Ultrastructure of melanin formation in Verticillium dahliae with (+)-scytalone as a biosynthetic intermediate

1976 ◽  
Vol 22 (5) ◽  
pp. 702-711 ◽  
Author(s):  
M. H. Wheeler ◽  
W. J. Tolmsoff ◽  
S. Meola
Keyword(s):  
Verticillium Dahliae ◽  
Cell Walls ◽  
Maximum Rate ◽  
Melanin Synthesis ◽  
Wild Type ◽  
Type Isolate ◽  
Albino Mutant ◽  
In The Wild ◽  
Fibrillar Network ◽  
Scanning Electron

Transmission and scanning electron microscopy showed that melanin of wild-type Verticillium dahliae occurred as granules in microsclerotial cell walls and in a fibrillar network encapsulating the walls. An albino microsclerotial mutant and a brown microsclerotial mutant of V. dahliae did not form melanin granules. When albino microsclerotia were treated with (+)-scytalone (a metabolite that the brown mutant accumulates), they formed melanin granules and turned black. These granules were similar in appearance and distribution to those in the wild type. Melanin granules of the wild-type isolate and the scytalone-treated albino mutant were formed at a maximum rate in microsclerotia from 5- to 8-day-old cultures. These observations suggest that scytalone is a natural intermediate of melanin synthesis in V. dahliae.

Caffeoyl Shikimate Esterase (CSE) Is an Enzyme in the Lignin Biosynthetic Pathway in Arabidopsis

Science ◽  
2013 ◽  
Vol 341 (6150) ◽  
pp. 1103-1106 ◽  
Author(s):  
Ruben Vanholme ◽  
Igor Cesarino ◽  
Katarzyna Rataj ◽  
Yuguo Xiao ◽  
Lisa Sundin ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Walls ◽  
Metabolite Profiling ◽  
Biosynthetic Pathway ◽  
Wild Type ◽  
Secondary Cell Walls ◽  
Phenolic Metabolite ◽  
In The Wild ◽  
Lignin Biosynthetic Pathway

Lignin is a major component of plant secondary cell walls. Here we describe caffeoyl shikimate esterase (CSE) as an enzyme central to the lignin biosynthetic pathway. Arabidopsis thaliana cse mutants deposit less lignin than do wild-type plants, and the remaining lignin is enriched in p-hydroxyphenyl units. Phenolic metabolite profiling identified accumulation of the lignin pathway intermediate caffeoyl shikimate in cse mutants as compared to caffeoyl shikimate levels in the wild type, suggesting caffeoyl shikimate as a substrate for CSE. Accordingly, recombinant CSE hydrolyzed caffeoyl shikimate into caffeate. Associated with the changes in lignin, the conversion of cellulose to glucose in cse mutants increased up to fourfold as compared to that in the wild type upon saccharification without pretreatment. Collectively, these data necessitate the revision of currently accepted models of the lignin biosynthetic pathway.

scholarly journals Unveiling the Role Displayed by Penicillium digitatum PdMut3 Transcription Factor in Pathogen–Fruit Interaction

2021 ◽  
Vol 7 (10) ◽  
pp. 828
Author(s):  
Marta de Ramón-Carbonell ◽  
Paloma Sánchez-Torres
Keyword(s):  
Fungal Growth ◽  
Dna Binding Protein ◽  
Invasive Growth ◽  
Wild Type ◽  
Morphological Alterations ◽  
Type Isolate ◽  
In The Wild ◽  
Expression Rate ◽  
Regulatory Functions ◽  
Null Mutants

Zn2Cys6 transcription factors are unique to fungi and are involved in different regulatory functions. In this study, we have identified the Penicillium digitatumPdMut3 gene, which encodes a putative Zn (II) 2Cys6 DNA-binding protein. Elimination of PdMut3 in Pd1 strain caused increased virulence during citrus infection. The transcription of the PdMut3 gene showed a higher expression rate during fungal growth and less transcription during fruit infection. Furthermore, the deletion of the gene in the wild-type isolate of P. digitatum did not produce any modification of the sensitivity to different fungicides, indicating that the gene is not associated with resistance to fungicides. In contrast, PdMut3 null mutants showed a reduction in growth in minimal media, which was associated with severe alterations in conidiophore development and morphological alterations of the hyphae. Mutants showed greater sensitivity to compounds that interfere with the cell wall and an invasive growth block. Thus, PdMut3 might have an indirect role in fungi virulence through metabolism and peroxisomes development.

scholarly journals Cytokinesis in fra2 Arabidopsis thaliana p60-katanin Mutant: Defects in Cell Plate/Daughter Wall Formation

2021 ◽  
Author(s):  
Emmanuel Panteris ◽  
Anna Kouskouveli ◽  
Dimitris Pappas ◽  
Ioannis-Dimosthenis S. Adamakis
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Cell Walls ◽  
Higher Plants ◽  
Cell Plate ◽  
Wild Type ◽  
Microtubule Organization ◽  
Root Cells ◽  
Wall Formation ◽  
In The Wild

Cytokinesis is accomplished in higher plants by the phragmoplast, creating and conducting the cell plate, to separate daughter nuclei by a new cell wall. The microtubule-severing enzyme p60-katanin plays an important role in the centrifugal expansion and timely disappearance of phragmoplast microtubules. Consequently, aberrant structure and delayed expansion rate of the phragmoplast occur in p60-katanin mutants. Here, the consequences of p60-katanin malfunction in cell plate/daughter wall formation were investigated by transmission electron microscopy (TEM), while deviations in the chemical composition of cell plate/new cell wall were identified by immunolabeling and confocal microscopy, in root cells of the fra2 Arabidopsis thaliana mutant. It was found that, apart from defective phragmoplast microtubule organization, cell plates/new cell walls appeared also faulty in structure, being unevenly thick and perforated by large gaps. In addition, demethylesterified homogalacturonans were prematurely present in fra2 cell plates, while callose content was significantly lower than in the wild-type. Furthermore, KNOLLE syntaxin disappeared from newly formed cell walls in fra2 earlier than in the wild-type. Taken together, these observations indicate that delayed cytokinesis, due to faulty phragmoplast organization and expansion, results in a loss of synchronization between cell plate growth and its chemical maturation.

Ultrastructure of Melanin Formation in Thielaviopsis Basicola

1976 ◽  
Vol 34 ◽  
pp. 50-51
Author(s):  
M. H. Wheeler ◽  
W. J. Tolmsoff ◽  
A. A. Bell ◽  
R. D. Stipanovic
Keyword(s):  
Agar Medium ◽  
Thielaviopsis Basicola ◽  
Wild Type ◽  
Transmission Microscopy ◽  
Electron Transmission ◽  
Type Isolate ◽  
Melanin Formation ◽  
Albino Mutant ◽  
Before And After ◽  
Electron Transmission Microscopy

Melanin formation in the fungus Thielaviopsis basicola was examined by light and electron-transmission microscopy with methods described previously in studies of Verticillium dahliae (1,2). A wild-type isolate and an albino mutant of T. basicola were grown on potato-carrot-dextrose-agar medium at 24°C prior to chemical treatment. The wild-type isolate was examined and compared with the albino mutant before and after treatment with each of the following compounds that have been proposed as melanin intermediates in various fungi (3): (+)-scytalone [3,4-dihydro-3,6,8-trihydroxy-l-(2H)- naphthalenone]; 1,8-dihydroxynaphthalene (DHN); L-3,4-dihydroxyphenylalanine (DOPA); and catechol.

Arabidopsis gynoecium structure in the wild and in ettin mutants

Development ◽  
1995 ◽  
Vol 121 (5) ◽  
pp. 1519-1532 ◽  
Author(s):  
R.A. Sessions ◽  
P.C. Zambryski
Keyword(s):  
Cell Types ◽  
Flowering Plants ◽  
Wild Type ◽  
Reproductive Structure ◽  
Developmental Abnormalities ◽  
Transmitting Tract ◽  
Type Pattern ◽  
In The Wild ◽  
Gynoecium Development ◽  
Scanning Electron

The gynoecium is the female reproductive structure of flowering plants. Here we present a description of the Arabidopsis thaliana gynoecium at anthesis. The cylindrical organ can be broken down into three longitudinal regions arranged in an apical-basal order: stigma, style, and ovary. Each region can be distinguished histologically and morphologically. The transmitting (pollination) tract is axially positioned along the center of the gynoecium and spans stigma, style and ovary. Histochemistry, scanning electron microscopy and a style-specific reporter gene are used to compare the wild-type pattern of gynoecium cell types and regions, with patterns formed in gynoecia of individuals homozygous for a series of allelic mutations at the ETTIN locus. ettin gynoecia show morphological and histological alterations that appear to result from the merging of apical and basal regions and the development of abaxial into adaxial tissues. These developmental abnormalities result in a reduction of the ovary region, an expansion of the stylar and stigmatic regions, and the abaxial (outward) proliferation of transmitting tract tissue. The alterations in the mutants can be interpreted as resulting from misspecifications of position along the longitudinal and transverse axes during gynoecium development. The results suggest that early patterning events underlie wild-type gynoecium development, and that ETT functions during this early programming.

scholarly journals Cytokinesis in fra2 Arabidopsis thaliana p60-Katanin Mutant: Defects in Cell Plate/Daughter Wall Formation

2021 ◽  
Vol 22 (3) ◽  
pp. 1405
Author(s):  
Emmanuel Panteris ◽  
Anna Kouskouveli ◽  
Dimitris Pappas ◽  
Ioannis-Dimosthenis S. Adamakis
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Cell Walls ◽  
Higher Plants ◽  
Cell Plate ◽  
Wild Type ◽  
Microtubule Organization ◽  
Root Cells ◽  
Wall Formation ◽  
In The Wild

Cytokinesis is accomplished in higher plants by the phragmoplast, creating and conducting the cell plate to separate daughter nuclei by a new cell wall. The microtubule-severing enzyme p60-katanin plays an important role in the centrifugal expansion and timely disappearance of phragmoplast microtubules. Consequently, aberrant structure and delayed expansion rate of the phragmoplast have been reported to occur in p60-katanin mutants. Here, the consequences of p60-katanin malfunction in cell plate/daughter wall formation were investigated by transmission electron microscopy (TEM), in root cells of the fra2 Arabidopsis thaliana loss-of-function mutant. In addition, deviations in the chemical composition of cell plate/new cell wall were identified by immunolabeling and confocal microscopy. It was found that, apart from defective phragmoplast microtubule organization, cell plates/new cell walls also appeared faulty in structure, being unevenly thick and perforated by large gaps. In addition, demethylesterified homogalacturonans were prematurely present in fra2 cell plates, while callose content was significantly lower than in the wild type. Furthermore, KNOLLE syntaxin disappeared from newly formed cell walls in fra2 earlier than in the wild type. Taken together, these observations indicate that delayed cytokinesis, due to faulty phragmoplast organization and expansion, results in a loss of synchronization between cell plate growth and its chemical maturation.

High tyrosinase activity in albino Xenopus laevis oocytes

Development ◽  
1976 ◽  
Vol 36 (3) ◽  
pp. 555-559
Author(s):  
A. H. Wyllie ◽  
E. M. De Robertis
Keyword(s):  
Molecular Weight ◽  
Xenopus Laevis ◽  
Specific Activity ◽  
High Specific Activity ◽  
Low Molecular Weight ◽  
Xenopus Laevis Oocytes ◽  
Melanin Synthesis ◽  
Wild Type ◽  
Albino Mutant

Tyrosinase was measured in oocytes of the recently described albino mutant (avav) of Xenopus laevis. Although these oocytes show no pigmentation and the eggs are known to contain no melanosomes, tyrosinase — which is probably the only enzyme necessary for melanin synthesis from tyrosine — was increased more than twofold relative to the wild type. Tyrosinase recovered from albino and wild type oocytes showed the same KM with respect to tyrosine, and this was not altered by previous gonadotrophin stimulation in vivo. The tyrosi-nase assay, based on [14]tyrosine incorporation into acid-insoluble products, was of greater sensitivity than previously described methods of the same type, through removal of low molecular weight material from the oocyte homogenate prior to incubation, and the use of tyrosine of high specific activity.

Anatomical and chemical characteristics of culm of rice brittle mutant bc7(t)

2011 ◽  
Vol 38 (3) ◽  
pp. 227
Author(s):  
Cunxu Wei ◽  
Peisong Xie ◽  
Yifang Chen ◽  
Huaguang Yu ◽  
Yanjing Su ◽  
...  
Keyword(s):  
Cell Walls ◽  
Oryza Sativa L ◽  
Normal Growth ◽  
Histochemical Staining ◽  
Agricultural Activity ◽  
Wild Type Plant ◽  
Wild Type ◽  
X Ray ◽  
In The Wild ◽  
Cp Mas Nmr

Brittleness culm is an important agronomic trait that has a potential usefulness in agricultural activity as animal forage. In the present study, the anatomy of culm of rice (Oryza sativa L.) brittle mutant bc7(t) was investigated with light microscopy and electron microscopy. Findings showed bc7(t) exhibited higher area percentages of mechanical and conducting tissues, and lower cell wall thickness of sclerenchyma cells. Chemical analyses and 13C CP/MAS NMR spectra of cell walls indicated that the content of cellulose decreased, and the contents of hemicellulose, lignin and silicon was increased in bc7(t). Lignin histochemical staining and cytochemical localisation revealed that the higher lignin was localised in epidermal, sclerenchyma and vascular bundle cells in bc7(t). The energy dispersive X-ray microanalysis showed that the contents of silicon were higher in bc7(t) than in the wild type. These results indicate that cellulose, hemicellulose, lignin, silicon and the area percentages of mechanical and conducting tissues could be regulated in a compensatory fashion, possibly contributing to metabolic flexibility and a growth advantage to sustain the bc7(t) normal growth habit like the wild-type plant.

Patterns in Dictyostelium discoideum: the role of myosin II in the transition from the unicellular to the multicellular phase

1993 ◽  
Vol 104 (2) ◽  
pp. 457-466 ◽  
Author(s):  
S. Eliott ◽  
G.H. Joss ◽  
A. Spudich ◽  
K.L. Williams
Keyword(s):  
Dictyostelium Discoideum ◽  
Myosin Ii ◽  
Morphological Development ◽  
Scanning Electron Micrographs ◽  
Wild Type ◽  
Null Cell ◽  
Cell Movements ◽  
In The Wild ◽  
Scanning Electron

Dictyostelium discoideum amoebae which lack the myosin II gene are motile and aggregate to form rudimentary mounds, but do not undergo further morphological development (Manstein et al., 1989). Here we use scanning electron microscopy, light microscopy, immunofluorescence and computer analysis of time-lapse video films to study how D. discoideum myosin null cells of strains HS2205 and HS2206 aggregate. Myosin null cells are sufficiently coordinated in their movements to form two-dimensional aggregation streams, although mutant cells within streams lack the elongated shape and parallel orientation of wild-type strains. In the wild-type, cell movements are coordinated, cells usually joining streams that spiral inwards and upwards as the mound extends into the standing papilla. In the aggregates of mutant strains, cell movements are chaotic, only occasionally forming short-term spirals that rotate at less than half the speed of wild-type spirals and frequently change direction. Unlike the situation in the wild-type where spirals continue with mound elongation, cells within the mutant mound eventually cease translocation altogether as the terminal shape of the mound is reached and only intracellular particle movement is observed. Scanning electron micrographs show that the surface of the wild-type mound consists of flattened cells which fit neatly together. The myosin null cell mound has an uneven surface, the orientation of the cells is chaotic and no tip is formed. This is consistent with the results of synergy experiments in which myosin null cells were absent from the tips of chimeric HS2205/AX2 slugs and pre-culminates. Immunofluorescence microscopy using prespore and spore cell markers reveals that a prestalk/prespore pattern forms within the mutant mound but that terminal spore differentiation is incomplete. These results are discussed in relation to the role of myosin II in aggregation and morphogenesis.

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.

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