Rice Blast
34.5K views | +57 today
Follow
 
Scooped by Elsa Ballini
onto Rice Blast
Scoop.it!

Analysis of genetic diversity of Magnaporthe oryzae in Hunan.

The genetic diversity of 169 blast fungus isolates collected from 44 susceptible rice varieties widely grown in 19 locations in Hunan Province was analyzed in 2010 by using 13 pairs of simple sequence repeat (SSR) markers. It was found that these isolates were classified into 8 genetic lineages at 0.8 similar levels, among which L01 was the dominant lineage and its isolates accounted for 66.86% of the total. Most genetic lineages contained isolates from several source areas and many rice varieties. The genetic relationships between the lineages and the source areas and between the lineages and the rice varieties were complex. The isolates from the same locations or from the same varieties had a relatively close genetic relationship, but the differentiation of the blast fungus physiological race varied in different locations. The genetic diversity of M. oryzae was related to the terrain and the number of rice varieties of a location. There was a greater genetic diversity of M. oryzae in mountainous regions with a high elevation than in hilly areas. The more rice varieties planted in a location was, the greater genetic diversity of M. oryzae was.

more...
No comment yet.
Rice Blast
Scientific articles on rice blast and wheat blast 20 new articles each month !
Curated by Elsa Ballini
Your new post is loading...
Your new post is loading...
Rescooped by Elsa Ballini from plant microbe interaction genomics
Scoop.it!

Differential Communications between Fungi and Host Plants Revealed by Secretome Analysis of Phylogenetically Related Endophytic and Pathogenic Fungi

Differential Communications between Fungi and Host Plants Revealed by Secretome Analysis of Phylogenetically Related Endophytic and Pathogenic Fungi | Rice Blast | Scoop.it
During infection, both phytopathogenic and endophytic fungi form intimate contact with living plant cells, and need to resist or disable host defences and modify host metabolism to adapt to their host. Fungi can achieve these changes by secreting proteins and enzymes. A comprehensive comparison of the secretomes of both endophytic and pathogenic fungi can improve our understanding of the interactions between plants and fungi. Although Magnaporthe oryzae , Gaeumannomyces graminis , and M . poae are economically important fungal pathogens, and the related species Harpophora oryzae is an endophyte, they evolved from a common pathogenic ancestor. We used a pipeline analysis to predict the H . oryzae , M . oryzae , G . graminis , and M . poae secretomes and identified 1142, 1370, 1001, and 974 proteins, respectively. Orthologue gene analyses demonstrated that the M . oryzae secretome evolved more rapidly than those of the other three related species, resulting in many species-specific secreted protein-encoding genes, such as avirulence genes. Functional analyses highlighted the abundance of proteins involved in the breakdown of host plant cell walls and oxidation-reduction processes. We identified three novel motifs in the H . and M . oryzae secretomes, which may play key roles in the interaction between rice and H . oryzae . Furthermore, we found that expression of the H . oryzae secretome involved in plant cell wall degradation was downregulated, but the M . oryzae secretome was upregulated with many more upregulated genes involved in oxidation-reduction processes. The divergent in planta expression patterns of the H . and M . oryzae secretomes reveal differences that are associated with mutualistic and pathogenic interactions, respectively.

Via Yogesh Gupta, Francis Martin, Jessie Uehling
more...
No comment yet.
Rescooped by Elsa Ballini from Plant Pathogens
Scoop.it!

Genome-Wide Comparison of Magnaporthe Species Reveals a Host-Specific Pattern of Secretory Proteins and Transposable Elements

Genome-Wide Comparison of  Magnaporthe  Species Reveals a Host-Specific Pattern of Secretory Proteins and Transposable Elements | Rice Blast | Scoop.it
Blast disease caused by the Magnaporthe species is a major factor affecting the productivity of rice, wheat and millets. This study was aimed at generating genomic information for rice and non-rice Magnaporthe isolates to understand the extent of genetic variation. We have sequenced the whole genome of the Magnaporthe isolates, infecting rice (leaf and neck), finger millet (leaf and neck), foxtail millet (leaf) and buffel grass (leaf). Rice and finger millet isolates infecting both leaf and neck tissues were sequenced, since the damage and yield loss caused due to neck blast is much higher as compared to leaf blast. The genome-wide comparison was carried out to study the variability in gene content, candidate effectors, repeat element distribution, genes involved in carbohydrate metabolism and SNPs. The analysis of repeat element footprints revealed some genes such as naringenin, 2-oxoglutarate 3-dioxygenase being targeted by Pot 2 and Occan, in isolates from different host species. Some repeat insertions were host-specific while other insertions were randomly shared between isolates. The distributions of repeat elements, secretory proteins, CAZymes and SNPs showed significant variation across host-specific lineages of Magnaporthe indicating an independent genome evolution orchestrated by multiple genomic factors.

Via Yogesh Gupta
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

Study of suitable culture media and other abiotic factors for the growth and sporulation of magnaporthe oryzae

In the present investigation the effect of media, photo-periods and isolation techniques influenced on mycelia growth and conidial production of M. oryzae were studied. Rice straw agar and oatmeal agar wre found to be suitable for culturing different isolates of M. oryzae. Colonies of M. oryzae appeared white on oat meal, whitish grey on rice agar and grey on potato dextrose agar. When spores of 26 isolates were compared, MTU 1010 and Karidoddi showed the maximum size of conidia whereas isolate Kempudoddi showed minimum size of conidia. Size of the conidia from the infected samples varied from 13.8-21.35 μm to 2.7-7.8 μm (L x B) in all isolates where there was no significant variation in shape of conidia. The spores of rice isolates collected from Ponnampet were smaller as compared to Mandya. Highest radial growth of mycelia on Sixteenth day was shown on three medias from three rice varietal isolates Viz, Kempudoddi (83.23 mm) on OMA, Gamnadabhatta (70.42 mm) PDA, Honasu (75.3 mm) on RSA.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

Mapping highly informative SSR markers in the genome of Magnaporthe oryzae from wheat

Wheat blast, caused by Magnaporthe oryzae (Triticum haplotype - MoT), is an important disease of wheat in Brazil. In this study, we designed 38 new SSR markers based on the genome sequence of different MoT isolates, compared the informativeness of those markers with other 52 from the literature and mapped the polymorphic ones. Among the 90 SSR markers, 53 were polymorphic resulting in, on average, 3.02 alleles per locus and polymorphism information content (PIC) of 0.41. Most (81.1 %) of the polymorphic markers presented 11 or more motif repeats. Seventeen highly informative markers were detected and mapped in all chromosomes except for chromosome 5. On average, polymorphic markers on chromosome 6 showed the highest PIC followed by chromosomes 2 and 7. Clustering analysis showed a clear separation of one isolate from rice from the rest of the isolates from wheat. In each of the three clusters detected, the MoT isolates were similar among them regardless of the year and location sampled, suggesting that the pathogen is widely dispersed across wheat growing regions in Brazil. The highly informative markers detailed here should be useful for population biology studies of the wheat blast pathogen.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

Fine mapping of a new race-specific blast resistance gene Pi-hk2 in Japonica Heikezijing from Taihu region of China

Fine mapping of a new race-specific blast resistance gene Pi-hk2 in Japonica Heikezijing from Taihu region of China | Rice Blast | Scoop.it
Heikezijing, a japonica rice landrace from Taihu region of China, exhibited broad-spectrum resistance to more than 300 isolates of the blast (Magnaporthe oryzae). In our previous research, we fine mapped a broad-spectrum resistance gene Pi-hk1 in chromosome 11. In this research, 2010-9(G1), one of the predominant race of the blast in Taihu Lake region of China, was inoculated into 162 recombinant inbred lines (RILs) and two parents Heikezijing and Suyunuo for mapping the resistance-blast quantitative trait loci (QTLs). Three QTLs Lsqtl4-1, Lsqtl9-1 and Lsqtl11-1 associated with lesion scores were detected on chromosomes 4, 9, and 11 and two QTLs, Lnqtl1-1 and Lnqtl9-1 associated with average lesion number on chromosomes 1 and 9. The QTL Lsqtl9-1 conferring race-specific resistance to 2010-9(G1) at seedling stages showed the logarithm of the odds (LOD) scores of 9.10 and phenotypic variance of 46.19% and might be a major QTL, named as Pi-hk2. The line RIL84 with Pi-hk2 derived from a cross between Heikezijing and Suyunuo was selected as Pi-hk2 gene donor for developing fine mapping populations. According to the resistance evaluation of recombinants of three generations (BC1F2, BC1F3 and BC1F4), Pi-hk2 was finally mapped to 143 kb region between ILP-19 and RM24048, and 18 candidate genes were predicted, including two pleiotropic drug resistance protein 4, one WRKY74, one cytochrome b5-like Heme/Steroid binding domain containing protein, one protein kinase and one ankyrin repeat family protein. These results provide essential information for cloning of Pi-hk2 and its potential utility in breeding resistant rice cultivars by marker-assisted selection.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

Ethylene biosynthesis and signaling is required for rice immune response and basal resistance against Magnaporthe oryzae infection

Ethylene biosynthesis and signaling is required for rice immune response and basal resistance against Magnaporthe oryzae infection | Rice Blast | Scoop.it
Recent studies have suggested that ethylene enhances host resistance to fungal pathogen Magnaporthe oryzae, the causal agent of rice blast disease. Among the six ACS genes in rice, OsACS1 and OsACS2 are induced within 24 hours of inoculation by M. oryzae. This induction occurs simultaneously with an increase in ethylene production that is noticeable 12 hours post inoculation. The purpose of this study was to examine the dynamics of ethylene production and signaling in wild type and RNAi-mediated suppression lines deficient in ethylene production (acs2) or signaling (eil1) after challenge with M. oryzae, as well as fungal cell wall elicitors. Ethylene-insensitive mutant lines show an attenuated basal defense response including lower basal expression of the genes encoding a chitin-binding receptor, pathogenesis-related (PR) proteins, and the enzymes involved in the synthesis of diterprenoid phytoalexins, a reduction on early HR-like cell death, and reduced incidence of callose deposition. Ethylene-deficient mutants showed an intermediate phenotype, with a significant reduction in expression of defense-related genes and callose deposition, but only a slight reduction in HR-like cell death. As a result, all ethylene-insensitive mutants show increased susceptibility to M. oryzae, whereas the ethylene-deficient lines show a slight, but less significant increase in disease severity. These results show that ethylene signaling, and to some extent ethylene production, are required for rice basal resistance against the blast fungus, Magnaporthe oryzae.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

A systematic view of the MLO family in rice suggests their novel roles in morphological development, diurnal responses, the light-signaling pathway, and various stress responses

A systematic view of the MLO family in rice suggests their novel roles in morphological development, diurnal responses, the light-signaling pathway, and various stress responses | Rice Blast | Scoop.it
The Mildew resistance Locus O (MLO) family is unique to plants, containing genes that were initially identified as a susceptibility factor to powdery mildew pathogens. However, little is known about the roles and functional diversity of this family in rice, a model crop plant. The rice genome has 12 potential MLO family members. To achieve systematic functional assignments, we performed a phylogenomic analysis by integrating meta-expression data obtained from public sources of microarray data and real-time expression data into a phylogenic tree. Subsequently, we identified 12 MLO genes with various tissue-preferred patterns, including leaf, root, pollen, and ubiquitous expression. This suggested their functional diversity for morphological agronomic traits. We also used these integrated transcriptome data within a phylogenetic context to estimate the functional redundancy or specificity among OsMLO family members. Here, OsMLO12 showed preferential expression in mature pollen; OsMLO4, in the root tips; OsMLO10, throughout the roots except at the tips; and OsMLO8, expression preferential to the leaves and trinucleate pollen. Of particular interest to us was the diurnal expression of OsMLO1, OsMLO3, and OsMLO8, which indicated that they are potentially significant in responses to environmental changes. In osdxr mutants that show defects in the light response, OsMLO1, OsMLO3, OsMLO8, and four calmodulin genes were down-regulated. This finding provides insight into the novel functions of MLO proteins associated with the light-responsive methylerythritol 4-phosphate pathway. In addition, abiotic stress meta-expression data and real-time expression analysis implied that four and five MLO genes in rice are associated with responses to heat and cold stress, respectively. Upregulation of OsMLO3 by Magnaporthe oryzae infection further suggested that this gene participates in the response to pathogens. Our analysis has produced fundamental information that will enhance future studies of the diverse developmental or physiological phenomena mediated by the MLO family in this model plant system.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

CONSTANS-like 9 (COL9) delays the flowering time in Oryza sativa by repressing the Ehd1 pathway

CONSTANS-like 9 (COL9) delays the flowering time in Oryza sativa by repressing the Ehd1 pathway | Rice Blast | Scoop.it
We have previously identified that the COL family member OsCOL9 can positively enhance the rice blast resistance. In the present study, we aimed to explore the functional role of OsCOL9 in modulating the photoperiodic flowering. OsCOL9 delayed the rice heading through repressing the Ehd1 pathway under both SD and LD conditions. In addition, OsRACK1 interacted with OsCOL9 in response to circadian photoperiod, which probably mediated the OsCOL9 degradation and played an important role in regulation of rice flowering.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

A New Recessive Gene Conferring Resistance Against Rice Blast

A New Recessive Gene Conferring Resistance Against Rice Blast | Rice Blast | Scoop.it
The blast resistance present in the aus type cultivar AS20-1 was shown, via an analysis of segregation in the F2 generation bred from a cross with the highly blast susceptible cultivar Aichi Asahi, to be due to the action of a single recessive gene, denoted pi66(t). The presence of pi66(t) gave an intermediate level control to plants infected with the blast pathogen isolate EHL0635. A bulked segregant analysis indicated that four microsatellite loci (SSRs) mapping to chromosome 3 were probably linked to pi66(t). Localized mapping using chromosome 3-based SSRs and Indels defined a genetic window for pi66(t), flanked by the markers F04-j2 and M19-i12, which physically equals to 27.7 and 49.0 kb, respectively, in the reference genomes of cultivars Nipponbare and 93–11. This physical interval does not harbor any major gene currently associated with disease resistance.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

The Diversification of Plant NBS-LRR Defense Genes Directs the Evolution of MicroRNAs That Target Them

The Diversification of Plant NBS-LRR Defense Genes Directs the Evolution of MicroRNAs That Target Them | Rice Blast | Scoop.it
High expression of plant nucleotide binding site leucine-rich repeat (NBS-LRR) defense genes is often lethal to plant cells, a phenotype perhaps associated with fitness costs. Plants implement several mechanisms to control the transcript level of NBS-LRR defense genes. As negative transcriptional regulators, diverse miRNAs target NBS-LRRs in eudicots and gymnosperms. To understand the evolutionary benefits of this miRNA-NBS-LRR regulatory system, we investigated the NBS-LRRs of 70 land plants, coupling this analysis with extensive small RNA data. A tight association between the diversity of NBS-LRRs and miRNAs was found. The miRNAs typically target highly duplicated NBS-LRRs. In comparison, families of heterogeneous NBS-LRRs were rarely targeted by miRNAs in Poaceae and Brassicaceae genomes. We observed that duplicated NBS-LRRs from different gene families periodically gave birth to new miRNAs. Most of these newly emerged miRNAs target the same conserved, encoded protein motif of NBS-LRRs, consistent with a model of convergent evolution for these miRNAs. By assessing the interactions between miRNAs and NBS-LRRs, we found nucleotide diversity in the wobble position of the codons in the target site drives the diversification of miRNAs. Taken together, we propose a co-evolutionary model of plant NBS-LRRs and miRNAs hypothesizing how plants balance the benefits and costs of NBS-LRR defense genes.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

Genetic structure and mating type analysis of the Pyricularia oryzae population causing widespread epidemics in southern Brazil

Blast is a major disease of rice in Brazil, the largest rice-producing country outside Asia. This study aimed to assess the genetic structure and mating-type frequency in a contemporary Pyricularia oryzae population, which caused widespread epidemics during the 2012/13 season in the Brazilian lowland subtropical region. Symptomatic leaves and panicles were sampled at flooded rice fields in the states of Rio Grande do Sul (RS, 34 fields) and Santa Catarina (SC, 21 fields). The polymorphism at ten simple sequence repeats (SSR or microsatellite) loci and the presence of MAT1-1 or MAT1-2 idiomorphs were assessed in a population comprised of 187 isolates. Only the MAT1-2 idiomorph was found and 162 genotypes were identified by the SSR analysis. A discriminant analysis of principal components (DAPC) of SSR data resolved four genetic groups, which were strongly associated with the cultivar of origin of the isolates. There was high level of genotypic diversity and moderate level of gene diversity regardless whether isolates were grouped in subpopulations based on geographic region, cultivar host or cultivar within region. While regional subpopulations were weakly differentiated, high genetic differentiation was found among subpopulations comprised of isolates from different cultivars. The data suggest that the rice blast pathogen population in southern Brazil is comprised of clonal lineages that are adapting to specific cultivar hosts. Farmers should avoid the use of susceptible cultivars over large areas and breeders should focus at enlarging the genetic basis of new cultivars.
more...
No comment yet.
Rescooped by Elsa Ballini from Plant Pathogens
Scoop.it!

Wheat blast: histopathology and transcriptome reprogramming in response to adapted and nonadapted Magnaporthe isolates

Wheat blast: histopathology and transcriptome reprogramming in response to adapted and nonadapted Magnaporthe isolates | Rice Blast | Scoop.it
Summary 

• Blast disease (causal agent Magnaporthe oryzae) has presented as a new and serious field disease of wheat in South America. Here, we investigated the responses of wheat to both adapted and nonadapted isolates of the blast fungus Magnaporthe, examining cellular defence and transcriptional changes. 
• Resistance towards the nonadapted isolate was associated with the formation of appositions, here termed halos, beneath attempted Magnaporthe grisea penetration sites that wheat-adapted, M. oryzae isolates were able to breach. 
• Transcriptome analysis indicated extensive transcriptional reprogramming following inoculation with both wheat-adapted and nonadapted isolates of Magnaporthe. Functional annotation of many of the differentially expressed transcripts classified into the categories: cell rescue and defence, plant metabolism, cellular transport and regulation of transcription (although a significant number of transcripts remain unclassified). 
• Defence-related transcripts induced in common by adapted and nonadapted isolates were differentially regulated in response to M. oryzae and M. grisea isolates over time. Differential expression of genes involved in cellular transport indicated the importance of this process in plant defence. Functional characterisation of these transcripts and their role in defence may eventually lead to the identification of broad-spectrum resistance mechanisms in wheat towards Magnaporthe.

Via Yogesh Gupta
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

Roles of Rack1 Proteins in Fungal Pathogenesis

Roles of Rack1 Proteins in Fungal Pathogenesis | Rice Blast | Scoop.it
Pathogenic fungi cause diseases on various organisms. Despite their differences in life cycles, fungal pathogens use well-conserved proteins and pathways to regulate developmental and infection processes. In this review, we focus on Rack1, a multifaceted scaffolding protein involved in various biological processes. Rack1 is well conserved in eukaryotes and plays important roles in fungi, though limited studies have been conducted. To accelerate the study of Rack1 proteins in fungi, we review the functions of Rack1 proteins in model and pathogenic fungi and summarize recent progress on how Rack1 proteins are involved in fungal pathogenesis.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

Marker-assisted Introgression of a Broad-spectrum Resistance Gene, Pi40 Improved Blast Resistance of Two Elite Rice ( Oryza sativa L.) Cultivars of Turkey

Rice blast, caused by Magnaporthe oryzae is the most serious fungal disease of cultivated rice (Oryza sativa). In serious disease infection, significant yield loss in japonica and indica rice occurs every year worldwide. Of the 100 blast resistance genes identified, majorities are race specific and resistance breaks down rapidly. However, the new resistance gene, Pi40 shows broad-spectrum resistance to blast races in many tropical and temperate rice growing countries including Turkey. In this study, the Pi40 gene was introgressed into two Turkish elite cultivars, Osmancik-97 and Halilbey, to improve with broad-spectrum durable blast resistance and high yield potential through marker-assisted backcross breeding. Advanced backcross lines (ABLs) of BC3F6 and BC4F6 generations were produced from the crosses of Osmancik-97 and Halilbey with the Pi40-donor line, IR83260-1-1-1-5-B-3-1-2-B. ABLs with homozygous Pi40 alleles were selected by foreground analysis using gene-specific CAPS DNA marker 9871.T7E2b. The two varieties were expressing high susceptibility to blast disease isolates in Turkey and Philippines. Eleven selected ABLs expressed strong resistance to blast races in natural field and spray inoculation conditions. Background analysis of selected ABLs with 6K SNP assays showed 90.07% and 70.78% recovery of the recurrent genotype for Osmancik-97 and Halilbey ABLs respectively. We have produced valuable resources for blast disease resistance and developed improved breeding lines with strong resistance to blast for their cultivation in Turkey. Our new strategy of transferring the novel blast resistance gene (Pi40) into Turkish varieties will enhance rice production and productivity in the temperate regions of the world.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

Synthesis and structure-activity relationship of oleanolic mono- or di-glycosides against Magnaporthe oryzae

Saponins are naturally-occurring units with broad diversity and are usually recognized as phytoanticipins. In order to develop new saponin chemical entities with high activity against Magnaporthe oryzae, we selected oleanolic acid (OA), which has wide natural distribution and rich content in plants. We used the ability of OA to act as an aglycone for glycosylation to obtain information on the structure-activity relationship (SAR) for rational molecular pesticide design. Oleanolic mono- or di-glycosides were synthesized at either the C3-hydroxy and/or C28-carboxyl position, using trichloroacetimidate or glycosyl bromide donors, respectively. Structures were confirmed by [1H]-,[13C]-NMR. Furthermore, the activity of the synthesized glycosides against M. oryzae was assessed in vitro, based on the mycelium growth rate. The twenty five oleanolic mono- or di-glycosides comprised fourteen saponins with 3-monosaccharide residue 1a-1n, six saponins with 28-monosaccharide residue 2a-2f, and five saponins with 3, 28-monosaccharide residue 3a-3e; all showed different activities against M. oryzae according to their different structures. We concluded that the optimal oleanolic mono- and di-glycoside structure for activity against M. oryzae is a C3 connection of a hexose such as mannose, galactose, or glucose, in combination with a C28 connection to a small group such as allyl or a C3 connection to a pentose accompanied by a larger group such as another pentose or heptenyl at C28.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

Evaluation of a New Strobilurin Group of Fungicide for the Management of Blast Disease of Paddy

A new strobilurin group of fungicide, pyraclostrobin 100 g/l CS (Seltima 100 g/l CS) was evaluated for its bio-efficacy against rice leaf blast disease under field condition during Kharif 2013 and 2014 at Agricultural research station, Gangavathi, Karnataka, India. The test fungicide, pyraclostrobin 100 g/l CS was found effective against leaf blast disease which recorded least percent disease index (PDI) of 14.20 and 16.48 @ 75 g a.i./h and @ 100 g a.i./h, respectively. Other fungicides such as tricyclazole 75 WP (300 g/h), Carbendazim 50 WP (500g/h) and Isoprothiolane 40 EC (750 ml/h) recorded significantly more PDI than pyraclostrobin 100 g/l CS. Due to difference in the PDI of leaf blast disease, different treatments recorded statistically significant yield differences. The highest yield (67.78 q/h) was recorded in the treatment of pyraclostrobin 100 g/l CS @ 75 g a.i./h followed by the same chemical @ 100 g a.i./h (66.87 q/h). Therefore, pyraclostrobin 100 g/l CS (Seltima 100 g/l CS) @ 75-100 g a.i/h can be used for effective management of leaf blast disease.
more...
No comment yet.
Rescooped by Elsa Ballini from Plant-Microbe Interactions: Immunity & Symbiosis
Scoop.it!

An assay for entry of secreted fungal effectors into plant cells - Lo Presti - 2016 - New Phytologist - Wiley Online Library

An assay for entry of secreted fungal effectors into plant cells - Lo Presti - 2016 - New Phytologist - Wiley Online Library | Rice Blast | Scoop.it
Summary

Successful colonization of plants by prokaryotic and eukaryotic pathogens requires active effector-mediated suppression of defense responses and host tissue reprogramming. Secreted effector proteins can either display their activity in the apoplast or translocate into host cells and function therein. Although characterized in bacteria, the molecular mechanisms of effector delivery by fungal phytopathogens remain elusive.
Here we report the establishment of an assay that is based on biotinylation of effectors in the host cytoplasm as hallmark of uptake. The assay exploits the ability of the bacterial biotin ligase BirA to biotinylate any protein that carries a short peptide (Avitag). It is based on the stable expression of BirA in the cytoplasm of maize plants and on engineering of Ustilago maydis strains to secrete Avitagged effectors.
We demonstrate translocation of a number of effectors in the U. maydis–maize system and show data that suggest that the uptake mechanism could be rather nonspecific
The assay promises to be a powerful tool for the classification of effectors as well as for the functional study of effector uptake mechanism not only in the chosen system but more generally for systems where biotrophic interactions are established.

Via Philip Carella
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

Plant Pathology: A Life and Death Struggle in Rice Blast Disease

The fungal pathogen Magnaporthe oryzae causes severe disease symptoms and yield losses on rice plants. A new study shows that this fungus elicits disease lesions by co-opting a host protein and reveals how rice plants fight back.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

Identification of Sternbin and Naringenin as Detoxified Metabolites from the Rice Flavanone Phytoalexin Sakuranetin by Pyricularia oryzae

Sakuranetin (1) is a flavanone phytoalexin that has been reported to play an important role in disease resistance in rice plants. The rice blast fungus Pyricularia oryzae (syn. Magnaporthe oryzae) has been reported to metabolize 1 to lower its antifungal activity. Here, two flavanones, sternbin (2) and naringenin (3), were identified as metabolites of 1 in P. oryzae suspension culture by liquid chromatography tandem mass spectrometry (LC/MS/MS). The inhibition of 1, 2, and 3 on P. oryzae mycelial growth were 45%, 19%, and 19%, respectively, at a concentration of 100 μM. Thus, 2 and 3 are detoxified metabolites of 1 by P. oryzae.
more...
No comment yet.
Rescooped by Elsa Ballini from Rice Blast
Scoop.it!

Regulatory cross-talks and cascades in rice hormone biosynthesis pathways contribute to stress signaling

Regulatory cross-talks and cascades in rice hormone biosynthesis pathways contribute to stress signaling | Rice Blast | Scoop.it
Crosstalk among different hormone signaling pathways play an important role in modulating plant response to both biotic and abiotic stress. Hormone activity is controlled by its bio-availability, which is again influenced by its biosynthesis. Thus independent hormone biosynthesis pathways must be regulated and co-ordinated to mount an integrated response. One of the possibilities is to use cis-regulatory elements to orchestrate expression of hormone biosynthesis genes. Analysis of CREs, associated with differentially expressed hormone biosynthesis related genes in rice leaf under Magnaporthe oryzae attack and drought stress enabled us to obtain insights about cross-talk among hormone biosynthesis pathways at the transcriptional level. We identified some master transcription regulators that co-ordinate different hormone biosynthesis pathways under stress. We found that Abscisic acid and Brassinosteroid regulate Cytokinin conjugation; conversely Brassinosteroid biosynthesis is affected by both Abscisic acid and Cytokinin. Jasmonic acid and Ethylene biosynthesis may be modulated by Abscisic acid through DREB transcription factors. Jasmonic acid or Salicylic acid biosynthesis pathways are co-regulated but they are unlikely to influence each other’s production directly. Thus multiple hormones may modulate hormone biosynthesis pathways through a complex regulatory network, where biosynthesis of one hormone is affected by several other contributing hormones.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

The germin-like protein OsGLP2-1 enhances resistance to fungal blast and bacterial blight in rice

The germin-like protein OsGLP2-1 enhances resistance to fungal blast and bacterial blight in rice | Rice Blast | Scoop.it
Rice (Oryza sativa) blast caused by Magnaporthe oryzae and bacterial blight caused by Xanthomonas oryzae pv. oryzae are the two most destructive rice diseases worldwide. Germin-like protein (GLP) gene family is one of the important defense gene families which have been reported to be involved in disease resistance in plants. Although GLP proteins have been demonstrated to positively regulate leaf blast resistance in rice, their involvement in resistance to panicle blast and bacterial blight, has not been reported. In this study, we reported that one of the rice GLP genes, OsGLP2-1, was significantly induced by blast fungus. Overexpression of OsGLP2-1 quantitatively enhanced resistance to leaf blast, panicle blast and bacterial blight. The temporal and spatial expression analysis revealed that OsGLP2-1is highly expressed in leaves and panicles and sub-localized in the cell wall. Compared with empty vector transformed (control) plants, the OsGLP2-1 overexpressing plants exhibited higher levels of H2O2 both before and after pathogen inoculation. Moreover, OsGLP2-1 was significantly induced by jasmonic acid (JA). Overexpression of OsGLP2-1 induced three well-characterized defense-related genes which are associated in JA-dependent pathway after pathogen infection. Higher endogenous level of JA was also identified in OsGLP2-1 overexpressing plants than in control plants both before and after pathogen inoculation. Together, these results suggest that OsGLP2-1 functions as a positive regulator to modulate disease resistance. Its good quantitative resistance to the two major diseases in rice makes it to be a promising target in rice breeding.
more...
No comment yet.
Rescooped by Elsa Ballini from PLANTs
Scoop.it!

Immunity to Rice Blast Disease by Suppression of Effector-Triggered Necrosis

Immunity to Rice Blast Disease by Suppression of Effector-Triggered Necrosis | Rice Blast | Scoop.it
Highlights

•AvrPiz-t interacts and co-localizes with APIP5 in the cytoplasm
•AvrPiz-t suppresses APIP5 transcriptional activity and protein accumulation
•APIP5, a negative regulator of cell death, interacts with the NLR receptor Piz-t
•Piz-t suppresses the AvrPiz-t-mediated APIP5 turnover

Summary

Hemibiotrophic pathogens are some of the most destructive plant pathogens, causing huge economic losses and threatening global food security. Infection with these organisms often involves an initial biotrophic infection phase, during which the pathogen spreads in host tissue asymptomatically, followed by a necrotrophic phase, during which host-cell death is induced. How hemibiotrophic pathogens trigger host necrosis and how plants inhibit the transition from the biotrophic stage to the necrotrophic stage in disease symptom expression are mainly unknown. The rice blast fungus Magnaporthe oryzae spreads in rice biotrophically early during infection, but this biotrophic stage is followed by a pronounced switch to cell death and lesion formation. Here, we show that the M. oryzae effector AvrPiz-t interacts with the bZIP-type transcription factor APIP5 in the cytoplasm and suppresses its transcriptional activity and protein accumulation at the necrotrophic stage. Silencing of APIP5 in transgenic rice leads to cell death, and the phenotype is enhanced by the expression of AvrPiz-t. Conversely, Piz-t interacts with and stabilizes APIP5 to prevent necrosis at the necrotrophic stage. At the same time, APIP5 is essential for Piz-t stability. These results demonstrate a novel mechanism for the suppression of effector-triggered necrosis at the necrotrophic stage by an NLR receptor in plants.

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

Moving nitrogen to the centre of plant defence against pathogens

Moving nitrogen to the centre of plant defence against pathogens | Rice Blast | Scoop.it
When a pathogen first comes into contact with a host, it is usually nutrient starved such that rapid assimilation of host nutrients is essential for successful pathogenesis. Equally, the host may reallocate its nutrients to defence responses or away from the site of attempted infection. Exogenous application of N fertilizer can, therefore, shift the balance in favour of the host or pathogen. In line with this, increasing N has been reported either to increase or to decrease plant resistance to pathogens, which reflects differences in the infection strategies of discrete pathogens. Beyond considering only N content, the use of NO–3 or NH+4 fertilizers affects the outcome of plant–pathogen interactions. NO–3 feeding augments hypersensitive response- (HR) mediated resistance, while ammonium nutrition can compromise defence. Metabolically, NO–3 enhances production of polyamines such as spermine and spermidine, which are established defence signals, with NH+4 nutrition leading to increased γ-aminobutyric acid (GABA) levels which may be a nutrient source for the pathogen. Within the defensive N economy, the roles of nitric oxide must also be considered. This is mostly generated from NO–2 by nitrate reductase and is elicited by both pathogen-associated microbial patterns and gene-for-gene-mediated defences. Nitric oxide (NO) production and associated defences are therefore NO–3 dependent and are compromised by NH+4.
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

@talbotlabexeter kicking off #BioDynamics2016 talking about the rice blast fungus magnaporthe

@talbotlabexeter kicking off #BioDynamics2016 talking about the rice blast fungus magnaporthe | Rice Blast | Scoop.it
more...
No comment yet.
Scooped by Elsa Ballini
Scoop.it!

Spermidine, a polyamine, confers resistance to rice blast

Spermidine, a polyamine, confers resistance to rice blast | Rice Blast | Scoop.it
Polyamines are involved not only in fundamental cellular processes such as growth, differentiation, and morphogenesis, but also in various environmental stresses. We demonstrated that spermidine, a polyamine, confers resistance to rice blast accompanied by the up-regulation of marker genes for the salicylic acid-mediated signaling pathway PR1b and PBZ1 and of phytoalexin biosynthesis genes CPS4 and NOMT. This is the first report about the involvement of spermidine in rice disease resistance.
more...
No comment yet.