Piricularia Oryzae Research Articles

Nucleotide-binding leucine-rich repeat receptor homologs Pib and PibH8 interact and contribute to immunity in rice.

Plant nucleotide-binding leucine-rich repeat receptors (NLRs) sense pathogen effectors and activate effector-triggered immunity (ETI). Many plant NLRs form pairs with other NLRs to recognize effectors and initiate ETI. PIRICULARIA ORYZAE RESISTANCE IN BL1 (Pib), an NLR protein in rice (Oryza sativa), activates resistance by recognizing the rice blast effector AvrPib. The activation of Pib is suppressed by SH3 DOMAIN-CONTAINING PROTEIN 2 (OsSH3P2) in the absence of AvrPib. However, how Pib triggers defense responses and whether Pib pairs with another NLR are not clear. In this study, we identified Pib by map-based cloning and showed that a homolog of Pib, PIB HOMOLOGUE 8 (PibH8), interacts with Pib. Pib and PibH8 mediate resistance to the Magnaporthe oryzae isolate Guy11, a rice blast strain carrying AvrPib. Interestingly, the pib/pibh8 double mutant exhibited enhanced susceptibility to Guy11 compared to the single mutant. Furthermore, PibH8 can oligomerize through its coiled-coil (CC) domain, which also contributes to the Pib-PibH8 interaction, suggesting that Pib and PibH8 may form a complex to recognize AvrPib. OsSH3P2 inhibited the interaction of Pib and PibH8 through association with the CC domain of PibH8. Taken together, these results indicate that both Pib and PibH8 are required for rice blast resistance to M. oryzae carrying AvrPib, which is negatively regulated by OsSH3P2. This study not only identifies an NLR that functions in rice blast resistance but also reveals a possible complex immune strategy in which homologous NLR proteins may regulate the complete activation of plant immunity.

The OsSPK1-OsRac1-RAI1 defense signaling pathway is shared by two distantly related NLR proteins in rice blast resistance.

Resistance (R) proteins are important components of plant innate immunity. Most known R proteins are nucleotide-binding site leucine-rich repeat (NLR) proteins. Although a number of signaling components downstream of NLRs have been identified, we lack a general understanding of the signaling pathways. Here, we used the interaction between rice (Oryza sativa) and Magnaporthe oryzae to study signaling of rice NLRs in response to blast infection. We found that in blast resistance mediated by the NLR PIRICULARIA ORYZAE RESISTANCE IN DIGU 3 (PID3), the guanine nucleotide exchange factor OsSPK1 works downstream of PID3. OsSPK1 activates the small GTPase OsRac1, which in turn transduces the signal to the transcription factor RAC IMMUNITY1 (RAI1). Further investigation revealed that the three signaling components also play important roles in disease resistance mediated by the distantly related NLR protein Pi9, suggesting that the OsSPK1-OsRac1-RAI1 signaling pathway could be conserved across rice NLR-induced blast resistance. In addition, we observed changes in RAI1 levels during blast infection, which led to identification of OsRPT2a, a subunit of the 19S regulatory particle of the 26S proteasome. OsRPT2a seemed to be responsible for RAI1 turnover in a 26S proteasome-dependent manner. Collectively, our results suggest a defense signaling route that might be common to NLR proteins in response to blast infection.

A novel mannose-binding lectin from Liparis nervosa with anti-fungal and anti-tumor activities.

Plant lectins are carbohydrate-binding proteins with nonimmune origin, which can reversibly bind with carbohydrates, agglutinate cells, and precipitate polysaccharides and glycoconjugates. Plant lectins have attracted much attention for their anti-virus, anti-proliferation, and pro-apoptosis properties. Thus the exploration of new lectins has received special attention. Here we purified a mannose-binding lectin from the rhizomes of Liparis nervosa by ion exchange chromatography on DEAE-Sepharose, affinity chromatography on Mannose-Sepharose 4B, and gel filtration chromatography on Sephacryl S-100. The purified L. nervosa lectin (LNL) was identified to be a monomeric protein with a molecular mass of 13kDa. LNL exhibited hemagglutinating activity towards rabbit erythrocytes, and its activity could be strongly inhibited by D-mannose, N-acetyl glucosamine and thyroglobulin. In vitro experiments showed that LNL exhibited a comparable anti-fungal activity against Piricularia oryzae (Cavara), Bipolaris maydis, Fusarium graminearum, and Sclerotium rolfsii, and anti-proliferation activity against tumor cells by inducing apoptosis. The full-length cDNA sequence of LNL is 715bp in length and contains a 525bp open reading frame (ORF) encoding a 110-residue mature protein. It was predicted to have three mannose-binding conserved motifs 'QXDXNXVXY'. The binding pattern of LNL was further revealed by homology modeling and molecular docking. We demonstrated that LNL is not only a potential therapeutic candidate against tumor but also a new anti-fungal agent.

Extraction, identification and antimicrobial activity of a new furanone, grifolaone A, from Grifola frondosa

A furanone (1), (S)-methyl 2-(2-hydroxy-3,4-dimethyl-5-oxo-2,5-dihydrofuran-2-yl)acetate, was isolated from the edible mushroom Grifola frondosa. Mass spectrometry and NMR analyses were used to elucidate the structure of this compound, and its absolute configuration was determined using circular dichroism spectroscopy. Compound 1 exhibited specific antifungal activity against the plant pathogens, Fusarium oxysporum, Gibberella zeae and Piricularia oryzae and the opportunistic human pathogen, Pseudallescheria boydii, resulting in minimum inhibitory concentration values of 2.5, 2.5, 1.25 and 0.15 μg/mL, respectively. In contrast, the furanone showed only weak activity towards Aspergillus spp., Candida albicans and several other fungal strains tested as well as no appreciable antibacterial activity.

(-)-Sclerotiorin from an Unidentified Marine Fungus as an Anti-meiotic and Antifungal Agent

(-)-Sclerotiorin, isolated and purified from the fermented broth of an unidentified marine fungus (98F134), inhibited the maturation of starfish oocytes induced by 1-methyl adenine with an IC50 value of 0.50 microM. (-)-Sclerotiorin also showed antifungal activity against Saccharomyces cerevisiae, Aspergilus fumigatus, Alternaria longipes, Piricularia oryzae, Verticillium albo-atrum, Fusarium culmorum, and F. nivale with IC50 values less than 20 microg/mL.

Chemical Composition and Antifungal Properties of the Essential Oil of Tanacetum annuum

Shoot oil of Tanacetum annuum was examined by GC and GC/MS and found to contain sabinene (22.3%) and camphor (13.2%) as major constituents. This oil was screened for its antifungal activity against Botrytis cinerea, Helminthosporium oryzae, Alternaria solani, Piricularia oryzae and Verticillium dahliae. T. annuum oil exhibited the strongest fungitoxicity by completely inhibiting the mycelial growth of each of the fungi at 5000 ppm.

Quinolinic acid, α-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid enhance the Fenton reaction in phosphate buffer

Quinolinic acid, α-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid enhanced the Fenton reaction in phosphate buffer, respectively. The enhancement by quinolinic acid, α-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid of the Fenton reaction may be partly related to their respective actions in the biological systems such as a neurotoxic effect (quinolinic acid), a marked growth-inhibitory action on rice seeding (α-picolinic acid and fusaric acid), and an antiseptic (2,6-pyridinedicarboxylic acid). The ultraviolet–visible absorption spectrum of the mixture of α-picolinic acid with ferrous ion showed a characteristic visible absorbance band with a λ max at 443 nm, suggesting that α-picolinic acid chelate of Fe 2+ ion forms in the solution. Similar characteristic visible absorbance band was also observed for the mixture of Fe 2+ ion with quinolinic acid (or fusaric acid, or 2,6-pyridinedicarboxylic acid). The chelation seems to be related to the enhancement by quinolinic acid, α-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid of the Fenton reaction. α-Picolinic acid was reported to be a toxic substance isolated from the culture liquids of blast mould ( Piricularia oryzae CAVARA). On the other hand, it has also been known that chlorogenic acid protects rice plants from the blast disease. The chlorogenic acid inhibited the formation of the hydroxyl radical in the reaction mixture of α-picolinic acid, FeSO 4(NH 4) 2SO 4, and H 2O 2. Thus the inhibition may be a possible mechanism of the protective action of the chlorogenic acid against the blast disease.

ChemInform Abstract: Synthesis of Thieno(2,3‐d)pyrimidine Derivatives and Their Antifungal Activities.

AbstractThe aminothiophenecarboxamides (I) are converted to the chlorothienopyrimidines (VI) which react with nucleophiles (VII) to yield the substituted thienopyrimidines (VIII).

Synthesis of thieno[2,3-d]pyrimidine derivatives and their antifungal activities

4-Chlorothieno[2,3-d]pyrimidines were prepared by the chlorination of 4-oxo-3,4-dihydrothieno[2,3-d]pyrimidines with phosphoryl chloride. 4-Oxo-3,4,5,6,7,8-hexahydro[1]-benzo- and 4-oxo-6-phenylthieno[2,3-d]pyrimidine were synthesized by the cyclization of 2-acylaminothiophene-3-carboxamide derivatives with base. 2-Methyl-4-oxo-3,4-dihydrothieno[2,3-d]pyrimidine was prepared by the treatment of 2-methyl-4-trichloromethylthieno-[2,3-d]pyrimidine with sodium hydroxide in aqueous methanol. A series of 4-alkylamino- and 4-arylaminothieno[2,3-d]pyrimidines were synthesized by the nucleophilic substitution of 4-chlorothieno[2,3-d]pyrimidines with various amines. These compounds were evaluated for antifungal activity against Piricularia oryzae. The preventive effects on Rice blast, Sheath blight, and Cucumber powdery mildew were also determined by pot tests.

Novel cytocidal antibiotics, glucopiericidinols A1 and A2. Taxonomy, fermentation, isolation, structure elucidation and biological characteristics.

Two novel antibiotics, glucopiericidinols A1 (1) and A2 (2) were isolated from the cultured broth of Streptomyces sp. OM-5689. The structures of these two compounds were deduced employing spectroscopic analyses. These antibiotics showed potent cytocidal activities against HeLa S3 cells in vitro (MIC 1: 0.39 microgram/ml, 2: 0.10 microgram/ml) when the cells were exposed to the antibiotics for 3 days. Although 1 and 2 showed no activity at 1,000 micrograms/ml against various Gram-positive and Gram-negative bacteria, yeast or fungi, they did have inhibitory activity against Piricularia oryzae (MIC of 1: 125 micrograms/ml, of 2: 31 micrograms/ml).

Quantitative structure-activity relationship studies of the fungitoxic properties of phenethyl 1,2,4-triazoles

A series of phenethyl triazoles was tested for activity in poisoned agar against Dreschlera sorokiniana, Piricularia oryzae, and a yeast sterol [ 14C]demethylase assay. The effects of substitution on the carbon adjacent to the phenyl ring and halogenation of the phenyl ring on activity was examined by regressing activity against substituent physicochemical parameters in a Hansch-type analysis. Results indicate that one substituent on the carbon adjacent to the phenyl ring should be 6–7 Å long. The terminal part of this substituent was negatively correlated to strong dipole moment, proton acceptor ability, or negative partial charge which implies a hydrophobic site. In general, the substitution patterns for the whole organism assays paralleled the activity of the demethylase assay. An exception was the para-phenyl position, whose optimum substituent varied by organism. The optimum substituent of the ortho-phenyl position varied with the substitution on the carbon adjacent to the phenyl ring. This interaction may be due to changes in the preferred conformation(s) of the molecule.

Quantitative structure-activity relationships of the fungicidal and herbicidal thiolcarbamates.

Ninety-two thiolcarbamates with various substituents at the nitrogen and sulfur atoms, and their related compounds were synthesized, and their fungicidal activity against rice blast, Piricularia oryzae, and herbicidal activity against barnyardgrass, Echinochloa crus-galli, were determined in laboratory tests. The thiolcarbamate structure was necessary for the high fungicidal and herbicidal activities. The hydrophobicity of the substituents at the nitrogen atom was shown by the adaptive least-squares (ALS) method to be favorable to the fungicidal activity. The bulkier the substituents at the nitrogen atom, the less was the fungicidal activity. However, bulkiness of the substituents at the nitrogen and sulfur atoms was unfavorable to the herbicidal activity. The existence of a hydrogen atom at the nitrogen atom was favorable to fungicidal activity, but not to herbicidal activity. Correlation analyses were made to find compounds with both fungicidal and herbicidal activities against rice pests.

Studies on a novel cytocidal antibiotic, trienomycin A. Taxonomy, fermentation, isolation, and physico-chemical and biological characteristics.

A new antibiotic, trienomycin A, has been isolated from the culture broth of Streptomyces sp. No. 83-16. The physico-chemical characteristics of the antibiotic suggested that it belongs to the group of ansamycin antibiotics with a triene moiety in the molecule. The molecular formula of trienomycin A is C36H50N2O7 (MW 622). The antibiotic possesses potent cytocidal activity against HeLa S3 and PLC hepatoma cells at concentrations of 0.1 and 0.01 micrograms/ml (IC50 value) respectively. However, trienomycin A showed no antimicrobial activity against the bacteria, fungi and yeasts examined with the exception of weak activity versus Piricularia oryzae at a concentration of 1,000 micrograms/ml.

Structures of trienomycins A, B and C, novel cytocidal ansamycin antibiotics.

The structures of novel antibiotics, trienomycins A, B and C produced by Streptomyces sp. No. 83-16, have been determined on the basis of their spectroscopical and chemical properties. Trienomycins are unique ansamycin antibiotics with a triene and an 1,3,5-trisubstituted benzene moieties in the molecule. The antibiotics possess potent cytocidal activity against HeLa S3 cells at concentrations of 0.005 (trienomycin A), 0.1 (trienomycin C) and 0.2 micrograms/ml (trienomycin B) (IC50 value), respectively. However, trienomycins showed no antimicrobial activity against the bacteria, fungi and yeasts examined with the exception of weak activity versus Piricularia oryzae at a concentration of 1,000 micrograms/ml.

Chemical Defense of Leguminosae. Are Quinolizidine Alkaloids Part of the Antimicrobial Defense System of Lupins?

Growth of 6 bacteria (Serratia marcescens, Bacillus megaterium, Bacillus subtilis, Streptococcus viridis, Micrococcus luteus, and Mycobacterium phlei) was inhibited by 50% if the growth medium contained sparteine at concentrations between 0.5-10mᴍ. Total growth inhibition, which was bacteriostatic in nature, was achieved at 20 mᴍ. The growth of 6 phytopathogenic fungi was also affected: at a sparteine concentration of 15 mᴍ the growth of Alternaria porri was reduced by 40% as compared to the untreated control. Respective values were 18% inhibition for Piricularia oryzae, 33% for Helminthosporium carbonum, 15% for Rhizoctonia solani, 5% for Fusarium oxysporum, and 42% for Asperquillus oryzae. Since the concentrations of quinolizidine alkaloids range from 1-200 mᴍ (roots, leaves, or stems) or 10-200 mmol/kg (seeds) in Leguminosae, it is discussed whether quinolizidine alkaloids are involved in the antimicrobial defense of lupins, in addition to their potential role as allelopathic or herbivore repellent defense compounds.

Synthesis of a model of an inner chain of cell-wall proteoheteroglycan isolated from Piricularia oryzae: Branched d-mannopentaosides

Efficient syntheses are described of the branched d-mannopentaosides methyl 2,6-di- O-(2- O-α- d-mannopyranosyl-α- d-mannopyranosyl)α- d-mannopyranoside and methyl 2,4-di- O-(2- O-α- d-mannopyranosyl-α- d-mannopyranosyl)-α- d-mannopyranoside, starting from the glycosyl acceptors methyl 3,4-di- O-benzyl-α- d-mannopyranoside and methyl 3,6-di- O-benzyl-α- d-mannopyranoside, and employing the protected d-mannotriosides methyl 3,4-di- O-benzyl-2,6-di- O-(3,4,6-tri- O-benzyl-α- d-mannopyranosyl)-α- d-mannopyranoside, and methyl 3,6-di- O-benzyl-2,4-di- O-(3,4,6-tri- O-benzyl-α- d-mannopyranosyl)-α- d-mannopyranoside as key intermediates.

A Cell Wall Proteo-Heteroglycan from Piricularia oryzae: Further Studies of the Structure

The carbohydrate part of a proteo-heteroglycan from Piricularia oryzae was further studied by chemical and immunological methods. Acetolysis studies of the proteo-heteroglycan and exo-alpha-D-mannanase resistant core showed a (1 leads to 6) mannan back-bone structure with side chains composed of one to four mannose units, and some of which are terminated by D-glucose or D-galactofuranose. The mode of attachment of the terminal glucose was characterized to be alphaGlc(1 leads to 6)Man by inhibition reaction with oligosaccharides. Rabbit anti-serum formed against P. oryzae cells had three specificities, the first one for alphaGlc(1 leads to 6)alphamannosyl, the second one for alphaMan(1 leads to 3)alphamannosyl, and the last one for alphaGal-f(1 leads to 2)alphamannosyl residues. The most immunodominant side chain structure of the P. oryzae heteroglycan was shown to be alphaGlc(1 leads to 6)alphaMan(1 leads to 2)alphaMan(1 leads to 2)Man.

A cell wall proteo-heteroglycan from Piricularia oryzae: isolation and partial structure.

A purified proteo-heterolgycan, [alpha]D + 72.5 degrees, was isolated from Piricularia oryzae, a pathogenic fungus of rice blast disease (Imochi-byo), by means of hot citrate buffer extraction, cetavlon fractionation, and DEAE-Sephade chromatography. It was found to be homogeneous by electrophoresis and by analytical ultracentrifugation to have an s value 6.1 and to contain 91% (w/w) of carbohydrate, which consists of D-mannose, D-glucose, and D-galactose in a molar ratio of 6:2:1. Partial acid hydrolysis and methylation analysis of the carbohydrate moiety of the proteo-heteroglycan indicate that the molecule is composed of mannan, the side chain terminals of which are partially modified with D-glucopyranose and D-galactofuranose. Enzymatic hydrolysis with bacterial alpha-D-mannanase has been shown to remove most of the side chains from the heteroglycan, leaving an (1-6) linked mannan back-bone with a small amount of side chains, the terminals of which must be modified with D-glucopyranose or D-galactofuranose. The carbohydrate to protein linkage of the proteo-heteroglycan was shown by alkaline beta-elimination, to be mannosyl serine or mannosyl threonine.

Chemical activation of host defence mechanisms as a basis for crop protection

THE possibility that a chemical for plant disease control might function by activating the natural resistance mechanisms of the host has been suggested previously1, but there are few well-documented examples. We report here that 2,2-dichloro-3,3-dimethyl cyclopropane carboxylic acid (WL 28325) may exert its systemic fungicidal activity against the rice blast disease (caused by the fungus Piricularia oryzae) in this way.

Purification and Properties of Saccharogenic Amylase from Piricularia oryzae

AbstractPiricularia oryzae, the pathogenic fungus of rice blast disease, produced a glucoamylase as a sole amylolytic enzyme with little concomitant activity of other related enzymes. The purified enzyme preparation showed a single band on electrophoresis. The enzyme had optimum pH at 6.5 and optimum temperature between 50 and 55°C. It was completely inactivated by heating for 15 min at 60°C. The molecular weight of the enzyme was estimated as about 94,000. The enzyme hydrolyzed various kinds of amylaceous substrates and some malto‐oligosaccharides into glucose. Glucobioses such as isomaltose, nigerose, kojibiose, α,α‐trehalose, β,β‐trehalose as well as phenyl‐α‐glucoside were also hydrolyzed.