Plant pathogens and pests
30.3K views | +12 today
Plant pathogens and pests
Mainly dedicated to plant pathogens , mechanisms of pathogenicity, life cycles, epidemiology and plant breeding methods and results helping to prevent their propagation.  This site is complementary to the Plant-microbe Interactions (on the plant's side); Scoop-It site :        http://www.scoop.it/t/plant-pathogen-interactions-by-christophe-jacquet
Your new post is loading...
Your new post is loading...
Scooped by Christophe Jacquet
Scoop.it!

Identification of differentially regulated maize proteins conditioning Sugarcane mosaic virus systemic infection

Identification of differentially regulated maize proteins conditioning Sugarcane mosaic virus systemic infection | Plant pathogens and pests | Scoop.it
Sugarcane mosaic virus (SCMV) is the most important cause of maize dwarf mosaic disease. To identify maize genes responsive to SCMV infection and that may be involved in pathogenesis, a comparative proteomic analysis was performed using the first and second systemically infected leaves (termed 1 SL and 2 SL, respectively).
Seventy-one differentially expressed proteins were identified in 1 SL and 2 SL upon SCMV infection. Among them, eight proteins showed the same changing patterns in both 1 SL and 2 SL. Functional annotations of regulated proteins and measurement of photosynthetic activity revealed that photosynthesis was more inhibited and defensive gene expression more pronounced in 1 SL than in 2 SL.
Knockdown of regulated proteins in both 1 SL and 2 SL by a brome mosaic virus-based gene silencing vector in maize indicated that protein disulfide isomerase-like and phosphoglycerate kinase were required for optimal SCMV replication. By contrast, knockdown of polyamine oxidase (ZmPAO) significantly increased SCMV accumulation, implying that ZmPAO activity might contribute to resistance or tolerance.
The results suggest that combining comparative proteomic analyses of different tissues and virus-induced gene silencing is an efficient way to identify host proteins supporting virus replication or enhancing resistance to virus infection.
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Frontiers | Aerial Warfare: A Volatile Dialogue between the Plant Pathogen Verticillium longisporum and Its Antagonist Paenibacillus polymyxa | Plant Science

Frontiers | Aerial Warfare: A Volatile Dialogue between the Plant Pathogen Verticillium longisporum and Its Antagonist Paenibacillus polymyxa | Plant Science | Plant pathogens and pests | Scoop.it
Verticillium wilt caused by Verticillium spp. results in severe yield losses in a broad range of crops. Verticillium outbreaks are challenging to control, and exacerbated by increases in soil temperatures and drought associated with global warming. Employing natural antagonists as biocontrol agents offers a promising approach to addressing this challenge. Paenibacillus polymyxa Sb3-1 was proven to reduce the growth of V. longisporum during in vitro experiments and was shown to promote the growth of oilseed rape seedlings infested with V. longisporum. Our novel approach combined in vitro and in planta methods with the study of the mode of interaction between Sb3-1 and V. longisporum EVL43 via their volatile organic compounds (VOCs). Volatile and soluble substances, produced by both microorganisms as a reaction to one another’s VOCs, were detected by using both gas and liquid chromatography-mass spectrometry. P. polymyxa Sb3-1 continually produced antimicrobial and plant growth promoting VOCs, such as 2-nonanone and 3-hydroxy-2-butanone. Several other antimicrobial volatile substances, such as isoamyl acetate and durenol, were downregulated. The general metabolic activity of Sb3-1, including protein and DNA biotransformations, was upregulated upon contact with EVL43 VOCs. V. longisporum increased its production of antimicrobial substances, such as 1-butanol, and downregulated its metabolic activities upon exposure to Sb3-1 VOCs. Additionally, several stress response substances such as arabitol and protein breakdown products (e.g. L-Isoleucyl-L-glutamic acid), were increased in the co-incubated samples. The results obtained depict an ongoing dialogue between these microorganisms resulting in growth inhibition, the slowing down of metabolism, and the cell death of V. longisporum due to contact with the P. polymyxa Sb3-1 VOCs. Moreover, the results indicate that VOCs make a substantial contribution to the interaction between pathogens and their natural antagonists and have the potential to control pathogens in a novel, environmentally friendly manner.
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Viral suppressors: Combatting RNA silencing

Viral suppressors: Combatting RNA silencing | Plant pathogens and pests | Scoop.it
Plants defend themselves from invading viruses using RNA silencing. However, plant viruses try to spoil this defensive mechanism by expressing one or more proteins that act as RNA silencing suppressors. One such protein spoils plant defence by transporting the silencing signal into the peroxisomes to avoid its systemic spread.
more...
No comment yet.
Rescooped by Christophe Jacquet from Crosstalks in Plant-microbes interactions
Scoop.it!

YAP1 homologue‐mediated redox sensing is crucial for a successful infection by Monilinia fructicola

YAP1 homologue‐mediated redox sensing is crucial for a successful infection by Monilinia fructicola | Plant pathogens and pests | Scoop.it
“ Monilinia fructicola (G. Winter) Honey is a devastating pathogen on Rosaceae which causes blossom blight and fruit rot. Only a few studies related to the plant–pathogen interaction have been published and there is limited knowledge on the relationship between oxidative stress and successful infection in M. fructicola. In this study, we cloned and characterized a redox-responsive transcription factor MFAP1, a YAP1 homologue. MfAP1-silenced strains were generated by polyethylene glycol-mediated protoplast transformation or Agrobacterium T-DNA-mediated transformation. Pathogenicity assay demonstrated that MfAP1-silenced strains caused smaller lesions on rose and peach petals. Transformants carrying extra copies of MfAP1, driven by the native promoter, were generated for MfAP1 overexpression. Interestingly, MfAP1-overexpressing strains also caused smaller lesions on rose petals. Strains carrying two copies of MfAP1 accumulated reactive oxygen species (ROS) at higher levels and exhibited delayed accumulation of MfAP1 transcripts compared with the wild-type during pathogenesis. By the analysis of ROS production and the expression patterns of redox- and virulence-related genes in the wild-type strain and an MfAP1-overexpressing strain, we found that the M. fructicola wild-type strain responded to oxidative stress at the infection site, activated the expression of MfAP1 and up-regulated the genes required for ROS detoxification and fungal virulence. In contrast, MfAP1 expression in the MfAP1-overexpressing strain was suppressed after the induction of a strong oxidative burst at the infection site, altering the expression of ROS detoxification and virulence-related genes. Our results highlight the importance of MfAP1 and ROS accumulation in the successful infection of M. fructicola. ”
Via Steve Marek, Rey Thomas
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Complete Genome Sequence of the Phytopathogenic Fungus Sclerotinia sclerotiorum Reveals Insights into the Genome Architecture of Broad Host Range Pathogens | Genome Biology and Evolution | Oxford...

Complete Genome Sequence of the Phytopathogenic Fungus  Sclerotinia sclerotiorum  Reveals Insights into the Genome Architecture of Broad Host Range Pathogens | Genome Biology and Evolution | Oxford... | Plant pathogens and pests | Scoop.it
Sclerotinia sclerotiorum is a phytopathogenic fungus with over 400 hosts including numerous economically important cultivated species. This contrasts many economically destructive pathogens that only exhibit a single or very few hosts. Many plant pathogens exhibit a “two-speed” genome. So described because their genomes contain alternating gene rich, repeat sparse and gene poor, repeat-rich regions. In fungi, the repeat-rich regions may be subjected to a process termed repeat-induced point mutation (RIP). Both repeat activity and RIP are thought to play a significant role in evolution of secreted virulence proteins, termed effectors. We present a complete genome sequence of S. sclerotiorum generated using Single Molecule Real-Time Sequencing technology with highly accurate annotations produced using an extensive RNA sequencing data set. We identified 70 effector candidates and have highlighted their in planta expression profiles. Furthermore, we characterized the genome architecture of S. sclerotiorum in comparison to plant pathogens that exhibit “two-speed” genomes. We show that there is a significant association between positions of secreted proteins and regions with a high RIP index in S. sclerotiorum but we did not detect a correlation between secreted protein proportion and GC content. Neither did we detect a negative correlation between CDS content and secreted protein proportion across the S. sclerotiorum genome. We conclude that S. sclerotiorum exhibits subtle signatures of enhanced mutation of secreted proteins in specific genomic compartments as a result of transposition and RIP activity. However, these signatures are not observable at the whole-genome scale.
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Pathogen exploitation of an abscisic acid- and jasmonate-inducible MAPK phosphatase and its interception by Arabidopsis immunity

Pathogen exploitation of an abscisic acid- and jasmonate-inducible MAPK phosphatase and its interception by Arabidopsis immunity | Plant pathogens and pests | Scoop.it
Phytopathogens promote virulence by, for example, exploiting signaling pathways mediated by phytohormones such as abscisic acid (ABA) and jasmonate (JA). Some plants can counteract pathogen virulence by invoking a potent form of immunity called effector-triggered immunity (ETI). Here, we report that ABA and JA mediate inactivation of the immune-associated MAP kinases (MAPKs), MPK3 and MPK6, in Arabidopsis thaliana. ABA induced expression of genes encoding the protein phosphatases 2C (PP2Cs), HAI1, HAI2, and HAI3 through ABF/AREB transcription factors. These three HAI PP2Cs interacted with MPK3 and MPK6 and were required for ABA-mediated MPK3/MPK6 inactivation and immune suppression. The bacterial pathogen Pseudomonas syringae pv. tomato (Pto) DC3000 activates ABA signaling and produces a JA-mimicking phytotoxin, coronatine (COR), that promotes virulence. We found that Pto DC3000 induces HAI1 through COR-mediated activation of MYC2, a master transcription factor in JA signaling. HAI1 dephosphorylated MPK3 and MPK6 in vitro and was necessary for COR-mediated suppression of MPK3/MPK6 activation and immunity. Intriguingly, upon ETI activation, A. thaliana plants overcame the HAI1-dependent virulence of COR by blocking JA signaling. Finally, we showed conservation of induction of HAI PP2Cs by ABA and JA in other Brassicaceae species. Taken together, these results suggest that ABA and JA signaling pathways, which are hijacked by the bacterial pathogen, converge on the HAI PP2Cs that suppress activation of the immune-associated MAPKs. Also, our data unveil interception of JA-signaling activation as a host counterstrategy against the bacterial suppression of MAPKs during ETI.
more...
No comment yet.
Rescooped by Christophe Jacquet from Plant pathogenic fungi
Scoop.it!

Life styles of Colletotrichum species and implications for plant biosecurity

Life styles of Colletotrichum species and implications for plant biosecurity | Plant pathogens and pests | Scoop.it

Colletotrichum is a genus of major plant pathogens causing anthracnose diseases in many plant crops worldwide. The genus comprises a highly diverse group of pathogens that infect a wide range of plant hosts. The life styles of Colletotrichum species can be broadly categorised as necrotrophic, hemibiotrophic, latent or quiescent and endophytic; of which hemibiotrophic is the most common. The differences in life style depend on the Colletotrichum species, the host species, the physiological maturity of the host and environmental conditions. Thus, the genus Colletotrichum provides a unique opportunity for analysing different life style patterns and features underlying a diverse range of plant–pathogen interactions. This review describes the various modes of life styles of Colletotrichum species, the underlying mechanisms of infection and colonisation, and implications the life styles have for plant biosecurity. Knowledge of life styles of Colletotrichum species will enable the development of improved diagnostics and application of integrated disease control methods to mitigate the risk of incursion of exotic Colletotrichum species.


Via Steve Marek
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

A Conceptual Framework for Integrated Pest Management

A Conceptual Framework for Integrated Pest Management | Plant pathogens and pests | Scoop.it
The concept of integrated pest management (IPM) has been accepted and incorporated in public policies and regulations in the European Union and elsewhere, but a holistic science of IPM has not yet been developed. Hence, current IPM programs may often be considerably less efficient than the sum of separately applied individual crop protection actions. Thus, there is a clear need to formulate general principles for synergistically combining traditional and novel IPM actions to improve efforts to optimize plant protection solutions. This paper addresses this need by presenting a conceptual framework for a modern science of IPM. The framework may assist attempts to realize the full potential of IPM and reduce risks of deficiencies in the implementation of new policies and regulations.
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

ABC protein CgABCF2 is required for asexual and sexual development, appressorial formation and plant infection in Colletotrichum gloeosporioides

ABC protein CgABCF2 is required for asexual and sexual development, appressorial formation and plant infection in Colletotrichum gloeosporioides | Plant pathogens and pests | Scoop.it
ATP-binding cassette (ABC) proteins are exclusively found in both prokaryotes and eukaryotes. In this study, we have characterized a gene from Glomerella leaf spot pathogen Colletotrichum gloeosporioides that encodes an ABC protein, whose function to date remains unknown. We designated this gene as CgABCF2. Deletion of CgABCF2 showed drastic reduction both growing rate and conidial production in C. gloeosporioides. The Δcgabcf2 mutant did not form the appressoria, lost the capability to infect apple and failed to form lesions on the wounded leaves and fruits. The C. gloeosporioides native CgABCF2 fully recovered defect of the Δcgabcf2 mutant. These data indicated that CgABCF2 was required for fungal development and invasion. The transcriptions of six pectolytic enzymes genes (CgPG1, CgPG2, pnl-1, pnl-2, pelA and pelB) significantly reduced in the Δcgabcf2 mutant, indicating that deletion of CgABCF2 impaired the fungal necrotrophic growth. In addition, CgABCF2 mediated sexual development through the positive regulation of the gene MAT1-2-1 expression. These results indicated that CgABCF2 underlies the complex process governing morphogenesis, sexual and asexual reproduction, appressorial formation and pathogenicity in C. gloeosporioides.
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Bacterial outer membrane vesicles at the plant–pathogen interface

Bacterial outer membrane vesicles at the plant–pathogen interface | Plant pathogens and pests | Scoop.it
Gram-negative bacteria outer membrane vesicles (OMVs) are extracellularly released blebs, constantly detaching from the bacterial cell surface. Being ubiquitous among bacteria and diverse in content, OMVs have a plethora of functions: promoting virulence, mediating bacterial cell–cell communication, modulating host immune response, and more. Though most research on OMVs has been carried out on animal pathogens, production of OMVs by plant pathogenic bacteria is predicted to be similarly intrinsic to their biology. Recent studies in the field of plant–bacteria interactions have begun to unravel the roles of OMVs, showing their involvement in biofilm formation, virulence, and modulation of plant immunity. With a range of general to highly specialized roles, these structures can act as an adaptive toolbox during pathogenesis and stress. This Pearl will crystallize current OMV research with a special focus on the role OMVs play in plant–bacteria interactions.
more...
No comment yet.
Rescooped by Christophe Jacquet from Plant pathogenic fungi
Scoop.it!

Subcellular compartmentation, interdependency and dynamics of the cyclic AMP‐dependent PKA subunits during pathogenic differentiation in rice blast

Subcellular compartmentation, interdependency and dynamics of the cyclic AMP‐dependent PKA subunits during pathogenic differentiation in rice blast | Plant pathogens and pests | Scoop.it
The cAMP-dependent PKA signalling plays a central role in growth, asexual development and pathogenesis in fungal pathogens. Here, we functionally characterised RPKA, the regulatory subunit of cAMP/PKA and studied the dynamics and organisation of the PKA subunits in the rice blast pathogen Magnaporthe oryzae. The RPKA subunit was essential for proper vegetative growth, asexual sporulation and surface hydrophobicity in M. oryzae. A spontaneous suppressor mutation, SMR19, that restored growth and conidiation in the RPKA deletion mutant was isolated and characterised. SMR19 enhanced conidiation and appressorium formation but failed to suppress the pathogenesis defects in rpkAΔ. The PKA activity was undetectable in the mycelial extracts of SMR19, which showed a single mutation (val242leu) in the highly conserved active site of the catalytic subunit (CPKA) of cAMP/PKA. The two subunits of cAMP/PKA showed different subcellular localisation patterns with RpkA being predominantly nucleocytoplasmic in conidia, while CpkA was largely cytosolic and/or vesicular. The CpkA anchored RpkA in cytoplasmic vesicles, and localisation of PKA in the cytoplasm was governed by CpkA in a cAMP-dependant or independent manner. We show that there exists a tight regulation of PKA subunits at the level of transcription, and the cAMP signalling is differentially compartmentalised in a stage-specific manner in rice blast.

Via Elsa Ballini, Steve Marek
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Cooperative Regulatory Functions of miR858 and MYB83 during Cyst Nematode Parasitism

Cooperative Regulatory Functions of miR858 and MYB83 during Cyst Nematode Parasitism | Plant pathogens and pests | Scoop.it
MicroRNAs (miRNAs) recently have been established as key regulators of transcriptome reprogramming that define cell function and identity. Nevertheless, the molecular functions of the greatest number of miRNA genes remain to be determined. Here, we report cooperative regulatory functions of miR858 and its MYB83 transcription factor target gene in transcriptome reprogramming during Heterodera cyst nematode parasitism of Arabidopsis (Arabidopsis thaliana). Gene expression analyses and promoter-GUS fusion assays documented a role of miR858 in posttranscriptional regulation of MYB83 in the Heterodera schachtii-induced feeding sites, the syncytia. Constitutive overexpression of miR858 interfered with H. schachtii parasitism of Arabidopsis, leading to reduced susceptibility, while reduced miR858 abundance enhanced plant susceptibility. Similarly, MYB83 expression increases were conducive to nematode infection because overexpression of a noncleavable coding sequence of MYB83 significantly increased plant susceptibility, whereas a myb83 mutation rendered the plants less susceptible. In addition, RNA-seq analysis revealed that genes involved in hormone signaling pathways, defense response, glucosinolate biosynthesis, cell wall modification, sugar transport, and transcriptional control are the key etiological factors by which MYB83 facilitates nematode parasitism of Arabidopsis. Furthermore, we discovered that miR858-mediated silencing of MYB83 is tightly regulated through a feedback loop that might contribute to fine-tuning the expression of more than a thousand of MYB83-regulated genes in the H. schachtii-induced syncytium. Together, our results suggest a role of the miR858-MYB83 regulatory system in finely balancing gene expression patterns during H. schachtii parasitism of Arabidopsis to ensure optimal cellular function.
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

The effector AvrRxo1 phosphorylates NAD in planta

The effector AvrRxo1 phosphorylates NAD in planta | Plant pathogens and pests | Scoop.it
Gram-negative bacterial pathogens of plants and animals employ type III secreted effectors to suppress innate immunity. Most characterized effectors work through modification of host proteins or transcriptional regulators, although a few are known to modify small molecule targets. The Xanthomonas type III secreted avirulence factor AvrRxo1 is a structural homolog of the zeta toxin family of sugar-nucleotide kinases that suppresses bacterial growth. AvrRxo1 was recently reported to phosphorylate the central metabolite and signaling molecule NAD in vitro, suggesting that the effector might enhance bacterial virulence on plants through manipulation of primary metabolic pathways. In this study, we determine that AvrRxo1 phosphorylates NAD in planta, and that its kinase catalytic sites are necessary for its toxic and resistance-triggering phenotypes. A global metabolomics approach was used to independently identify 3’-NADP as the sole detectable product of AvrRxo1 expression in yeast and bacteria, and NAD kinase activity was confirmed in vitro. 3’-NADP accumulated upon transient expression of AvrRxo1 in Nicotiana benthamiana and in rice leaves infected with avrRxo1-expressing strains of X. oryzae. Mutation of the catalytic aspartic acid residue D193 abolished AvrRxo1 kinase activity and several phenotypes of AvrRxo1, including toxicity in yeast, bacteria, and plants, suppression of the flg22-triggered ROS burst, and ability to trigger an R gene-mediated hypersensitive response. A mutation in the Walker A ATP-binding motif abolished the toxicity of AvrRxo1, but did not abolish the 3’-NADP production, virulence enhancement, ROS suppression, or HR-triggering phenotypes of AvrRxo1. These results demonstrate that a type III effector targets the central metabolite and redox carrier NAD in planta, and that this catalytic activity is required for toxicity and suppression of the ROS burst.
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Frontiers | Association Genetics in Plant Pathogens: Minding the Gap between the Natural Variation and the Molecular Function | Plant Science

One of the main goal in phytopathology is to better understand the molecular basis of plant–pathogen co-evolution through the identification of effectors and effector targets that play a role in natural phenotypic variation. Fortunately, next generation sequencing (NGS)—which can measure genetic variation at hundreds of thousands of markers across a genome, including for non-model organisms—is now helping to reach this goal. Among all possible strategies using NGS data, we expect that genome-wide association studies (GWAS) have the most potential to revolutionize the field of phytopathology. In contrast to QTL mapping, GWAS use outbred populations to capture the standing genetic variation, thus characterizing the raw material for evolution. By examining the natural phenotypic and genetic variation, association mapping can elucidate the genetic basis underlying complex traits. In the two decades since association mapping successfully detected common variants for human complex diseases (Risch and Merikangas, 1996) and with the publication of the first successful GWAS in humans in 2005 (Klein et al., 2005), the number of published GWAS keeps increasing. Researchers in the field of plant pathogens are now embarking on GWAS, with the promise to open new frontiers of research.
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

A dsRNA virus with filamentous viral particles

A dsRNA virus with filamentous viral particles | Plant pathogens and pests | Scoop.it
Viruses with double-stranded RNA genomes form isometric particles or are capsidless. Here we report a double-stranded RNA virus, Colletotrichum camelliae filamentous virus 1 (CcFV-1) isolated from a fungal pathogen, that forms filamentous particles. CcFV-1 has eight genomic double-stranded RNAs, ranging from 990 to 2444 bp, encoding 10 putative open reading frames, of which open reading frame 1 encodes an RNA-dependent RNA polymerase and open reading frame 4 a capsid protein. When inoculated, the naked CcFV-1 double-stranded RNAs are infectious and induce the accumulation of the filamentous particles in vivo. CcFV-1 is phylogenetically related to Aspergillus fumigatus tetramycovirus-1 and Beauveria bassiana polymycovirus-1, but differs in morphology and in the number of genomic components. CcFV-1 might be an intermediate virus related to truly capsidated viruses, or might represent a distinct encapsidating strategy. In terms of genome and particle architecture, our findings are a significant addition to the knowledge of the virosphere diversity.
more...
No comment yet.
Rescooped by Christophe Jacquet from Crosstalks in Plant-microbes interactions
Scoop.it!

Fluorescent markers of various organelles in the wheat pathogen Zymoseptoria tritici - ScienceDirect

Fluorescent markers of various organelles in the wheat pathogen Zymoseptoria tritici - ScienceDirect | Plant pathogens and pests | Scoop.it

• 17 vectors are described that allow labelling of 7 subcellular structures. • The fluorescent markers target the plasma membrane, endoplasmic reticulum, nucleus. • Markers also target the actin cytoskeleton, peroxisomes and autophagosomes. • These markers complete are toolkit of fluorescent reporters. • Reporters allow cell biological studies in the Septoria tritici blotch fungus.


Via Steve Marek, Rey Thomas
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Mapping resistance responses to Sclerotinia infestation in introgression lines of Brassica juncea carrying genomic segments from wild Brassicaceae B . fruticulosa

Mapping resistance responses to Sclerotinia infestation in introgression lines of Brassica juncea carrying genomic segments from wild Brassicaceae B . fruticulosa | Plant pathogens and pests | Scoop.it
Sclerotinia stem rot (Sclerotinia sclerotiorum) is a major disease of Brassica oilseeds. As suitable donors to develop resistant cultivars are not available in crop Brassicas, we introgressed resistance from a wild Brassicaceae species, B. fruticulosa. We produced 206 B. juncea-B. fruticulosa introgression lines (ILs). These were assessed for pollen grain fertility, genome size variations and resistance responses to Sclerotinia following stem inoculations under disease-conducive conditions. Of these, 115 ILs showing normal fertility and genome size were selected for cytogenetic characterization using florescent genomic in situ hybridization (Fl-GISH). B. fruticulosa segment substitutions were indicated in 28 ILs. These were predominantly terminal and located on B-genome chromosomes. A final set of 93 highly fertile and euploid (2n = 36) ILs were repeat-evaluated for their resistance responses during 2014–15. They were also genotyped with 202 transferable and 60 candidate gene SSRs. Association mapping allowed detection of ten significant marker trait associations (MTAs) after Bonferroni correction. These were: CNU-m157-2, RA2G05, CNU-m353-3, CNU-m442-5, ACMP00454-2, ACMP00454-3, EIN2-3-1, M641-1, Na10D09-1 and Na10D11-1. This is the first time such a molecular mapping technique has been deployed with introgression lines carrying genomic segments from B. fruticulosa, and the first to show that they possess high levels of resistance against S. sclerotiorum.
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Frontiers | Ultrastructural and Cytological Studies on Mycosphaerella pinodes Infection of the Model Legume Medicago truncatula | Plant Science

Frontiers | Ultrastructural and Cytological Studies on Mycosphaerella pinodes Infection of the Model Legume Medicago truncatula | Plant Science | Plant pathogens and pests | Scoop.it
Ascochyta (Mycosphaerella) blight on cultivated peas is primarily caused by infection through asexual spores (pycnospores) of Mycosphaerella pinodes (Berk. et Blox.) Vestergren [recently renamed Peyronellaea pinodes (Berk. & A. Bloxam) Aveskamp, Gruyter & Verkley]. Using a recently developed model pathosystem involving Medicago truncatula and M. pinodes strain OMP-1, we examined the histology and ultrastructure of early infection events and fungal development including penetration by appressoria, vegetative growth of infection hyphae, and host responses. On the susceptible ecotype R108-1, pycnospores germinated and grew over the surface of the epidermis, then formed an appressoria and penetrated the cuticle. Beneath the cuticle, the infection peg expanded into a hyphae that grew within the outer wall of the epidermis. Subsequently, the hyphae penetrated down within mesophyll cells and proliferated vigorously, eventually, forming asexual fruiting bodies (pycnidia). In contrast, successful penetration and subsequent growth of infection hyphae were considerably restricted in the ecotype Caliph. Detected by its reaction with cerium chloride (CeCl3) to produce electron-dense cerium perhydroxides in transmission electron micrographs, hydrogen peroxide (H2O2) accumulated in epidermal and mesophyll cells of Caliph challenged with pyconospores of M. pinodes. This intracellular localization was confirmed by energy-dispersive X-ray (EDX) spectroscopy. Our observations thus indicate that the oxidative burst reaction leading to the generation of reactive oxygen species is associated with a local host defense response in Caliph, since no clear H2O2 accumulation was detectable in susceptible R108-1. Indeed, aberrant hyphae such as intrahyphal hyphae and dead hyphae, probably due to a local defense elicited by the fungus, were abundant in Caliph but not in R108-1. Our results on the cellular interactions between the fungus and host cells provide additional insights to understand foliar infection by M. pinodes on cultivated peas.
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

An Emerging Paradigm? RxLR Cleavage before Effector Secretion

An Emerging Paradigm? RxLR Cleavage before Effector Secretion | Plant pathogens and pests | Scoop.it
Eukaryotic pathogens are responsible for devastating plant diseases that threaten food supplies globally—think potato blight caused by the oomycete Phytophora infestans, rice blast caused by the fungus Magnaporthe oryzae, and wheat stem rust caused by the fungus Puccinia graminis f. sp tritici. These pathogens secrete effector proteins that condition the host cells for successful infection, some by acting in the apoplast and others after entering into the host cells. Many oomycete effectors have an RxLR sequence motif in their N-terminal region that seems to function in host cell targeting, although the mechanisms are a matter of debate (reviewed in Wawra et al., 2012; Petre and Kamoun, 2014). It is notoriously difficult to study the secretion and targeting of effectors, as these processes occur only at the interface of the pathogen with the host and only during infection. In fact, there are mounting indications that some alternative approaches often used to assess pathogen effector secretion and entry in the host plant could be flawed (see, for example, Petre et al., 2016). In a new Breakthrough Report, Wawra et al. (2017) provide evidence that the RxLR motif is important for effector secretion from the pathogen, rather than for direct interaction with the host cells.
more...
No comment yet.
Rescooped by Christophe Jacquet from Rice Blast
Scoop.it!

Evolution of the wheat blast fungus through functional losses in a host specificity determinant

Evolution of the wheat blast fungus through functional losses in a host specificity determinant | Plant pathogens and pests | Scoop.it

Wheat blast first emerged in Brazil in the mid-1980s and has recently caused heavy crop losses in Asia. Here we show how this devastating pathogen evolved in Brazil. Genetic analysis of host species determinants in the blast fungus resulted in the cloning of avirulence genes PWT3 and PWT4, whose gene products elicit defense in wheat cultivars containing the corresponding resistance genes Rwt3 and Rwt4. Studies on avirulence and resistance gene distributions, together with historical data on wheat cultivation in Brazil, suggest that wheat blast emerged due to widespread deployment of rwt3 wheat (susceptible to Lolium isolates), followed by the loss of function of PWT3. This implies that the rwt3 wheat served as a springboard for the host jump to common wheat.

 

Via Yogesh Gupta, Tofazzal Islam's Research Group, Elsa Ballini
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Pathogen exploitation of an abscisic acid- and jasmonate-inducible MAPK phosphatase and its interception by Arabidopsis immunity

Pathogen exploitation of an abscisic acid- and jasmonate-inducible MAPK phosphatase and its interception by Arabidopsis immunity | Plant pathogens and pests | Scoop.it
Phytopathogens promote virulence by, for example, exploiting signaling pathways mediated by phytohormones such as abscisic acid (ABA) and jasmonate (JA). Some plants can counteract pathogen virulence by invoking a potent form of immunity called effector-triggered immunity (ETI). Here, we report that ABA and JA mediate inactivation of the immune-associated MAP kinases (MAPKs), MPK3 and MPK6, in Arabidopsis thaliana. ABA induced expression of genes encoding the protein phosphatases 2C (PP2Cs), HAI1, HAI2, and HAI3 through ABF/AREB transcription factors. These three HAI PP2Cs interacted with MPK3 and MPK6 and were required for ABA-mediated MPK3/MPK6 inactivation and immune suppression. The bacterial pathogen Pseudomonas syringae pv. tomato (Pto) DC3000 activates ABA signaling and produces a JA-mimicking phytotoxin, coronatine (COR), that promotes virulence. We found that Pto DC3000 induces HAI1 through COR-mediated activation of MYC2, a master transcription factor in JA signaling. HAI1 dephosphorylated MPK3 and MPK6 in vitro and was necessary for COR-mediated suppression of MPK3/MPK6 activation and immunity. Intriguingly, upon ETI activation, A. thaliana plants overcame the HAI1-dependent virulence of COR by blocking JA signaling. Finally, we showed conservation of induction of HAI PP2Cs by ABA and JA in other Brassicaceae species. Taken together, these results suggest that ABA and JA signaling pathways, which are hijacked by the bacterial pathogen, converge on the HAI PP2Cs that suppress activation of the immune-associated MAPKs. Also, our data unveil interception of JA-signaling activation as a host counterstrategy against the bacterial suppression of MAPKs during ETI.
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

The Impact of Steroidal Glycoalkaloids on the Physiology of Phytophthora infestans, the Causative Agent of Potato Late Blight | Molecular Plant-Microbe Interactions

The Impact of Steroidal Glycoalkaloids on the Physiology of Phytophthora infestans, the Causative Agent of Potato Late Blight | Molecular Plant-Microbe Interactions | Plant pathogens and pests | Scoop.it
Steroidal glycoalkaloids (SGAs) are plant secondary metabolites known to be toxic to animals and humans and that have putative roles in defense against pests. The proposed mechanisms of SGA toxicity are sterol-mediated disruption of membranes and inhibition of cholinesterase activity in neurons. It has been suggested that phytopathogenic microorganisms can overcome SGA toxicity by enzymatic deglycosylation of SGAs. Here, we have explored SGA-mediated toxicity toward the invasive oomycete Phytophthora infestans, the causative agent of the late blight disease in potato and tomato, as well as the potential for SGA deglycosylation by this species. Our growth studies indicate that solanidine, the nonglycosylated precursor of the potato SGAs α-chaconine and α-solanine, has a greater physiological impact than its glycosylated forms. All of these compounds were incorporated into the mycelium, but only solanidine could strongly inhibit the growth of P. infestans in liquid culture. Genes encoding several glycoside hydrolases with potential activity on SGAs were identified in the genome of P. infestans and were shown to be expressed. However, we found no indication that deglycosylation of SGAs takes place. We present additional evidence for apparent host-specific adaptation to potato SGAs and assess all results in terms of future pathogen management strategies.
more...
No comment yet.
Rescooped by Christophe Jacquet from Plant pathogenic fungi
Scoop.it!

How light affects the life of Botrytis

How light affects the life of Botrytis | Plant pathogens and pests | Scoop.it

• Botrytis cinerea is an aggressive plant pathogen causing gray mold diseases.
• Near-UV, blue, green, red and far-red light affect its growth characteristics.
• Eleven (plus X?) potential photoreceptors cover the entire light spectrum.
• A sophisticated signaling machinery allows for processing the light signals.
• Light regulates morphogenesis, tropism, entrainment and stress responses.


Via Steve Marek
more...
No comment yet.
Rescooped by Christophe Jacquet from Actualités végétales
Scoop.it!

Aphanomyces and Fusarium root rots of pulse crops

Aphanomyces and Fusarium root rots of pulse crops | Plant pathogens and pests | Scoop.it
In 2016, we conducted field surveys for root rot of pea and lentil in Alberta and Saskatchewan. In Alberta we surveyed 27 lentil and 89 pea fields during flowering, and 67 lentil and 68 pea fields in Saskatchewan.

In Alberta, we observed approximately 30 per cent incidence of moderate and severe root rot disease, but there was no obvious pattern to the geographic distribution. In Saskatchewan, we saw a higher incidence of moderate and severe root rot, with the same random distribution throughout the province. At moderate and severe root rot levels, we would expect to see a negative impact of root rot on shoot growth and yield.

The surveys found Aphanomyces is widely distributed across the Prairies. For a pathogen that is a fairly new player on the scene, only detected and confirmed in 2012/2013, this widespread distribution across pretty much everywhere peas and lentils are grown would indicate this pathogen has been present for a number of years.

Via plantsci-UT3
more...
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

MoEnd3 regulates appressorium formation and virulence through mediating endocytosis in rice blast fungus Magnaporthe oryzae

MoEnd3 regulates appressorium formation and virulence through mediating endocytosis in rice blast fungus Magnaporthe oryzae | Plant pathogens and pests | Scoop.it
Eukaryotic cells respond to environmental stimuli when cell surface receptors are bound by environmental ligands. The binding initiates a signal transduction cascade that results in the appropriate intracellular responses. Studies have shown that endocytosis is critical for receptor internalization and signaling activation. In the rice blast fungus Magnaporthe oryzae, a non-canonical G-protein coupled receptor, Pth11, and membrane sensors MoMsb2 and MoSho1 are thought to function upstream of G-protein/cAMP signaling and the Pmk1 MAPK pathway to regulate appressorium formation and pathogenesis. However, little is known about how these receptors or sensors are internalized and transported into intracellular compartments. We found that the MoEnd3 protein is important for endocytic transport and that the ΔMoend3 mutant exhibited defects in efficient internalization of Pth11 and MoSho1. The ΔMoend3 mutant was also defective in Pmk1 phosphorylation, autophagy, appressorium formation and function. Intriguingly, restoring Pmk1 phosphorylation levels in ΔMoend3 suppressed most of these defects. Moreover, we demonstrated that MoEnd3 is subject to regulation by MoArk1 through protein phosphorylation. We also found that MoEnd3 has additional functions in facilitating the secretion of effectors, including Avr-Pia and AvrPiz-t that suppress rice immunity. Taken together, our findings suggest that MoEnd3 plays a critical role in mediating receptor endocytosis that is critical for the signal transduction-regulated development and virulence of M. oryzae.
more...
No comment yet.