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Nematode management important for top yield soybeans | Southern Corn and Soybean Production Guide content from Delta Farm Press

Nematode management important for top yield soybeans | Southern Corn and Soybean Production Guide content from Delta Farm Press | Plant Research Topics | Scoop.it
Terry Kirkpatrick, University of Arkansas Extension plant pathologist at Hope, says knowing which nematodes you have and having the right crop rotation are important in managing the microscopic worm parasites.
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NEMATIC: a Simple and Versatile Tool for the In Silico Analysis of Plant-Nematode Interactions - Cabrera - Molecular Plant Pathology - Wiley Online Library

NEMATIC: a Simple and Versatile Tool for the In Silico Analysis of Plant-Nematode Interactions - Cabrera - Molecular Plant Pathology - Wiley Online Library | Plant Research Topics | Scoop.it
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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) | Plant Research Topics | 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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PNAS: Stepwise artificial evolution of a plant disease resistance gene (2013)

PNAS: Stepwise artificial evolution of a plant disease resistance gene (2013) | Plant Research Topics | 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.


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Two closely related members of Arabidopsis 13-LOXs, LOX3 and LOX4, reveal distinct functions in response to plant-parasitic nematode infection

Two closely related members of Arabidopsis 13-LOXs, LOX3 and LOX4, reveal distinct functions in response to plant-parasitic nematode infection | Plant Research Topics | Scoop.it

The responses of two closely related members of Arabidopsis 13-lipoxygenase (13-LOX)- LOX3 and LOX4-to infection by the sedentary nematodes root-knot nematode (Meloidogyne javanica) and cyst nematode (Heterodera schachtii) were analyzed in transgenic Arabidopsis seedlings. Tissue localization of LOX3 and LOX4 gene expression using β-glucuronidase (GUS) reporter gene constructs showed local induction of LOX3 expression when second-stage juveniles reached the vascular bundle and during early stages of plant–nematode interaction through gall and syncytia formation. Thin sections of nematode-infested knots indicated LOX3 expression in mature giant cells, and high expression in neighboring cells and those surrounding the female body. LOX4 promoter was also activated by nematode infection, although GUS signal weakened as infection and disease progressed. Homozygous insertion mutants lacking LOX3 were less susceptible than wild-type plants to root-knot nematode infection, as reflected by a decrease in female counts. Conversely, deficiency in LOX4 function led to a marked increase in females and egg masses number or in females/ males ratio of M. javanica and H. schachtii, respectively. Susceptibility of lox4 was accompanied by increased expression of allene oxide synthase, allene oxide cyclase, ethylene-responsive transcription factor 4, and accumulation of jasmonic acid measured in roots of lox4. This response was not found in lox3 mutants. Taken together, our results reveal that LOX4 and LOX3 interfere differentially with distinct metabolic and signaling pathways and that LOX4 plays a major role in controlling plant defense against nematode infection.


Via Jennifer Mach
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Overexpression of a soybean salicylic acid methyltransferase gene confers resistance to soybean cyst nematode - Lin - 2013 - Plant Biotechnology Journal - Wiley Online Library

Overexpression of a soybean salicylic acid methyltransferase gene confers resistance to soybean cyst nematode - Lin - 2013 - Plant Biotechnology Journal - Wiley Online Library | Plant Research Topics | Scoop.it
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Resistance gene enrichment sequencing (RenSeq) enables reannotation of the NB-LRR gene family from sequenced plant genomes and rapid mapping of resistance loci in segregating populations - Jupe - 2...

Resistance gene enrichment sequencing (RenSeq) enables reannotation of the NB-LRR gene family from sequenced plant genomes and rapid mapping of resistance loci in segregating populations - Jupe - 2... | Plant Research Topics | Scoop.it
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How Microbes Can Help Feed the World, August 2013

How Microbes Can Help Feed the World, August 2013 | Plant Research Topics | Scoop.it

How Microbes can Help Feed the World" looks in depth at the intimate relationship between microbes and agriculture including why plants need microbes, what types of microbes they need, how they interact and the scientific challenges posed by the current state of knowledge.  It then makes a series of recommendations, including greater investment in research, the taking on of one or more grand challenges such as characterization of the complete microbiome of one important crop plant, and the establishment of a formal process for moving scientific discoveries from the lab to the field.


Via Jean-Michel Ané
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Genetic loss of susceptibility: a costly route to disease resistance? - Hückelhoven - 2013 - Plant Pathology - Wiley Online Library

Genetic loss of susceptibility: a costly route to disease resistance? - Hückelhoven - 2013 - Plant Pathology - Wiley Online Library | Plant Research Topics | Scoop.it
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Trends Plant Science: Unifying concepts and mechanisms in the specificity of plant–enemy interactions (2012)

Trends Plant Science: Unifying concepts and mechanisms in the specificity of plant–enemy interactions (2012) | Plant Research Topics | Scoop.it

Host ranges are commonly quantified to classify herbivores and plant pathogens as either generalists or specialists. Here, we summarize patterns and mechanisms in the interactions of plants with these enemies along different axes of specificity. We highlight the many dimensions within which plant enemies can specify and consider the underlying ecological, evolutionary and molecular mechanisms. Host resistance traits and enemy effectors emerge as central players determining host utilization and thus host range. Finally, we review approaches to studying the causes and consequences of variation in the specificity of plant–enemy interactions. Knowledge of the molecular mechanisms that determine host range is required to understand host shifts, and evolutionary transitions among specialist and generalist strategies, and to predict potential host ranges of pathogens and herbivores.


Via Kamoun Lab @ TSL
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Eve Emshwiller's curator insight, August 5, 2013 8:04 PM

Probably too advanced for an introductory class like Botany 130, but might be able to use in some form in teaching another class.

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Curr Opin Plant Biol: Genetic and cellular mechanisms regulating plant responses to necrotrophic pathogens (2013)

Curr Opin Plant Biol: Genetic and cellular mechanisms regulating plant responses to necrotrophic pathogens (2013) | Plant Research Topics | Scoop.it

Necrotrophs are plant pathogens that kill host cells and proliferate on nutrients from dead or dying tissues causing devastating diseases of horticultural and agronomic crops. Their interactions with plants involve a complex network of pathogen disease factors and corresponding plant immune response regulators. Mechanisms of quantitative resistance and the major regulators intersect regardless of pathogen life style. By contrast, some plant immune responses, such as effector-triggered immunity (ETI), a major source of qualitative resistance to biotrophs, are co-opted by necrotrophs to promote disease, which highlights the disparate plant immunity systems. Advances towards understanding mechanisms and processes underlying host responses to necrotrophs are summarized.


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From immunity to susceptibility: virus resistance induced in tomato by a silenced transgene is lost as TGS overcomes PTGS - Catoni - The Plant Journal - Wiley Online Library

From immunity to susceptibility: virus resistance induced in tomato by a silenced transgene is lost as TGS overcomes PTGS - Catoni - The Plant Journal - Wiley Online Library | Plant Research Topics | Scoop.it

The tomato line 30.4 has been obtained engineering the nucleocapsid (N) gene of Tomato spotted wilt virus (TSWV) in plant genome, and immunity to TSWV infection of its self-pollinated homozygous progeny has been observed. Despite the presence of high amount of transgenic transcripts, the transgenic protein has never been detected, suggesting a mechanism of resistance mediated by RNA. In the present study we identify post-transcriptional gene silencing (PTGS) as the main mechanism of resistance, which is able to spread systemically through grafting, and show that the 30.4 resistant plants produce both 24 and 21-22 nt N-gene specific siRNA classes. The transgenic locus in chromosome 4 shows complex multiple insertions of four T-DNA copies in different orientations, all with 3'-end deletions in the terminator and part of the N gene. However, for three of them, polyadenylated transcripts are produced, due to flanking tomato genome sequences acting as alternative terminators. Interestingly, starting at the fifth generation following the transformation event, some individual plants show a TSWV-susceptible phenotype. The change is associated with the disappearance of transgene-specific transcripts and siRNAs, and with the hyper-methylation of the transgene, that proceeds gradually through the generations. The shift from PTGS to a transcriptional silencing of the transgene, once reached a critical threshold, wipes out a previously well established virus resistance. This article is protected by copyright. All rights reserved.


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We need GMOs to feed a growing population

We need GMOs to feed a growing population | Plant Research Topics | Scoop.it
Now that many environmentalists are coming around to the idea that GMOs don't have to be evil, we need a more nuanced view of how we want to use GMOs in agriculture. When is it a good idea to use GMOs, and when is it overkill?
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Pathogenesis-related protein 4b interacts with leucine-rich repeat protein 1 to suppress PR4b-triggered cell death and defense response in pepper - Hwang - The Plant Journal - Wiley Online Library

Pathogenesis-related protein 4b interacts with leucine-rich repeat protein 1 to suppress PR4b-triggered cell death and defense response in pepper - Hwang - The Plant Journal - Wiley Online Library | Plant Research Topics | Scoop.it
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PLOS Biology: A Downy Mildew Effector Attenuates Salicylic Acid–Triggered Immunity in Arabidopsis by Interacting with the Host Mediator Complex (2013)

PLOS Biology: A Downy Mildew Effector Attenuates Salicylic Acid–Triggered Immunity in Arabidopsis by Interacting with the Host Mediator Complex (2013) | Plant Research Topics | Scoop.it

Plants are continually exposed to pathogen attack but usually remain healthy because they can activate defences upon perception of microbes. However, pathogens have evolved to overcome plant immunity by delivering effectors into the plant cell to attenuate defence, resulting in disease. Recent studies suggest that some effectors may manipulate host transcription, but the specific mechanisms by which such effectors promote susceptibility remain unclear. We study the oomycete downy mildew pathogen of Arabidopsis,Hyaloperonospora arabidopsidis (Hpa), and show here that the nuclear-localized effector HaRxL44 interacts with Mediator subunit 19a (MED19a), resulting in the degradation of MED19a in a proteasome-dependent manner. The Mediator complex of ~25 proteins is broadly conserved in eukaryotes and mediates the interaction between transcriptional regulators and RNA polymerase II. We found MED19a to be a positive regulator of immunity against Hpa. Expression profiling experiments reveal transcriptional changes resembling jasmonic acid/ethylene (JA/ET) signalling in the presence of HaRxL44, and also 3 d after infection withHpa. Elevated JA/ET signalling is associated with a decrease in salicylic acid (SA)–triggered immunity (SATI) in Arabidopsis plants expressing HaRxL44 and in med19a loss-of-function mutants, whereas SATI is elevated in plants overexpressing MED19a. Using a PR1::GUS reporter, we discovered that Hpa suppresses PR1 expression specifically in cells containing haustoria, into which RxLR effectors are delivered, but not in nonhaustoriated adjacent cells, which show high PR1::GUS expression levels. Thus, HaRxL44 interferes with Mediator function by degrading MED19, shifting the balance of defence transcription from SA-responsive defence to JA/ET-signalling, and enhancing susceptibility to biotrophs by attenuating SA-dependent gene expression.


Via Kamoun Lab @ TSL
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Pietro Spanu's curator insight, December 17, 2013 2:39 AM

This looks very much like the "green island" effect that powdery mildews induce in stressed plants

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Root-knot nematodes caught in action - attacking plant root

This video describes the penetration and feeding site induction of infective juveniles in plant roots.

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nematodes's curator insight, December 9, 2013 4:59 PM

Thanks to Florian Grundler for sharing a nice video showing how root-knot nematode juveniles are attracted towards roots and how they enter and feed in roots.

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The plant genetic background affects the efficiency of the pepper major nematode resistance genes Me1 and Me3

The plant genetic background affects the efficiency of the pepper major nematode resistance genes Me1 and Me3 | Plant Research Topics | Scoop.it

The plant genetic background influences the efficiency of major resistance genes to root-knot nematodes in pepper and has to be considered in breeding strategies.

Abstract

Root-knot nematodes (RKNs), Meloidogyne spp., are extremely polyphagous plant parasites worldwide. Since the use of most chemical nematicides is being prohibited, genetic resistance is an efficient alternative way to protect crops against these pests. However, nematode populations proved able to breakdown plant resistance, and genetic resources in terms of resistance genes (R-genes) are limited. Sustainable management of these valuable resources is thus a key point of R-gene durability. In pepper, Me1 and Me3 are two dominant major R-genes, currently used in breeding programs to control M. arenaria, M. incognita and M. javanica, the three main RKN species. These two genes differ in the hypersensitive response induced by nematode infection. In this study, they were introgressed in either a susceptible or a partially resistant genetic background, in either homozygous or heterozygous allelic status. Challenging these genotypes with an avirulent M. incognita isolate demonstrated that (1) the efficiency of the R-genes in reducing the reproductive potential of RKNs is strongly affected by the plant genetic background, (2) the allelic status of the R-genes has no effect on nematode reproduction. These results highlight the primary importance of the choice of both the R-gene and the genetic background into which it is introgressed during the selection of new elite cultivars by plant breeders.

 

 


Via Christophe Jacquet
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What you can't see can hurt you

What you can't see can hurt you | Plant Research Topics | Scoop.it
By Adam Harper It's hard to imagine something so small having such a huge impact and yet grain crops and profit margins are slowly being eaten away, all from beneath growers' very feet. The culprit is root lesion nematodes.

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nematodes's curator insight, October 30, 2013 10:18 PM

Plant-parasitic nematodes are aptly described as a farmer's hidden enemy

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CLE Signaling Systems During Plant Development and Nematode Infection

CLE Signaling Systems During Plant Development and Nematode Infection | Plant Research Topics | Scoop.it
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MPMI: The immunity regulator BAK1 contributes to resistance against diverse RNA viruses (2013)

MPMI: The immunity regulator BAK1 contributes to resistance against diverse RNA viruses (2013) | Plant Research Topics | Scoop.it

The plant’s innate immune system detects potential biotic threats through recognition of microbe-associated molecular patterns (MAMPs), or danger-associated molecular patterns (DAMPs), by pattern recognition receptors (PRRs). A central regulator of pattern-triggered immunity (PTI) is the BRI1 associated kinase 1 (BAK1) which undergoes complex formation with PRRs upon ligand binding. Although viral patterns inducing PTI are well known from animal systems, nothing similar has been reported for plants. Antiviral defense in plants is rather thought to be mediated by posttranscriptional gene silencing of viral RNA, or through effector-triggered immunity, i.e. recognition of virus-specific "effectors" by resistance proteins. Nevertheless, infection by compatible viruses can also lead to the induction of defense gene expression, indicating that plants may also recognize viruses through PTI. Here we show that PTI, or at least the presence of the regulator BAK1, is important for antiviral defense of Arabidopsis plants. Arabidopsis bak1 mutants show increased susceptibility to three different RNA viruses during compatible interactions. Furthermore, crude viral extracts, but not purified virions, induce several PTI marker responses in a BAK1-dependent manner. Overall, we conclude that BAK1-dependent PTI contributes to antiviral resistance in plants.


Via Kamoun Lab @ TSL
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Science: Is There Social RNA? (2013)

Science: Is There Social RNA? (2013) | Plant Research Topics | Scoop.it

Our understanding of the forms, functions, and movement of RNA continues to expand. Not only can RNA control gene expression by multiple mechanisms within a cell, it appears to travel outside the cell within an organism as well. This raises the interesting question of whether the RNA world extends beyond the boundaries of the organism. Can RNA traffic integrate an organism into its environment—is there “social RNA”? Examining the mechanism of RNA interference (RNAi) may be a good route for seeking the answer.


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J. Exp. Bot.: Pathogen-associated molecular pattern-triggered immunity and resistance to the root pathogen Phytophthora parasitica in Arabidopsis (2013)

J. Exp. Bot.: Pathogen-associated molecular pattern-triggered immunity and resistance to the root pathogen Phytophthora parasitica in Arabidopsis (2013) | Plant Research Topics | Scoop.it

The cellulose binding elicitor lectin (CBEL) of the genus Phytophthora induces necrosis and immune responses in several plant species, including Arabidopsis thaliana. However, the role of CBEL-induced responses in the outcome of the interaction is still unclear. This study shows that some of CBEL-induced defence responses, but not necrosis, required the receptor-like kinase BAK1, a general regulator of basal immunity in Arabidopsis, and the production of a reactive oxygen burst mediated by respiratory burst oxidases homologues (RBOH). Screening of a core collection of 48 Arabidopsis ecotypes using CBEL uncovered a large variability in CBEL-induced necrotic responses. Analysis of non-responsive CBEL lines Ws-4, Oy-0, and Bla-1 revealed that Ws-4 and Oy-0 were also impaired in the production of the oxidative burst and expression of defence genes, whereas Bla-1 was partially affected in these responses. Infection tests using two Phytophthora parasitica strains, Pp310 and Ppn0, virulent and avirulent, respectively, on the Col-0 line showed that BAK1 and RBOH mutants were susceptible to Ppn0, suggesting that some immune responses controlled by these genes, but not CBEL-induced cell death, are required for Phytophthora parasitica resistance. However, Ws-4, Oy-0, and Bla-1 lines were not affected in Ppn0 resistance, showing that natural variability in CBEL responsiveness is not correlated to Phytophthora susceptibility. Overall, the results uncover a BAK1- and RBOH-dependent CBEL-triggered immunity essential for Phytophthora resistance and suggest that natural quantitative variation of basal immunity triggered by conserved general elicitors such as CBEL does not correlate to Phytophthora susceptibility.

 

Mathieu Larroque, Elodie Belmas, Thomas Martinez, Sophie Vergnes, Nathalie Ladouce, Claude Lafitte, Elodie Gaulin, and Bernard Dumas


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PLOS ONE: Genetically Modified Crops and Food Security

PLOS ONE: Genetically Modified Crops and Food Security | Plant Research Topics | Scoop.it

The role of genetically modified (GM) crops for food security is the subject of public controversy. GM crops could contribute to food production increases and higher food availability. There may also be impacts on food quality and nutrient composition. Finally, growing GM crops may influence farmers’ income and thus their economic access to food. Smallholder farmers make up a large proportion of the undernourished people worldwide. Our study focuses on this latter aspect and provides the first ex post analysis of food security impacts of GM crops at the micro level. We use comprehensive panel data collected over several years from farm households in India, where insect-resistant GM cotton has been widely adopted. Controlling for other factors, the adoption of GM cotton has significantly improved calorie consumption and dietary quality, resulting from increased family incomes. This technology has reduced food insecurity by 15–20% among cotton-producing households. GM crops alone will not solve the hunger problem, but they can be an important component in a broader food security strategy.

 

 


Via Jean-Pierre Zryd
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