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Plant-Microbe Interaction
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Curated by Guogen Yang
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Identification and genome organization of saponin pathway genes from a wild crucifer, and their use for transient production of saponins in Nicotiana benthamiana

The ability to evolve novel metabolites has been instrumental for the defence of plants against antagonists. A few species in the Barbarea genus are the only crucifers known to produce saponins, some of which make plants resistant to specialist herbivores, like Plutella xylostella, the diamondback moth. Genetic mapping in Barbarea vulgaris revealed that genes for saponin biosynthesis are not clustered but are located in different linkage groups. Using co-location with quantitative trait loci (QTLs) for resistance, transcriptome and genome sequences, we identified two 2,3-oxidosqualene cyclases that form the major triterpenoid backbones. LUP2 mainly produces lupeol, and is preferentially expressed in insect-susceptible B. vulgaris plants, whereas LUP5 produces β-amyrin and α-amyrin, and is preferentially expressed in resistant plants; β-amyrin is the backbone for the resistance-conferring saponins in Barbarea. Two loci for cytochromes P450, predicted to add functional groups to the saponin backbone, were identified: CYP72As co-localized with insect resistance, whereas CYP716As did not. When B. vulgaris sapogenin biosynthesis genes were transiently expressed by CPMV-HT technology in Nicotiana benthamiana, high levels of hydroxylated and carboxylated triterpenoid structures accumulated, including oleanolic acid, which is a precursor of the major resistance-conferring saponins. When the B. vulgaris gene for sapogenin 3-O-glucosylation was co-expressed, the insect deterrent 3-O-oleanolic acid monoglucoside accumulated, as well as triterpene structures with up to six hexoses, demonstrating that N. benthamiana further decorates the monoglucosides. We argue that saponin biosynthesis in the Barbarea genus evolved by a neofunctionalized glucosyl transferase, whereas the difference between resistant and susceptible B. vulgaris chemotypes evolved by different expression of oxidosqualene cyclases (OSCs).

Via Christophe Jacquet
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Rescooped by Guogen Yang from Rice Blast
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Sexual Reproduction in Pyricularia oryzae

Sexual Reproduction in Pyricularia oryzae | Plant-Microbe Interaction | Scoop.it

Blast is caused by the Ascomycete Pyricularia oryzae and is the most important disease affecting rice in the world. Besides rice, wheat is affected by blast caused by P. oryzae in Brazil, Paraguay and Bolivia. The high genetic-pathotypic variability observed in local populations of P. oryzae is probably responsible for the low resistance durability of rice and wheat cultivarsto this disease and may also be determinant in eventsof 'host shift' by the pathogen. This review aims to present important aspects of the sexual reproduction of P. oryzae, as well as information about the regulatory mechanisms of the pathogen sexual cycle by the genes mating type and pheromones in a specific recognition system. Understanding the reproductive biology and the importance of P. oryzae sexual cycle is essential for blast disease management based on durable resistance.


Via Elsa Ballini
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Rescooped by Guogen Yang from Plant-microbe interaction
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Frontiers | Cellular reprogramming through mitogen-activated protein kinases | Frontiers in Plant Science

Frontiers | Cellular reprogramming through mitogen-activated protein kinases | Frontiers in Plant Science | Plant-Microbe Interaction | Scoop.it
Mitogen-activated protein kinase (MAPK) cascades are conserved eukaryote signaling modules where MAPKs, as the final kinases in the cascade, phosphorylate protein substrates to regulate cellular processes. While some progress in the identification of MAPK substrates has been made in plants, the knowledge on the spectrum of substrates and their mechanistic action is still fragmentary. In this focused review, we discuss the biological implications of the data in our original paper (Sustained mitogen-activated protein kinase activation reprograms defense metabolism and phosphoprotein profile in Arabidopsis thaliana; Frontiers in Plant Science 5: 554) in the context of related research. In our work, we mimicked in vivo activation of two stress-activated MAPKs, MPK3 and MPK6, through transgenic manipulation of Arabidopsis thaliana and used phosphoproteomics analysis to identify potential novel MAPK substrates. Here, we plotted the identified putative MAPK substrates (and downstream phosphoproteins) as a global protein clustering network. Based on a highly stringent selection confidence level, the core networks highlighted a MAPK-induced cellular reprogramming at multiple levels of gene and protein expression – including transcriptional, post-transcriptional, translational, post-translational (such as protein modification, folding and degradation) steps, and also protein re-compartmentalization. Additionally, the increase in putative substrates/phosphoproteins of energy metabolism and various secondary metabolite biosynthesis pathways coincides with the observed accumulation of defense antimicrobial substances as detected by metabolome analysis. Furthermore, detection of protein networks in phospholipid or redox elements suggests activation of downstream signaling events. Taken in context with other studies, MAPKs are key regulators that reprogram cellular events to orchestrate defense signaling in eukaryotes.

Via Suayib Üstün
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Rescooped by Guogen Yang from WU_Phyto-Publications
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PhD defence Mansoor Karimi Jashni (2015): Identification and functional characterization of proteases and protease inhibitors involved in virulence of fungal tomato pathogens

PhD defence Mansoor Karimi Jashni (2015): Identification and functional characterization of proteases and protease inhibitors involved in virulence of fungal tomato pathogens | Plant-Microbe Interaction | Scoop.it

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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Algal ancestor of land plants was preadapted for symbiosis

Algal ancestor of land plants was preadapted for symbiosis | Plant-Microbe Interaction | Scoop.it
Significance

Colonization of land by plants was a critical event for the emergence of extant ecosystems. The innovations that allowed the algal ancestor of land plants to succeed in such a transition remain unknown. Beneficial interaction with symbiotic fungi has been proposed as one of these innovations. Here we show that the genes required for this interaction appeared in a stepwise manner: Some evolved before the colonization of land by plants and others first appeared in land plants. We thus propose that the algal ancestor of land plants was preadapted for interaction with beneficial fungi and employed these gene networks to colonize land successfully.
Abstract

Colonization of land by plants was a major transition on Earth, but the developmental and genetic innovations required for this transition remain unknown. Physiological studies and the fossil record strongly suggest that the ability of the first land plants to form symbiotic associations with beneficial fungi was one of these critical innovations. In angiosperms, genes required for the perception and transduction of diffusible fungal signals for root colonization and for nutrient exchange have been characterized. However, the origin of these genes and their potential correlation with land colonization remain elusive. A comprehensive phylogenetic analysis of 259 transcriptomes and 10 green algal and basal land plant genomes, coupled with the characterization of the evolutionary path leading to the appearance of a key regulator, a calcium- and calmodulin-dependent protein kinase, showed that the symbiotic signaling pathway predated the first land plants. In contrast, downstream genes required for root colonization and their specific expression pattern probably appeared subsequent to the colonization of land. We conclude that the most recent common ancestor of extant land plants and green algae was preadapted for symbiotic associations. Subsequent improvement of this precursor stage in early land plants through rounds of gene duplication led to the acquisition of additional pathways and the ability to form a fully functional arbuscular mycorrhizal symbiosis.

Via Christophe Jacquet
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Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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Structure Analysis Uncovers a Highly Diverse but Structurally Conserved Effector Family in Phytopathogenic Fungi

Structure Analysis Uncovers a Highly Diverse but Structurally Conserved Effector Family in Phytopathogenic Fungi | Plant-Microbe Interaction | Scoop.it
Phytopathogenic ascomycete fungi possess huge effector repertoires that are dominated by hundreds of sequence-unrelated small secreted proteins. The molecular function of these effectors and the evolutionary mechanisms that generate this tremendous number of singleton genes are largely unknown. To get a deeper understanding of fungal effectors, we determined by NMR spectroscopy the 3-dimensional structures of the Magnaporthe oryzae effectors AVR1-CO39 and AVR-Pia. Despite a lack of sequence similarity, both proteins have very similar 6 β-sandwich structures that are stabilized in both cases by a disulfide bridge between 2 conserved cysteins located in similar positions of the proteins. Structural similarity searches revealed that AvrPiz-t, another effector from M. oryzae, and ToxB, an effector of the wheat tan spot pathogen Pyrenophora tritici-repentis have the same structures suggesting the existence of a family of sequence-unrelated but structurally conserved fungal effectors that we named MAX-effectors (Magnaporthe Avrs and ToxB like). Structure-informed pattern searches strengthened this hypothesis by identifying MAX-effector candidates in a broad range of ascomycete phytopathogens. Strong expansion of the MAX-effector family was detected in M. oryzae and M. grisea where they seem to be particularly important since they account for 5–10% of the effector repertoire and 50% of the cloned avirulence effectors. Expression analysis indicated that the majority of M. oryzae MAX-effectors are expressed specifically during early infection suggesting important functions during biotrophic host colonization. We hypothesize that the scenario observed for MAX-effectors can serve as a paradigm for ascomycete effector diversity and that the enormous number of sequence-unrelated ascomycete effectors may in fact belong to a restricted set of structurally conserved effector families.

Via Francis Martin
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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SCARN a Novel Class of SCAR Protein That Is Required for Root-Hair Infection during Legume Nodulation

SCARN a Novel Class of SCAR Protein That Is Required for Root-Hair Infection during Legume Nodulation | Plant-Microbe Interaction | Scoop.it
Rhizobial infection of legume root hairs requires a rearrangement of the actin cytoskeleton to enable the establishment of plant-made infection structures called infection threads. In the SCAR/WAVE (Suppressor of cAMP receptor defect/WASP family verpolin homologous protein) actin regulatory complex, the conserved N-terminal domains of SCAR proteins interact with other components of the SCAR/WAVE complex. The conserved C-terminal domains of SCAR proteins bind to and activate the actin-related protein 2/3 (ARP2/3) complex, which can bind to actin filaments catalyzing new actin filament formation by nucleating actin branching. We have identified, SCARN (SCAR-Nodulation), a gene required for root hair infection of Lotus japonicus by Mesorhizobium loti. Although the SCARN protein is related to Arabidopsis thaliana SCAR2 and SCAR4, it belongs to a distinct legume-sub clade. We identified other SCARN-like proteins in legumes and phylogeny analyses suggested that SCARN may have arisen from a gene duplication and acquired specialized functions in root nodule symbiosis. Mutation of SCARN reduced formation of infection-threads and their extension into the root cortex and slightly reduced root-hair length. Surprisingly two of the scarn mutants showed constitutive branching of root hairs in uninoculated plants. However we observed no effect of scarn mutations on trichome development or on the early actin cytoskeletal accumulation that is normally seen in root hair tips shortly after M. loti inoculation, distinguishing them from other symbiosis mutations affecting actin nucleation. The C-terminal domain of SCARN binds to ARPC3 and ectopic expression of the N-terminal SCAR-homology domain (but not the full length protein) inhibited nodulation. In addition, we found that SCARN expression is enhanced by M. loti in epidermal cells and that this is directly regulated by the NODULE INCEPTION (NIN) transcription factor.
Author Summary

Characterization of Lotus japonicus mutants defective for nodule infection by rhizobia led to the identification of a gene we named SCARN. Two of the five alleles caused formation of branched root-hairs in uninoculated seedlings, suggesting SCARN plays a role in the microtubule and actin-regulated polar growth of root hairs. SCARN is one of three L. japonicus proteins containing the conserved N and C terminal domains predicted to be required for rearrangement of the actin cytoskeleton. SCARN expression is induced in response to rhizobial nodulation factors by the NIN (NODULE INCEPTION) transcription factor and appears to be adapted to promoting rhizobial infection, possibly arising from a gene duplication event. SCARN binds to ARPC3, one of the predicted components in the actin-related protein complex involved in the activation of actin nucleation.

Via Christophe Jacquet
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Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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Below-ground plant–fungus network topology is not congruent with above-ground plant–animal network topology

Below-ground plant–fungus network topology is not congruent with above-ground plant–animal network topology | Plant-Microbe Interaction | Scoop.it
In nature, plants and their pollinating and/or seed-dispersing animals form complex interaction networks. The commonly observed pattern of links between specialists and generalists in these networks has been predicted to promote species coexistence. Plants also build highly species-rich mutualistic networks below ground with root-associated fungi, and the structure of these plant–fungus networks may also affect terrestrial community processes. By compiling high-throughput DNA sequencing data sets of the symbiosis of plants and their root-associated fungi from three localities along a latitudinal gradient, we uncovered the entire network architecture of these interactions under contrasting environmental conditions. Each network included more than 30 plant species and hundreds of mycorrhizal and endophytic fungi belonging to diverse phylogenetic groups. The results were consistent with the notion that processes shaping host-plant specialization of fungal species generate a unique linkage pattern that strongly contrasts with the pattern of above-ground plant–partner networks. Specifically, plant–fungus networks lacked a “nested” architecture, which has been considered to promote species coexistence in plant–partner networks. Rather, the below-ground networks had a conspicuous “antinested” topology. Our findings lead to the working hypothesis that terrestrial plant community dynamics are likely determined by the balance between above-ground and below-ground webs of interspecific interactions.

Via Francis Martin
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Redox proteomics of tomato in response to Pseudomonas syringae infection

Redox proteomics of tomato in response to Pseudomonas syringae infection | Plant-Microbe Interaction | Scoop.it
Unlike mammals with adaptive immunity, plants rely on their innate immunity based on pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) for pathogen defense. Reactive oxygen species, known to play crucial roles in PTI and ETI, can perturb cellular redox homeostasis and lead to changes of redox-sensitive proteins through modification of cysteine sulfhydryl groups. Although redox regulation of protein functions has emerged as an important mechanism in several biological processes, little is known about redox proteins and how they function in PTI and ETI. In this study, cysTMT proteomics technology was used to identify similarities and differences of protein redox modifications in tomato resistant (PtoR) and susceptible (prf3) genotypes in response to Pseudomonas syringae pv tomato (Pst) infection. In addition, the results of the redox changes were compared and corrected with the protein level changes. A total of 90 potential redox-regulated proteins were identified with functions in carbohydrate and energy metabolism, biosynthesis of cysteine, sucrose and brassinosteroid, cell wall biogenesis, polysaccharide/starch biosynthesis, cuticle development, lipid metabolism, proteolysis, tricarboxylic acid cycle, protein targeting to vacuole, and oxidation–reduction. This inventory of previously unknown protein redox switches in tomato pathogen defense lays a foundation for future research toward understanding the biological significance of protein redox modifications in plant defense responses.

Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Genome-Wide Association of Rice Blast Disease Resistance and Yield-Related Components of Rice — Molecular Plant-Microbe Interactions

Genome-Wide Association of Rice Blast Disease Resistance and Yield-Related Components of Rice — Molecular Plant-Microbe Interactions | Plant-Microbe Interaction | Scoop.it
Robust disease resistance may require an expenditure of energy that may limit crop yield potential. In the present study, a subset of a United States Department of Agriculture rice core collection consisting of 151 accessions was selected using a major blast resistance (R) gene, Pi-ta, marker and was genotyped with 156 simple sequence repeat (SSR) markers. Disease reactions to Magnaporthe oryzae, the causal agent of rice blast disease, were evaluated under greenhouse and field conditions, and heading date, plant height, paddy and brown seed weight in two field environments were analyzed, using an association mapping approach. A total of 21 SSR markers distributed among rice chromosomes 2 to 12 were associated with blast resistance, and 16 SSR markers were associated with seed weight, heading date, and plant height. Most noticeably, shorter plants were significantly correlated with resistance to blast, rice genomes with Pi-ta were associated with lighter seed weights, and the susceptible alleles of RM171 and RM6544 were associated with heavier seed weight. These findings unraveled a complex relationship between disease resistance and yield-related components.

Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Transcriptome analysis highlights preformed defences and signalling pathways controlled by the prAe1 QTL, conferring partial resistance to Aphanomyces euteiches in Medicago truncatula.

Transcriptome analysis highlights preformed defences and signalling pathways controlled by the prAe1 QTL, conferring partial resistance to Aphanomyces euteiches in Medicago truncatula. | Plant-Microbe Interaction | Scoop.it
To gain an insight into the molecular mechanisms of quantitative disease resistance in Medicago truncatula to the root-infecting oomycete Aphanomyces euteiches, we selected two near-isogenic lines (NILs), NR and NS, partially resistant and susceptible, respectively, differing in the allelic state of the quantitative resistance locus (QRL) prAe1 (partially resistant to A. euteiches 1). Complementary molecular and cytological phenotyping methods showed that prAe1 alone confers quantitative resistance to A. euteiches. Root and stem tissues were colonized in NS plants and 80% of NS plants died by 21 days post-inoculation (dpi). In contrast, A. euteiches mycelium was restricted to the root cortex and the spread of symptoms was arrested in aerial parts of NR plants. A transcriptome analysis performed at 0, 1 and 6 dpi identified 1198 differentially expressed genes (DEGs) between NR and NS lines. More than 87% of the DEGs were significantly more expressed in NR. The highest number of DEGs was found in control conditions, with 723 genes over-expressed in NR versus 85 in NS. Genes belonging to secondary metabolism, pathogenesis-related (PR) proteins and kinases were significantly enriched. The significant role of the flavonoid pathway in resistance was corroborated by the detection of larger amounts of flavonoids in NR roots and the inhibition of A. euteiches zoospore germination by 2′-O-methyl-isoliquiritigenin, a compound synthesized by enzymes specifically induced in NR. Our study revealed that prAe1-dependent resistance relies mainly on the constitutive expression of defence-related pathways and signalling elements, which can be re-amplified in later time points of the infection.

Via Christophe Jacquet
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Christophe Jacquet's curator insight, October 27, 2015 3:17 AM

MPP cover for our last article!

Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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Effector discovery in the fungal wheat pathogen Zymoseptoria tritici

Effector discovery in the fungal wheat pathogen Zymoseptoria tritici | Plant-Microbe Interaction | Scoop.it

Fungal plant pathogens, such as Zymoseptoria tritici (formerly known as Mycosphaerella graminicola), secrete repertoires of effectors to facilitate infection or trigger host defence mechanisms. The discovery and functional characterization of effectors provides valuable knowledge that can contribute to the design of new and effective disease management strategies. Here, we combined bioinformatics approaches with expression profiling during pathogenesis to identify candidate effectors of Z. tritici. In addition, a genetic approach was conducted to map quantitative trait loci (QTLs) carrying putative effectors, enabling the validation of both complementary strategies for effector discovery. In planta expression profiling revealed that candidate effectors were up-regulated in successive waves corresponding to consecutive stages of pathogenesis, contrary to candidates identified by QTL mapping that were, overall, expressed at low levels. Functional analyses of two top candidate effectors (SSP15 and SSP18) showed their dispensability for Z. tritici pathogenesis. These analyses reveal that generally adopted criteria, such as protein size, cysteine residues and expression during pathogenesis, may preclude an unbiased effector discovery. Indeed, genetic mapping of genomic regions involved in specificity render alternative effector candidates that do not match the aforementioned criteria, but should nevertheless be considered as promising new leads for effectors that are crucial for the Z. tritici–wheat pathosystem.


Via Francis Martin
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Rescooped by Guogen Yang from Plant Immunity And Microbial Effectors
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RTP1 encodes a novel endoplasmic reticulum (ER)-localized protein in Arabidopsis and negatively regulates resistance against biotrophic pathogens - Pan - 2015 - New Phytologist - Wiley Online Library


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RNAseq Analysis Highlights Specific Transcriptome Signatures of Yeast and Mycelial Growth Phases in the Dutch Elm Disease Fungus Ophiostoma novo-ulmi

RNAseq Analysis Highlights Specific Transcriptome Signatures of Yeast and Mycelial Growth Phases in the Dutch Elm Disease Fungus Ophiostoma novo-ulmi | Plant-Microbe Interaction | Scoop.it

Fungal dimorphism is a complex trait and our understanding of the ability of fungi to display different growth morphologies is limited to a small number of model species. Here we study a highly aggressive dimorphic fungus, the ascomycete Ophiostoma novo-ulmi, which is a model in plant pathology and the causal agent of Dutch elm disease. The two growth phases that this fungus displays, i.e., a yeast phase and mycelial phase, are thought to be involved in key steps of disease development. We used RNAseq to investigate the genome-wide gene expression profiles that are associated with yeast and mycelial growth phases in vitro. Our results show a clear molecular distinction between yeast and mycelial phase gene expression profiles. Almost 12% of the gene content is differentially expressed between the two phases, which reveals specific functions related to each growth phase. We compared O. novo-ulmi transcriptome profiles with those of two model dimorphic fungi, Candida albicans and Histoplasma capsulatum. Few orthologs showed similar expression regulation between the two growth phases, which suggests that, globally, the genes associated with these two life forms are poorly conserved. This poor conservation underscores the importance of developing specific tools for emerging model species that are distantly related to the classical ones. Taken together, our results provide insights into transcriptome regulation and molecular specificity in O. novo-ulmi and offer a new perspective for understanding fungal dimorphism.


Via Francis Martin
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Rescooped by Guogen Yang from Plant Immunity And Microbial Effectors
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Protocol: an improved and universal procedure for whole-mount immunolocalization in plants

Rapid advances in microscopy have boosted research on cell biology.

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Rescooped by Guogen Yang from WU_Phyto-Publications
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PhD Thesis Joyce Woudenberg (2015): Restyling Alternaria

PhD Thesis Joyce Woudenberg (2015): Restyling Alternaria | Plant-Microbe Interaction | Scoop.it

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Rescooped by Guogen Yang from Plant Biology Teaching Resources (Higher Education)
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Plant-made pharmaceuticals: from ‘Edible Vaccines’ to Ebola therapeutics - Arntzen - 2015 - Plant Biotechnology Journal - Wiley Online Library

Plant-made pharmaceuticals: from ‘Edible Vaccines’ to Ebola therapeutics - Arntzen - 2015 - Plant Biotechnology Journal - Wiley Online Library | Plant-Microbe Interaction | Scoop.it
As I sat writing this ‘personal reflections’ manuscript in the spring of 2015, I was seeing press reports related to the use of tobacco to make an Ebola therapeutic called ZMapp. For several months newspaper articles, radio shows and hour-long TV documentaries have given the public unprecedented exposure to the fact that ‘plant-made pharmaceuticals’ (PMP) can be life-saving drugs. I have been asked by many nonspecialists – why tobacco? How can this work? After spending over twenty years doing research in this field and many, many hours in public policy meetings promoting PMPs as an important tool of public health, I do not tire of hearing the same questions. Although there is an increasing pipeline of new protein drugs that will come from plants for both human and animal health, the general public has little knowledge of these specialized tools and therefore limited support for the field. ZMapp has given us free advertising on an international scale that I could never have anticipated.

Via Jean-Pierre Zryd, Mary Williams
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Chitinase-resistant hydrophilic symbiotic factors secreted by Frankia activate both Ca2+ spiking and NIN gene expression in the actinorhizal plant Casuarina glauca - New Phytologist

Although it is now well-established that decorated lipo-chitooligosaccharide Nod factors are the key rhizobial signals which initiate infection/nodulation in host legume species, the identity of the equivalent microbial signaling molecules in the Frankia/actinorhizal association remains elusive.
With the objective of identifying Frankia symbiotic factors we present a novel approach based on both molecular and cellular pre-infection reporters expressed in the model actinorhizal species Casuarina glauca.
By introducing the nuclear-localized cameleon Nup-YC2.1 into Casuarina glauca we show that cell-free culture supernatants of the compatible Frankia CcI3 strain are able to elicit sustained high frequency Ca2+ spiking in host root hairs. Furthermore, an excellent correlation exists between the triggering of nuclear Ca2+ spiking and the transcriptional activation of the ProCgNIN:GFP reporter as a function of the Frankia strain tested. These two pre-infection symbiotic responses have been used in combination to show that the signal molecules present in the Frankia CcI3 supernatant are hydrophilic, of low molecular weight and resistant to chitinase degradation.
In conclusion, the biologically active symbiotic signals secreted by Frankia appear to be chemically distinct from the currently known chitin-based rhizobial/arbuscular mycorrhizal signaling molecules. Convenient bioassays in Casuarina glauca are now available for their full characterization.

Via Christophe Jacquet
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Insights from the genome of Ophiocordyceps polyrhachis-furcata to pathogenicity and host specificity in insect fungi

Insights from the genome of Ophiocordyceps polyrhachis-furcata to pathogenicity and host specificity in insect fungi | Plant-Microbe Interaction | Scoop.it

Background. Ophiocordyceps unilateralis is an outstanding insect fungus for its biology to manipulate host ants’ behavior and for its extreme host-specificity. Through the sequencing and annotation of Ophiocordyceps polyrhachis-furcata, a species in the O. unilateralis species complex specific to the ant Polyrhachis furcata, comparative analyses on genes involved in pathogenicity and virulence between this fungus and other fungi were undertaken in order to gain insights into its biology and the emergence of host specificity.


Results.O. polyrhachis-furcata possesses various genes implicated in pathogenicity and virulence common with other fungi. Overall, this fungus possesses protein-coding genes similar to those found on other insect fungi with available genomic resources (Beauveria bassiana, Metarhizium robertsii (formerly classified as M. anisopliae s.l.), Metarhizium acridum, Cordyceps militaris, Ophiocordyceps sinensis). Comparative analyses in regard of the host ranges of insect fungi showed a tendency toward contractions of various gene families for narrow host-range species, including cuticle-degrading genes (proteases, carbohydrate esterases) and some families of pathogen-host interaction (PHI) genes. For many families of genes, O. polyrhachis-furcata had the least number of genes found; some genes commonly found in other insect fungi are even absent (e.g. Class 1 hydrophobin). However, there are expansions of genes involved in 1) the production of bacterial-like toxins in O. polyrhachis-furcata, compared with other entomopathogenic fungi, and 2) retrotransposable elements.


Conclusions.The gain and loss of gene families helps us understand how fungal pathogenicity in insect hosts evolved. The loss of various genes involved throughout the pathogenesis for O. unilateralis would result in a reduced capacity to exploit larger ranges of hosts and therefore in the different level of host specificity, while the expansions of other gene families suggest an adaptation to particular environments with unexpected strategies like oral toxicity, through the production of bacterial-like toxins, or sophisticated mechanisms underlying pathogenicity through retrotransposons.


Via Francis Martin
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Strand-Specific RNA-Seq Analyses of Fruiting Body Development in Coprinopsis cinerea

Strand-Specific RNA-Seq Analyses of Fruiting Body Development in  Coprinopsis cinerea | Plant-Microbe Interaction | Scoop.it
The basidiomycete fungus Coprinopsis cinerea is an important model system for multicellular development. Fruiting bodies of C . cinerea are typical mushrooms, which can be produced synchronously on defined media in the laboratory. To investigate the transcriptome in detail during fruiting body development, high-throughput sequencing (RNA-seq) was performed using cDNA libraries strand-specifically constructed from 13 points (stages/tissues) with two biological replicates. The reads were ali

Via Francis Martin
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Stereochemical Assignment of Strigolactone Analogues Confirms Their Selective Biological Activity

Stereochemical Assignment of Strigolactone Analogues Confirms Their Selective Biological Activity | Plant-Microbe Interaction | Scoop.it
Strigolactones (SLs) are new plant hormones with various developmental functions. They are also soil signaling chemicals that are required for establishing beneficial mycorrhizal plant/fungus symbiosis. In addition, SLs play an essential role in inducing seed germination in root-parasitic weeds, which are one of the seven most serious biological threats to food security. There are around 20 natural SLs that are produced by plants in very low quantities. Therefore, most of the knowledge on SL signal transduction and associated molecular events is based on the application of synthetic analogues. Stereochemistry plays a crucial role in the structure–activity relationship of SLs, as compounds with an unnatural D-ring configuration may induce biological effects that are unrelated to SLs. We have synthesized a series of strigolactone analogues, whose absolute configuration has been elucidated and related with their biological activity, thus confirming the high specificity of the response. Analogues bearing the R-configured butenolide moiety showed enhanced biological activity, which highlights the importance of this stereochemical motif.

Via Jean-Michel Ané, Francis Martin
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Rapid screening for citrus canker resistance employing pathogen-associated molecular pattern-triggered immunity responses

Rapid screening for citrus canker resistance employing pathogen-associated molecular pattern-triggered immunity responses | Plant-Microbe Interaction | Scoop.it
Citrus canker, caused by the bacterial pathogen Xanthomonas citri ssp. citri (Xcc), has been attributed to millions of dollars in loss or damage to commercial citrus crops in subtropical production areas of the world. Since identification of resistant plants is one of the most effective methods of disease management, the ability to screen for resistant seedlings plays a key role in the production of a long-term solution to canker. Here, an inverse correlation between reactive oxygen species (ROS) production by the plant and the ability of Xcc to grow and form lesions on infected plants is reported. Based on this information, a novel screening method that can rapidly identify citrus seedlings that are less susceptible to early infection by Xcc was devised by measuring ROS accumulation triggered by a 22-amino acid sequence of the conserved N-terminal part of flagellin (flg22) from X. citri ssp. citri (Xcc-flg22). In addition to limiting disease symptoms, ROS production was also correlated with the expression of basal defense-related genes such as the pattern recognition receptors LRR8 and FLS2, the leucine-rich repeat receptor-like protein RLP12, and the defense-related gene PR1, indicating an important role for pathogen-associated molecular pattern-triggered immunity (PTI) in determining resistance to citrus canker. Moreover, the differential expression patterns observed amongst the citrus seedlings demonstrated the existence of genetic variations in the PTI response among citrus species/varieties.

Via Christophe Jacquet
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The pineapple genome and the evolution of CAM photosynthesis : Nature Genetics

The pineapple genome and the evolution of CAM photosynthesis : Nature Genetics | Plant-Microbe Interaction | Scoop.it
Pineapple (Ananas comosus (L.) Merr.) is the most economically valuable crop possessing crassulacean acid metabolism (CAM), a photosynthetic carbon assimilation pathway with high water-use efficiency, and the second most important tropical fruit. We sequenced the genomes of pineapple varieties F153 and MD2 and a wild pineapple relative, Ananas bracteatus accession CB5. The pineapple genome has one fewer ancient whole-genome duplication event than sequenced grass genomes and a conserved karyotype with seven chromosomes from before the ρ duplication event. The pineapple lineage has transitioned from C3 photosynthesis to CAM, with CAM-related genes exhibiting a diel expression pattern in photosynthetic tissues. CAM pathway genes were enriched with cis-regulatory elements associated with the regulation of circadian clock genes, providing the first cis-regulatory link between CAM and circadian clock regulation. Pineapple CAM photosynthesis evolved by the reconfiguration of pathways in C3 plants, through the regulatory neofunctionalization of preexisting genes and not through the acquisition of neofunctionalized genes via whole-genome or tandem gene duplication.

Via Francis Martin
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Monocot and dicot MLO powdery mildew susceptibility factors are functionally conserved in spite of the evolution of class-specific molecular features

Monocot and dicot MLO powdery mildew susceptibility factors are functionally conserved in spite of the evolution of class-specific molecular features | Plant-Microbe Interaction | Scoop.it
Background

Specific members of the plant Mildew Locus O (MLO) protein family act as susceptibility factors towards powdery mildew (PM), a worldwide-spread fungal disease threatening many cultivated species. Previous studies indicated that monocot and dicot MLO susceptibility proteins are phylogenetically divergent.
Methods

A bioinformatic approach was followed to study the type of evolution of Angiosperm MLO susceptibility proteins. Transgenic complementation tests were performed for functional analysis.
Results

Our results show that monocot and dicot MLO susceptibility proteins evolved class-specific conservation patterns. Many of them appear to be the result of negative selection and thus are likely to provide an adaptive value. We also tested whether different molecular features between monocot and dicot MLO proteins are specifically required by PM fungal species to cause pathogenesis. To this aim, we transformed a tomato mutant impaired for the endogenous SlMLO1 gene, and therefore resistant to the tomato PM species Oidium neolycopersici, with heterologous MLO susceptibility genes from the monocot barley and the dicot pea. In both cases, we observed restoration of PM symptoms. Finally, through histological observations, we demonstrate that both monocot and dicot susceptibility alleles of the MLO genes predispose to penetration of a non-adapted PM fungal species in plant epidermal cells.
Conclusions

With this study, we provide insights on the evolution and function of MLO genes involved in the interaction with PM fungi. With respect to breeding research, we show that transgenic complementation assays involving phylogenetically distant plant species can be used for the characterization of novel MLO susceptibility genes. Moreover, we provide an overview of MLO protein molecular features predicted to play a major role in PM susceptibility. These represent ideal targets for future approaches of reverse genetics, addressed to the selection of loss-of-function resistant mutants in cultivated species.

Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant Immunity And Microbial Effectors
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The genome of Xylona heveae provides a window into fungal endophytism

The genome of Xylona heveae provides a window into fungal endophytism | Plant-Microbe Interaction | Scoop.it

Via IPM Lab
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