Effects of Antifungal Compounds on Conidial Germination and on the Induction of Appressorium Formation of Magnaporthe grisea

1999 ◽  
Vol 54 (11) ◽  
pp. 903-908 ◽  
Author(s):  
Frank Eilbert ◽  
Eckhard Thines ◽  
Heidrun Anke
Keyword(s):  
Magnaporthe Grisea ◽  
Sodium Cyanide ◽  
Coupling Agents ◽  
Antifungal Compounds ◽  
Appressorium Formation ◽  
Respiratory Inhibitors ◽  
High Concentrations ◽  
Different Strains ◽  
Cyanide Resistant Respiration ◽  
Higher Sensitivity

Abstract Appressorium formation in germinating conidia of Magnaporthe grisea was induced on a hydrophilic (noninductive) surface by antifungal compounds. Respiratory inhibitors or un­ coupling agents such as strobilurins, antimycin A , myxothiazol, rotenone, pterulone A , and oligomycin A were particularly effective whereas sodium cyanide had no effect. Cyclosporin A was effective only at high concentrations. These differentiation-inducing effects were only observed at subfungicidal concentrations at which more than 50% of the germinating conidia formed appressoria. Cycloheximide, nystatin, amphotericin B, and papulacandin A did not induce appressoria. Different strains of M. grisea displayed the same overall response to the inhibitors, varying merely in the percentage of appressoria formed. A combination of the respiratory inhibitors with 2-phenyl-4H -1-benzopyran-4-one (flavone), diphenyleneiodonium (DPI), or salicylhydroxamic acid (SHAM), compounds which interfere with the cyanide-resistant respiration, resulted in a higher sensitivity of the strains towards the respiratory inhibitors, but had no effect on appressorium formation.

scholarly journals A Target-Site-Specific Screening System for Antifungal Compounds on Appressorium Formation in Magnaporthe grisea

2000 ◽  
Vol 90 (10) ◽  
pp. 1162-1168 ◽  
Author(s):  
Hong-Sik Oh ◽  
Yong-Hwan Lee
Keyword(s):  
Ethyl Acetate ◽  
Rice Blast ◽  
Magnaporthe Grisea ◽  
Pathogenic Fungi ◽  
Antifungal Compounds ◽  
Screening System ◽  
Appressorium Formation ◽  
Culture Filtrates ◽  
Water Fractions ◽  
Chemical Fungicides

Chemical fungicides are a major method of control for plant diseases in spite of potential negative effects on the environment and the appearance of resistant strains. Development of new chemical fungicides has been largely dependent upon in vivo efficacy tests in the greenhouse or in fields, which is in contrast to target-oriented in vitro screening systems widely used in the pharmaceutical field. To establish a target-site—specific screening system for antifungal compounds, specific inhibition on appressorium formation of the rice blast fungus Magnaporthe grisea was employed. For many plant-pathogenic fungi, including M. grisea, appressorium formation is an essential step to infect host plants. Among 1,000 culture filtrates of members of the class Actinomycetes and fungi, five (A5005, A5008, A5314, A5387, and A5397) from the class Actinomycetes showed differential inhibitory effects on appressorium formation of M. grisea in a dosage-dependent manner. Three (A5005, A5314, and A5387) of these were further fractionated into ethyl acetate and water fractions. The ethyl acetate fraction of A5005 and both the ethyl acetate and water fractions from A5314 and A5387 inhibited appressorium formation, while conidial germination remained little affected. Inhibition of appressorium formation by the ethyl acetate or water fraction was reversed by the exogenous addition of cyclic AMP. Significantly reduced numbers of conidia with appressoria were observed on rice leaves in the presence of culture filtrates. Furthermore, these culture filtrates also exhibited significant disease control of rice blast in the greenhouse. This rapid and target-oriented screening system could be adopted to screen candidate compounds for rice blast control and could be applicable for other appressorium-forming, plant-pathogenic fungi.

scholarly journals Inhibition of Fungal Appressorium Formation by Pepper (Capsicum annuum) Esterase

2001 ◽  
Vol 14 (1) ◽  
pp. 80-85 ◽  
Author(s):  
Young Soon Kim ◽  
Hyun Hwa Lee ◽  
Moon Kyung Ko ◽  
Chae Eun Song ◽  
Cheol-Yong Bae ◽  
...  
Keyword(s):  
Recombinant Protein ◽  
Capsicum Annuum ◽  
Magnaporthe Grisea ◽  
Dependent Manner ◽  
Appressorium Formation ◽  
Glutathione S Transferase ◽  
Porcine Liver ◽  
Esterase Gene ◽  
Dose Dependent ◽  
Dependent Signaling Pathway

A pepper esterase gene (PepEST) that is highly expressed during an incompatible interaction between pepper (Capsicum annuum) and the anthracnose fungus Colletotrichum gloeosporioides has been previously cloned. Glutathione-S-transferase-tagged recombinant PepEST protein expressed in Escherichia coli showed substrate specificity for p-nitrophenyl esters. Inoculation of compatible unripe pepper fruits with C. gloeosporioides spores amended with the recombinant protein did not cause anthracnose symptoms on the fruit. The recombinant protein has no fungicidal activity, but it significantly inhibits appressorium formation of the anthracnose fungus in a dose-dependent manner. An esterase from porcine liver also inhibited appressorium formation, and the recombinant protein inhibited appressorium formation in the rice blast fungus, Magnaporthe grisea. Inhibition of appressorium formation in M. grisea by the recombinant protein was reversible by treatment with cyclic AMP (cAMP) or 1,16-hexadecanediol. The results suggest that the recombinant protein regulates appressorium formation by modulating the cAMP-dependent signaling pathway in this fungus. Taken together, the PepEST esterase activity can inhibit appressorium formation of C. gloeosporioides, which may result in protection of the unripe fruit against the fungus.

scholarly journals A comparison of ten USEPA approved total coliform/E. coli tests

2007 ◽  
Vol 5 (2) ◽  
pp. 267-282 ◽  
Author(s):  
Jeremy Olstadt ◽  
James Jay Schauer ◽  
Jon Standridge ◽  
Sharon Kluender
Keyword(s):  
Environmental Protection Agency ◽  
False Positive ◽  
The United States ◽  
Total Coliform ◽  
Test System ◽  
E Coli ◽  
Test Systems ◽  
High Concentrations ◽  
Different Strains ◽  
Positive Results

Since 2002, the United States Environmental Protection Agency (USEPA) has approved ten enzyme-based total coliform and E. coli detection tests for examination of drinking water. These tests include: Colilert®, Colilert-18®, Colisure®, m-Coli Blue 24®, Readycult® Coliforms 100, Chromocult®, Coliscan®, E*Colite®, Colitag™ and MI Agar. The utility of the enzyme based test systems is based on both the ability of the test to detect the target organisms at low levels and the ability of the test system to suppress the growth of non-target organisms that might result in false positive results. Differences in the ability of some of these methods to detect total coliform and E. coli, as well as suppress Aeromonas spp., a common cause of “false positive” results, have been observed. As a result, this study was undertaken to elucidate the strengths and weaknesses of each method. Water samples were collected from three geographically and chemically diverse groundwaters in Wisconsin. One-hundred milliliter aliquots were individually spiked with both low concentrations (one to ten organisms) and high concentrations (fifty to one-hundred) of each of five different total coliform organisms (Serratia, Citrobacter, Enterobacter, E. coli, & Klebsiella). These spiked samples were used to test the capability of ten enzyme-based test systems to both detect and enumerate the spiked organisms. In addition, 100 ml samples were independently spiked with two different strains of Aeromonas spp. at six different levels, to assess the ability of each enzyme-based test to suppress Aeromonas spp. Analysis of the data indicated that wide variability exists among USEPA approved tests to detect and quantify total coliforms, as well as suppress Aeromonas spp.

Proteome analysis of rice blast fungus (Magnaporthe grisea) proteome during appressorium formation

PROTEOMICS ◽  
2004 ◽  
Vol 4 (11) ◽  
pp. 3579-3587 ◽  
Author(s):  
Sun Tae Kim ◽  
Seok Yu ◽  
Sang Gon Kim ◽  
Han Ju Kim ◽  
Sun Young Kang ◽  
...  
Keyword(s):  
Rice Blast ◽  
Magnaporthe Grisea ◽  
Proteome Analysis ◽  
Rice Blast Fungus ◽  
Appressorium Formation ◽  
Blast Fungus

scholarly journals G Protein α Subunit Genes Control Growth, Development, and Pathogenicity of Magnaporthe grisea

1997 ◽  
Vol 10 (9) ◽  
pp. 1075-1086 ◽  
Author(s):  
Shaohua Liu ◽  
Ralph A. Dean
Keyword(s):  
Neurospora Crassa ◽  
G Protein ◽  
Vegetative Growth ◽  
Magnaporthe Grisea ◽  
Cryphonectria Parasitica ◽  
Appressorium Formation ◽  
Α Subunit ◽  
Targeted Deletion ◽  
Control Growth ◽  
G Protein Α Subunit

Three G protein α subunit genes have been cloned and characterized from Magnaporthe grisea: magA is very similar to CPG-2 of Cryphonectria parasitica; magB is virtually identical to CPG-1 of Cryphonectria parasitica, to gna1 of Neurospora crassa, and to fadA of Emericella nidulans; and magC is most similar to gna2 of Neurospora crassa. Homologous recombination resulting in targeted deletion of magA had no effect on vegetative growth, conidiation, or appressorium formation. Deletion of magC reduced conidiation, but did not affect vegetative growth or appressorium formation. However, disruption of magB significantly reduced vegetative growth, conidiation, and appressorium formation. magB¯ transformants, unlike magA¯ and magC¯ transformants, exhibited a reduced ability to infect and colonize susceptible rice leaves. G protein α subunit genes are required for M. grisea mating. magB¯ transformants failed to form perithecia, whereas magA¯ and magC¯ transformants did not produce mature asci. These results suggest that G protein α subunit genes are involved in signal transduction pathways in M. grisea that control vegetative growth, conidiation, conidium attachment, appressorium formation, mating, and pathogenicity.

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