hpa and Arabidopsis to measure gene-expression changes in both Hpa and Arabidopsis simultaneously during infection. Using a high-throughput cDNA tag sequencing method, we reveal expression patterns of Hpa predicted effectors and Arabidopsis genes in compatible and incompatible interactions, and promoter elements associated with Hpa genes expressed during infection. By resequencing Hpa isolate Waco9, we found it evades Arabidopsis resistance gene RPP1through deletion of the cognate recognized effector ATR1. Arabidopsis salicylic acid (SA)-responsive genes including PR1 were activated not only at early time points in the incompatible interaction but also at late time points in the compatible interaction. By histochemical analysis, we found that Hpa suppresses SA-inducible PR1 expression, specifically in the haustoriated cells into which host-translocated effectors are delivered, but not in non-haustoriated adjacent cells. Finally, we found a highly-expressed Hpa effector candidate that suppresses responsiveness to SA. As this approach can be easily applied to host-pathogen interactions for which both host and pathogen genome sequences are available, this work opens the door towards transcriptome studies in infection biology that should help unravel pathogen infection strategies and the mechanisms by which host defense responses are overcome.

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Cell Host & Microbe: Proline Isomerization of the Immune Receptor-Interacting Protein RIN4 by a Cyclophilin Inhibits Effector-Triggered Immunity in Arabidopsis (2014)

Cell Host & Microbe: Proline Isomerization of the Immune Receptor-Interacting Protein RIN4 by a Cyclophilin Inhibits Effector-Triggered Immunity in Arabidopsis (2014) | Plants and Microbes | Scoop.it

In the absence of pathogen infection, plant effector-triggered immune (ETI) receptors are maintained in a preactivation state by intermolecular interactions with other host proteins. Pathogen effector-induced alterations activate the receptor. In Arabidopsis, the ETI receptor RPM1 is activated via bacterial effector AvrB-induced phosphorylation of the RPM1-interacting protein RIN4 at Threonine 166. We find that RIN4 also interacts with the prolyl-peptidyl isomerase (PPIase) ROC1, which is reduced upon RIN4 Thr166 phosphorylation. ROC1 suppresses RPM1 immunity in a PPIase-dependent manner. Consistent with this, RIN4 Pro149 undergoes cis/transisomerization in the presence of ROC1. While the RIN4P149V mutation abolishes RPM1 resistance, the deletion of Pro149 leads to RPM1 activation in the absence of RIN4 phosphorylation. These results support a model in which RPM1 directly senses conformational changes in RIN4 surrounding Pro149 that is controlled by ROC1. RIN4 Thr166 phosphorylation indirectly regulates RPM1 resistance by modulating the ROC1-mediated RIN4 isomerization.

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bioRxiv: A putative antiviral role of plant cytidine deaminases (2014)

bioRxiv: A putative antiviral role of plant cytidine deaminases (2014) | Plants and Microbes | Scoop.it

A mechanism of innate antiviral immunity operating against viruses infecting mammalian cells has been described during the last decade. Host cytidine deaminases (e.g., APOBEC3 proteins) edit viral genomes giving raise to hypermutated nonfunctional viruses; consequently, viral fitness is reduced through lethal mutagenesis. By contrast, sub-lethal hypermutagenesis may contribute to virus evolvability by increasing population diversity. To prevent genome editing, some viruses have evolved proteins that mediate APOBEC3 degradation. The model plant Arabidopsis thaliana encodes for nine cytidine deaminases (AtCDAs), raising the question of whether deamination is an antiviral mechanism in plants as well. Here we tested the effects of AtCDAs expression on the pararetrovirus Cauliflower mosaic virus (CaMV). We show that A. thaliana AtCDA1 gene product exerts a mutagenic activity, which indeed generates a negative correlation between the level of AtCDA1 expression and CaMV accumulation in the plant, suggesting that deamination may also work as an antiviral mechanism in plants.

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Nature Communications: Long-distance endosome trafficking drives fungal effector production during plant infection (2014)

Nature Communications: Long-distance endosome trafficking drives fungal effector production during plant infection (2014) | Plants and Microbes | Scoop.it

To cause plant disease, pathogenic fungi can secrete effector proteins into plant cells to suppress plant immunity and facilitate fungal infection. Most fungal pathogens infect plants using very long strand-like cells, called hyphae, that secrete effectors from their tips into host tissue. How fungi undergo long-distance cell signalling to regulate effector production during infection is not known. Here we show that long-distance retrograde motility of early endosomes (EEs) is necessary to trigger transcription of effector-encoding genes during plant infection by the pathogenic fungus Ustilago maydis. We demonstrate that motor-dependent retrograde EE motility is necessary for regulation of effector production and secretion during host cell invasion. We further show that retrograde signalling involves the mitogen-activated kinase Crk1 that travels on EEs and participates in control of effector production. Fungal pathogens therefore undergo long-range signalling to orchestrate host invasion.

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PNAS: A receptor-like protein mediates the response to pectin modification by activating brassinosteroid signaling (2014)

PNAS: A receptor-like protein mediates the response to pectin modification by activating brassinosteroid signaling (2014) | Plants and Microbes | Scoop.it

Plant growth and development depend on the biosynthesis and remodeling of the cell wall. To coordinate these two processes, surveillance mechanisms have evolved to monitor the state of the cell wall. The brassinosteroid (BR) hormone signaling pathway plays an essential role in growth control and regulates the expression of a plethora of cell wall-related genes. We have previously shown that feedback signaling from the wall can modulate the outputs of the BR pathway, ensuring cell wall homeostasis and integrity. Here, we identified a receptor-like protein (RLP44), which mediates the activation of BR signaling through direct interaction with the BR coreceptor BAK1. Thus, RLP44 integrates cell wall surveillance with hormone signaling to control cell wall integrity and growth.


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The Sainsbury Lab's curator insight, October 7, 4:18 AM

Plant growth and development depend on the biosynthesis and remodeling of the cell wall. To coordinate these two processes, surveillance mechanisms have evolved to monitor the state of the cell wall. The brassinosteroid (BR) hormone signaling pathway plays an essential role in growth control and regulates the expression of a plethora of cell wall-related genes. We have previously shown that feedback signaling from the wall can modulate the outputs of the BR pathway, ensuring cell wall homeostasis and integrity. Here, we identified a receptor-like protein (RLP44), which mediates the activation of BR signaling through direct interaction with the BR coreceptor BAK1. Thus, RLP44 integrates cell wall surveillance with hormone signaling to control cell wall integrity and growth.

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PLOS Pathogens: Adaptive Prediction As a Strategy in Microbial Infections (2014)

PLOS Pathogens: Adaptive Prediction As a Strategy in Microbial Infections (2014) | Plants and Microbes | Scoop.it

Microorganisms need to sense and respond to constantly changing microenvironments, and adapt their transcriptome, proteome, and metabolism accordingly to survive [1]. However, microbes sometimes react in a way which does not make immediate biological sense in light of the current environment—for example, by up-regulating an iron acquisition system in times of metal abundance. The reason for this seemingly nonsensical behavior can lie in the microbe's ability to predict a coming change in conditions by cues from the current environment. If the microbe (pre-)adapts accordingly, it will increase its fitness and chances of survival under subsequent selection pressures—a concept known as adaptive prediction.

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Donald Danforth Plant Science Center’s 16th annual Fall Symposium: Macroinfluence of Microogranisms: Host-Microbe Interactions and Inspired Technologies (September 2014)

Donald Danforth Plant Science Center’s 16th annual Fall Symposium: Macroinfluence of Microogranisms: Host-Microbe Interactions and Inspired Technologies (September 2014) | Plants and Microbes | Scoop.it
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New Phytologist: Different shades of JAZ during plant growth and defines (2014)

New Phytologist: Different shades of JAZ during plant growth and defines (2014) | Plants and Microbes | Scoop.it

Ever since their discovery as key regulators of the jasmonate (JA) signaling pathway (Chini et al., 2007; Thines et al., 2007; Yan et al., 2007), repressor proteins of the JASMONATE ZIM-domain (JAZ) family have been rising stars in research on hormonal regulation of plant growth and defense. In plant cells, JAZ repressor proteins interact with an E3 ubiquitin ligase complex (SCFCOI1) that together function as a JA receptor. In resting cells, JAZs block the activity of transcriptional regulators of JA responses by physically binding to them. Upon perception of bioactive JAs, JAZ proteins are rapidly degraded via the ubiquitin/26S proteasome-dependent proteolytic pathway. This releases the JAZ-bound transcription factors, resulting in the activation of downstream JA responses (Fig. 1a). JAs play a dominant role in regulating defense responses against herbivorous insects and necrotrophic pathogens, and in adaptive responses to beneficial soilborne microbes (Wasternack & Hause, 2013; Pieterse et al., 2014). In addition, JAs have a signal function in a myriad other processes, including abiotic stress reactions and plant growth responses to environmental cues (Wasternack & Hause, 2013). The JA pathway functions in the context of a complex network of hormone-regulated signaling pathways that, depending on the environmental or developmental condition, can act antagonistically or synergistically on each other to finely balance resource allocation between growth and defense and minimize fitness tradeoffs (Pieterse et al., 2012; Vos et al., 2013). In the process of balancing plant growth and defense, gibberellins (GAs) have emerged as dominant antagonists of the JA signaling output (Hou et al., 2013).


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David Kuykendall's curator insight, September 20, 4:30 PM

This is something I was interested in studying.

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Global Ecology and Biogeography: The global spread of crop pests and pathogens (2014)

Global Ecology and Biogeography: The global spread of crop pests and pathogens (2014) | Plants and Microbes | Scoop.it

Aim - To describe the patterns and trends in the spread of crop pests and pathogens around the world, and determine the socioeconomic, environmental and biological factors underlying the rate and degree of redistribution of crop-destroying organisms.


Location - Global.


Methods - Current country- and state-level distributions of 1901 pests and pathogens and historical observation dates for 424 species were compared with potential distributions based upon distributions of host crops. The degree of ‘saturation’, i.e. the fraction of the potential distribution occupied, was related to pest type, host range, crop production, climate and socioeconomic variables using linear models.


Results - More than one-tenth of all pests have reached more than half the countries that grow their hosts. If current trends continue, many important crop-producing countries will be fully saturated with pests by the middle of the century. While dispersal increases with host range overall, fungi have the narrowest host range but are the most widely dispersed group. The global dispersal of some pests has been rapid, but pest assemblages remain strongly regionalized and follow the distributions of their hosts. Pest assemblages are significantly correlated with socioeconomics, climate and latitude. Tropical staple crops, with restricted latitudinal ranges, tend to be more saturated with pests and pathogens than temperate staples with broad latitudinal ranges. We list the pests likely to be the most invasive in coming years.


Main conclusions - Despite ongoing dispersal of crop pests and pathogens, the degree of biotic homogenization of the globe remains moderate and regionally constrained, but is growing. Fungal pathogens lead the global invasion of agriculture, despite their more restricted host range. Climate change is likely to influence future distributions. Improved surveillance would reveal greater levels of invasion, particularly in developing countries.

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Nature Biotechnology: Wheat rescued from fungal disease (2014)

Nature Biotechnology: Wheat rescued from fungal disease (2014) | Plants and Microbes | Scoop.it

Knockout of all six alleles of a gene in the large wheat genome confers resistance to powdery mildew --- Genetic engineering to improve crops is entering a new era as conventional transgenesis technology, which involves random insertion of genes into the genome, is superseded by newer approaches that enable precise genetic alterations. A particular technological challenge in carrying out targeted genome modification in crops is that many plant genomes are polyploid, including such important species as wheat, potato and canola1. In this issue, Wang et al.2 report engineering of the hexaploid wheat genome using sequence-specific nucleases (SSNs)—the first demonstration in a polyploid crop of SSN-mediated genetic alterations that are stably transmitted to the next generation. By knocking out all six alleles encoding the MILDEW-RESISTANCE LOCUS (MLO) protein, the authors generated a mutant line that shows strong resistance to powdery mildew, a devastating fungal disease. This is a remarkable feat, given the ploidy and enormous size (17.1 Gb) of the wheat genome, and showcases the power of SSNs for engineering complex plant genomes and for creating crops with valuable traits.

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Storify: #NPW10 Origin and evolution of plants and their interactions with fungi. 9–10 September 2014

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