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Solution structure of the Magnaporthe oryzae avirulence protein AvrPiz-t - Online First - Springer

Solution structure of the Magnaporthe oryzae avirulence protein AvrPiz-t - Online First - Springer | Rice Blast | Scoop.it

The AvrPiz-t gene encodes a small protein predicted to be secreted that shows
no homology to known proteins and is 108 amino acids in length. AvrPiz-t can suppress programmed cell death (PCD) induced by BAX in tobacco, suggesting that it might contribute to the pathogenicity of M. oryzae. These data suggested that AvrPiz-t functions primarily as a virulence effector contributing to the pathogenicity of M. oryzae. To further understand the mechanism of the pathogenicity-associated function of AvrPiz-t, we determined
its solution structure.

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Scientific articles on rice blast and wheat blast 20 new articles each month !
Curated by Elsa Ballini
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Development of Gene-Pyramid Lines of the Elite Restorer Line, RPHR-1005 Possessing Durable Bacterial Blight and Blast Resistance

Development of Gene-Pyramid Lines of the Elite Restorer Line, RPHR-1005 Possessing Durable Bacterial Blight and Blast Resistance | Rice Blast | Scoop.it
RPHR-1005, the stable restorer line of the popular medium slender (MS) grain type rice hybrid, DRRH-3 was improved in this study for resistance against bacterial blight (BB) and blast diseases through marker-assisted backcross breeding (MABB). In this study, four major resistance genes (i.e., Xa21 and Xa33 for BB resistance and Pi2 and Pi54 for blast resistance) have been transferred to RPHR-1005 using RPBio Patho-1 (possessing Xa21 + Pi2), RPBio Patho-2 (possessing Xa21 + Pi54) and FBR1-15EM (possessing Xa33) as the donors. Foreground selection was carried out using PCR-based molecular markers specific for the target resistance genes and the major fertility restorer genes, Rf3 and Rf4, while background selection was carried out using a set of parental polymorphic rice SSR markers and backcrossing was continued uptoBC2 generation. At BC2F2, plants possessing the gene combination- Xa21 + Pi2, Xa21 + Pi54 and Xa33 in homozygous condition and with >92% recovery of the recurrent parent genome (RPG) were identified and intercrossed to combine all the four resistance genes. Twenty-two homozygous, pyramid lines of RPHR-1005 comprising of three single-gene containing lines, six 2-gene containing lines, eight 3-gene containing lines, and five 4-gene containing lines were identified among the double intercross lines at F3 generation (DICF3). They were then evaluated for their resistance against BB and blast, fertility restoration ability and for key agro-morphological traits. While single gene containing lines were resistant to either BB or blast, the 2-gene, 3-gene, and 4-gene pyramid lines showed good level of resistance against both and/or either of the two diseases. Most of the 2-gene, 3-gene, and 4-gene containing pyramid lines showed yield levels and other key agro-morphological and grain quality traits comparable to the original recurrent parent and showed complete fertility restoration ability, with a few showing higher yield as compared to RPHR-1005. Further, the experimental hybrids derived by crossing the gene-pyramid lines of RPHR-1005 with APMS6A (the female parent of DRRH-3), showed heterosis levels equivalent to or higher than DRRH-3. The results of present study exemplify the utility of MABB for targeted improvement of multiple traits in hybrid rice.
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The Nipponbare genome and the next-generation of rice genomics research in Japan

The Nipponbare genome and the next-generation of rice genomics research in Japan | Rice Blast | Scoop.it
The map-based genome sequence of the japonica rice cultivar Nipponbare remains to date as the only monocot genome that has been sequenced to a high-quality level. It has become the reference sequence for understanding the diversity among thousands of rice cultivars and its wild relatives as well as the major cereal crops that comprised the food source for the entire human race. This review focuses on the accomplishments in rice genomics in Japan encompassing the last 10 years which have led into deeper understanding of the genome, characterization of many agronomic traits, comprehensive analysis of the transcriptome, and the map-based cloning of many genes associated with agronomic traits.
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Regulatory cross-talks and cascades in rice hormone biosynthesis pathways contribute to stress signaling

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.
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Linker Flexibility Facilitates Module Exchange in Fungal Hybrid PKS-NRPS Engineering

Polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs) each give rise to a vast array of complex bioactive molecules with further complexity added by the existence of natural PKS-NRPS fusions. Rational genetic engineering for the production of natural product derivatives is desirable for the purpose of incorporating new functionalities into pre-existing molecules, or for optimization of known bioactivities. We sought to expand the range of natural product diversity by combining modules of PKS-NRPS hybrids from different hosts, hereby producing novel synthetic natural products. We succeeded in the construction of a functional cross-species chimeric PKS-NRPS expressed in Aspergillus nidulans. Module swapping of the two PKS-NRPS natural hybrids CcsA from Aspergillus clavatus involved in the biosynthesis of cytochalasin E and related Syn2 from rice plant pathogen Magnaporthe oryzae lead to production of novel hybrid products, demonstrating that the rational re-design of these fungal natural product enzymes is feasible. We also report the structure of four novel pseudo pre-cytochalasin intermediates, niduclavin and niduporthin along with the chimeric compounds niduchimaeralin A and B, all indicating that PKS-NRPS activity alone is insufficient for proper assembly of the cytochalasin core structure. Future success in the field of biocombinatorial synthesis of hybrid polyketide-nonribosomal peptides relies on the understanding of the fundamental mechanisms of inter-modular polyketide chain transfer. Therefore, we expressed several PKS-NRPS linker-modified variants. Intriguingly, the linker anatomy is less complex than expected, as these variants displayed great tolerance with regards to content and length, showing a hitherto unreported flexibility in PKS-NRPS hybrids, with great potential for synthetic biology-driven biocombinatorial chemistry.
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The Role of Cell Wall Degrading Enzymes in Pathogenesis of Magnaporthe oryzae

The plant cell wall is always the physical barrier in which phytopathogenic fungi must overcome by producing an array of cell wall degrading enzymes (CWDEs) that allow them to invade host tissues through the degradation of cell wall components of plants. Magnaporthe oryzae is a causal agent of blast disease, one of the most devastating disease in rice resulting significant crop losses worldwide. The penetration of plant cuticle and cell walls induced by infection structures of M.oryzae has been known to be acquired by the association of turgor pressure and CWDEs for successful infection of M.oryzae. In this review, we focus on recent discoveries of M.oryzae CWDEs, gene regulation and their biological roles as fungal virulence factors and elicitors of host defense response leading to plant resistance against fungal pathogens.
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Rice Blast Control Efficacy of Three Genes (Pib, pi21, and Pb1) Conferring Complete and Partial Resistance

The rice blast control efficacy of three genes—complete resistance gene Pib in isogenic line ‘Koshihikari Toyama BL 3’ and partial resistance genes Pb1 in near-isogenic line ‘Koshihikari Aichi SBL’ and pi21 in a variety ‘Tomohonami’—was evaluated in pot and upland trials with spray inoculation of the blast isolate Ina 86-137 (Japanese race 007.0) or Ao 92-06-2 (Japanese race 337.1). The evaluation was conducted by assessing their leaf and panicle blast severity, and then comparing their severity with that of blasticide (probenazole or tricyclazole) applied ‘Koshihikari’ and three control varieties with different levels of partial resistance to blast, including ‘Koshihikari’. ‘Koshihikari Toyama BL3’ harboring Pib showed very high levels of efficacy with few leaf and panicle blast lesions in both trials. The efficacy of ‘Tomohonami’ having pi21 to leaf blast was also high and equal to or higher than that of the blasticide-applied ‘Koshihikari’ in both trials. However, ‘Tomohonami’ had no panicle blast control efficacy in the pot trial, although it showed high panicle blast reduction in the upland trial. The panicle blast control efficacy of ‘Koshihikari Aichi SBL’ with Pb1 was moderate, while its leaf blast reduction was low to moderate in both trials. For expansion of the leaf blast lesions with punch inoculation on the uppermost leaves of rice plants in the booting stage of the pot trial, the areas (length x width) of the lesions on ‘Koshihikari Toyama BL 3’ with Pib were the smallest and significantly different from those of all other lines and varieties, including probenazole-applied ‘Koshihikari’. The results showed the blast control efficacy of the three resistance genes Pib, Pb1, and pi21, and confirmed a quantitative reduction of blast severity with partial resistance genes Pb1 and pi21.
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A Rice Gene Homologous to Arabidopsis AGD2-LIKE DEFENSE1 Participates in Disease Resistance Response against Infection with Magnaporthe oryzae

A Rice Gene Homologous to Arabidopsis AGD2-LIKE DEFENSE1 Participates in Disease Resistance Response against Infection with Magnaporthe oryzae | Rice Blast | Scoop.it
ALD1 (ABERRANT GROWTH AND DEATH2 [AGD2]-LIKE DEFENSE1) is one of the key defense regulators in Arabidopsis thaliana and Nicotiana benthamiana. In these model plants, ALD1 is responsible for triggering basal defense response and systemic resistance against bacterial infection. As well ALD1 is involved in the production of pipecolic acid and an unidentified compound(s) for systemic resistance and priming syndrome, respectively. These previous studies proposed that ALD1 is a potential candidate for developing genetically modified (GM) plants that may be resistant to pathogen infection. Here we introduce a role of ALD1-LIKE gene of Oryza sativa, named as OsALD1, during plant immunity. OsALD1 mRNA was strongly transcribed in the infected leaves of rice plants by Magnaporthe oryzae, the rice blast fungus. OsALD1 proteins predominantly localized at the chloroplast in the plant cells. GM rice plants over-expressing OsALD1 were resistant to the fungal infection. The stable expression of OsALD1 also triggered strong mRNA expression of PATHOGENESIS-RELATED PROTEIN1 genes in the leaves of rice plants during infection. Taken together, we conclude that OsALD1 plays a role in disease resistance response of rice against the infection with rice blast fungus.
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Genetic diversity and structure in hill rice (Oryza sativa L.) landraces from the North-Eastern Himalayas of India

Genetic diversity and structure in hill rice (Oryza sativa L.) landraces from the North-Eastern Himalayas of India | Rice Blast | Scoop.it
According to farmers’ classification, hill rices were categorized into two groups: umte (large-grained, late maturing) and tening (small-grained, early maturing). We did not find significant difference in days to 50 % flowering between the groups. Principal component analysis revealed that two groups can be distinguished on the basis of kernel length-to-width ration (KLW), kernel length (KL), grain length (GrL), grain length-to-width ration (GrLW) and plant height (Ht). Stepwise canonical discriminant analysis identified KL and Ht as the main discriminatory characters between the cultivar groups. Genetic diversity analysis with 35 SSR markers revealed considerable genetic diversity in the hill rice germplasm (gene diversity: 0.66; polymorphism information content: 0.62). Pair-wise allelic difference between umte and tening groups was not statistically significant. The model-based population structure analysis showed that the hill rices were clustered into two broad groups corresponding to Indica and Japonica. The geographic distribution and cultivars grouping of hill rices were not congruent in genetic clusters. Both distance- and model-based approaches indicated that the hill rices were predominantly japonica or admixture among the groups within the subspecies. These findings were further supported by combined analysis hill rices with 150 reference rice accessions representing major genetic groups of rice.
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Calpains are involved in asexual and sexual development, cell wall integrity and pathogenicity of the rice blast fungus

Calpains are involved in asexual and sexual development, cell wall integrity and pathogenicity of the rice blast fungus | Rice Blast | Scoop.it
Calpains are ubiquitous and well-conserved proteins that belong to the calcium-dependent, non-lysosomal cysteine protease family. In this study, 8 putative calpains were identified using Pfam domain analysis and BlastP searches in M. oryzae. Three single gene deletion mutants (ΔMocapn7, ΔMocapn9 and ΔMocapn14) and two double gene deletion mutants (ΔMocapn4ΔMocapn7 and ΔMocapn9ΔMocapn7) were obtained using the high-throughput gene knockout system. The calpain disruption mutants showed defects in colony characteristics, conidiation, sexual reproduction and cell wall integrity. The mycelia of the ΔMocapn7, ΔMocapn4ΔMocapn7 and ΔMocapn9ΔMocapn7 mutants showed reduced pathogenicity on rice and barley.
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Autophagy-associated alpha-arrestin signaling is required for conidiogenous cell development in Magnaporthe oryzae

Autophagy-associated alpha-arrestin signaling is required for conidiogenous cell development in Magnaporthe oryzae | Rice Blast | Scoop.it
Conidiation patterning is evolutionarily complex and mechanism concerning conidiogenous cell differentiation remains largely unknown. Magnaporthe oryzae conidiates in a sympodial way and uses its conidia to infect host and disseminate blast disease. Arrestins are multifunctional proteins that modulate receptor down-regulation and scaffold components of intracellular trafficking routes. We here report an alpha-arrestin that regulates patterns of conidiation and contributes to pathogenicity in M. oryzae. We show that disruption of ARRDC1 generates mutants which produce conidia in an acropetal array and ARRDC1 significantly affects expression profile of CCA1, a virulence-related transcription factor required for conidiogenous cell differentiation. Although germ tubes normally develop appressoria, penetration peg formation is dramatically impaired and Δarrdc1 mutants are mostly nonpathogenic. Fluorescent analysis indicates that EGFP-ARRDC1 puncta are well colocalized with DsRed2-Atg8, and this distribution profile could not be altered in Δatg9 mutants, suggesting ARRDC1 enters into autophagic flux before autophagosome maturation. We propose that M. oryzae employs ARRDC1 to regulate specific receptors in response to conidiation-related signals for conidiogenous cell differentiation and utilize autophagosomes for desensitization of conidiogenous receptor, which transmits extracellular signal to the downstream elements of transcription factors. Our investigation extends novel significance of autophagy-associated alpha-arrestin signaling to fungal parasites.
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Nudix Effectors: A Common Weapon in the Arsenal of Plant Pathogens

Nudix Effectors: A Common Weapon in the Arsenal of Plant Pathogens | Rice Blast | Scoop.it
Plant pathogens secrete a variety of unique and highly specialized effectors to manipulate host immunity. Only a small proportion of the conserved effector genes are present in the genomes of pathogens across kingdoms, providing us with good opportunities to study plant immunity and disease mechanisms. Nucleoside diphosphate-linked moiety X (Nudix) effectors, a group of secreted proteins containing the Nudix hydrolase domain, have been identified in a broad range of pathogens including bacteria, oomycetes, and fungi. Nudix effectors have been validated as pathogenesis players in a few host–pathogen systems, indicating that an important virulence strategy might be shared by distinct plant pathogens. Although progress has been made, many questions remain yet unsolved. Here, we summarize our current knowledge of Nudix effectors. We will also provide thoughts and discussions for the next phase of research.
Elsa Ballini's insight:
he genome of Magnaporthe oryzae, the rice blast fungus, also revealed two duplicate copies of putative Nudix effectors
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Defence responses in rice plants in prior and simultaneous applications of Cladosporium sp. during leaf blast suppression

Defence responses in rice plants in prior and simultaneous applications of Cladosporium sp. during leaf blast suppression | Rice Blast | Scoop.it
An alternative method to control rice blast (Magnaporthe oryzae) is to include biological agent in the disease management strategy. The objective of this study was to assess the leaf blast-suppressing effects of rice phylloplane fungi. One Cladosporium sp. phylloplane fungus was shown to possess biocontrolling traits based on its morphological characteristics and an analysis of its 18S ribosomal DNA. Experiments aimed at determining the optimal time to apply the bioagent and the mechanisms involved in its rice blast-suppressing activities were performed under controlled greenhouse conditions. We used foliar spraying to apply the Cladosporium sp. 48 h prior to applying the pathogen, and we found that this increased the enzymatic activity. Furthermore, in vitro tests performed using isolate C24 showed that it possessed the ability to secrete endoxylanases and endoglucanases. When Cladosporium sp. was applied either prior to or simultaneous with the pathogen, we observed a significant increase in defence enzyme activity, and rice blast was suppressed by 84.0 and 78.6 %, respectively. However, some enzymes showed higher activity at 24 h while others did so at 48 h after the challenge inoculation. Cladosporium sp. is a biological agent that is capable of suppressing rice leaf blast by activating biochemical defence mechanisms in rice plants. It is highly adapted to natural field conditions and should be included in further studies aimed at developing strategies to support ecologically sustainable disease management and reduce environmental pollution by the judicious use of fungicidal sprays.
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Population structure analysis and association mapping of blast resistance in indica rice (Oryza sativa L.) landraces

Population structure analysis and association mapping of blast resistance in indica rice (Oryza sativa L.) landraces | Rice Blast | Scoop.it
Rice blast caused by Magnaporthe oryzae is one of the most devastating rice diseases worldwide. To understand the genetic diversity of indica landrace accessions and identify simple sequence repeat (SSR) markers that are associated with blast resistance, a population of 276 indica landraces from across the world was constructed. This population was then used to evaluate the blast-resistance phenotype through artificial inoculation under controlled conditions in 2012 and 2013. The genetic diversity and association of the population with resistance were analyzed by examining the phenotype for 160 SSR markers distributed on 12 rice chromosomes. The 276 accessions were classified into seven groups using model- and distance-based cluster analyses. Associations between SSR markers and blast resistance showed that 26 SSR markers were significantly associated with blast resistance in 2012 and 2013 (P < 0.01) and that the phenotypic variation ranged from 2.68 to 13.11%. Nineteen of the markers associated with blast resistance were located in regions where genes or quantitative trait loci (QTLs) have been previously reported, and seven were newly identified in this study. These results indicate that marker-trait association has potential advantages over classical linkage analysis and QTL mapping, and that these markers could be used for marker-assisted selection in rice blast-resistance-breeding programs.
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MoDnm1 Dynamin Mediating Peroxisomal and Mitochondrial Fission in Complex with MoFis1 and MoMdv1 Is Important for Development of Functional Appressorium in Magnaporthe oryzae

MoDnm1 Dynamin Mediating Peroxisomal and Mitochondrial Fission in Complex with MoFis1 and MoMdv1 Is Important for Development of Functional Appressorium in  Magnaporthe oryzae | Rice Blast | Scoop.it
Dynamin superfamily members are involved in budding of transport vesicles and division of organelles in eukaryotic cells. To further understand how dynamins function in phytopathogenic fungi, we characterized several dynamin-related proteins from the rice blast fungus M. oryzae. In addition to revealing major conserved dynamin functions, we described how MoDnm1 interacts with mitochondrial fission protein MoFis1 and WD repeat adaptor protein MoMdv1 to mediate peroxisomal and mitochondrial fission, pexophagy and mitophagy. Importantly, we provided evidence to demonstrate that MoDnm1-, MoFis1- and MoMdv1-dependent peroxisomal and mitochondrial functions are linked to differentiation and pathogenicity of the rice blast fungus.
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Analysis of the diversity and function of the alleles of the rice blast resistance genes Piz-t, Pita and Pik in 24 rice cultivars

Analysis of the diversity and function of the alleles of the rice blast resistance genes Piz-t, Pita and Pik in 24 rice cultivars | Rice Blast | Scoop.it
Understanding the sequence diversity of rice blast resistance genes is important for breeding new resistant rice cultivars against the rice blast fungus Magnaporthe oryzae. In this study, we selected 24 rice cultivars with different genetic backgrounds to study the allelic diversity of rice blast resistance genes Piz-t, Pita and Pik. For Piz-t, a total of 17 allelic types were found within the 24 cultivars. Blast inoculations showed that most of the mutations can affect the function of the resistance gene. For Pita, except for the difference at the 918th amino acid, a majority of the 21 mutations were detected among the cultivars. Inoculations with blast isolates carrying Avr-Pita revealed that cultivars with mutations in other sites except for the 918th amino acid did not affect the function of the Pita gene. For Pik, a total of six allelic types were found within the 24 cultivars, but five of them lost the function of the resistance gene. In addition, we found that Piz-t, Pita and Pik were expressed constitutively in the 24 rice cultivars and the expression level was not related to resistance. Our results have provided the sequence diversity information of the resistance genes Piz-t, Pita and Pik among the popular rice cultivars grown in the northeast region of China.
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4th Annual and Final Conference of the Sustain COST Action - Pathogen-informed strategies for sustainable broad-spectrum crop resistance

4th Annual and Final Conference of the Sustain COST Action - Pathogen-informed strategies for sustainable broad-spectrum crop resistance | Rice Blast | Scoop.it
The 4th Annual and Final Conference of the Sustain COST Action (FA1208) on "Pathogen-informed strategies for sustainable broad-spectrum crop resistance" will take place from 1/03/2017 to 3/03/2017 in Bled, Slovenia.

The conference will be held in the Hotel Kompas in Bled, a town on Lake Bled in the North-Western Slovenia, a popular tourist destination in Slovenia. Bled is one hour from the Ljubljana International Airport by public transport.

It will welcome around 120 participants and is organized by Dr. Barbara Gerič Stare (Agricultural Institute of Slovenia) and Dr. Saša Širca (Agricultural Institute of Slovenia).

The pre-registration for the conference closes September 15th.
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Roles of Peroxisomes in the Rice Blast Fungus

Roles of Peroxisomes in the Rice Blast Fungus | Rice Blast | Scoop.it

The rice blast fungus, Magnaporthe oryzae, is a model plant pathogenic fungus and is a severe threat to global rice production. Over the past two decades, it has been found that the peroxisomes play indispensable roles during M. oryzae infection. Given the importance of the peroxisomes for virulence, we review recent advances of the peroxisomes roles during M. oryzae infection processes. We firstly introduce the molecular mechanisms and life cycles of the peroxisomes. And then, metabolic functions related to the peroxisomes are also discussed. Finally, we provide an overview of the relationship between peroxisomes and pathogenicity.

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Updated Rice Kinase Database RKD 2.0: enabling transcriptome and functional analysis of rice kinase genes

Updated Rice Kinase Database RKD 2.0: enabling transcriptome and functional analysis of rice kinase genes | Rice Blast | Scoop.it
An updated version of rice kinase database (RKD) that contains metadata derived from NCBI GEO expression datasets has been developed. RKD 2.0 facilitates in-depth transcriptomic analyses of kinase-encoding genes in diverse rice tissues and in response to biotic and abiotic stresses and hormone treatments. We identified 261 kinases specifically expressed in particular tissues, 130 that are significantly up- regulated in response to biotic stress, 296 in response to abiotic stress, and 260 in response to hormones. Based on this update and Pearson correlation coefficient (PCC) analysis, we estimated that 19 out of 26 genes characterized through loss-of-function studies confer dominant functions. These were selected because they either had paralogous members with PCC values of <0.5 or had no paralog.
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Registration of 42 Blast Resistant Medium Grain Rice Genetic Stocks with Suitable Agronomic, Yield, Milling Yield, and Seed Characteristics

Rice blast disease caused by the filamentous ascomycete fungus Magnaporthe oryzae Cav. [Magnaporthe grisea (Herbert) Barr.] is one of the most threatening rice (Oryza sativa L.) diseases in the southern United States. Forty-two rice blast resistant genetic stocks (Reg. No. GS-34 to Reg. No. GS-75, GSOR 102501 to GSOR 102542) were developed and released by the USDA-ARS Dale Bumpers National Rice Research Center, Stuttgart, AR. The genetic stocks were developed from a cross of ‘M-202’ (PI 494105), a medium grain cultivar of premium quality, with the blast resistant long grain rice cultivar Katy (PI 527707), followed by five generations of backcrossing to the medium grain parent M-202. Two progenies of each of the 22 BC5F1 were genotyped with simple sequence repeat markers and evaluated with blast pathogen to verify the existence of the large blast resistance gene cluster on chromosome 12 being inherited from Katy. A total of 42 BC5F2 progenies resistant to blast were grown under field conditions during 2013 to 2014 at Stuttgart for agronomic and grain quality characterization. Agronomic traits, yield components, seed characteristics, yield, and milling quality of these lines were very similar to M-202. The genetic stocks will be useful for rice breeders to develop new medium grain cultivars with broad spectrum blast resistance.
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Dissection of the genetic architecture of rice resistance to the blast fungus Magnaporthe oryzae

Dissection of the genetic architecture of rice resistance to the blast fungus Magnaporthe oryzae | Rice Blast | Scoop.it
Resistance in rice cultivars to the rice blast fungus Magnaporthe oryzae is complex and is controlled by both major genes and quantitative trait loci (QTLs). We undertook a genome-wide association study (GWAS) using the rice diversity panel 1 (RDP1) that was genotyped using a high-density (700 000 single nucleotide polymorphisms) array and inoculated with five diverse M. oryzae isolates. We identified 97 loci associated with blast resistance (LABRs). Among them, 82 were new regions and 15 co-localized with known blast resistance loci. The top 72 LABRs explained up to 98% of the phenotypic variation. The candidate genes in the LABRs encode nucleotide-binding site leucine-rich repeat (NBS-LRR) resistance proteins, receptor-like protein kinases, transcription factors and defence-related proteins. Among them, LABR_64 was strongly associated with resistance to all five isolates. We analysed the function of candidate genes underlying LABR_64 using RNA interference (RNAi) technology and identified two new resistance alleles at the Pi5 locus. We demonstrate an efficient strategy for rapid allele discovery using the power of GWAS, coupled with RNAi technology, for the dissection of complex blast resistance in rice.
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A Simple and Accurate Resistance Identification Method of Rice to Neck Blast Disease In Vitro

A Simple and Accurate Resistance Identification Method of Rice to Neck Blast Disease In Vitro | Rice Blast | Scoop.it
Twelve rice cultivars with differential resistance to rice blast disease (Magnaporthe oryzae (Hebert) Barr), including Tetep (R), IR36 (MR) and Lijiangxituanhegu (HS), and nine locally planted rice cultivars in Jiangxi helped establish an identification method for rice resistance to neck blast. We describe a new technique of dropping a spore suspension on the panicle segment in vitro (DSSPS). This technique involved rice panicles that were initially 0.5–2 cm in length and then cut into a 7- to 8-cm segment (i.e. an upper node of 1 cm and a lower node of 6–7 cm). The segment was placed into a Petri dish with a stack of sterile water saturated filter paper. The suspension (4 μl 1 × 105spores/ml) was placed at each of three locations on the segment (with an approximate interval of 3 cm). Disease severity was then assessed according to a 0–9 scale after incubating for 9 days with a 12 h/12 h (light/day cycle) at 28°C. Choosing a suitable developmental stage of the rice panicle and blast strains was a key to evaluate resistance accurately. DSSPS is a simple and accurate method of identifying rice resistance to neck blast as compared to injecting the spore suspension into the rice panicle in vivo and resistance identification in natural nurseries. It is stressed that at least 20 single-spore strains are needed to accurately assess rice resistance to neck blast. We tested 1005 rice cultivars for neck blast resistance in Jiangxi province during 2010–2015, which showed an accuracy of 85.77% by DSSPS as compared with natural nursery data.
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Sowing date reduces the incidence of wheat blast disease

The objective of this work was to assess the effect of sowing date on the intensity of wheat blast disease, as well as the yield losses caused by this disease in different wheat (Triticum aestivum) genotypes. The experiments were conducted in 2013 at the Sertãozinho experimental station of Empresa de Pesquisa Agropecuária de Minas Gerais (Epamig), in the municipality of Patos de Minas, in the state of Minas Gerais, Brazil. Fourteen wheat genotypes and two sowing dates were evaluated. The experimental design was a randomized complete block with three replicates. The evaluated variables were: incidence, severity, thousand grain weight (TGW), grain yield, and yield losses. A disease index (DI) was calculated, based both on the incidence and the severity of the disease, to measure blast intensity in wheat. The sowing date significantly affected DI, TGW, and grain yield. Significant linear correlations were observed between DI and yield losses (0.89), between losses and TGW (-0.85), and between losses and grain yield (-0.93). For wheat blast, DIs greater than or equal to 0.5 indicate potential yield losses equal to or greater than 70%. The EP063030 line and the MGS Brilhante and BRS 264 cultivars are the most tolerant to blast, when exposed to high disease pressure.
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Two novel antimicrobial defensins from rice identified by gene coexpression network analyses

Two novel antimicrobial defensins from rice identified by gene coexpression network analyses | Rice Blast | Scoop.it

Recombinant OsDEF7 and OsDEF8 inhibit several rice pathogens.
Different dimeric structures of OsDEF7 and OsDEF8 were proposed.
Coexpression network analyses can identify novel antimicrobial peptides.

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An autophagy gene, HoATG5, is involved in sporulation, cell wall integrity and infection of wounded barley leaves

An autophagy gene, HoATG5, is involved in sporulation, cell wall integrity and infection of wounded barley leaves | Rice Blast | Scoop.it
The endophytic fungus Harpophora oryzae is a beneficial endosymbiont isolated from wild rice. H. oryzae can not only promote rice growth and biomass accumulation but also protect rice roots from invasion by its close relative Magnaporthe oryzae. Autophagy is a highly evolutionary conserved process from lower to higher eukaryotic organisms, and is involved in the maintenance of normal cell differentiation and development. In this study, we isolated a gene (HoATG5) which encodes an essential protein required for autophagy from the beneficial endophyte fungus H. oryzae. Using targeted gene replacement, a ΔHoATG5 mutant was generated and used to investigate the biological functions of autophagy in H. oryzae. We found that the autophagic process was blocked in the HoATG5 deletion mutant. The mutant showed increased vegetative growth and sporulation, and was sensitive to nutrient starvation. The ΔHoATG5 mutant lost its ability to penetrate and infect the wounded barley leaves. These results provide new knowledge to elaborate the molecular machinery of autophagy in endophytic fungi.
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Suppression of Magnaporthe oryzae and interaction between Bacillus subtilis and rice plants in the control of rice blast

Suppression of Magnaporthe oryzae and interaction between Bacillus subtilis and rice plants in the control of rice blast | Rice Blast | Scoop.it
Magnaporthe oryzae, the causative pathogen of rice blast, has caused extensive losses to rice cultivation worldwide. Strains of the bacterium Bacillus subtilis have been used as biocontrol agents against rice blast. However, little has been reported about the interaction between B. subtilis and the rice plant and its mechanism of action. Here, the colonization process and induced disease resistance by B. subtilis SYX04 and SYX20 in rice plants was examined. Strains of B. subtilis labeled with green fluorescent protein reached population of more than 5 × 106 CFU/g after 20 days on mature rice leaves and were detected after 3 days on newly grown leaves. Results showed that SYX04 and SYX20 not only inhibited spore germination, germ tube length, and appressorial formation but also caused a series of alterations in the structures of hyphae and conidia. The cell walls and membrane structures of the fungus showed ultrastructural abnormalities, which became severely degraded as observed through scanning electron microscopy and transmission electron microscopy. The mixture of both B. subtilis and M. oryzae resulted in enhanced activity of peroxidase, and polyphenol oxidase while there was significantly more superoxide dismutase activity in plants that had been sprayed with B.subtilis alone. The present study suggests that colonized SYX04 and SYX20 strains protected rice plants and exhibited antifungal activity and induced systemic resistance, thus indicating their potential biological control agents
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