Plant, Insect and Microbe Interactions
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Comparison of fitness traits and their plasticity on multiple plants for Sitobion avenae infected and cured of a secondary endosymbiont

Comparison of fitness traits and their plasticity on multiple plants for Sitobion avenae infected and cured of a secondary endosymbiont | Plant, Insect and Microbe Interactions | Scoop.it
Regiella insecticola has been found to enhance the performance of host aphids on certain plants, but its functional role in adaptation of host aphids to plants is still controversial. Here we evaluate the impacts of R. insecticola infections on vita
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A highly infective plant-associated bacterium influences reproductive rates in pea aphids

A highly infective plant-associated bacterium influences reproductive rates in pea aphids | Plant, Insect and Microbe Interactions | Scoop.it

Pea aphids, Acyrthosiphon pisum, have the potential to increase reproduction as a defence against pathogens, though how frequently this occurs or how infection with live pathogens influences this response is not well understood. Here we determine the minimum infective dose of an environmentally common bacterium and possible aphid pathogen, Pseudomonas syringae, to determine the likelihood of pathogenic effects to pea aphids. Additionally, we used P. syringae infection to investigate how live pathogens may alter reproductive rates. We found that oral bacterial exposure decreased subsequent survival of aphids in a dose-dependent manner and we estimate that ingestion of less than 10 bacterial cells is sufficient to increase aphid mortality. Pathogen dose was positively related to aphid reproduction. Aphids exposed to low bacterial doses showed decreased, although statistically indistinguishable, fecundity compared to controls. Aphids exposed to high doses reproduced significantly more than low dose treatments and also more, but not significantly so, than controls. These results are consistent with previous studies suggesting that pea aphids may use fecundity compensation as a response to pathogens. Consequently, even low levels of exposure to a common plant-associated bacterium may therefore have significant effects on pea aphid survival and reproduction.

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Condition-dependent alteration of cellular immunity by secondary symbionts in the pea aphid, Acyrthosiphon pisum

Endosymbionts can fundamentally alter host physiology. Whether such changes are beneficial or detrimental
to one or both partners may depend on the dynamics of the symbiotic relationship. Here we
investigate the relationship between facultative symbionts and host immune responses. The pea aphid,
Acyrthosiphon pisum, maintains an obligate primary symbiont, but may also harbour one or more facultative,
secondary symbionts. Given their more transient nature and relatively recent adoption of a symbiotic
lifestyle compared to primary symbionts, secondary symbionts may present a challenge for the
host immune system. We assessed the response of several key components of the cellular immune system
(phenoloxidase activity, encapsulation, immune cell counts) in the presence of alternative secondary
symbionts, investigating the role of host and secondary symbiont genotype in specific responses. There
was no effect of secondary symbiont presence on the phenoloxidase response, but we found variation
in the encapsulation response and in immune cell counts based largely on the secondary symbiont.
Host genotype was less influential in determining immunity outcomes. Our results highlight the importance
of secondary symbionts in shaping host immunity. Understanding the complex physiological
responses that can be propagated by host-symbiont associations has important consequences for host
ecology, including symbiont and pathogen transmission dynamics.

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Insect Gut Symbiont Susceptibility to Host Antimicrobial Peptides Caused by Alteration of the Bacterial Cell Envelope

Capsule

Background: The elucidation of molecular changes of symbionts is important for understanding symbiotic adaptation.

Results: Insect gut symbionts are highly susceptible to host immunity because of dramatic cell envelope changes.

Conclusion: Cell envelope changes in gut symbionts are required for successful symbiosis with hosts.

Significance: Biochemical analyses of intact gut symbionts revealed a novel mechanism of gut symbiosis.

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Is there a role for symbiotic bacteria in plant virus transmission by insects?

Highlights•

Insect-borne, circulative plant viruses exploit existing pathways in their vectors to promote plant-to-plant spread.

Conflicting evidence exists regarding the role of insect bacterial symbionts in circulative plant virus transmission.

The involvement of GroEL in transmission is difficult to assess because GroEL antibodies cross-react and GroEL is a chaperone.

A simple test can determine the relative contribution of a bacterial symbiont to plant virus transmission by insects.

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Found and lost: the fates of horizontally acquired genes in arthropod-symbiotic Spiroplasma

Horizontal gene transfer (HGT) is an important mechanism that contributed to biological diversity, particularly in bacteria. Through acquisition of novel genes, the recipient cell may change its ecological preference and the process could promote speciation. In this study, we determined the complete genome sequence of two Spiroplasma species for comparative analyses and inferred the putative gene gains and losses. Although most Spiroplasma species are symbionts of terrestrial insects, S. eriocheiris has evolved to be a lethal pathogen of freshwater crustaceans. We found that ~7% of the genes in this genome may have originated from HGT and these genes expanded the metabolic capacity of this organism. Through comparison with the closely related S. atrichopogonis, as well as other more divergent lineages, our results indicated that these HGT events could be traced back to the most recent common ancestor (MRCA) of these two species. However, most of these horizontally acquired genes have been pseudogenized in S. atrichopogonis, suggesting that they did not contribute to the fitness of this lineage that maintained the association with terrestrial insects. Thus, accumulation of small deletions that disrupted these foreign genes was not countered by natural selection. On the other hand, the long-term survival of these horizontally acquired genes in the S. eriocheiris genome hinted that they might play a role in the ecological shift of this species. Finally, the implications of these findings and the conflicts among gene content, 16S rRNA gene sequencing, and serological typing, are discussed in light of defining bacterial species.

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Dheilly Nolwenn's curator insight, October 29, 2015 5:04 PM

Horizontal gene tranfer could have contributed to the transition of Spiroplasma from mutualism to parasitism

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BBC: France acts against olive disease outbreak in Corsica (2015)

BBC: France acts against olive disease outbreak in Corsica (2015) | Plant, Insect and Microbe Interactions | Scoop.it

A bacterial infection ravaging olive trees in the far south of Italy has spread to Corsica, where emergency measures are being implemented.

 

Xylella fastidiosa, spread by insects, was found at Propriano in southern Corsica. The bacterium can also attack citrus trees and vineyards.

 

France has destroyed plants around the infected bush found in Propriano.

 

Xylella is one of the biggest disease threats to plants worldwide, the European Commission says.

 

There is no effective treatment for infected plants and new Commission regulations say the only solution is to destroy them and establish Xylella-free buffer zones around them.

 

Corsica - a Mediterranean island near Italy - has a small olive oil industry, with about 500 employees and more than 2,000ha (4,940 acres) of trees.

 

But the bacterium is a threat to about 300 plant species. It was first detected on the island last week.

 

On Wednesday France's Agriculture Minister Stephane Le Foll visited Propriano and pledged "a total commitment" to isolating the outbreak.

 

French authorities suspect that the bacterium arrived via a ferry from the nearby Italian island of Sardinia.

 

French health inspectors are checking ferry passengers arriving at the small Corsican port of Bonifacio, in an effort to prevent any further Xylella contamination.


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A facultative endosymbiont in aphids can provide diverse ecological benefits. - PubMed - NCBI

Abstract

Ecologically important traits of insects are often affected by facultative bacterial endosymbionts. This is best studied in the pea aphid Acyrthosiphon pisum, which is frequently infected by one or more of eight facultative symbiont species. Many of these symbiont species have been shown to provide one ecological benefit, but we have little understanding of the range of effects that a single strain can have. Here, we describe the phenotypes conferred by three strains of the recently discovered bacterium known as X-type (Enterobacteriaceae), each in their original aphid genotype which also carries a Spiroplasma symbiont. All comparisons are made between aphids at that are coinfected with Spiroplasma and X-type and aphids of the same genotype that harbor only Spiroplasma. We show that in all cases, infection with X-type protects aphids from the lethal fungal pathogen Pandora neoaphidis, and in two cases resistance to the parasitoid Aphidius ervi also increases. X-type can additionally affect aphid stress responses - the presence of X-type increased reproduction after the aphids were heat stressed. Two of the three strains of X-type are able to provide all of these benefits. Under benign conditions the aphids tended to suffer from reduced fecundity when harboring X-type, a mechanism that might maintain intermediate frequencies in field populations. These findings highlight that a single strain of a facultative endosymbiont has the potential to provide diverse benefits to its aphid host. This article is protected by copyright. All rights reserved.

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Dheilly Nolwenn's curator insight, October 29, 2015 5:08 PM

This study should pressure researchers into reconsidering the ecological effect of any symbiont.

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The first crop plant genetically engineered to release an insect pheromone for defence : Scientific Reports : Nature Publishing Group

The first crop plant genetically engineered to release an insect pheromone for defence : Scientific Reports : Nature Publishing Group | Plant, Insect and Microbe Interactions | Scoop.it

Insect pheromones offer potential for managing pests of crop plants. Volatility and instability are problems for deployment in agriculture but could be solved by expressing genes for the biosynthesis of pheromones in the crop plants. This has now been achieved by genetically engineering a hexaploid variety of wheat to release (E)-β-farnesene (Eβf), the alarm pheromone for many pest aphids, using a synthetic gene based on a sequence from peppermint with a plastid targeting amino acid sequence, with or without a gene for biosynthesis of the precursor farnesyl diphosphate. Pure Eβf was produced in stably transformed wheat lines with no other detectable phenotype but requiring targeting of the gene produced to the plastid. In laboratory behavioural assays, three species of cereal aphids were repelled and foraging was increased for a parasitic natural enemy. Although these studies show considerable potential for aphid control, field trials employing the single and double constructs showed no reduction in aphids or increase in parasitism. Insect numbers were low and climatic conditions erratic suggesting the need for further trials or a closer imitation, in the plant, of alarm pheromone release.

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Two host clades, two bacterial arsenals: evolution through gene losses in facultative endosymbionts

Abstract

Bacterial endosymbiosis is an important evolutionary process in insects, which can harbor both obligate and facultative symbionts. The evolution of these symbionts is driven by evolutionary convergence, and they exhibit among the tiniest genomes in prokaryotes. The large host spectrum of facultative symbionts and the high diversity of strategies they use to infect new hosts probably impacts the evolution of their genome and explains why they undergo less severe genomic erosion than obligate symbionts. Candidatus Hamiltonella defensa is suitable for the investigation of the genomic evolution of facultative symbionts because the bacteria are engaged in specific relationships in two clades of insects. In aphids, H. defensa is found in several species with an intermediate prevalence and confers protection against parasitoids. In whiteflies, H. defensa is almost fixed in some species of Bemisia tabaci, which suggests an important role of and a transition towards obligate symbiosis. In the present study, comparisons of the genome of H. defensa present in two B. tabaci species (MEAM1 and MED) and in the aphid Acyrthosiphon pisum revealed that they belong to two distinct clades and underwent specific gene losses. In aphids, it contains highly virulent factors that could allow protection and horizontal transfers. In whiteflies, the genome lost these factors and seems to have a limited ability to acquire genes. However it contains genes that could be involved in the production of essential nutrients, which is consistent with a primordial role for this symbiont. In conclusion, while both lineages of H. defensa have mutualistic interactions with their hosts, their genomes follow distinct evolutionary trajectories that reflect their phenotype and could have important consequences on their evolvability.

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

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

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

 

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


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pearfriday's comment, June 4, 2015 6:09 AM
Thats amazing...
gobsmackedmumble's comment, July 1, 2015 6:32 AM
Thats striking...
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Full crop protection from an insect pest by expression of long double-stranded RNAs in plastids

Double-stranded RNAs (dsRNAs) targeted against essential genes can trigger a
lethal RNA interference (RNAi) response in insect pests. The application of this
concept in plant protection is hampered by the presence of an endogenous plant
RNAi pathway that processes dsRNAs into short interfering RNAs.We found that long
dsRNAs can be stably produced in chloroplasts, a cellular compartment that appears to
lack an RNAi machinery. When expressed from the chloroplast genome, dsRNAs accumulated
to as much as 0.4% of the total cellular RNA.Transplastomic potato plants producing dsRNAs
targeted against the b-actin gene of the Colorado potato beetle, a notorious agricultural
pest, were protected from herbivory and were lethal to its larvae. Thus, chloroplast
expression of long dsRNAs can provide crop protection without chemical pesticides.

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A Massive Expansion of Effector Genes Underlies Gall-Formation in the Wheat Pest Mayetiola destructor: Current Biology

Highlights•The plant-galling Mayetiola destructor genome is replete with putative effector genes•The SSGP-71 effector gene family is the largest known arthropod gene family•SSGP-71 genes encode E3-ubiquitin-ligase mimics•Two SSGP-71 genes elicit effector-triggered immunity in resistant wheatSummary

Gall-forming arthropods are highly specialized herbivores that, in combination with their hosts, produce extended phenotypes with unique morphologies [ 1 ]. Many are economically important, and others have improved our understanding of ecology and adaptive radiation [ 2 ]. However, the mechanisms that these arthropods use to induce plant galls are poorly understood. We sequenced the genome of the Hessian fly (Mayetiola destructor; Diptera: Cecidomyiidae), a plant parasitic gall midge and a pest of wheat (Triticum spp.), with the aim of identifying genic modifications that contribute to its plant-parasitic lifestyle. Among several adaptive modifications, we discovered an expansive reservoir of potential effector proteins. Nearly 5% of the 20,163 predicted gene models matched putative effector gene transcripts present in the M. destructor larval salivary gland. Another 466 putative effectors were discovered among the genes that have no sequence similarities in other organisms. The largest known arthropod gene family (family SSGP-71) was also discovered within the effector reservoir. SSGP-71 proteins lack sequence homologies to other proteins, but their structures resemble both ubiquitin E3 ligases in plants and E3-ligase-mimicking effectors in plant pathogenic bacteria. SSGP-71 proteins and wheat Skp proteins interact in vivo. Mutations in different SSGP-71 genes avoid the effector-triggered immunity that is directed by the wheat resistance genes H6 and H9. Results point to effectors as the agents responsible for arthropod-induced plant gall formation.

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Symbiont-mediated RNA interference in insects

Symbiont-mediated RNA interference in insects | Plant, Insect and Microbe Interactions | Scoop.it
Abstract

RNA interference (RNAi) methods for insects are often limited by problems with double-stranded (ds) RNA delivery, which restricts reverse genetics studies and the development of RNAi-based biocides. We therefore delegated to insect symbiotic bacteria the task of: (i) constitutive dsRNA synthesis and (ii) trauma-free delivery. RNaseIII-deficient, dsRNA-expressing bacterial strains were created from the symbionts of two very diverse pest species: a long-lived blood-sucking bug, Rhodnius prolixus, and a short-lived globally invasive polyphagous agricultural pest, western flower thrips (Frankliniella occidentalis). When ingested, the manipulated bacteria colonized the insects, successfully competed with the wild-type microflora, and sustainably mediated systemic knockdown phenotypes that were horizontally transmissible. This represents a significant advance in the ability to deliver RNAi, potentially to a large range of non-model insects.

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Hybridization of powdery mildew strains gives rise to pathogens on novel agricultural crop species : Nature Genetics : Nature Publishing Group

Hybridization of powdery mildew strains gives rise to pathogens on novel agricultural crop species : Nature Genetics : Nature Publishing Group | Plant, Insect and Microbe Interactions | Scoop.it

Beat Keller, Thomas Wicker and colleagues compare the genomes of 46 isolates of powdery mildew, Blumeria graminis. They find that B. graminis f. sp. triticale, a pathogen growing on triticale (a wheat [times] rye hybrid plant), is a hybrid of B.


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Aphids Pick Their Poison: Selective Sequestration of Plant Chemicals Affects Host Plant Use in a Specialist Herbivore - Online First - Springer

Aphids Pick Their Poison: Selective Sequestration of Plant Chemicals Affects Host Plant Use in a Specialist Herbivore - Online First - Springer | Plant, Insect and Microbe Interactions | Scoop.it

In some plant-insect interactions, specialist herbivores exploit the chemical defenses of their food plant to their own advantage. Brassica plants produce glucosinolates that are broken down into defensive toxins when tissue is damaged, but the specialist aphid, Brevicoryne brassicae, uses these chemicals against its own natural enemies by becoming a “walking mustard-oil bomb”. Analysis of glucosinolate concentrations in plant tissue and associated aphid colonies reveals that not only do aphids sequester glucosinolates, but they do so selectively. Aphids specifically accumulate sinigrin to high concentrations while preferentially excreting a structurally similar glucosinolate, progoitrin. Surveys of aphid infestation in wild populations of Brassica oleracea show that this pattern of sequestration and excretion maps onto host plant use. The probability of aphid infestation decreases with increasing concentrations of progoitrin in plants. Brassica brassicae, therefore, appear to select among food plants according to plant secondary metabolite profiles, and selectively store only some compounds that are used against their own enemies. The results demonstrate chemical and behavioral mechanisms that help to explain evidence of geographic patterns and evolutionary dynamics in Brassica-aphid interactions.

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Recent Advances in the Integrative Nutrition of Arthropods - Annual Review of Entomology, 60(1):293

In this review we highlight recent advances in four areas in which nutrition shapes the relationships between organisms: between plants and herbivores, between hosts and their microbiota, between individuals within groups and societies, and between species within food webs. We demonstrate that taking an explicitly multidimensional view of nutrition and employing the logic of the geometric framework for nutrition provide novel insights and offer a means of integration across different levels of organization, from individuals to ecosystems.

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Lineage-specific patterns of genome deterioration in obligate symbionts of sharpshooter leafhoppers

Plant sap-feeding insects (Hemiptera) rely on obligate bacterial symbionts that provision nutrients. Some of these symbionts are ancient and have evolved tiny genomes, while others are younger and retain larger, dynamic genomes. Baumannia cicadellinicola, an obligate symbiont of sharpshooter leafhoppers, is derived from a relatively recent symbiont replacement. To better understand evolutionary decay of genomes, we compared Baumannia from three host species. A newly sequenced genome for Baumannia from the green sharpshooter (B-GSS) was compared to genomes of Baumannia from the blue-green sharpshooter (B-BGSS, 759 kilobases [kb]) and of the glassy-winged sharpshooter (B-GWSS, 680 kb). B-GSS has the smallest Baumannia genome sequenced to date (633 kb), with only three unique genes, all involved in membrane function. It has lost nearly all pathways involved in vitamin and cofactor synthesis, as well as amino acid biosynthetic pathways that are redundant with pathways of the host or the symbiotic partner, Sulcia muelleri. The entire biosynthetic pathway for methionine is eliminated, suggesting that methionine has become a dietary requirement for hosts. B-GSS and B-BGSS share 33 genes involved in bacterial functions (e.g., cell division, membrane synthesis, metabolite transport, etc.) that are lost from the more distantly related B-GWSS and most other tiny genome symbionts. Finally, pairwise divergence estimates indicate that B-GSS has experienced a lineage-specific increase in substitution rates. This increase correlates with accelerated protein-level changes and widespread gene loss. Thus, the mode and tempo of genome reduction vary widely among symbiont lineages and result in wide variation in metabolic capabilities across hosts.

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Xylella Fastidiosa : Avis d'information aux voyageurs (2015)

Xylella Fastidiosa : Avis d'information aux voyageurs (2015) | Plant, Insect and Microbe Interactions | Scoop.it

La Préfecture de Haute-Corse informe les voyageurs de l'interdiction d'introduction des végétaux dans le cadre de la lutte contre la Xylella Fastidiosa.

 

The prefecture of Haute-Corse inform passengers of the prohibition of introduction of plants as part of the fight against Xylella fastidiosa.


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Olive Oil Times: European Commission Publishes Xylella Fastidiosa Factsheet (2015)

Olive Oil Times: European Commission Publishes Xylella Fastidiosa Factsheet (2015) | Plant, Insect and Microbe Interactions | Scoop.it

The European Commission recently published a question-and-answer factsheet on the bacterium Xylella fastidiosa on its Food Safety website.


The Xylella fastidiosa bacterium has been responsible for the destruction of olive groves in Italy’s Apulia region resulting in the adoption of urgent European Union (EU) measures to try to combat and contain the outbreak and prevent its spread to other member states of the EU.


The introduction to the factsheet points out that Xylella fastidiosa is one of the world’s deadliest plant bacteria which can have an enormous economic impact, and confirms that the outbreak affecting olive groves in Apulia is the only confirmed outbreak in the EU.


It explains that there are four different subspecies of Xylella fastidiosa and that the strain identified in Apulia is a new genetic variant which has so far only attacked olive and plum trees. The bacterium is spread by spittlebugs, cicadas and sharpshooters which feed on the infected plant tissue.


A study by the EU’s Food Safety Authority had warned that the risk of the deadly bacterium spreading to regions in other EU countries was very high. In the face of uncertainty and misinformation about the bacterium and in an effort to educate the general public, the European Commission has released the factsheet which answers six questions:


What measures have been taken by the Commission to prevent further spread into the Union territory?
How will the Commission prevent the further introduction of Xylella fastidiosa from non-EU countries?
Is there any financial support available for farmers affected by Xylella fastidiosa
Could there be other causes for the decline of olive trees since some scientific papers argue that it is caused by a combination of fungi which weaken the plants before being attacked by Xylella fastidiosa, and specific treatments seem to exist?
How can Xylella fastidiosa be controlled?
What can I do as citizen to prevent further spread of Xylella fastidiosa in the EU?


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A Secreted MIF Cytokine Enables Aphid Feeding and Represses Plant Immune Responses: Current Biology

A Secreted MIF Cytokine Enables Aphid Feeding and Represses Plant Immune Responses: Current Biology | Plant, Insect and Microbe Interactions | Scoop.it
Highlights•A macrophage migration inhibitory factor (MIF) is secreted in aphid saliva•Expression of aphid MIFs in planta inhibits plant immune responses•Expression of aphid MIF1 is necessary for aphid survival and feeding on a host plantSummary

Aphids attack virtually all plant species and cause serious crop damages in agriculture [ 1 ]. Despite their dramatic impact on food production, little is known about the molecular processes that allow aphids to exploit their host plants. To date, few aphid salivary proteins have been identified that are essential for aphid feeding, and their nature and function remain largely unknown [ 2–4 ]. Here, we show that a macrophage migration inhibitory factor (MIF) is secreted in aphid saliva. In vertebrates, MIFs are important pro-inflammatory cytokines regulating immune responses [ 5, 6 ]. MIF proteins are also secreted by parasites of vertebrates, including nematodes, ticks, and protozoa, and participate in the modulation of host immune responses [ 7–9 ]. The finding that a plant parasite secretes a MIF protein prompted us to question the role of the cytokine in the plant-aphid interaction. We show here that expression of MIF genes is crucial for aphid survival, fecundity, and feeding on a host plant. The ectopic expression of aphid MIFs in leaf tissues inhibits major plant immune responses, such as the expression of defense-related genes, callose deposition, and hypersensitive cell death. Functional complementation analyses in vivo allowed demonstrating that MIF1 is the member of the MIF protein family that allows aphids to exploit their host plants. To our knowledge, this is the first report of a cytokine that is secreted by a parasite to modulate plant immune responses. Our findings suggest a so-far unsuspected conservation of infection strategies among parasites of animal and plant species.

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BMC Genomics | Abstract | The genome of Diuraphis noxia, a global aphid pest of small grains

The Russian wheat aphid, Diuraphis noxia Kurdjumov, is one of the most important pests of small grains throughout the temperate regions of the world. This phytotoxic aphid causes severe systemic damage symptoms in wheat, barley, and other small grains as a direct result of the salivary proteins it injects into the plant while feeding.
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Nature Biotechnology: Engineering insect-free cereals (2015)

Nature Biotechnology: Engineering insect-free cereals (2015) | Plant, Insect and Microbe Interactions | Scoop.it

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

 

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

 

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

 

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

 

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

 

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


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Insecticidal RNA, the long and short of it

Insecticidal RNA, the long and short of it | Plant, Insect and Microbe Interactions | Scoop.it

Insects cost the agricultural sector billions of dollars every year in lost crop yields and insecticide expenditures. The continued use of chemical insecticides has inadvertently selected for more resistant pest strains, prompting higher doses and more frequent applications to control them. The advent of transgenic plants, such as those expressing insecticidal Bacillus thuringiensis (Bt) toxins, reduces the use of chemicals while offering protection to some crops (1), but not all insects are affected by Bt toxins, and continued use of Bt technologies will eventually see the rise of Bt-resistant insects. To stay ahead of the pests will require additional technologies. On page 991 of this issue, Zhang et al. (2) describe a clever modification to an existing transgenic plant technology that produces insecticidal RNAs. The trick is to express lethal RNA in the plant's photosynthetic organelles, the chloroplasts.

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Current Opinion in Insect Science: Disruption of insect transmission of plant viruses (2015)

Current Opinion in Insect Science: Disruption of insect transmission of plant viruses (2015) | Plant, Insect and Microbe Interactions | Scoop.it

Plant-infecting viruses are transmitted by a diverse array of organisms including insects, mites, nematodes, fungi, and plasmodiophorids. Virus interactions with these vectors are diverse, but there are some commonalities. Generally the infection cycle begins with the vector encountering the virus in the plant and the virus is acquired by the vector. The virus must then persist in or on the vector long enough for the virus to be transported to a new host and delivered into the plant cell. Plant viruses rely on their vectors for breaching the plant cell wall to be delivered directly into the cytosol. In most cases, viral capsid or membrane glycoproteins are the specific viral proteins that are required for transmission and determinants of vector specificity. Specific molecules in vectors also interact with the virus and while there are few-identified to no-identified receptors, candidate recognition molecules are being further explored in these systems. Due to the specificity of virus transmission by vectors, there are defined steps that represent good targets for interdiction strategies to disrupt the disease cycle. This review focuses on new technologies that aim to disrupt the virus–vector interaction and focuses on a few of the well-characterized virus–vector interactions in the field. In closing, we discuss the importance of integration of these technologies with current methods for plant virus disease control.


Via Kamoun Lab @ TSL
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Steve Marek's curator insight, February 26, 2015 9:27 AM

Not fungal, but still an excellent review with great insights on important plant pathosystems.

Bharat Employment's curator insight, February 27, 2015 4:46 AM

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