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Rescooped by Ricardo Oliva from Rice origins and cultural history
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Population structure of the primary gene pool of Oryza sativa in Thailand

Population structure of the primary gene pool of Oryza sativa in Thailand | pathogens | Scoop.it

Genetic Resources and Crop Evolution, Online First™ - SpringerLink.

The gene pool of cultivated Asian rice consists of wild rice (Oryza rufipogon Griff.), cultivated rice (O. sativa L.) and a weedy form (O. sativa f. spontanea). All three components are widespread in Thailand, frequently co-occurring within fields and providing the opportunity for gene flow and introgression. The purpose to this study is to understand the on-going evolutionary processes that affect the gene pool of rice by analysis of microsatellite variation. Results indicate that O. rufipogon, the wild ancestor of rice, has high levels of genetic variation both within and among populations. Moreover, the variation is structured predominantly by annual and perennial life history. High levels of variation are detected among cultivars indicating Thai cultivated rice has a broad genetic base with only a 20 % reduction in diversity from its wild ancestor. The weedy rice populations reveal varying levels of genetic variation, from nearly as high as wild rice to near zero. Weedy rice is genetically structured into 2 groups. Some populations of invasive weedy rice are the result of hybridization and gene flow between local wild rice and local cultivated rice in the regions of co-occurrence. Other populations of weedy rice are genetically nearly identical to the local cultivated rice. The diversity analysis indicates that the rice gene pool in Thailand is a dynamic genetic system. Gene flow is ongoing among its three main components, first between cultivated and wild rice resulting in weedy rice. Weedy rice in turn crosses with both cultivated varieties and wild rice.


Via Dorian Q Fuller
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Rescooped by Ricardo Oliva from Plants and Microbes
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News: Tracking potato famine pathogen to its home may aid $6 billion global fight (2014)

News: Tracking potato famine pathogen to its home may aid $6 billion global fight (2014) | pathogens | Scoop.it

The cause of potato late blight and the Great Irish Famine of the 1840s has been tracked to a pretty, alpine valley in central Mexico, which is ringed by mountains and now known to be the ancestral home of one of the most costly and deadly plant diseases in human history.

 

Research published today in the Proceedings of the National Academy of Sciences, by researchers from Oregon State University, the USDA Agricultural Research Service and five other institutions, concludes that Phytophthora infestans originated in this valley and co-evolved with potatoes over hundreds or maybe a few thousand years, and later spread repeatedly to much of the world.

 

Goss et al. The Irish potato famine pathogen Phytophthora infestans originated in central Mexico rather than the Andes. PNAS http://www.pnas.org/content/early/2014/05/29/1401884111.abstract


Via Niklaus Grunwald, Kamoun Lab @ TSL
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Rescooped by Ricardo Oliva from TAL effector science
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Identification of putative TAL effector targets of the citrus canker pathogens shows functional convergence underlying disease development and defense response - BMC Genomics

Identification of putative TAL effector targets of the citrus canker pathogens shows functional convergence underlying disease development and defense response - BMC Genomics | pathogens | Scoop.it

(via T. Lahaye & T. Schreiber, thx both)

Pereira et al, 2014

Based on, 1) the TAL effector-DNA binding code, 2) gene expression data of Xc and XaC-infiltrated sweet orange leaves, and 3) citrus hypocotyls transformed with PthA2, PthA4 or PthC1, we have identified a collection of Citrus sinensis genes potentially targeted by Xc and XaC TAL effectors. Our results suggest that similar with other strains of Xanthomonas TAL effectors, PthA2 and PthA4, and PthC1 to some extent, functionally converge. In particular, towards induction of genes involved in the auxin and gibberellin synthesis and response, cell division, and defense response. We also present evidence indicating that the TAL effectors act as transcriptional repressors and that the best scoring predicted DNA targets of PthA"s" and PthC"s" in citrus promoters predominantly overlap with or localize near to TATA boxes of core promoters, supporting the idea that TAL effectors interact with the host basal transcriptional machinery to recruit the RNA pol II and start transcription.


Via dromius
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Rescooped by Ricardo Oliva from Plants and Microbes
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Plant Cell: Geminivirus Vectors Deliver Reagents for Plant Genome Engineering (2014)

Plant Cell: Geminivirus Vectors Deliver Reagents for Plant Genome Engineering (2014) | pathogens | Scoop.it

Jennifer Mach commentary http://www.plantcell.org/content/early/2014/01/16/tpc.114.122606.full.pdf+html

 

Baltes et al. article http://www.plantcell.org/content/early/2014/01/16/tpc.113.119792.abstract


Via Kamoun Lab @ TSL
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Rescooped by Ricardo Oliva from Plants and Microbes
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PNAS: Chitin-induced activation of immune signaling by the rice receptor CEBiP relies on a unique sandwich-type dimerization (2014)

PNAS: Chitin-induced activation of immune signaling by the rice receptor CEBiP relies on a unique sandwich-type dimerization (2014) | pathogens | Scoop.it

Perception of microbe-associated molecular patterns (MAMPs) through pattern recognition receptors (PRRs) triggers various defense responses in plants. This MAMP-triggered immunity plays a major role in the plant resistance against various pathogens. To clarify the molecular basis of the specific recognition of chitin oligosaccharides by the rice PRR, CEBiP (chitin-elicitor binding protein), as well as the formation and activation of the receptor complex, biochemical, NMR spectroscopic, and computational studies were performed. Deletion and domain-swapping experiments showed that the central lysine motif in the ectodomain of CEBiP is essential for the binding of chitin oligosaccharides. Epitope mapping by NMR spectroscopy indicated the preferential binding of longer-chain chitin oligosaccharides, such as heptamer-octamer, to CEBiP, and also the importance of N-acetyl groups for the binding. Molecular modeling/docking studies clarified the molecular interaction between CEBiP and chitin oligosaccharides and indicated the importance of Ile122 in the central lysine motif region for ligand binding, a notion supported by site-directed mutagenesis. Based on these results, it was indicated that two CEBiP molecules simultaneously bind to one chitin oligosaccharide from the opposite side, resulting in the dimerization of CEBiP. The model was further supported by the observations that the addition of (GlcNAc)8 induced dimerization of the ectodomain of CEBiP in vitro, and the dimerization and (GlcNAc)8-induced reactive oxygen generation were also inhibited by a unique oligosaccharide, (GlcNβ1,4GlcNAc)4, which is supposed to have N-acetyl groups only on one side of the molecule. Based on these observations, we proposed a hypothetical model for the ligand-induced activation of a receptor complex, involving both CEBiP and Oryza sativa chitin-elicitor receptor kinase-1.


Via Kamoun Lab @ TSL
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Rescooped by Ricardo Oliva from Plant-microbe interactions (on the plant's side)
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Comparative Transcriptome Analysis of Two Rice Varieties in Response to Rice Stripe Virus and Small Brown Planthoppers during Early Interaction

Comparative Transcriptome Analysis of Two Rice Varieties in Response to Rice Stripe Virus and Small Brown Planthoppers during Early Interaction | pathogens | Scoop.it

Rice stripe, a virus disease, transmitted by a small brown planthopper (SBPH), has greatly reduced production of japonica rice in East Asia, especially in China. Although we have made great progress in mapping resistance genes, little is known about the mechanism of resistance.

 

By de novo transcriptome assembling, we gained sufficient transcript data to analyze changes in gene expression of early interaction in response to SBPH and RSV infection in rice. Respectively 648 and 937 DEGs were detected from the disease-resistant (Liaonong 979) and the susceptible (Fengjin) varieties, most of which were up-regulated. We found 37 genes related to insect resistance, which mainly included genes for jasmonate-induced protein, TIFY protein, lipoxygenase, as well as trypsin inhibitor genes and transcription factor genes. In the interaction process between RSV and rice, 87 genes were thought to be related to RSV resistance; these primarily included 12 peroxidase biosynthesis genes, 12 LRR receptor-like protein kinase genes, 6 genes coding pathogenesis-related proteins, 4 glycine-rich cell wall structural protein genes, 2 xyloglucan hydrolase genes and a cellulose synthase. The results indicate that the rice-pathogen interaction happened both in disease-resistant and susceptible varieties, and some genes related to JA biosynthesis played key roles in the interaction between SBPHs and rice. When rice was infected by RSV a hypersensitive reaction (HR) in the disease-resistant variety was suppressed, which resulted from an increase in peroxidase expression and down-regulation of LRR receptor-like protein kinase and pathogenesis-related proteins, while, the changes of peroxidase biosynthesis, glycine-rich cell wall structural protein, cellulose synthase and xyloglucan endotransglucosylase/hydrolase could lead to the strengthening of physical barriers of rice, which may be an important resistance mechanism to RSV in rice.

 

 


Via Christophe Jacquet
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Rescooped by Ricardo Oliva from TAL effector science
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Targeted Mutagenesis in Zea mays Using TALENs and the CRISPR/Cas System - J. Gen. Genomics

Targeted Mutagenesis in Zea mays Using TALENs and the CRISPR/Cas System - J. Gen. Genomics | pathogens | Scoop.it

(via T. Lahaye, thx)

Liang et al, 2013

Here, we report, for the first time, targeted mutagenesis in Zea mays using TALENs and the CRISPR/Cas system. We designed five TALENs targeting 4 genes, namely ZmPDS, ZmIPK1A, ZmIPK, ZmMRP4, and obtained targeting efficiencies of up to 23.1% in protoplasts, and about 13.3% to 39.1% of the transgenic plants were somatic mutations. Also, we constructed two gRNAs targeting the ZmIPK gene in maize protoplasts, at frequencies of 16.4% and 19.1%, respectively. In addition the CRISPR/Cas system induced targeted mutations in Zea mays protoplasts with efficiencies (13.1%) similar to those obtained with TALENs (9.1%). Our results show that both TALENs and the CRISPR/Cas system can be used for genome modification in maize.


Via dromius
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Ilyas Muhammad's comment, December 17, 2013 6:19 AM
thnx, Seb
Rescooped by Ricardo Oliva from Rice Blast
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South-East Asia is the center of origin, diversity and dispersion of the rice blast fungus, Magnaporthe oryzae

South-East Asia is the center of origin, diversity and dispersion of the rice blast fungus, Magnaporthe oryzae | pathogens | Scoop.it

Inferring invasion routes and identifying reservoirs of diversity of plant pathogens are essential in proposing new strategies for their control. Magnaporthe oryzae, the fungus responsible for rice blast disease, has invaded all rice growing areas. Virulent genotypes regularly (re)emerge, causing rapid resistance breakdowns. However, the world-wide genetic subdivision of M. oryzae populations on rice and its past history of invasion have never been elucidated.In order to investigate the centers of diversity, origin and migration of M. oryzae on rice, we analyzed the genetic diversity of 55 populations from 15 countries.Three genetic clusters were identified world-wide. Asia was the center of diversity and the origin of most migrations to other continents. In Asia, two centers of diversity were revealed in the Himalayan foothills: South China–Laos–North Thailand, and western Nepal. Sexual reproduction persisted only in the South China–Laos–North Thailand region, which was identified as the putative center of origin of all M. oryzae populations on rice.Our results suggest a scenario of early evolution of M. oryzae on rice that matches the past history of rice domestication. This study confirms that crop domestication may have considerable influence on the pestification process of natural enemies.

 


Via Christophe Jacquet, Elsa Ballini
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Rescooped by Ricardo Oliva from TAL effector science
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The broad bacterial blight resistance of rice line CBB23 is triggered by a novel TAL effector of Xanthomonas oryzae pv. oryzae - Wang - Mol. Plant Pathol.

The broad bacterial blight resistance of rice line CBB23 is triggered by a novel TAL effector of Xanthomonas oryzae pv. oryzae - Wang - Mol. Plant Pathol. | pathogens | Scoop.it

Wang et al, 2013

Bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo), is not only a disease devastating rice production worldwide but also an ideal model system for studying the interaction between plants and their bacterial pathogens. The rice near-isogenic line (NIL) CBB23, derived from a cross between a wild rice Oryza rufipogon accession (RBB16) and a susceptible indica rice variety Jingang 30, is highly resistant to all field Xoo strains tested so far. Although the BB-resistance of CBB23 has been widely used in rice breeding programs, the mechanism of its extremely broad-spectrum resistance remains unknown. Here, we report the molecular cloning of an avirulence gene, designated as avrXa23, from Xoo strain PXO99A. We validate that AvrXa23, a novel transcription activator-like effector, specifically triggers the broad-spectrum BB-resistance in CBB23. Prevalence of avrXa23 in all 38 Xoo strains surveyed may explain the broad-spectrum feature of BB-resistance in CBB23. The results will significantly facilitate the molecular cloning of the corresponding R-gene in the host, and provide new insights into our understanding of molecular mechanism for broad-spectrum disease resistance in plants.


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Rescooped by Ricardo Oliva from Plant Immunity And Microbial Effectors
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The haustorial transcriptomes of Uromyces appendiculatus and Phakopsora pachyrhizi and their candidate effector families

Summary
Haustoria of biotrophic rust fungi are responsible for uptake of nutrients from their hosts and for production of secreted proteins known as effectors that modulate the host immune system.

Via IPM Lab
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Rescooped by Ricardo Oliva from Effectors and Plant Immunity
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PLOS ONE: Cell Wall Degrading Enzyme Induced Rice Innate Immune Responses Are Suppressed by the Type 3 Secretion System Effectors XopN, XopQ, XopX and XopZ of Xanthomonas oryzae pv. oryzae (2013)

PLOS ONE: Cell Wall Degrading Enzyme Induced Rice Innate Immune Responses Are Suppressed by the Type 3 Secretion System Effectors XopN, XopQ, XopX and XopZ of Xanthomonas oryzae pv. oryzae (2013) | pathogens | Scoop.it

Innate immune responses are induced in plants and animals through perception of Damage Associated Molecular Patterns. These immune responses are suppressed by pathogens during infection. A number of studies have focussed on identifying functions of plant pathogenic bacteria that are involved in suppression of Pathogen Associated Molecular Pattern induced immune responses. In comparison, there is very little information on functions used by plant pathogens to suppress Damage Associated Molecular Pattern induced immune responses. Xanthomonas oryzae pv. oryzae, a gram negative bacterial pathogen of rice, secretes hydrolytic enzymes such as LipA (Lipase/Esterase) that damage rice cell walls and induce innate immune responses. Here, we show that Agrobacterium mediated transient transfer of the gene for XopN, a X. oryzae pv. oryzae type 3 secretion (T3S) system effector, results in suppression of rice innate immune responses induced by LipA. A xopN- mutant of X. oryzae pv. oryzae retains the ability to suppress these innate immune responses indicating the presence of other functionally redundant proteins. In transient transfer assays, we have assessed the ability of 15 other X. oryzae pv. oryzae T3S secreted effectors to suppress rice innate immune responses. Amongst these proteins, XopQ, XopX and XopZ are suppressors of LipA induced innate immune responses. A mutation in any one of the xopN, xopQ, xopX or xopZ genes causes partial virulence deficiency while a xopN- xopX- double mutant exhibits a greater virulence deficiency. A xopN- xopQ- xopX- xopZ- quadruple mutant of X. oryzae pv. oryzae induces callose deposition, an innate immune response, similar to a X. oryzae pv. oryzae T3S- mutant in rice leaves. Overall, these results indicate that multiple T3S secreted proteins of X. oryzae pv. oryzae can suppress cell wall damage induced rice innate immune responses.

 

Dipanwita Sinha, Mahesh Kumar Gupta, Hitendra Kumar Patel, Ashish Ranjan, Ramesh V. Sonti

 


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Rescooped by Ricardo Oliva from Plant Breeding and Genomics News
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PLOS ONE: Genomewide Variation in an Introgression Line of Rice-Zizania Revealed by Whole-Genome re-Sequencing

PLOS ONE: Genomewide Variation in an Introgression Line of Rice-Zizania Revealed by Whole-Genome re-Sequencing | pathogens | Scoop.it

Background

Hybridization between genetically diverged organisms is known as an important avenue that drives plant genome evolution. The possible outcomes of hybridization would be the occurrences of genetic instabilities in the resultant hybrids. It remained under-investigated however whether pollination by alien pollens of a closely related but sexually "incompatible" species could evoke genomic changes and to what extent it may result in phenotypic novelties in the derived progenies.

Methodology/Principal Findings

In this study, we have re-sequenced the genomes of Oryza sativa ssp. japonica cv. Matsumae and one of its derived introgressant RZ35 that was obtained from an introgressive hybridization between Matsumae and Zizania latifolia Griseb. in general, 131 millions 90 base pair (bp) paired-end reads were generated which covered 13.2 and 21.9 folds of the Matsumae and RZ35 genomes, respectively. Relative to Matsumae, a total of 41,724 homozygous single nucleotide polymorphisms (SNPs) and 17,839 homozygous insertions/deletions (indels) were identified in RZ35, of which 3,797 SNPs were nonsynonymous mutations. Furthermore, rampant mobilization of transposable elements (TEs) was found in the RZ35 genome. The results of pathogen inoculation revealed that RZ35 exhibited enhanced resistance to blast relative to Matsumae. Notably, one nonsynonymous mutation was found in the known blast resistance gene Pid3/Pi25 and real-time quantitative (q) RT-PCR analysis revealed constitutive up-regulation of its expression, suggesting both altered function and expression of Pid3/Pi25 may be responsible for the enhanced resistance to rice blast by RZ35.

Conclusions/Significance

Our results demonstrate that introgressive hybridization by Zizania has provoked genomewide, extensive genomic changes in the rice genome, and some of which have resulted in important phenotypic novelties. These findings suggest that introgressive hybridization by alien pollens of even a sexually incompatible species may represent a potent means to generate novel genetic diversities, and which may have played relevant roles in plant evolution and can be manipulated for crop improvements.


Via Plant Breeding and Genomics News
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Rescooped by Ricardo Oliva from Plants and Microbes
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Trends in Plant Science: Evolution of the plant–microbe symbiotic ‘toolkit’ (2013)

Trends in Plant Science: Evolution of the plant–microbe symbiotic ‘toolkit’ (2013) | pathogens | Scoop.it

Beneficial associations between plants and arbuscular mycorrhizal fungi play a major role in terrestrial environments and in the sustainability of agroecosystems. Proteins, microRNAs, and small molecules have been identified in model angiosperms as required for the establishment of arbuscular mycorrhizal associations and define a symbiotic ‘toolkit’ used for other interactions such as the rhizobia–legume symbiosis. Based on recent studies, we propose an evolutionary framework for this toolkit. Some components appeared recently in angiosperms, whereas others are highly conserved even in land plants unable to form arbuscular mycorrhizal associations. The exciting finding that some components pre-date the appearance of arbuscular mycorrhizal fungi suggests the existence of unknown roles for this toolkit and even the possibility of symbiotic associations in charophyte green algae.


Via Kamoun Lab @ TSL
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Rescooped by Ricardo Oliva from Plant Immunity And Microbial Effectors
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Intrinsic Disorder in Pathogen Effectors: Protein Flexibility as an Evolutionary Hallmark in a Molecular Arms Race

Effector proteins represent a refined mechanism of bacterial pathogens to overcome plants’ innate immune systems. These modular proteins often manipulate host physiology by directly interfering with immune signaling of plant cells.

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Rescooped by Ricardo Oliva from TAL effector science
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Repeat 1 of TAL effectors affects target specificity for the base at position zero - Nucl. Acids Res.

Repeat 1 of TAL effectors affects target specificity for the base at position zero - Nucl. Acids Res. | pathogens | Scoop.it

Schreiber & Bonas 2014

AvrBs3, the founding member of the Xanthomonas transcription-activator-like effectors (TALEs), is translocated into the plant cell where it localizes to the nucleus and acts as transcription factor. The DNA-binding domain of AvrBs3 consists of 17.5 nearly-identical 34 amino acid-repeats. Each repeat specifies binding to one base in the target DNA via amino acid residues 12 and 13 termed repeat variable diresidue (RVD). Natural target sequences of TALEs are generally preceded by a thymine (T0), which is coordinated by a tryptophan residue (W232) in a degenerated repeat upstream of the canonical repeats. To investigate the necessity of T0 and the conserved tryptophan for AvrBs3-mediated gene activation we tested TALE mutant derivatives on target sequences preceded by all possible four bases. In addition, we performed domain swaps with TalC from a rice pathogenic Xanthomonas because TalC lacks the tryptophan residue, and the TalC target sequence is preceded by cytosine. We show that T0 works best and that T0 specificity depends on the repeat number and overall RVD-composition. T0 and W232 appear to be particularly important if the RVD of the first repeat is HD (‘rep1 effect’). Our findings provide novel insights into the mechanism of T0 recognition by TALE proteins and are important for TALE-based biotechnological applications.


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Rescooped by Ricardo Oliva from Rice Blast
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Genome-Wide Evolutionary Characterization and Expression Analyses of WRKY Family Genes in Brachypodium distachyon

Genome-Wide Evolutionary Characterization and Expression Analyses of WRKY Family Genes in Brachypodium distachyon | pathogens | Scoop.it

It has been demonstrated that WRKY genes were not only involved in the activation of plant defence systems, but also played key roles in the control of plants' response to environmental stimuli.

For phytopathogen treatment, 2-week-old seedlings were sprayed with Fusarium graminearum (F0968) and two strains of Magnaporthe grisea (Guy11, avirulent ACE1 genotype; PH14, virulent ACE1 genotype) for 4 or 12 h. The BdWRKY array constituted of 86 primer sets representing all members of the B. distachyon WRKY gene family. The expression of the 86 BdWRKY genes was assessed upon the qPCR result analysis.

The results showed that the expression of BdWRKY genes was rapidly regulated by stresses and phytohormones, and there was a strong correlation between promoter cis-elements and the phytohormones-induced BdWRKY gene expression.


Via Elsa Ballini
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Rescooped by Ricardo Oliva from How microbes emerge
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PLOS ONE: Population History and Pathways of Spread of the Plant Pathogen Phytophthora plurivora

PLOS ONE: Population History and Pathways of Spread of the Plant Pathogen Phytophthora plurivora | pathogens | Scoop.it

Human activity has been shown to considerably affect the spread of dangerous pests and pathogens worldwide. Therefore, strict regulations of international trade exist for particularly harmful pathogenic organisms. Phytophthora plurivora, which is not subject to regulations, is a plant pathogen frequently found on a broad range of host species, both in natural and artificial environments. It is supposed to be native to Europe while resident populations are also present in the US. We characterized a hierarchical sample of isolates from Europe and the US and conducted coalescent-, migration, and population genetic analysis of sequence and microsatellite data, to determine the pathways of spread and the demographic history of this pathogen. We found P. plurivora populations to be moderately diverse but not geographically structured. High levels of gene flow were observed within Europe and unidirectional from Europe to the US. Coalescent analyses revealed a signal of a recent expansion of the global P. plurivora population. Our study shows that P. plurivora has most likely been spread around the world by nursery trade of diseased plant material. In particular, P. plurivora was introduced into the US from Europe. International trade has allowed the pathogen to colonize new environments and/or hosts, resulting in population growth.


Via Niklaus Grunwald
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Louis Rotella's curator insight, January 14, 2:44 PM

It's not unknown that disease spreads through trade. This article explains a good bit on other disease through the ecosystem along with old human activity.

 

Rescooped by Ricardo Oliva from Plant-microbe interactions (on the plant's side)
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PNAS: Stepwise artificial evolution of a plant disease resistance gene (2013)

PNAS: Stepwise artificial evolution of a plant disease resistance gene (2013) | pathogens | Scoop.it

Genes encoding plant nucleotide-binding leucine-rich repeat (NB-LRR) proteins confer dominant resistance to diverse pathogens. The wild-type potato NB-LRR protein Rx confers resistance against a single strain of potato virus X (PVX), whereas LRR mutants protect against both a second PVX strain and the distantly related poplar mosaic virus (PopMV). In one of the Rx mutants there was a cost to the broad-spectrum resistance because the response to PopMV was transformed from a mild disease on plants carrying wild-type Rx to a trailing necrosis that killed the plant. To explore the use of secondary mutagenesis to eliminate this cost of broad-spectrum resistance, we performed random mutagenesis of the N-terminal domains of this broad-recognition version of Rx and isolated four mutants with a stronger response against the PopMV coat protein due to enhanced activation sensitivity. These mutations are located close to the nucleotide-binding pocket, a highly conserved structure that likely controls the “switch” between active and inactive NB-LRR conformations. Stable transgenic plants expressing one of these versions of Rx are resistant to the strains of PVX and the PopMV that previously caused trailing necrosis. We conclude from this work that artificial evolution of NB-LRR disease resistance genes in crops can be enhanced by modification of both activation and recognition phases, to both accentuate the positive and eliminate the negative aspects of disease resistance.


Via Kamoun Lab @ TSL, Christophe Jacquet
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Rescooped by Ricardo Oliva from Plant-microbe interactions (on the plant's side)
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Aluminum induces cross-resistance of potato to Phytophthora infestans

Aluminum induces cross-resistance of potato to Phytophthora infestans | pathogens | Scoop.it
The phenomenon of cross-resistance allows plants to acquire resistance to a broad range of stresses after previous exposure to one specific factor. Although this stress–response relationship has been known for decades, the sequence of events that underpin cross-resistance remains unknown. Our experiments revealed that susceptible potato (Solanum tuberosum L. cv. Bintje) undergoing aluminum (Al) stress at the root level showed enhanced defense responses correlated with reduced disease symptoms after leaf inoculation with Phytophthora infestans. The protection capacity of Al to subsequent stress was associated with the local accumulation of H2O2 in roots and systemic activation of salicylic acid (SA) and nitric oxide (NO) dependent pathways. The most crucial Al-mediated changes involved coding of NO message in an enhanced S-nitrosothiol formation in leaves tuned with an abundant SNOs accumulation in the main vein of leaves. Al-induced distal NO generation was correlated with the overexpression of PR-2 and PR-3 at both mRNA and protein activity levels. In turn, after contact with a pathogen we observed early up-regulation of SA-mediated defense genes, e.g. PR1,PR-2, PR-3 and PAL, and subsequent disease limitation. Taken together Al exposure induced distal changes in the biochemical stress imprint, facilitating more effective responses to a subsequent pathogen attack.

Via Christophe Jacquet
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Rescooped by Ricardo Oliva from Plants and Microbes
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PLOS ONE: The Pseudomonas syringae pv. tomato Type III Effector HopM1 Suppresses Arabidopsis Defenses Independent of Suppressing Salicylic Acid Signaling and of Targeting AtMIN7 (2013)

PLOS ONE: The Pseudomonas syringae pv. tomato Type III Effector HopM1 Suppresses Arabidopsis Defenses Independent of Suppressing Salicylic Acid Signaling and of Targeting AtMIN7 (2013) | pathogens | Scoop.it

Pseudomonas syringae pv tomato strain DC3000 (Pto) delivers several effector proteins promoting virulence, including HopM1, into plant cells via type III secretion. HopM1 contributes to full virulence of Pto by inducing degradation of Arabidopsis proteins, including AtMIN7, an ADP ribosylation factor-guanine nucleotide exchange factor. Pseudomonas syringae pvphaseolicola strain NPS3121 (Pph) lacks a functional HopM1 and elicits robust defenses inArabidopsis thaliana, including accumulation of pathogenesis related 1 (PR-1) protein and deposition of callose-containing cell wall fortifications. We have examined the effects of heterologously expressed HopM1Pto on Pph-induced defenses. HopM1 suppresses Pph-induced PR-1 expression, a widely used marker for salicylic acid (SA) signaling and systemic acquired resistance. Surprisingly, HopM1 reduces PR-1 expression without affecting SA accumulation and also suppresses the low levels of PR-1 expression apparent in SA-signaling deficient plants. Further, HopM1 enhances the growth of Pto in SA-signaling deficient plants. AtMIN7 contributes to Pph-induced PR-1 expression. However, HopM1 fails to degrade AtMIN7 during Pph infection and suppresses Pph-induced PR-1 expression and callose deposition in wild-type and atmin7 plants. We also show that the HopM1-mediated suppression of PR-1 expression is not observed in plants lacking the TGA transcription factor, TGA3. Our data indicate that HopM1 promotes bacterial virulence independent of suppressing SA-signaling and links TGA3, AtMIN7, and other HopM1 targets to pathways distinct from the canonical SA-signaling pathway contributing to PR-1 expression and callose deposition. Thus, efforts to understand this key effector must consider multiple targets and unexpected outputs of its action.


Via Kamoun Lab @ TSL
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Rescooped by Ricardo Oliva from Plants&Bacteria
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Repertoire, unified nomenclature and evolution of the Type III effector gene set in the Ralstonia solanacearum species complex

Repertoire, unified nomenclature and evolution of the Type III effector gene set in the Ralstonia solanacearum species complex | pathogens | Scoop.it

Scooped from: BMC Genomics, 2013 (/via Nicolas Denancé Scoop.it)

Authors: Nemo Peeters, Sébastien Carrère, Maria Anisimova, Laure Plener, Anne-Claire Cazalé and Stephane Genin

 

Summary:

Ralstonia solanacearum is a soil-borne beta-proteobacterium that causes bacterial wilt disease in many food crops and is a major problem for agriculture in intertropical regions. R. solanacearum is a heterogeneous species, both phenotypically and genetically, and is considered as a species complex. Pathogenicity of R. solanacearum relies on the Type III secretion system that injects Type III effector (T3E) proteins into plant cells. T3E collectively perturb host cell processes and modulate plant immunity to enable bacterial infection. We provide the catalogue of T3E in the R. solanacearum species complex, as well as candidates in newly sequenced strains. 95 T3E orthologous groups were defined on phylogenetic bases and ordered using a uniform nomenclature. This curated T3E catalog is available on a public website and a bioinformatic pipeline has been designed to rapidly predict T3E genes in newly sequenced strains. Systematical analyses were performed to detect lateral T3E gene transfer events and identify T3E genes under positive selection. Our analyses also pinpoint the RipF translocon proteins as major discriminating determinants among the phylogenetic lineages. Establishment of T3E repertoires in strains representatives of the R. solanacearum biodiversity allowed determining a set of 22 T3E present in all the strains but provided no clues on host specificity determinants. The definition of a standardized nomenclature and the optimization of predictive tools will pave the way to understanding how variation of these repertoires is correlated to the diversification of this species complex and how they contribute to the different strain pathotypes. 

 

 

Database interface: https://iant.toulouse.inra.fr/bacteria/annotation/cgi/ralso_effectome/ralso_effectome.cgi


Via Nicolas Denancé, Freddy Monteiro
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Rescooped by Ricardo Oliva from Plants and Microbes
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Video: Xanthomonas-plant interactions (2012)

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Via Kamoun Lab @ TSL
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Abigail Rumsey's comment, November 13, 2013 10:46 AM
Very cool. This would be good to explain how plant diseases work even to people that don't know anything about plant pathology (if you took out all of the highly scientific words!).
Teresa M. Nash's comment, November 28, 2013 1:34 AM
thanks for this.
Rescooped by Ricardo Oliva from Rice Blast
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Sugar homeostasis mediated by cell wall invertase GRAIN INCOMPLETE FILLING 1 (GIF1) plays a role in pre-existing and induced defence in rice - Sun - 2013 - Molecular Plant Pathology - Wiley Online ...

Sugar homeostasis mediated by cell wall invertase GRAIN INCOMPLETE FILLING 1 (GIF1) plays a role in pre-existing and induced defence in rice - Sun - 2013 - Molecular Plant Pathology - Wiley Online ... | pathogens | Scoop.it

Sugar metabolism and sugar signalling are not only critical for plant growth and development, but are also important for stress responses. However, how sugar homeostasis is involved in plant defence against pathogen attack in the model crop rice remains largely unknown. In this study, we observed that the grains of gif1, a loss-of-function mutant of the cell wall invertase gene GRAIN INCOMPLETE FILLING 1 (GIF1), were hypersusceptible to postharvest fungal pathogens, with decreased levels of sugars and a thinner glume cell wall in comparison with the wild-type. Interestingly, constitutive expression of GIF1 enhanced resistance to both the rice bacterial pathogen Xanthomonas oryzae pv. oryzae and the fungal pathogen Magnaporthe oryzae. The GIF1-overexpressing (GIF1-OE) plants accumulated higher levels of glucose, fructose and sucrose compared with the wild-type plants. More importantly, higher levels of callose were deposited in GIF1-OE plants during pathogen infection. Moreover, the cell wall was much thicker in the infection sites of the GIF1-OE plants when compared with the wild-type plants. We also found that defence-related genes were constitutively activated in the GIF1-OE plants. Taken together, our study reveals that sugar homeostasis mediated by GIF1 plays an important role in constitutive and induced physical and chemical defence.


Via Christophe Jacquet, Elsa Ballini
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Rescooped by Ricardo Oliva from Rice Blast
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Modulation of plant immunity by light, circadian rhythm, and temperature

Modulation of plant immunity by light, circadian rhythm, and temperature | pathogens | Scoop.it

Via Elsa Ballini
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Elsa Ballini's curator insight, September 26, 2013 7:35 AM

Similarly, high temperature induces expression of rice blast resistance Pib R genes, and this transcriptional upregulation is likely responsible for enhanced resistance to the rice blast fugus at higher temperatures. In sum, temperature seemingly exerts its effect on disease resistance by regulating the expression and activities of key defense components.

Rescooped by Ricardo Oliva from Plant-microbe interactions (on the plant's side)
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A rice lectin receptor-like kinase that is involved in innate immune responses also contributes to seed germination

A rice lectin receptor-like kinase that is involved in innate immune responses also contributes to seed germination | pathogens | Scoop.it

Keywords:Rice;Seed germination;Innate immunity;Pleiotropy;Progressive fitnessSummary

 

Seed germination and innate immunity both have significant effects on plant lifespans because they control the plant's entry into the ecosystem and provide defenses against various external stresses, respectively. Much ecological evidence has shown that seeds with high vigor are generally more tolerant of various environmental stimuli in the field than those with low vigor. However, there is little genetic evidence linking germination and immunity in plants. Here, we show that the rice lectin receptor-like kinase OslecRK contributes to both seed germination and plant innate immunity. We demonstrate that knocking down the OslecRK gene depresses the expression of α-amylase genes, reducing seed viability and thereby decreasing the rate of seed germination. Moreover, it also inhibits the expression of defense genes and so reduces the resistance of rice plants to fungal and bacterial pathogens as well as herbivorous insects. Y2H and Co-IP experiments revealed that OslecRK interacts with an actin-depolymerizing factor (ADF) in vivo via its kinase domain. Moreover, the rice mutant adf exhibited a reduced seed germination rate due to the suppression of α-amylase gene expression. This mutant also exhibited depressed immune responses and reduced resistance to biotic stresses. Our results thus provide direct genetic evidence for a common physiological pathway connecting germination and immunity in plants. They also partially explain the common observation that high vigor seeds often perform well in the field. The dual effects of OslecRK may be indicative of progressive adaptive evolution in rice.


Via Christophe Jacquet
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Rescooped by Ricardo Oliva from Plant Biology Teaching Resources (Higher Education)
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PNAS: Herbivore exploits orally secreted bacteria to suppress plant defenses

PNAS: Herbivore exploits orally secreted bacteria to suppress plant defenses | pathogens | Scoop.it

The importance of symbiotic gut bacteria in insect oral secretions to elicit SA-mediated defenses (against the bacteria) rather than JA-mediated defenses (against the herbivore).

Image credit: Gary Felton, from here http://news.psu.edu/story/286884/2013/09/09/research/microbes-help-beetles-defeat-plant-defenses


Via Mary Williams
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