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QTL-seq: Rapid mapping of quantitative trait loci in rice by whole genome resequencing of DNA from two bulked populations - The Plant Journal

QTL-seq: Rapid mapping of quantitative trait loci in rice by whole genome resequencing of DNA from two bulked populations - The Plant Journal | Rice Blast | Scoop.it

Here we report a rapid identification of plant QTL by whole genome resequencing of DNAs from two populations each composed of 20-50 individuals showing extreme opposite trait values for a given phenotype in a segregating progeny. We applied QTL-seq to rice recombinant inbred lines (RILs) and F2 populations and successfully identified QTL for important agronomic traits, such as partial resistance to the fungal rice blast disease and seedling vigor.

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Scientific articles on rice blast and wheat blast 20 new articles each month !
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Assessment of sensitivity and virulence fitness costs of the AvrPik alleles from Magnaporthe oryzae to isoprothiolane

The in vitro sensitivity of AvrPik allele isolates of Magnaporthe oryzae to isoprothiolane was examined and the virulence fitness costs of AvrPik allele isolates to isoprothiolane were assessed. Isoprothiolane was found to suppress the radial growth of AvrPik allele isolates at all concentrations (1, 5, 10, 15, and 20 μg/mL). Generally, a higher isoprothiolane concentration has a stronger inhibitory effect on mycelial growth in AvrPik allele isolates at 6 and 10 days after inoculation. The inhibitory effect of isoprothiolane also increased with treatment time. To determine whether a correlation existed between the in vitro sensitivity of AvrPik allele isolates and virulence, the half-maximal inhibitor concentration and 75% of the maximum inhibitor concentration were calculated for each mutation isolate and wild-type isolate. Based on these values and virulence, no significant correlation between the susceptibility of AvrPik allele isolates and virulence was detected. In summary, no fitness costs were associated with sensitivity of blast isolates carrying specific AvrPik alleles to different virulence.

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Transcriptional Profiling of Rice Early Response to Magnaporthe oryzae Identified OsWRKYs as Important Regulators in Rice Blast Resistance

Transcriptional Profiling of Rice Early Response to Magnaporthe oryzae Identified OsWRKYs as Important Regulators in Rice Blast Resistance | Rice Blast | Scoop.it

The functional analysis showed that the genes involved in signaling and secondary metabolism were extensively up-regulated. In particular, WRKY transcription factor genes were significantly enriched among the up-regulated genes. Overexpressing one of these WRKY genes,OsWRKY47, in transgenic rice plants conferred enhanced resistance against rice blast fungus. Our results revealed the sophisticated transcriptional reprogramming of signaling and metabolic pathways during rice early response to M. oryzae and demonstrated the critical roles of WRKY transcription factors in rice blast resistance.

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36th New Phytologist Symposium: Cell biology at the plant–microbe interface, Munich, Germany 29 Nov – 1 Dec 2015

36th New Phytologist Symposium: Cell biology at the plant–microbe interface, Munich, Germany 29 Nov – 1 Dec 2015 | Rice Blast | Scoop.it

Symposium aim - We aim to organize a cutting edge meeting focused on the application of cell biology approaches to understand the mechanisms that diverse microbes use to manipulate plant cells to benefit their life styles. The meeting will bring together researchers working on a broad spectrum of microbes across different taxa (bacteria, fungi, oomycetes) that form a variety of different interactions (pathogenic, symbiotic) with plant organs/tissues (leaves, roots). With the explosion in microbial/host genome sequences and the identification of genes/proteins involved in these interactions, the focus of the field is moving rapidly towards using cell and molecular biology techniques and new imaging technologies to understand the molecular dialogue between plants and their microbial pathogens/symbionts. The need for a conference on this topic, the first of its type, is evidenced by the growing prominence of cell biology in the literature. Students and scientists in this field face many challenges in the application and interpretation of cell biology data and would greatly benefit from a specialized conference on this topic. The symposium will bring together a broad representation of researchers focussing on different cell biology aspects and will allow researchers across the different disciplines to present and exchange their recent advances in this important topic of plant biology.

Symposium rationale and scope - Plant organs are subject to colonisation and manipulation by microbes, and this requires reprogramming of host cell biology to accommodate microbial structures within tissues/cells and to mediate responses for proper immunity or for symbiosis. Host cell biology changes during microbial invasion were first reported more than 100 years ago based on microscopy studies revealing that many microbes project structures (haustoria, arbuscules) into plant cells that are enveloped with a specialized plant-­derived membrane and evidence now suggests an intimate molecular exchange takes place across these membrane interfaces. However, recent identification of some of the molecular players in these interactions is only now providing appropriate tools to analyse these events. The symposium will focus on advances in understanding the molecular interactions that occur between a microbe and its host at a cellular and subcellular level, such as:

how root and leaf cells accommodate microbial structures through biogenesis of specialized plant derived membranes, microbial invasion and spreading strategies (via stomata, roots, vasculature, plasmodesmata), the dynamic localization of cell surface and cytosolic receptors recognizing microbial signals the reprogramming of host membrane trafficking (focal accumulation, secretion), the delivery of microbial molecules from fungal and oomycete species into plant cells.

With recent advances in high resolution/throughput bioimaging we are gaining new insights into the cell biology mechanisms and pathways of plant cell interactions with diverse microbes. Therefore the symposium provides a timely and important opportunity to overview the application of these technologies to plant–microbe interactions, and to discuss recent discoveries emerging from diverse host–microbe interactions illustrating common underlying principles and differences of strategies used by the microbes to gain access to plant tissues/cells. The symposium will certainly trigger a wealth of discussions, exchange of findings and methodologies, and will promote new lines of research and ideas in this rapidly expanding field.


Via Kamoun Lab @ TSL, Francis Martin
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Over-expression of a glutamate dehydrogenase gene, MgGDH , from Magnaporthe grisea confers tolerance to dehydration stress in transgenic rice

Over-expression of a glutamate dehydrogenase gene, MgGDH , from Magnaporthe grisea confers tolerance to dehydration stress in transgenic rice | Rice Blast | Scoop.it

Main conclusionHeterologous expression of a fungal NADP(H)-GDH gene ( MgGDH ) from Magnaporthe grisea can improve dehydration stress tolerance in rice by preventing toxic accumulation of ammonium.Glutamate dehydrogenase (GDH; EC 1.4.1.2 and EC 1.4.1.4) may act as a stress-responsive enzyme in detoxification of high intracellular ammonia and production of glutamate for proline synthesis under stress conditions. In present study, a fungal NADP(H)-GDH gene (MgGDH) from Magnaporthe grisea was over-expressed in rice (Oryza sativa L. cv. ‘kitaake’), and the transgenic plants showed the improvement of tolerance to dehydration stress. The kinetic analysis showed that His-TF-MgGDH preferentially utilizes ammonium to produce l-glutamate. Moreover, the affinity of His-TF-MgGDH for ammonium was dramatically higher than that of His-TF-OsGDH for ammonium. Over-expressing MgGDH transgenic rice plants showed lower water-loss rate and higher completely close stomata than the wild-type plants under dehydration stress conditions. In transgenic plants, the NADP(H)-GDH activities were markedly higher than those in wild-type plants and the amination activity was significantly higher than the deamination activity. Compared with wild-type plants, the transgenic plants accumulated much less NH4 + but higher amounts of glutamate, proline and soluble sugar under dehydration stress conditions. These results indicate that heterologous expression of MgGDH can prevent toxic accumulation of ammonium and in return improve dehydration stress tolerance in rice.


Via Christophe Jacquet
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Synthesis and antifungal activity of 3-aryl-1,2,4-triazin-6-one derivatives

Thirty nine analogs (compounds 5 to 43) were prepared to explore structure–activity relationships at R1 and R2, and all targeted structures were characterized by 1H NMR and MS. All compounds were in vitro tested against three ascomycetes [Leptosphaeria nodorum,Magnaporthe grisea and Zymoseptoria tritici (syn. Mycosphaerella graminicola)] and one basidiomycete (Ustilago maydis) pathogen. When R2 was trifluoroethyl, fungicidal activity was enhanced by a single electron-withdrawing substitution, such as Br, Cl and CF3 in the 3-position at R1 (compounds 9, 10 and 12), of which the 3-bromo compound (10) was the most active (EC50 = 0.08, averaged across four pathogens). More subtle activity improvement was found by addition of a second halogen substituent in the 4-position, with the 3-Br-4-F analog (20) being the most active against the commercially important cereal pathogen Z. tritici. Replacement of the R2 haloalkyl group with benzyl, alkyl (e.g. n-butyl, i-butyl, n-pentyl) and, particularly, CH2-cycloalkyls (e.g. CH2-cyclopropyl, CH2-cyclobutyl) resulted in further activity enhancements against the ascomycete fungi, but was either neutral or detrimental to activity against U. maydis. One of the most active compounds in this series (41) gave control of Z. tritici, with an EC50 of 0.005 ppm, comparable with that of the commercial strobilurin fungicide azoxystrobin (EC50 0.002 ppm).

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Sequence Variation and Recognition Specificity of the Avirulence Gen AvrPiz-T in Magnaporthe Oryzae Field Populations

Sequence Variation and Recognition Specificity of the Avirulence Gen AvrPiz-T in Magnaporthe Oryzae Field Populations | Rice Blast | Scoop.it

In this study, we focused on a newly identified AVR gene AvrPiz-t.
We PCR amplified open reading frames (ORFs) of AvrPiz-t as well as promoter regions to detect size variation at this locus in 711 isolates of M. oryzae collected from 38 countries and regions. Through sequencing and Southern hybridization of the amplified locus, strains with polymorphisms in the ORF were classified into groups based on mutation type and site. Natural selection intensity on this gene was calculated and pathogenicity assays were applied
to evaluate the association between AvrPiz-t ORF/promoter polymorphism and virulence. In conclusion, sequences
at the AvrPiz-t locus were revealed to contain variations at both promoter and ORF regions. This locus is undergoing
a relatively strong positive selection. The diversity in coding sequence and the insertions of transposable elements
in the promoter region enable M. oryzae to evade recognition by the cognate Piz-t R gene in the host

 

 

http://omicsgroup.org/journals/sequence-variation-and-recognition-specificity-of-the-avirulence-gene-avrpizt-in-magnaporthe-oryzae-field-populations-2165-8056.1000113.pdf

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The Pathogen-Host Interactions database (PHI-base): additions and future developments

The Pathogen-Host Interactions database (PHI-base): additions and future developments | Rice Blast | Scoop.it

The Pathogen-Host Interactions database (PHI-base) catalogues experimentally verified pathogenicity, virulence and effector genes from bacterial, fungal and protist pathogens. Mutant phenotypes are associated with gene information. The included pathogens infect a wide range of hosts including humans, animals, plants, insects, fish and other fungi. The current version, PHI-base 3.6, available at http://www.phi-base.org, stores information on 2875 genes, 4102 interactions, 110 host species, 160 pathogenic species (103 plant, 3 fungal and 54 animal infecting species) and 181 diseases drawn from 1243 references. 

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The receptor kinase CERK1 has dual functions in symbiosis and immunity signalling

The receptor kinase CERK1 has dual functions in symbiosis and immunity signalling | Rice Blast | Scoop.it
The establishment of symbiotic interactions between mycorrhizal fungi, rhizobial bacteria and their legume hosts involves a common symbiosis signalling pathway. This signalling pathway is activated by Nod factors produced by rhizobia and these are recognised by the Nod factor receptors NFR1/LYK3 and NFR5/NFP. Mycorrhizal fungi produce lipochitooligosaccharides (LCOs) similar to Nod factors, as well as short-chain chitin oligomers (CO4/5), implying commonalities in signalling during mycorrhizal and rhizobial associations. Here we show that NFR1/LYK3, but not NFR5/NFP, is required for the establishment of the mycorrhizal interaction in legumes. NFR1/LYK3 is necessary for the recognition of mycorrhizal fungi and the activation of the symbiosis signalling pathway leading to induction of calcium oscillations and gene expression. Chitin oligosaccharides also act as microbe associated molecular patterns that promote plant immunity via similar LysM receptor-like kinases. CERK1 in rice has the highest homology to NFR1 and we show that this gene is also necessary for the establishment of the mycorrhizal interaction as well as for resistance to the rice blast fungus. Our results demonstrate that NFR1/LYK3/OsCERK1 represents a common receptor for chitooligosaccharide-based signals produced by mycorrhizal fungi, rhizobial bacteria (in legumes) and fungal pathogens. It would appear that mycorrhizal recognition has been conserved in multiple receptors across plant species, but additional diversification in certain plant species has defined other signals that this class of receptors can perceive.

Via Christophe Jacquet
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Identification of a novel major locus for gray leaf spot resistance in Italian ryegrass ( Lolium multiflorum Lam.)

Identification of a novel major locus for gray leaf spot resistance in Italian ryegrass ( Lolium multiflorum Lam.) | Rice Blast | Scoop.it
Gray leaf spot (GLS), caused by Magnaporthe oryzae (anamorph Pyricularia oryzae), in ryegrasses is a very serious problem. Heavily infected small seedlings die within a matter of days, and stands of the grasses are seriously damaged by the disease. Thus, the development of GLS-resistant cultivars has become a concern in ryegrass breeding.
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Genome-wide association study of blast resistance in indica rice

Genome-wide association study of blast resistance in indica rice | Rice Blast | Scoop.it

Totally, thirty associated loci were identified. The strongest signal (Chr11_6526998, P =1.17 × 10−17) was located within the gene Os11g0225100, one of the rice Pia-blast resistance gene. Another association signal (Chr11_30606558) was detected around the QTL Pif. Our study identified the gene Os11g0704100, a disease resistance protein containing nucleotide binding site-leucine rich repeat domain, as the main candidate gene of Pif. In order to explore the potential mechanism underlying the blast resistance, we further examined a locus in chromosome 12, which was associated with CH149 (P =7.53 × 10−15). The genes, Os12g0424700 and Os12g0427000, both described as kinase-like domain containing protein, were presumed to be required for the full function of this locus. Furthermore, we found some association on chromosome 3, in which it has not been reported any loci associated with rice blast resistance. In addition, we identified novel functional candidate genes, which might participate in the resistance regulation.

 

This work provides the basis of further study of the potential function of these candidate genes. A subset of true associations would be weakly associated with outcome in any given GWAS; therefore, large-scale replication is necessary to confirm our results. Future research will focus on validating the effects of these candidate genes and their functional variants using genetic transformation and transferred DNA insertion mutant screens, to verify that these genes engender resistance to blast disease in rice.

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Molecular progress on the mapping and cloning of functional genes for blast disease in rice (Oryza sativa L.): current status and future considerations.

Rice blast disease, which is caused by the fungal pathogen Magnaporthe oryzae, is a recurring problem in all rice-growing regions of the world. The use of resistance (R) genes in rice improvement breeding programmes has been considered to be one of the best options for crop protection and blast management. Alternatively, quantitative resistance conferred by quantitative trait loci (QTLs) is also a valuable resource for the improvement of rice disease resistance. In the past, intensive efforts have been made to identify major R-genes as well as QTLs for blast disease using molecular techniques. A review of bibliographic references shows over 100 blast resistance genes and a larger number of QTLs (∼500) that were mapped to the rice genome. Of the blast resistance genes, identified in different genotypes of rice, ∼22 have been cloned and characterized at the molecular level. In this review, we have summarized the reported rice blast resistance genes and QTLs for utilization in future molecular breeding programmes to introgress high-degree resistance or to pyramid R-genes in commercial cultivars that are susceptible to M. oryzae. The goal of this review is to provide an overview of the significant studies in order to update our understanding of the molecular progress on rice and M. oryzae. This information will assist rice breeders to improve the resistance to rice blast using marker-assisted selection which continues to be a priority for rice-breeding programmes.


Read More: http://informahealthcare.com/doi/abs/10.3109/07388551.2014.961403

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Antimicrobial Activity of UV-Induced Phenylamides from Rice Leaves

Antimicrobial Activity of UV-Induced Phenylamides from  Rice Leaves | Rice Blast | Scoop.it
Rice produces a wide array of phytoalexins in response to pathogen attacks and UV-irradiation. Except for the flavonoid sakuranetin, most phytoalexins identified in rice are diterpenoid compounds. Analysis of phenolic-enriched fractions from UV-treated rice leaves showed that several phenolic compounds in addition to sakuranetin accumulated remarkably in rice leaves. We isolated two compounds from UV-treated rice leaves using silica gel column chromatography and preparative HPLC. The isolated ph
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RNA Silencing in Filamentous Fungi: From Basics to Applications

n the post-genomics era, RNAi has rapidly become a powerful reverse genetic tool for elucidating gene function in a wide range of eukaryotes including fungi. In this review, we focus on recent discoveries of RNAi-related biological phenomena in fungi and their underlying molecular mechanisms. In addition, recent advances in RNA-mediated gene silencing technologies and their potential use for functional genomics studies in fungi are discussed.

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Identification of quantitative trait loci conferring blast resistance in Bodao, a japonica rice landrace

Using a quantitative trait locus (QTL) mapping approach, 13 QTL on chromosomes 1, 2, 9, 11, and 12 were detected from Bodao. 
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Analysis of in planta Expressed Orphan Genes in the Rice Blast Fungus Magnaporthe oryzae

Analysis of in planta Expressed Orphan Genes in the Rice Blast Fungus Magnaporthe oryzae | Rice Blast | Scoop.it

Here, we analyzed seven orphan genes (MoSPC1 to MoSPC7) prioritized based on in planta expressed  sequence tag data in the rice blast fungus,Magnaporthe  oryzae. Expression analysis using qRT-PCR confirmed  the expression of four genes (MoSPC1, MoSPC2, Mo-SPC3and MoSPC7) during plant infection. However,  individual deletion mutants of these four genes did  not differ from the wild-type strain for all phenotypes  examined, including pathogenicity. Based on these results, the four  orphan genes may be products of de novo gene birth  processes, and their adaptive potential is in the course  of being tested for retention or extinction through natural  selection.

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Selection of optimized candidate reference genes for qRT-PCR normalization in rice (Oryza sativa L.) during Magnaporthe oryzae infection and drought

Drought and rice blast disease caused by Magnaporthe oryzae are two of the most serious threats to global rice production. To explore the mechanisms underlying gene expression induced in rice by stresses, studies involving transcriptome analyses have been conducted over the past few years. Thus, it is crucial to have a reliable set of reference genes to normalize the expression levels of rice genes affected by different stresses. To identify potential reference genes for studies of the differential expression of target genes in rice under M. oryzae infection and drought conditions, the present study evaluated five housekeeping genes for the normalization of gene expression. The stability of the expression of these genes was assessed using the analytical software packages geNorm and NormFinder. For all samples analyzed, the stability rank was UBQ5 > GAPDH > eIF-4α> β-TUB > 18S rRNA. The data showed that theUBQ5, GAPDH, and eIF-4αgenes are appropriate, high-performing reference genes and will be highly useful in future expression studies of fungal infections and drought in rice.

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Development of disease-resistant rice by optimized expression of WRKY45

The rice transcription factor WRKY45 plays a central role in the salicylic acid signalling pathway and mediates chemical-induced resistance to multiple pathogens, including Magnaporthe oryzae and Xanthomonas oryzae pv. oryzae. Previously, we reported that rice transformants overexpressing WRKY45 driven by the maize ubiquitin promoter were strongly resistant to both pathogens; however, their growth and yield were negatively affected because of the trade-off between the two conflicting traits. Also, some unknown environmental factor(s) exacerbated this problem. Here, we report the development of transgenic rice lines resistant to both pathogens and with agronomic traits almost comparable to those of wild-type rice. 

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Nat Comm: Combining high-throughput phenotyping and genome-wide association studies to reveal natural genetic variation in rice

Nat Comm: Combining high-throughput phenotyping and genome-wide association studies to reveal natural genetic variation in rice | Rice Blast | Scoop.it

ABSTRACT: Even as the study of plant genomics rapidly develops through the use of high-throughput sequencing techniques, traditional plant phenotyping lags far behind. Here we develop a high-throughput rice phenotyping facility (HRPF) to monitor 13 traditional agronomic traits and 2 newly defined traits during the rice growth period. Using genome-wide association studies (GWAS) of the 15 traits, we identify 141 associated loci, 25 of which contain known genes such as the Green Revolution semi-dwarf gene, SD1. Based on a performance evaluation of the HRPF and GWAS results, we demonstrate that high-throughput phenotyping has the potential to replace traditional phenotyping techniques and can provide valuable gene identification information. The combination of the multifunctional phenotyping tools HRPF and GWAS provides deep insights into the genetic architecture of important traits.


Via fundoshi
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Morphoanatomical and Biochemical Changes in the Roots of Rice Plants Induced by Plant Growth-Promoting Microorganisms

Morphoanatomical and Biochemical Changes in the Roots of Rice Plants Induced by Plant Growth-Promoting Microorganisms | Rice Blast | Scoop.it

The goal of the present study was to characterize anatomical and biochemical changes in rice plant roots in response to seed treatment with rhizobacteria (Burkholderia pyrrocinia (R-46) + Pseudomonas fluorescens (R-55)) and Trichoderma asperellum (Ta: mixture of strains T-06, T-09, T-12, and T-52). The experimental design was completely randomized, with six treatments (R-46, R-55, R-46 + R-55, Ta+ R-46 + R-55, Ta, and control) and ten replicates. Treatments Ta and R-46 + R-55 increased the root length and diameter as well as the cortex expansion and induced a 2% expansion of the aerenchymal space. Treatments Ta and R-46 increased the vascular cylinder diameter. The number of protoxylem poles and metaxylem vessel elements was increased by R-46 and R-55. The total phenol content increased with treatments Ta, R-46 + R-55, R-46, and R-55, and all the treatments increased the flavonoid content. The lignin content increased with the Ta and R-55 treatments. All the root architecture modifications resulting from the interaction between seedlings and bioagents (rhizobacteria and Trichoderma spp.) observed in the present study favored the root plasticity of rice seedlings.

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Interfacing Whispering Gallery Mode Optical Microresonator Biosensors with the Plant Defense Elicitor Chitin

Interfacing Whispering Gallery Mode Optical Microresonator Biosensors with the Plant Defense Elicitor Chitin | Rice Blast | Scoop.it

Chitin oligosaccharides were conjugated to optical biosensors.

Optical biosensor sensitivity was maintained after conjugation.

The conjugated surfaces demonstrate activity toward chitin receptors.

The conjugated devices successfully detected lectin, a model chitin receptor

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Investigating the Role of the Exocyst Complex in Infection-related Development of the Rice Blast Fungus Magnaporthe Oryzae

Host colonization is mediated through the secretion of effector proteins in order to neutralize host immune responses. However, the mechanism of the effector delivery during biotrophic invasion is not well defined in M. oryzae. In this thesis, I define the role of the exocyst complex, an evolutionarily conserved octameric protein complex involved in vesicle docking to the plasma membrane (composed of Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70 and Exo84), during infection-related development in M. oryzae. Like other filamentous fungi, M. oryzae, exocyst components localize to the vegetative hyphal tip distinct from the Spitzenkörper. However, at the initial stage of infection-related development all the exocyst components localise as a ring at the cortex of the appressorium and re-assembles around the appressorium pore in an actin-dependent manner in mature appressoria. I report that the septin network is required for the transition of exocyst ring from periphery to the appressorium pore. Deletion of Exo70 and Sec5 showed significant reduction in protein secretion and plant infection. I show that Sec6 is required for the exocyst assembly around the appressorium pore and effector secretion from the appressorium. I report that, during biotrophic invasion, effectors are secreted through a distinct pathway. Apoplastic effectors, Bas4 and Slp1 are secreted via a Golgi-dependent pathway while secretion of cytoplasmic effectors, Pwl2 and Bas1 meditates through a Golgi-independent pathway in which exocyst components Exo70 and Sec5 are involved.

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Expression analysis of innate immunity related genes in the true/field blast resistance gene-mediated defence response

Expression analysis of innate immunity related genes in the true/field blast resistance gene-mediated defence response | Rice Blast | Scoop.it

In this work, the expression profiles of innate rice immunity related genes were examined in the mediated resistance response of true/field resistance genes. Three sets of rice near-isogenic lines (NILs) were used: the resistant NILs carrying true resistance genes in the genetic background of the susceptible cultivar Nipponbare (NB), NB-Pib, NB-Pizt, NB-Pik and NB-Pita2; NILs bearing field resistance genes pi21 in the susceptible cultivar Aichiasahi (AA) AA-pi21, Kahei (KHR). The marker gene OsWRKY45 of salicylic acid (SA) signalling was upregulated in all tested cultivars. And, JAmyb (marker gene of jasmonic acid signalling) showed higher upregulation in the resistance lines with nucleotide-binding sites and leucine-rich repeat (NBS-LRR) R genes Pib, Pizt, Pik, Pita2 and Pikahei than in NB and KHS. SalT of abscisic acid (ABA) signalling may be involved in the R/Avr interaction, including Pizt, Pik, pi21 and Pikahei. However, SalT was shown to negatively regulate Pib/AvrPib interaction. OsPR1b and PBZ1 were differentially expressed and strongly activated at a later stage by 48 h post-inoculation. Interestingly, there was evidence that OsPR1b and PBZ1 played an important role in the pi21-mediated response. It was shown that OsRAR1 could be upregulated in the true resistance line NB-Pita2 and the field resistance line KHR, while OsSGT1 and OsHSP90 could be upregulated in all tested lines. The involvement of these genes illustrated the complexity of the downstream signalling pathways in the mediated resistance response of true/field resistance genes.

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Elucidation of molecular and biochemical determinants in a natural rice rhizospheric isolate to attenuate rice blast pathogen Magnaporthe oryzae

Elucidation of molecular and biochemical determinants in a natural rice rhizospheric isolate to attenuate rice blast pathogen Magnaporthe oryzae | Rice Blast | Scoop.it

One isolate in particular, Pseudomonas chlororaphis EA105, was striking in its antifungal activity, drastically reducing vegetative growth of M. oryzae and almost completely halting the formation of M. oryzae's appressoria, a structure which is required for penetration into the host. When rice plants were root-treated with EA105 prior toM. oryzae infection, there were fewer lesions and the size of lesions was reduced. Plant defense mechanisms are typically mediated through salicylic acid (SA), jasmonic acid (JA), and/or ethylene (ETH). In plants which were treated with EA105, there was induction of genes involved in JA and ETH signaling while the expression of genes involved in salicylic acid (SA) signaling were largely unaffected. In addition SA, JA, and ETH, another critical plant hormone, abscisic acid (ABA) was also investigated. Some phytopathogens, including M. oryzae, have evolved mechanisms to trigger increased ABA biosynthesis in plants as part of the virulence process. EA105 prevented M. oryzae from up-regulating NCED3, the key enzyme involved in ABA biosynthesis. Similarly, EA105 prevented M. oryzae from up-regulating a putative rice beta glucosidase that is likely involved in activating conjugated inactive forms of the hormone. ABA appears to function not only as a suppressor of plant defense, but also a promoter of pathogenesis in M. oryzae through the acceleration of spore germination and appressoria formation. Spores and mycelia of M. oryzae produced ABA, though at levels lower than in plants, further indicating that ABA also plays an important role in fungi. However, even with the addition of exogenous ABA, EA105 was able to counter the virulence-promoting effects of this compound. In summary, EA105 can directly antagonize fungal growth and pathogenesis as well as increase host resistance to blast, mediated through JA and ETH signaling, and through the suppression of ABA-related susceptibility. 

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pFPL vectors for high-throughput protein localization in fungi: detecting cytoplasmic accumulation of putative effector proteins.

pFPL vectors for high-throughput protein localization in fungi: detecting cytoplasmic accumulation of putative effector proteins. | Rice Blast | Scoop.it

As part of a large scale project whose goal was to identify candidate effector proteins in Magnaporthe oryzae, we developed a suite of vectors that facilitate high throughput protein localization experiments in fungi. These vectors utilize GatewayTM recombinational cloning to place a gene’s promoter and coding sequences upstream and in frame with the fluorescent proteins eCFP, eGFP, mRFP, eYFP, or a nucleus-targeted mCHERRY variant. The respective GatewayTM cassettes were incorporated into Agrobacterium-based plasmids to allow efficient fungal transformation using hygromycin or geneticin resistance selection. Use of pFPL vectors with two different selectable markers provided a convenient way to label fungal cells with different fluorescent proteins, which, in turn, yielded new insights into M. oryzae appressorium structure and function. We demonstrate the utility of the pFPL vectors for identifying candidate effector proteins and we highlight a number of important factors that must be taken into consideration when screening for putative effectors that are translocated across the host plasma membrane.

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Genome-wide analyses of DNA-binding proteins harboring AT-hook motifs and their functional roles in the rice blast pathogen, Magnaporthe oryzae

The AT-hook is a DNA-binding motif originally described in the high mobility group A of non-histone chromatin components. The AT-hook proteins bind to the minor groove of adenine–thymine (AT) rich regions of DNA and act as transcriptional cofactors coordinating nucleoproteins during transcriptional regulation. In this study, a genome-widein silico analysis of AT-hook proteins was performed on the ascomycete plant pathogenic fungus,Magnaporthe oryzae. Targeted deletion of MoATH10 significantly increased pigmentation and conidiation, indicating that MoATH10 is negatively involved in the regulation of pigmentation and conidiation in M. oryzae. Pathogenicity assays revealed that theΔMoath10 mutant was less virulent. The reduced disease development of the ΔMoath10 mutant was due to a partial defect in invasive growth inside plant cells, but not appressorium-mediated penetration. These results suggest that MoATH10 is important for growth, development, and virulence in M. oryzae.

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