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Plant, Insect and Microbe Interactions
New and old articles on plant-insect-microbe interactions
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BOTRYTIS-INDUCED KINASE1 Modulates Arabidopsis Resistance to Green Peach Aphids via PHYTOALEXIN DEFICIENT4

BOTRYTIS-INDUCED KINASE1 (BIK1) plays important roles in induced defense against fungal and bacterial pathogens in
Arabidopsis (Arabidopsis thaliana). Its tomato (Solanum lycopersicum) homolog is required for host plant resistance to a chewing
insect herbivore. However, it remains unknown whether BIK1 functions in plant defense against aphids, a group of insects with
a specialized phloem sap-feeding style. In this study, the potential role of BIK1 was investigated in Arabidopsis infested with the
green peach aphid (Myzus persicae). In contrast to the previously reported positive role of intact BIK1 in defense response, loss of
BIK1 function adversely impacted aphid settling, feeding, and reproduction. Relative to wild-type plants, bik1 displayed higher
aphid-induced hydrogen peroxide accumulation and more severe lesions, resembling a hypersensitive response (HR) against
pathogens. These symptoms were limited to the infested leaves. The bik1 mutant showed elevated basal as well as induced
salicylic acid and ethylene accumulation. Intriguingly, elevated salicylic acid levels did not contribute to the HR-like symptoms
or to the heightened aphid resistance associated with the bik1 mutant. Elevated ethylene levels in bik1 accounted for an initial,
short-term repellence. Introducing a loss-of-function mutation in the aphid resistance and senescence-promoting gene PHYTOALEXIN
DEFICIENT4 (PAD4) into the bik1 background blocked both aphid resistance and HR-like symptoms, indicating bik1-mediated
resistance to aphids is PAD4 dependent. Taken together, Arabidopsis BIK1 confers susceptibility to aphid infestation through its
suppression of PAD4 expression. Furthermore, the results underscore the role of reactive oxygen species and cell death in plant
defense against phloem sap-feeding insects.

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Widespread expression of conserved small RNAs in small symbiont genomes.

Genome architecture of a microbe markedly changes when it transitions from a free-living lifestyle to an obligate symbiotic association within eukaryotic cells. These symbiont genomes experience numerous rearrangements and massive gene loss, which is expected to radically alter gene regulatory networks compared with those of free-living relatives. As such, it remains unclear whether and how these small symbiont genomes regulate gene expression. Here, using a label-free mass-spec quantification approach we found that differential protein regulation occurs in Buchnera, a model symbiont with a reduced genome, when it transitions between two distinct life stages. However, differential mRNA expression could not be detected between Buchnera life stages, despite the presence of a small number of putative transcriptional regulators. Instead a comparative analysis of small RNA expression profiles among five divergent Buchnera lineages, spanning a variety of Buchnera life stages, reveals 140 novel intergenic and antisense small RNAs and 517 untranslated regions that were significantly expressed, some of which have been conserved for ~65 million years. In addition, the majority of these small RNAs exhibit both sequence covariation and thermodynamic stability, indicators of a potential structural RNA role. Together, these data suggest that gene regulation at the post-transcriptional level may be important in Buchnera. This is the first study to empirically identify Buchnera small RNAs, and we propose that these novel small RNAs may facilitate post-transcriptional regulation through translational inhibition/activation, and/or transcript stability. Ultimately, post-transcriptional regulation may shape metabolic complementation between Buchnera and its aphid host, thus impacting the animal’s ecology and evolution.

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Insect endosymbiont proliferation is limited by lipid availability

Insect endosymbiont proliferation is limited by lipid availability | Plant, Insect and Microbe Interactions | Scoop.it
Spiroplasma poulsonii is a maternally transmitted bacterial endosymbiont that is naturally associated with Drosophila melanogaster. S. poulsonii resides extracellularly in the hemolymph, where it must acquire metabolites to sustain proliferation. In this study, we find that Spiroplasma proliferation specifically depletes host hemolymph diacylglyceride, the major lipid class transported by the lipoprotein, Lpp. RNAi-mediated knockdown of Lpp expression, which reduces the amount of circulating lipids, inhibits Spiroplasma proliferation demonstrating that bacterial proliferation requires hemolymph-lipids. Altogether, our study shows that an insect endosymbiont acquires specific lipidic metabolites from the transport lipoproteins in the hemolymph of its host. In addition, we show that the proliferation of this endosymbiont is limited by the availability of hemolymph lipids. This feature could limit endosymbiont over-proliferation under conditions of host nutrient limitation as lipid availability is strongly influenced by the nutritional state. - See more at: http://elifesciences.org/content/early/2014/07/15/eLife.02964.abstract?maxtoshow=&HITS=10&hits=18&RESULTFORMAT=&andorexacttitle=and&andorexacttitleabs=and&fulltext=aphid%25252C%20insect&andorexactfulltext=or&searchid=1&usestrictdates=yes&resourcetype=HWCIT&ct=#sthash.AUZ3mHRb.dpufSpiroplasma poulsonii is a maternally transmitted bacterial endosymbiont that is naturally associated with Drosophila melanogaster. S. poulsonii resides extracellularly in the hemolymph, where it must acquire metabolites to sustain proliferation. In this study, we find that Spiroplasma proliferation specifically depletes host hemolymph diacylglyceride, the major lipid class transported by the lipoprotein, Lpp. RNAi-mediated knockdown of Lpp expression, which reduces the amount of circulating lipids, inhibits Spiroplasma proliferation demonstrating that bacterial proliferation requires hemolymph-lipids. Altogether, our study shows that an insect endosymbiont acquires specific lipidic metabolites from the transport lipoproteins in the hemolymph of its host. In addition, we show that the proliferation of this endosymbiont is limited by the availability of hemolymph lipids. This feature could limit endosymbiont over-proliferation under conditions of host nutrient limitation as lipid availability is strongly influenced by the nutritional state. - See more at: http://elifesciences.org/content/early/2014/07/15/eLife.02964.abstract?maxtoshow=&HITS=10&hits=18&RESULTFORMAT=&andorexacttitle=and&andorexacttitleabs=and&fulltext=aphid%25252C%20insect&andorexactfulltext=or&searchid=1&usestrictdates=yes&resourcetype=HWCIT&ct=#sthash.AUZ3mHRb.dpuf
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PLOS Biology : The Promise of Plant Translational Research (2014)

PLOS Biology : The Promise of Plant Translational Research (2014) | Plant, Insect and Microbe Interactions | Scoop.it

As the world's human population continues to expand, and as water resources come under increasing pressure and pathogens that cause devastating crop losses continue to spread in the face of increased global commerce and climate change, there is a pressing need for plant research to contribute solutions to improving food security in a sustainable and safe way.

 

Plant translational research - the development of basic plant research discoveries into technologies or approaches that improve agriculture - has a vital role to play in meeting these challenges, and given the importance of research in this field, PLOS believes that such work should be published in open access journals, ensuring that it reaches the widest possible audience without any barriers to access.

 

The technical advances highlighted in this PLOS Collection exemplify how basic research discoveries are being translated into methods to develop and improve, both agriculturally and environmentally, important crop traits.

 

At PLOS, we are committed to supporting breakthroughs in both basic and translational plant science. We encourage plant researchers to submit their high quality plant research and, in particular, plant research that has clear translational possibilities.

 

The Collection was produced with the support of The Bill & Melinda Gates Foundation.

 

The Collection will be updated periodically with new Plant Translational Research.

 

www.ploscollections.org/planttranslationalresearch


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Accelerated Evolution of Morph-Biased Genes in Pea Aphids

Accelerated Evolution of Morph-Biased Genes in Pea Aphids | Plant, Insect and Microbe Interactions | Scoop.it

Phenotypic plasticity, the production of alternative phenotypes (or morphs) from the same genotype due to environmental factors, results in some genes being expressed in a morph-biased manner. Theoretically, these morph-biased genes experience relaxed selection, the consequence of which is the buildup of slightly deleterious mutations at these genes. Over time, this is expected to result in increased protein divergence at these genes between species and a signature of relaxed purifying selection within species. Here we test these theoretical expectations using morph-biased genes in the pea aphid, a species that produces multiple morphs via polyphenism. We find that morph-biased genes exhibit faster rates of evolution (in terms of dN/dS) relative to unbiased genes and that divergence generally increases with increasing morph bias. Further, genes with expression biased toward rarer morphs (sexual females and males) show faster rates of evolution than genes expressed in the more common morph (asexual females), demonstrating that the amount of time a gene spends being expressed in a morph is associated with its rate of evolution. And finally, we show that genes expressed in the rarer morphs experience decreased purifying selection relative to unbiased genes, suggesting that it is a relaxation of purifying selection that contributes to their faster rates of evolution. Our results provide an important empirical look at the impact of phenotypic plasticity on gene evolution.

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Implication of the Bacterial Endosymbiont Rickettsia spp. in Interactions of the Whitefly Bemisia tabaci with Tomato yellow leaf curl virus

Implication of the Bacterial Endosymbiont Rickettsia spp. in Interactions of the Whitefly Bemisia tabaci with Tomato yellow leaf curl virus | Plant, Insect and Microbe Interactions | Scoop.it

Numerous animal and plant viruses are transmitted by arthropod vectors in a persistent, circulative manner. Tomato yellow leaf curl virus (TYLCV) is transmitted by the sweet potato whitefly Bemisia tabaci. We report here that infection with Rickettsia spp., a facultative endosymbiont of whiteflies, altered TYLCV-B. tabaci interactions. A B. tabaci strain infected with Rickettsia acquired more TYLCV from infected plants, retained the virus longer, and exhibited nearly double the transmission efficiency compared to an uninfected B. tabaci strain with the same genetic background. Temporal and spatial antagonistic relationships were discovered between Rickettsia and TYLCV within the whitefly. In different time course experiments, the levels of virus and Rickettsia within the insect were inversely correlated. Fluorescence in situ hybridization analysis of Rickettsia-infected midguts provided evidence for niche exclusion between Rickettsia and TYLCV. In particular, high levels of the bacterium in the midgut resulted in higher virus concentrations in the filter chamber, a favored site for virus translocation along the transmission pathway, whereas low levels of Rickettsia in the midgut resulted in an even distribution of the virus. Taken together, these results indicate that Rickettsia, by infecting the midgut, increases TYLCV transmission efficacy, adding further insights into the complex association between persistent plant viruses, their insect vectors, and microorganism tenants that reside within these insects.

IMPORTANCE Interest in bacterial endosymbionts in arthropods and many aspects of their host biology in agricultural and human health systems has been increasing. A recent and relevant studied example is the influence of Wolbachia on dengue virus transmission by mosquitoes. In parallel with our recently studied whitefly-Rickettsia-TYLCV system, other studies have shown that dengue virus levels in the mosquito vector are inversely correlated with bacterial load. Our work here presents evidence of unifying principles between vectors of plant and animal viruses in a role for endosymbionts in manipulating vector biology and pathogen transmission. Our results demonstrate the influence of an interesting and prominent bacterial endosymbiont in Bemisia tabaci in TYLCV transmission, a worldwide disease infecting tomatoes. Besides its agricultural importance, this system provides interesting insights into Bemisia interaction with these newly discovered endosymbionts.

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Analysis of the Salivary Gland Transcriptome of Frankliniella occidentalis

Analysis of the Salivary Gland Transcriptome of Frankliniella occidentalis | Plant, Insect and Microbe Interactions | Scoop.it

Saliva is known to play a crucial role in insect feeding behavior and virus transmission. Currently, little is known about the salivary glands and saliva of thrips, despite the fact that Frankliniella occidentalis (Pergande) (the western flower thrips) is a serious pest due to its destructive feeding, wide host range, and transmission of tospoviruses. As a first step towards characterizing thrips salivary gland functions, we sequenced the transcriptome of the primary salivary glands of F. occidentalis using short read sequencing (Illumina) technology. A de novo-assembled transcriptome revealed 31,392 high quality contigs with an average size of 605 bp. A total of 12,166 contigs had significant BLASTx or tBLASTx hits (E≤1.0E−6) to known proteins, whereas a high percentage (61.24%) of contigs had no apparent protein or nucleotide hits. Comparison of the F. occidentalis salivary gland transcriptome (sialotranscriptome) against a published F. occidentalis full body transcriptome assembled from Roche-454 reads revealed several contigs with putative annotations associated with salivary gland functions. KEGG pathway analysis of the sialotranscriptome revealed that the majority (18 out of the top 20 predicted KEGG pathways) of the salivary gland contig sequences match proteins involved in metabolism. We identified several genes likely to be involved in detoxification and inhibition of plant defense responses including aldehyde dehydrogenase, metalloprotease, glucose oxidase, glucose dehydrogenase, and regucalcin. We also identified several genes that may play a role in the extra-oral digestion of plant structural tissues including β-glucosidase and pectin lyase; and the extra-oral digestion of sugars, including α-amylase, maltase, sucrase, and α-glucosidase. This is the first analysis of a sialotranscriptome for any Thysanopteran species and it provides a foundational tool to further our understanding of how thrips interact with their plant hosts and the viruses they transmit.

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The genome of Cardinium cBtQ1 provides insights into genome reduction, symbiont motility and its settlement in Bemisia tabaci

The genome of Cardinium cBtQ1 provides insights into genome reduction, symbiont motility and its settlement in Bemisia tabaci | Plant, Insect and Microbe Interactions | Scoop.it

Many insects harbour inherited bacterial endosymbionts. Although some of them are not strictly essential and are considered facultative, they can be a key to host survival under specific environmental conditions, such as parasitoid attacks, climate changes or insecticide pressures. The whitefly Bemisia tabaci is top of the list of organisms inflicting agricultural damage and outbreaks, and changes in its distribution may be associated to global warming. In this work, we have sequenced and analysed the genome of Cardinium cBtQ1, a facultative bacterial endosymbiont of B. tabaci and propose that it belongs to a new taxonomic family, which also includes Candidatus Amoebophilus asiaticus and Cardinium cEper1, endosymbionts of amoeba and wasps, respectively. Reconstruction of their last common ancestors' gene contents revealed an initial massive gene loss from the free-living ancestor. This was followed in Cardinium by smaller losses, associated with settlement in arthropods. Some of these losses, affecting cofactor and amino acid biosynthetic encoding genes, took place in Cardinium cBtQ1 after its divergence from the Cardinium cEper1 lineage and were related to its settlement in the whitefly and its endosymbionts. Furthermore, the Cardinium cBtQ1 genome displays a large proportion of transposable elements, which have recently inactivated genes and produced chromosomal rearrangements. The genome also contains a chromosomal duplication and a multicopy plasmid, which harbours several genes putatively associated with gliding motility, as well as two other genes encoding proteins with potential insecticidal activity. As gene amplification is very rare in endosymbionts, an important function of these genes cannot be ruled out.

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Nature News: Bacterial tricks for turning plants into zombies (2014)

Nature News: Bacterial tricks for turning plants into zombies  (2014) | Plant, Insect and Microbe Interactions | Scoop.it

Many parasites commandeer the bodies of their hosts in order to spread. Examples of this include horsehair worms that reach water by forcing their cricket hosts to drown themselves, and liver flukes that drive infected ants to climb blades of grass, where cows can eat the insects, and so the flukes. But parasites can turn plants into zombies, too — and a team of scientists from the John Innes Centre in Norwich, UK, has now discovered how they do it.

 

When plants are infected by parasitic bacteria called phytoplasmas, their flowers turn into leafy shoots, their petals turn green and they develop a mass of shoots called ‘witches’ brooms’. This transformation sterilizes the plant, while attracting the sap-sucking insects that carry the bacteria to new hosts. “The plant appears alive, but it’s only there for the good of the pathogen,” says plant pathologist Saskia Hogenhout from the John Innes Centre in Norwich, UK. “In an evolutionary sense, the plant is dead and will not produce offspring.” “Many might baulk at the concept of a zombie plant because the idea of plants behaving is strange,” says David Hughes, a parasitologist at Pennsylvania State University in University Park. “But they do, and since they do, why wouldn't parasites have evolved to take over their behaviour, as they do for ants and crickets?”


Via Kamoun Lab @ TSL
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Microbial Pathogens Trigger Host DNA Double-Strand Breaks Whose Abundance Is Reduced by Plant Defense Responses

Microbial Pathogens Trigger Host DNA Double-Strand Breaks Whose Abundance Is Reduced by Plant Defense Responses | Plant, Insect and Microbe Interactions | Scoop.it
by Junqi Song, Andrew F. Bent
Immune responses and DNA damage repair are two fundamental processes that have been characterized extensively, but the links between them remain largely unknown.

Via IPM Lab
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Bacterial autolysins trim cell surface peptidoglycan to prevent detection by the Drosophila innate immune system

Bacterial autolysins trim cell surface peptidoglycan to prevent detection by the Drosophila innate immune system | Plant, Insect and Microbe Interactions | Scoop.it

Bacteria have to avoid recognition by the host immune system in order to establish a successful infection. Peptidoglycan, the principal constituent of virtually all bacterial surfaces, is a specific molecular signature recognized by dedicated host receptors, present in animals and plants, which trigger an immune response. Here we report that autolysins from Gram-positive pathogenic bacteria, enzymes capable of hydrolyzing peptidoglycan, have a major role in concealing this inflammatory molecule from Drosophila peptidoglycan recognition proteins (PGRPs). We show that autolysins trim the outermost peptidoglycan fragments and that in their absence bacterial virulence is impaired, as PGRPs can directly recognize leftover peptidoglycan extending beyond the external layers of bacterial proteins and polysaccharides. The activity of autolysins is not restricted to the producer cells but can also alter the surface of neighboring bacteria, facilitating the survival of the entire population in the infected host.

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New Phytologist: Cospeciation vs host-shift speciation: methods for testing, evidence from natural associations and relation to coevolution (2013)

New Phytologist: Cospeciation vs host-shift speciation: methods for testing, evidence from natural associations and relation to coevolution (2013) | Plant, Insect and Microbe Interactions | Scoop.it

Hosts and their symbionts are involved in intimate physiological and ecological interactions. The impact of these interactions on the evolution of each partner depends on the time-scale considered. Short-term dynamics – ‘coevolution’ in the narrow sense – has been reviewed elsewhere. We focus here on the long-term evolutionary dynamics of cospeciation and speciation following host shifts. Whether hosts and their symbionts speciate in parallel, by cospeciation, or through host shifts, is a key issue in host–symbiont evolution. In this review, we first outline approaches to compare divergence between pairwise associated groups of species, their advantages and pitfalls. We then consider recent insights into the long-term evolution of host–parasite and host–mutualist associations by critically reviewing the literature. We show that convincing cases of cospeciation are rare (7%) and that cophylogenetic methods overestimate the occurrence of such events. Finally, we examine the relationships between short-term coevolutionary dynamics and long-term patterns of diversification in host–symbiont associations. We review theoretical and experimental studies showing that short-term dynamics can foster parasite specialization, but that these events can occur following host shifts and do not necessarily involve cospeciation. Overall, there is now substantial evidence to suggest that coevolutionary dynamics of hosts and parasites do not favor long-term cospeciation.


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The bacterial communities in plant phloem-sap-feeding insects - Jing - 2014 - Molecular Ecology - Wiley Online Library

The bacterial communities in plant phloem-sap-feeding insects - Jing - 2014 - Molecular Ecology - Wiley Online Library | Plant, Insect and Microbe Interactions | Scoop.it

The resident microbiota of animals represents an important contribution to the global microbial diversity, but it is poorly known in many animals. This study investigated the bacterial diversity in plant phloem-sap-feeding whiteflies, aphids and psyllids by pyrosequencing bacterial 16S rRNA gene amplicons. After correction for sequencing error, just 3–7 bacterial operational taxonomic units were recovered from each insect sample sequenced to sufficient depth for saturation of rarefaction curves. Most samples were dominated by primary and secondary symbionts, which are localized to insect cells or the body cavity, indicative of a dearth of bacterial colonists of the gut lumen. Diversity indices of the bacterial communities (Shannon's index: 0.40–1.46, Simpson's index: 0.15–0.74) did not differ significantly between laboratory and field samples of the phloem-feeding insects, but were significantly lower than in drosophilid flies quantified by the same methods. Both the low bacterial content of the phloem sap diet and biological processes in the insect may contribute to the apparently low bacterial diversity in these phloem-feeding insects.

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Insect Gut Bacterial Diversity Determined by Environmental Habitat, Diet, Developmental Stage, and Phylogeny of Host

Insects are the most abundant animals on Earth, and the microbiota within their guts play important roles by engaging in beneficial and pathological interactions with these hosts. In this study, we comprehensively characterized insect-associated gut bacteria of 305 individuals belonging to 218 species in 21 taxonomic orders, using 454 pyrosequencing of 16S rRNA genes. In total, 174,374 sequence reads were obtained, identifying 9,301 bacterial operational taxonomic units (OTUs) at the 3% distance level from all samples, with an average of 84.3 (±97.7) OTUs per sample. The insect gut microbiota were dominated by Proteobacteria (62.1% of the total reads, including 14.1% Wolbachia sequences) and Firmicutes (20.7%). Significant differences were found in the relative abundances of anaerobes in insects and were classified according to the criteria of host environmental habitat, diet, developmental stage, and phylogeny. Gut bacterial diversity was significantly higher in omnivorous insects than in stenophagous (carnivorous and herbivorous) insects. This insect-order-spanning investigation of the gut microbiota provides insights into the relationships between insects and their gut bacterial communities.

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Factors limiting the spread of the protective symbiont Hamiltonella defensa in the aphid Aphis craccivora

Many insects are associated with heritable symbionts that mediate ecological interactions, including host protection against natural enemies. The cowpea aphid, Aphis craccivora, is a polyphagous pest that harbors Hamiltonella defensa, which defends against parasitic wasps. Despite these protective benefits this symbiont occurs only at intermediate frequencies in field populations. To identify factors constraining H. defensa invasion in Ap. craccivora, we estimated symbiont transmission rates, performed fitness assays, and measured infection dynamics in population cages to evaluate effects of infection. Similar to results with the pea aphid, Acyrthosiphon pisum, we found no consistent costs to infection using component fitness assays, but did identify clear costs to infection in population cages when no enemies are present. Maternal transmission rates of H. defensa in Ap. craccivora were high (ca. 99%), but not perfect. Transmission failures and infection costs likely limit the spread of protective H. defensa in Ap. craccivora. We also characterized several parameters of H. defensa infection potentially relevant to the protective phenotype. We confirmed the presence of H. defensa in aphid hemolymph, where it potentially interacts with endoparasites, and performed real-time qPCR to estimate symbiont and phage abundance during aphid development. We also examined strain variation of H. defensa and its bacteriophage at multiple loci and despite our lines being collected in different regions of North America they were infected with a nearly identical strains of H. defensa and APSE4 phage. The limited strain diversity observed for these defensive elements may result in relatively static protection profile for this defensive symbiosis.

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Transmission and retention of Salmone... [Appl Environ Microbiol. 2014] - PubMed - NCBI

Several pest insects of human and livestock habitations are known as vectors of Salmonella enterica; however, the role of plant-feeding insects as vectors of S. enterica to agricultural crops remains unexamined. Using a hemipteran insect pest-lettuce system, we investigated the potential for transmission and retention of S. enterica. Specifically, Macrosteles quadrilineatus and Myzus persicae were fed on S. enterica-inoculated lettuce leaf discs or artificial liquid diets confined in parafilm sachets to allow physical contact or exclusively oral ingestion of the pathogen, respectively. After a 24 h acquisition access period, insects were moved onto two consecutive non-inoculated leaf discs or liquid diets, and allowed a 24 h inoculation access period on each of the two discs or sachets. Similar proportions of individuals from both species ingested S. enterica after a 24 h acquisition access period from inoculated leaf discs, but a significantly higher proportion of M. quadrilineatus retained the pathogen internally after a 48 h inoculation access period. S. enterica was also recovered from the honeydew of both species. After a 48 h inoculation access period, bacteria were recovered from a significantly higher proportion of honeydew samples from M. quadrilineatus compared to M. persicae. The recovery of S. enterica from leaf discs and liquid diets post feeding demonstrated that both species of insects were capable of transmitting the bacteria in ways that are not limited to mechanical transmission. Overall, these results suggest that phytophagous insects may serve as potential vectors of S. enterica in association with plants.

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GroEL from the endosymbiont Buchnera aphidicola betrays the aphid by triggering plant defense

Aphids are sap-feeding plant pests and harbor the endosymbiont Buchnera aphidicola, which is essential for their fecundity and survival. During plant penetration and feeding, aphids secrete saliva that contains proteins predicted to alter plant defenses and metabolism. Plants recognize microbe-associated molecular patterns and induce pattern-triggered immunity (PTI). No aphid-associated molecular pattern has yet been identified. By mass spectrometry, we identified in saliva from potato aphids (Macrosiphum euphorbiae) 105 proteins, some of which originated from Buchnera, including the chaperonin GroEL. Because GroEL is a widely conserved bacterial protein with an essential function, we tested its role in PTI. Applying or infiltrating GroEL onto Arabidopsis (Arabidopsis thaliana) leaves induced oxidative burst and expression of PTI early marker genes. These GroEL-induced defense responses required the known coreceptor BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED RECEPTOR KINASE 1. In addition, in transgenic Arabidopsis plants, inducible expression of groEL activated PTI marker gene expression. Moreover, Arabidopsis plants expressing groEL displayed reduced fecundity of the green peach aphid (Myzus persicae), indicating enhanced resistance against aphids. Furthermore, delivery of GroEL into tomato (Solanum lycopersicum) or Arabidopsis through Pseudomonas fluorescens, engineered to express the type III secretion system, also reduced potato aphid and green peach aphid fecundity, respectively. Collectively our data indicate that GroEL is a molecular pattern that triggers PTI.

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Cytokinins for immunity beyond growth, galls and green islands

Cytokinins for immunity beyond growth, galls and green islands | Plant, Insect and Microbe Interactions | Scoop.it

Cytokinins are essential plant hormones that control almost every aspect of plant growth and development. Their function in mediating plant susceptibility to fungal biotrophs and gall-causing pathogens is well known. Here we highlight the interaction between cytokinins and salicylic acid pathways. Furthermore, we discuss ways in which cytokinin signaling could crosstalk with plant immune networks. Some of these networks are modulated by pathogens to propagate disease, whereas others help the host to mitigate an infection.


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How to Win the War on Bugs? Listen to Plants. They’ve Been Fighting Longer Than We Have.

How to Win the War on Bugs? Listen to Plants. They’ve Been Fighting Longer Than We Have. | Plant, Insect and Microbe Interactions | Scoop.it
We are losing the war on bugs. Every year, we dump 1 billion tons of insecticides on them; every year, they eat up to a fifth of the crops we grow. It’s a lose-lose scenario. Insecticides are expensive to make and use: Apple trees, for example, must be sprayed 20...

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Manger des insectes ? Ok mais est ce que c'est bon ? - Korben

Manger des insectes ? Ok mais est ce que c'est bon ? - Korben | Plant, Insect and Microbe Interactions | Scoop.it
Les amis, aujourd'hui, on va parler insectes ! Oui, car La Boutique Insolite m'a envoyé des insectes comestibles à déguster (merci !) pour que je puisse me faire une idée sur ce que les spécialistes appelle les aliments de demain. En effet, vous le savez tous, la production mondiale de viande (boeuf, volaille, porc...etc.) explose, …

 


Via Bernadette Cassel
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PLOS Biology: Phytoplasma Effector SAP54 Hijacks Plant Reproduction by Degrading MADS-box Proteins and Promotes Insect Colonization in a RAD23-Dependent Manner (2014)

PLOS Biology: Phytoplasma Effector SAP54 Hijacks Plant Reproduction by Degrading MADS-box Proteins and Promotes Insect Colonization in a RAD23-Dependent Manner (2014) | Plant, Insect and Microbe Interactions | Scoop.it

Pathogens that rely upon multiple hosts to complete their life cycles often modify behavior and development of these hosts to coerce them into improving pathogen fitness. However, few studies describe mechanisms underlying host coercion. In this study, we elucidate the mechanism by which an insect-transmitted pathogen of plants alters floral development to convert flowers into vegetative tissues. We find that phytoplasma produce a novel effector protein (SAP54) that interacts with members of the MADS-domain transcription factor (MTF) family, including key regulators SEPALLATA3 and APETALA1, that occupy central positions in the regulation of floral development. SAP54 mediates degradation of MTFs by interacting with proteins of the RADIATION SENSITIVE23 (RAD23) family, eukaryotic proteins that shuttle substrates to the proteasome. Arabidopsis rad23 mutants do not show conversion of flowers into leaf-like tissues in the presence of SAP54 and during phytoplasma infection, emphasizing the importance of RAD23 to the activity of SAP54. Remarkably, plants with SAP54-induced leaf-like flowers are more attractive for colonization by phytoplasma leafhopper vectors and this colonization preference is dependent on RAD23. An effector that targets and suppresses flowering while simultaneously promoting insect herbivore colonization is unprecedented. Moreover, RAD23 proteins have, to our knowledge, no known roles in flower development, nor plant defence mechanisms against insects. Thus SAP54 generates a short circuit between two key pathways of the host to alter development, resulting in sterile plants, and promotes attractiveness of these plants to leafhopper vectors helping the obligate phytoplasmas reproduce and propagate (zombie plants).


Via Kamoun Lab @ TSL
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An ecological cost associated with protective symbionts of aphids

Beneficial symbioses are widespread and diverse in the functions they provide to the host ranging from nutrition to protection. However, these partnerships with symbionts can be costly for the host. Such costs, so called “direct costs”, arise from a trade-off between allocating resources to symbiosis and other functions such as reproduction or growth. Ecological costs may also exist when symbiosis negatively affects the interactions between the host and other organisms in the environment. Although ecological costs can deeply impact the evolution of symbiosis, they have received little attention. The pea aphid Acyrthosiphon pisum benefits a strong protection against its main parasitoids from protective bacterial symbionts. The ecological cost of symbiont-mediated resistance to parasitism in aphids was here investigated by analyzing aphid behavior in the presence of predatory ladybirds. We showed that aphids harboring protective symbionts expressed less defensive behaviors, thus suffering a higher predation than symbiont-free aphids. Consequently, our study indicates that this underlined ecological cost may affect both the coevolutionary processes between symbiotic partners and the prevalence of such beneficial bacterial symbionts in host natural populations.

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Differential induction of Pisum sativum defense signaling molecules in response to pea aphid infestation

Highlights•

Signal molecules are enhanced in a sequence in pea response to A. pisum infestation.

Following aphid infestation, JA, SA, ET and NO are accumulated at different time points.

A post-infestation increase was observed in the activity of LOX, PAL and BA2H.

Convergence of signaling pathways can occur in pea response to pea aphid infestation.

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Previous infestation of pea aphids Acyrthosiphon pisum on broad bean plants resulted in the increased performance of conspecific nymphs on the plants

Previous infestation of pea aphids Acyrthosiphon pisum on broad bean plants resulted in the increased performance of conspecific nymphs on the plants | Plant, Insect and Microbe Interactions | Scoop.it

We studied the effects of previous infestation of broad bean plants by pea aphids Acyrthosiphon pisum on the performance of conspecific nymphs on the plants and the involvement of jasmonic acid (JA)-related defenses. The time needed for newly emerged nymphs to become reproductive adults on broad bean plants previously infested by conspecifics (pre-infested plants) was significantly shorter than on uninfested (control) broad bean plants. The total numbers of nymphs produced by aphids on preinfested and control plants were not significantly different. Preinfested plants produced significantly less endogenous JA than that control plants did. To test the effect of JA decreases, we conducted experiments on the developmental duration of nymphs on broad bean plants treated with JA (JA-treated plants) before infestation. The time needed for nymphs to become reproductive adults on JA treated preinfested broad bean plants was not significantly different from that on JA-treated control plants. The results suggested a possible parental care by pea aphids: the adult aphids manipulated JA-related defenses in broad bean plants that had positive effects for their offspring.

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Nature's microbiome: introduction - Molecular Ecology Special Issue

Nature's microbiome: introduction - Molecular Ecology Special Issue | Plant, Insect and Microbe Interactions | Scoop.it

In this special issue of Molecular Ecology, we present 28 articles incorporating molecular and bioinformatics tools to dissect the intimate and prolonged associations that define symbioses. We have organized these studies into three sections, focused on (i) the composition of symbiotic communities and how this varies across hosts, tissues and development, and in response to environmental change (‘The Dynamic Microbiome’); (ii) the roles that microbes play for their hosts and the underlying mechanisms behind these functions (‘Microbiome Function’); and (iii) the nature and mechanisms of interactions between hosts and symbionts and between the co-inhabiting symbionts themselves (‘The Interactive Microbiome’). These articles highlight the state-of-the-art in microbiome research, with novel discoveries for well-developed models and for other budding systems beyond the human realm.


Via Francis Martin
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