Ultrastructural and chemical distinction of melanins formed by Verticillium dahliae from (+)-scytalone, 1,8-dihydroxynaphthalene, catechol, and L-3,4-dihydroxyphenylalanine

1978 ◽  
Vol 24 (3) ◽  
pp. 289-297 ◽  
Author(s):  
M. H. Wheeler ◽  
W. J. Tolmsoff ◽  
A. A. Bell ◽  
H. H. Mollenhauer
Keyword(s):  
Verticillium Dahliae ◽  
Wild Type ◽  
Melanin Biosynthesis

Microsclerotia of three melanin-deficient mutants of Verticillium dahliae formed melanin from (+)-scytalone, 1,8-dihydroxynaphthalene, catechol, and L-3.4-dihydroxyphenylalanine. The melanins formed from (+)-scytalone or 1,8-dihydroxynaphthalene resembled wild-type melanin chemically and ultrastructurally, whereas the melanins formed from catechol and L-3,4-dihydroxyphenylalanine were different. This suggests that scytalone and 1,8-dihydroxynaphthalene but not catechol or L-3,4-dihydroxyphenylalanine are natural intermediates of melanin biosynthesis in V. dahliae.

Use of mutants to establish (+)-scytalone as an intermediate in melanin biosynthesis by Verticillium dahliae

1976 ◽  
Vol 22 (6) ◽  
pp. 787-799 ◽  
Author(s):  
A. A. Bell ◽  
J. E. Puhalla ◽  
W. J. Tolmsoff ◽  
R. D. Stipanovic
Keyword(s):  
Physical Properties ◽  
Verticillium Dahliae ◽  
Recessive Gene ◽  
The Other ◽  
Thielaviopsis Basicola ◽  
Single Recessive Gene ◽  
Wild Type ◽  
Melanin Biosynthesis ◽  
In The Wild ◽  
Verticillium Dahliae Kleb

Melanin biosynthesis in Verticillium dahliae Kleb. was studied with mutants deficient for normal black melanin or for production of microsclerotia. Seven genetically different mutants had apparent blocks in melanin biosynthesis. Four mutants (brm-I to -4) produced brown microsclerotia and extruded pigments into media; three (alm-1 to -3) produced albino microsclerotia. Other mutants produced no microsclerotia (nms) or had greatly reduced numbers of microsclerotia (rms). Mutation alm-1 was due to a single recessive gene; the other melanin-deficient characters were recessive but their genetic bases were not determined. Cultures of the brown mutants brm-1 and -3 extruded and accumulated a metabolite that blackened the albino microsclerotia of alm-1 to -3. The metabolite was identified as (+)-scytalone (3, 4-dihydro-3, 6, 8-trihydroxy-1(2H)naphthalenone). Pigment formed by alm-1 microsclerotia from (+)-scytalone had chemical and physical properties identical with those of melanin in the wild-type fungus. (+)-Scytalone was produced and converted to melanin by microsclerotia but not by conidia or hyphae. Conversion of (+)-scytalone to melanin appeared to involve two or more enzymes and probably involved conversions to 1, 3, 8-trihydroxynaphthalene and 1, 8-dihydroxynaphthalene. Albino mutants of Thielaviopsis basicola, Drechslera sorokiniana, Pleospora infectoria (Alternaria), Ulocladium sp., and Curvularia sp. also converted scytalone to pigments indistinguishable from the melanins found in their respective wild types. Scytalone melanin may be common in fungi with dark brown or black pigments.

scholarly journals THE MECHANISM OF HETEROKARYOTIC GROWTH IN VERTICILLIUM DAHLIAE

Genetics ◽  
1974 ◽  
Vol 76 (3) ◽  
pp. 411-422
Author(s):  
John E Puhalla ◽  
John E Mayfield
Keyword(s):  
High Temperature ◽  
Verticillium Dahliae ◽  
Nuclear Migration ◽  
Sharp Contrast ◽  
Wild Type ◽  
Continue Growth ◽  
Hyphal Anastomosis

ABSTRACT Heterokaryons of Verticillium dahliae, forced between complementary auxotrophs, were stable at 21° and resembled the wild type morphologically. In such heterokaryons the hyphal cells were predominantly uninucleate, and no nuclear migration from cell to cell was observed. Heterokaryosis was apparently confined to binucleate, interhyphal, anastomosed cells that arose 1-2 mm behind the colony front. Such anastomosed cells thereby fed and maintained large homokaryotic areas including the colony edge. This stable mosaic colony is in sharp contrast to the heterokaryon of Neurospora.—Heterokaryons of V. dahliae cannot continue growth at 30° because the high temperature prevents hyphal anastomosis. Heterozygous diploids sector out from heterokaryons after 8-12 days at 30°. Interhyphal anastomosed cells are apparently the site of karyogamy.

scholarly journals An endogenous retrovirus presumed to have been endogenized or relocated recently in a marsupial, the red-necked wallaby

Genome ◽  
2022 ◽  
Author(s):  
Sakura Hayashi ◽  
Konami Shimizu ◽  
Yusuke Honda ◽  
Yukako Katsura ◽  
Akihiko Koga
Keyword(s):  
Endogenous Retrovirus ◽  
Amino Acid Sequences ◽  
Open Reading Frames ◽  
Length Variation ◽  
Wild Type ◽  
Long Terminal Repeats ◽  
Recent Event ◽  
Melanin Biosynthesis ◽  
Dna Fragment ◽  
Reading Frames

An albino infant wallaby was born to a mother with the wild-type body color. PCR and sequencing analyses of <i>TYR</i> (encoding tyrosinase, which is essential for melanin biosynthesis) of this albino wallaby revealed a 7.1-kb-long DNA fragment inserted in the first exon. Because the fragment carried long terminal repeats, we assumed it to be a copy of an endogenous retrovirus, which we named <i>walb</i>. We cloned other <i>walb</i> copies residing in the genomes of this species and another wallaby species. The copies exhibited length variation, and the longest copy (>8.0 kb) contained open reading frames whose deduced amino acid sequences were well aligned with those of <i>gag</i>, <i>pol</i>, and <i>env</i> of retroviruses. It is not known through which of the following likely processes the walb copy was inserted into <i>TYR</i>: endogenization (infection of a germline cell by an exogenous virus), reinfection (infection by a virus produced from a previously endogenized provirus), or retrotransposition (intracellular relocation of a provirus). In any case, the insertion into <i>TYR</i> is considered to have been a recent event on an evolutionary timescale because albino mutant alleles generally do not persist for long because of their deleterious effects in wild circumstances. 

scholarly journals CgSCD1 Is Essential for Melanin Biosynthesis and Pathogenicity of Colletotrichum gloeosporioides

Pathogens ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 141
Author(s):  
Tan Wang ◽  
Dandan Ren ◽  
Han Guo ◽  
Xue Chen ◽  
Pinkuan Zhu ◽  
...  
Keyword(s):  
Magnaporthe Grisea ◽  
Colletotrichum Gloeosporioides ◽  
Turgor Pressure ◽  
Phytopathogenic Fungus ◽  
Melanin Synthesis ◽  
Wild Type ◽  
Melanin Biosynthesis ◽  
Penetration Ability ◽  
Appressoria Formation ◽  
Gene Deletion Mutant

Colletotrichum gloeosporioides, an important phytopathogenic fungus, mainly infects tropical fruits and results in serious anthracnose. Previous studies have shown that melanin biosynthesis inhibitor can inhibit the melanization of the appressoria of Magnaporthe grisea and Colletotrichum orbiculare, resulting in limited infection of the hosts. In this study, we identified and characterized a scytalone dehydratase gene (CgSCD1) from C. gloeosporioides which is involved in melanin synthesis. The CgSCD1 gene deletion mutant ΔCgscd1 was obtained using homologous recombination. The ΔCgscd1 mutant showed no melanin accumulation on appressoria formation and vegetative hyphae. Furthermore, the virulence of ΔCgscd1 was significantly reduced in comparison with the wild-type (WT) strain. Further investigations showed that the growth rate as well as germination and appressorium formation of ΔCgscd1 displayed no difference compared to the wild-type and complemented transformant Cgscd1com strains. Furthermore, we found that the appressorial turgor pressure in the ΔCgscd1 mutant showed no difference compared to that in the WT and Cgscd1com strains in the incipient cytorrhysis experiment. However, fewer infectious hyphae of ΔCgscd1 were observed in the penetration experiments, suggesting that the penetration ability of nonpigmented appressoria was partially impaired. In conclusion, we identified the CgSCD1 gene, which is involved in melanin synthesis and pathogenicity, and found that the melanization defect did not affect appressorial turgor pressure in C. gloeosporioides.

scholarly journals Improved Medium for Selecting Nitrate-Nonutilizing (nit) Mutants of Verticillium dahliae

1997 ◽  
Vol 87 (10) ◽  
pp. 1067-1070 ◽  
Author(s):  
Nadia Korolev ◽  
Talma Katan
Keyword(s):  
Verticillium Dahliae ◽  
Minimal Medium ◽  
Vegetative Compatibility ◽  
Potassium Chlorate ◽  
Wild Type ◽  
Nit Mutants ◽  
Cornmeal Agar

Nitrate-nonutilizing (nit) mutants are commonly used to determine vegetative compatibility between isolates of Verticillium dahliae by complementation (heterokaryon) testing. These mutants emerge spontaneously as chlorate-resistant sectors growing out of partially restricted, wild-type colonies on chlorate-amended media. The commonly used chlorate media are based on minimal medium (MMC) or cornmeal agar (CMC), amended with potassium chlorate. nit mutants recovered on these media constituted 10 to 36%(on MMC) and 25 to 45%(on CMC) of the apparently resistant sectors. An improved water agar chlorate medium (WAC) is described that is more effective for selecting chlorate-resistant nit mutants. WAC medium consists of agar (2%), glucose (0.02%), and potassium chlorate (2 to 5%). On WAC, growth of most V. dahliae isolates was strongly inhibited, and 66 to 100%(average >80%) of the chlorate-resistant sectors formed were nit mutants. Most mutants were characterized as nit1, and about 6% as NitM.

scholarly journals VdSNF1, the Sucrose Nonfermenting Protein Kinase Gene of Verticillium dahliae, Is Required for Virulence and Expression of Genes Involved in Cell-Wall Degradation

2011 ◽  
Vol 24 (1) ◽  
pp. 129-142 ◽  
Author(s):  
Aliki K. Tzima ◽  
Epaminondas J. Paplomatas ◽  
Payungsak Rauyaree ◽  
Manuel D. Ospina-Giraldo ◽  
Seogchan Kang
Keyword(s):  
Cell Wall ◽  
Verticillium Dahliae ◽  
Type Strain ◽  
Wild Type Strain ◽  
Fluorescent Protein ◽  
Wild Type ◽  
Cell Wall Degrading Enzymes ◽  
Catabolic Repression ◽  
Kinase Gene ◽  
Fluid Medium

Verticillium dahliae is a soilborne fungus causing vascular wilt in a diverse array of plant species. Its virulence has been attributed, among other factors, to the activity of hydrolytic cell wall–degrading enzymes (CWDE). The sucrose nonfermenting 1 gene (VdSNF1), which regulates catabolic repression, was disrupted in V. dahliae tomato race 1. Expression of CWDE in the resulting mutants was not induced in inductive medium and in simulated xylem fluid medium. Growth of the mutants was significantly reduced when grown with pectin or galactose as a carbon source whereas, with glucose, sucrose, and xylose, they grew similarly to wild-type and ectopic transformants. The mutants were severely impaired in virulence on tomato and eggplant (final disease severity reduced by an average of 87%). Microscopic observation of the infection behavior of a green fluorescent protein (gfp)-labeled VdSNF1 mutant (70ΔSF-gfp1) showed that it was defective in initial colonization of roots. Cross sections of tomato stem at the cotyledonary level showed that 70ΔSF-gfp1 colonized xylem vessels considerably less than the wild-type strain. The wild-type strain heavily colonized xylem vessels and adjacent parenchyma cells. Quantification of fungal biomass in plant tissues further confirmed reduced colonization of roots, stems, and cotyledons by 70ΔSF-gfp1 relative to that by the wild-type strain.

scholarly journals Raman Characterization of Fungal DHN and DOPA Melanin Biosynthesis Pathways

2021 ◽  
Vol 7 (10) ◽  
pp. 841
Author(s):  
Benjamin D. Strycker ◽  
Zehua Han ◽  
Aysan Bahari ◽  
Tuyetnhu Pham ◽  
Xiaorong Lin ◽  
...  
Keyword(s):  
Mutational Analysis ◽  
Wild Type ◽  
Melanin Biosynthesis ◽  
Composition And Structure ◽  
Raman Spectral Data ◽  
Dopa Melanin ◽  
Inhibition Studies ◽  
Raman Spectral ◽  
Fungal Melanins

Fungal melanins represent a resource for important breakthroughs in industry and medicine, but the characterization of their composition, synthesis, and structure is not well understood. Raman spectroscopy is a powerful tool for the elucidation of molecular composition and structure. In this work, we characterize the Raman spectra of wild-type Aspergillus fumigatus and Cryptococcus neoformans and their melanin biosynthetic mutants and provide a rough “map” of the DHN (A. fumigatus) and DOPA (C. neoformans) melanin biosynthetic pathways. We compare this map to the Raman spectral data of Aspergillus nidulans wild-type and melanin biosynthetic mutants obtained from a previous study. We find that the fully polymerized A. nidulans melanin cannot be classified according to the DOPA pathway; nor can it be solely classified according to the DHN pathway, consistent with mutational analysis and chemical inhibition studies. Our approach points the way forward for an increased understanding of, and methodology for, investigating fungal melanins.

scholarly journals The study of pathogenicity genes in ascomycete fungus Verticillium dahliae

2012 ◽  
Author(s):  
Lugard Eboigbe
Keyword(s):  
Cell Wall ◽  
Verticillium Dahliae ◽  
Plant Cell Wall ◽  
Genomic Library ◽  
Wild Type ◽  
Tomato Plants ◽  
Knock Out ◽  
Race 2

When Verticillium dahliae enters the host plant, the first line of defense that it encounters is the cell wall. Plant pathogenic fungi (including V. dahliae) produce extracellular enzymes which degrade plant cell wall components in a coordinated action. Some of the genes that encode these cell wall degrading enzymes, i.e., xylanases, cellulases and non-specific-action genes, were the major focus of this Ph.D. programme. Gene inactivation bears a remarkable model for the determination of the functions of genes in any organism. In this research, this molecular genetic tool has been applied to examine the functional role of β-1,6-endoglucanase and β-1,4-endoxylanase genes in the pathogenicity of filamentous fungus Verticillium dahliae. The gene coding for β-1,6-endoglucanase is considered as one of the important genes that code for hydrolyzing enzymes released at the initial stages of infection by fungi for the depolymerization of the cell wall. To address the hypothesis that these enzymes are important in V. dahliae virulence, a gene encoding a β-1,6-endoglucanase (vdg6) was isolated from V. dahliae using genome walking technique. Nucleotide sequence analysis of the 3’ and 5’ ends of clones from a genomic library of the fungus showed the presence of part of the endo-1,6-β-glucanase gene in a 3.5kb genomic fragment. Using this clone as probe and by employing genome walking approaches the 3’ and 5’; of the gene were determined bringing the entire gene (vdg6) size to ~1800 bp. An internal fragment (1.2kb) of vdg6 was used to disrupt the wild-type gene of the tomato race 2 V. dahliae strain 123V and the knock-out mutant (VdB) strain was tested for pathogenicity on tomato plants. The result showed a 7.5% reduction in disease symptoms caused on tomato plants in comparison with the wild type. Growth on minimal medium supplemented with different carbon sources showed reduced ability of the mutant to breakdown cellulose, whereas growth on glucose, pectin and sucrose were similar to the wild type. Endo-β-1,4-xylanase catalyze the endohydrolysis of xylan, the major structural polysaccharide of the plant cell wall. In order to investigate the role of the β-1,4-endoxylanase gene(xylA) in virulence of V. dahliae, through the analysis of clones from a genomic library of V. dahliae strain 76 and shotgun ESTs from xylem sap growing fungus the xylA gene was isolated. Its nucleotide sequence was determined and the predicted amino acid sequence showed significant homology with family 11 xylanases. The gene was disrupted by targeted inactivation due to a single cross-over event in a V. dahliae race 2 tomato strain. The knock-out mutant (XA) was compared with the wild type strain for disease symptoms on tomato plants. The result showed a small (7%) reduction in disease severity in the mutant strain. Growth of the mutant strain on minimal medium containing cellulose as the sole carbon source was reduced compared to the wild type indicating for a role of xylA in the breakdown of complex components of the cell wall. Other cell wall degrading genes cloned were β-1,3-exoglucanase, β-1,4-endoglucanse and endoglucanase II. The major obstacle to the determination of the genes involved in the depolymerisation of cell wall and pathogenicity is function redundancy. In an attempt to overcome the hurdle created by this function redundancy in analyzing the functions of the above genes, first, the regulation of vdg6 by sucrose non-fermenting gene (VdSNF1) was checked. The results showed that vdg6 gene is under catabolite repression, it is expressed during pathogencity and is important for the virulence of V. dahliae. Secondly, double disruption mutants were constructed from the single VdB mutant and the signalling PKA (cAMP-mediated protein kinase A) gene, namely VP1, VP2, VP3 and VP4. Analysis of these double mutants showed an obvious link between vdg6 gene and cAMP-mediated PKA (VdPKAC1) and that the β-1,6-endoglucanase cell wall degrading gene contributes to the pathogenicity of the fungus. In conclusion, all experimental evidence from this study showed that cell wall degrading genes contribute to virulence and pathogenicity of the fungus, however, since most of them belong to families of genes with similar functions the system is very complex to unravel and fully understand the genetic basis of pathogenicity.

scholarly journals Biological Control of Sclerotium rolfsii and Verticillium dahliae by Talaromyces flavus Is Mediated by Different Mechanisms

1997 ◽  
Vol 87 (10) ◽  
pp. 1054-1060 ◽  
Author(s):  
Lea Madi ◽  
Talma Katan ◽  
Jaacov Katan ◽  
Yigal Henis
Keyword(s):  
Biological Control ◽  
Verticillium Dahliae ◽  
Extracellular Enzymes ◽  
Sclerotium Rolfsii ◽  
Resistant Mutant ◽  
Wild Type ◽  
Cell Wall Degrading Enzymes ◽  
Antifungal Substance ◽  
Talaromyces Flavus ◽  
Type Strains

Ten wild-type strains and two benomyl-resistant mutants of Talaromyces flavus were examined for their ability to secrete the cell wall-degrading enzymes chitinase, β-1,3-glucanase, and cellulase, to parasitize sclerotia of Sclerotium rolfsii, to reduce bean stem rot caused by S. rolfsii, and to secrete antifungal substance(s) active against Verticillium dahliae. The benomyl-resistant mutant BenRTF1-R6 overproduced extracellular enzymes and exhibited enhanced antagonistic activity against S. rolfsii and V. dahliae compared to the wild-type strains and other mu tants. Correlation analyses between the extracellular enzymatic activities of different isolates of T. flavus and their ability to antagonize S. rolfsii indicated that mycoparasitism by T. flavus and biological control of S rolfsii were related to the chitinase activity of T. flavus. On the other hand, production of antifungal compounds and glucose-oxidase activity may play a role in antagonism of V. dahliae by retardation of germination and hyphal growth and melanization of newly formed microsclerotia.

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