Detection Of Genetic Variation In Populations

Burnett (2003) described a population as a pattern of distribution of individuals with distinctive but comparable morphology and genotypes. A basic requirement for the study of populations is that the fungus is recognized in nature and enough samples are collected over a wide range of geographical distances for inferences. A fungus suited admirably for population studies is Neurospora (Ascomycotina) since it produces distinctive orange conidia that allow its practically unambiguous recognition...

Secretory Enzymes

There is a great practical interest in thermophilic fungi because of the prospects of finding enzyme variants with high temperature optima and long shelf life, desirable properties for enzymes used in various industries. Chiefly, the extracellular (secreted) enzymes have been studied as the mycelium is easily removed by the filtration method and large amounts of culture filtrates obtained as starting material for enzyme purification. The extracellular enzymes of thermophilic fungi have...

Asynchronous Nuclear Divisions

Nuclear transplantation experiments with frog eggs and cell fusion experiments with cultured animal cells revealed that nuclear division (mitosis) is induced by diffusible factors present in cytoplasm. For example, when a cell in G1 phase was fused with a cell in M phase, the G1 nucleus in the fused cell prematurely entered into nuclear division (Rao and Johnson, 1970). This observation suggests that the division of fungal nuclei that are in a common cytoplasm is synchronous. Assuming complete...

Protein Turnover

An early hypothesis put forward to explain thermophily in bacteria proposed that growth at high temperatures occurs because the denatured cellular proteins are quickly replaced by resynthesis. Two different groups compared the rate of protein breakdown in thermophilic and mesophilic fungi by feeding mycelia with radioactively labeled amino acid and monitoring the radioactivity in mycelial proteins after transferring mycelia to nonradioactive media (Miller et al., 1974 Rajasekaran and...

Biochemistry Of Degradation Of Cell Wall Polymers

Lignin is formed by random cross-linking of three monomer phenylpropanoid units p-hydroxycinnamyl (coumaryl) alcohol, 4-hydroxy-3-methoxycinnamyl (coniferyl) alcohol and 3,5-dimethoxy-4-hydroxycinnamyl (sinapyl) alcohol with several different carbon-carbon and carbon-oxygen linkages (Figure 12.2). Lignin encrusts the cellulose microfibrils within plant cell walls, giving the vascular plant the rigidity and protecting the plant from weather, insects and pathogenic organisms. It is remarkable,...

Concluding Remarks

Although widespread in terrestrial habitats, thermophilic fungi remain underexplored. Because they occur in habitats that are heterogeneous in temperature, the types and concentration of nutrients, competing species and other variables, they probably also adapted to factors other than a high temperature. They can be grown in minimal media with metabolic rates and growth yields comparable to those of mesophilic fungi. Studies of their growth kinetics, respiration, mixed-substrate utilization,...

M

Macroconidia, see Neurospora, 65-79 Magnaporthe grisea, 20, 50, 53 Markers, use of genetic in study of life history, 69 in study of senescence, 209, 214-215 restriction fragment length polymorphism, 4, 199-201 random amplified polymorphic DNA, 5, 201 Mating reaction, in Ustilago maydis 124 Mating type, 68 Meiotic events crossing-over, 72 first division segregation, 72 second division segregation, 72 Meiotic silencing by unpaired DNA, 134 Melanin, 54 Mesophilic fungi, 145 Metabolic pathway, 77...

Cushion Of Conidiogenous

Figure Pycnidium

Figure A2 Ascomycotina. (a) A swelling ascus bursting the wall of cleistothecium. (b) Ruptured cleistothecium and ascus. (c) Ascus immediately after discharge of ascospores. (From Ingold, C.T. and Hudson, H.J. (1993). Kluwer Academic Publishers. With permission.) Figure A3 Basidiomycotina. Diagram of basidium development. From Ingold, C.T. and Hudson, H.J. (1993). With kind permission of Kluwer Academic Publishers. Figure A4 Basidiomycotina. Fruit body (sporophore) with cap (pileus) and...

Pilobolus spp

Pilobolus Fungi

A common fungus that grows on the dung of herbivorous animals is Pilobolus (Zygomycotina). The dung contains nitrogen, vitamins, growth factors and minerals and satisfies the fungus' unusual nutritional requirement of a chelated form of iron. The fungus can be grown in media incorporating a decoction of dung or on a synthetic medium containing a complex iron-containing compound called coprogen. Exposure to visible light (380 to 510 nm) triggers the formation of a large bulbous cell called a...

Info

Figure 11.4 Diagram of distribution of Pilobolus sporangia adhering to a glass plate interposed between a culture and light dispersed by a prism. Traced from Page (1962). photoreceptor is most likely a carotenoid or a flavin. The adaptive response of Pilobolus to light ensures the dissemination of its spores and the survival of the fungus. The fungus Phycomyces blakesleeanus (Zygomycotina) occurs in decaying organic matter but is easily grown in laboratory media that is supplemented with...

Extracellular Recognition 831 The a Locus

The fusion of sporidia is controlled by two unlinked mating type loci, designated as a and b. Compatible mates have different alleles of genes at both loci. The a mating type locus has two alleles, a1 and a2, that are structurally quite dissimilar even though they are at the same position in the chromosome. This unusual situation of dissimilar mating type genes being present at the same locus in the chromosome is distinguished from the term allele by the term idiomorph. The idiomorphs are...

Nuclear Division Cycle

The cell cycle is divided into four phases G1 phase (between mitosis and the beginning of DNA synthesis), S phase (the period of DNA synthesis), G2 phase (the interval following the S phase and the beginning of mitosis) and M phase (separation of daughter nuclei). The G1, S and G2 phases are typically a longer part of the cell cycle than the M phase (Figure 2.2). Whereas in plant and animal cells the nuclear membrane breaks down during cell division, fungi including yeasts have a closed mitosis...

Conidiation Genes

Mutants of A. nidulans were obtained that are normal in hyphal growth and sexual reproduction but are defective in conidiophore development (Clutterbuck, 1969). Since conidia are not formed, the conidiation mutants are detected by the lack of the wild green color and by their inability to be replica plated a simple technique that allows colonies producing loose conidia in a petri dish to be sampled by pressing a velvet cloth secured over the top of a cylinder and onto the surface of new medium...

Some Striking Fungal Diseases 421 Diseases of Crop Plants

We stop the press, with great regret, to announce that potato murrain has unequivocally declared itself in Ireland. The crops around Dublin are suddenly perishing. Where will Ireland be in the event of a universal potato rot. Gardner's Chronicle, September 13, 1845 The potato was once the staple crop of Ireland and people depended on this single crop as their primary food source. In the late summer of 1845, the fungus (see Appendix) Phytophthora infestans (Straminipila) almost completely...

Classification

Asexual Reproduction Rhizoids

Classification is the placing of an individual in categories. This not only aids in determining whether it is identical or similar to an already known fungus but also in understanding its evolutionary affiliation. Naming and classification go hand in hand. The modern trend is to classify fungi based on genealogy. Some interpretations of relationships based on their evolutionary sequence conflict with the classification schemes that were developed based on morphological characters. A genus is a...

Positioning Of Nuclei And Gene Regulation

In the Basidiomycotina, the processes of hyphal fusion, nuclear migration and subsequently the selective association of nuclei convert a monokaryotic hypha into a dikaryotic hypha. The dikaryotic hyphae produce the fruit bodies. A small backwardly projecting outgrowth (hook) occurs from the end cell of hypha into which one of the two daughter nuclei passes (Figure 2.5). Septa form and the hook cell then fuses with the penultimate cell, forming clamp connections at the septa and the process is...

Detoxification of Saponins

Many plants constitutively produce triterpenoid, steroid or steroidal glycosylated compounds that are generally inhibitory to fungi Figure 4.9 . These are known by the general term saponin because of their soap-like properties, derived from the plant Saponaria officinalis, the extracts of which were once used to make soap Osbourn, 1996 . Saponins make complexes with membrane sterols, resulting in pore formation and leakage of cell constituents. The leaves and green fruits of the tomato plant...

Transformation Procedure

Methods were developed for transferring DNA into fungal cells and to select the transformed cells that have taken up this DNA. In the prototype experiment done in Edward Tatum's laboratory, wild type DNA was introduced into an inositol-requiring mutant Figure 9.1 Neurospora crassa growing on a sugarcane factory-waste dump. The genes encoding pink-orange color have been used as a visual reporter system in gene-silencing experiments. Photo courtesy of P. Maruthi Mohan. See color insert following...

Ustilago maydis Mechanisms in Sexual Reproduction

Sexual reproduction in fungi involves the detection of potential mating partners among multiple mating partners present in the environment, coordination of choices by making contact, commitment to a particular mating partner by adhesion, fusion of compatible cells followed by the fusion of gametic nuclei karyogamy and the meiotic division of the diploid nucleus to produce haploid progeny in the form of spores. Where the fusing nuclei differ genetically, the haploid progeny have new combinations...

Early Ideas On Plant Diseases

Chlamydospore

Although wheat rust was sometimes very destructive in Europe, the most generally prevalent disease of wheat was the bunt or the stinking smut Figure 4.1 . In 1750, the Academy of Arts offered a prize for the best dissertation on cause and cure of bunt. It was at that time variously ascribed as due to the use of pigeon droppings, sheep, or horse dung as manure. A French farmer named Matthieu Tillet 1714-1791 put most of these guesses to the test. He divided a piece of land crosswise into five...

Purification Of Transformant

Purification of the transformed nucleus is facilitated in those fungi that form uninucleate conidia for example, Aspergillus Chapter 7 or that can be manipulated to selectively produce uninucleate cells, as with N. crassa Maheshwari, 2000 . In N. crassa, macroconidia are easily obtained and are therefore routinely used for transformation. However, as these cells are usually multinucleate, the transforming DNA integrates at random locations in the genome and in different numbers of copies in...

Number Of Fungal Species

Previously, a species was defined as a group of individuals having common morphological characters. Based on the degree of discrimination adopted by the taxonomist a scientist who identifies and classifies according to a nomenclature and classification system approximately 70,000 species of fungi have been described based on morphological features such as the structure of conidiophores, the color and the method of formation of spores, the types of ascocarps, the features of basidium and many...

Infection Structures

Albugo Diagram

Nearly all fungal plant pathogens gain entry into their host via a structure called the appres-sorium. The firm attachment of the appressorium to the hydrophobic host surface prevents lift-off as the infection penetration peg from the underside forces entry through the narrow stomata pore or pierces through the cuticle and cell wall. Mutants of Magnaporthe grisea that are deficient in hydrophobin show reduced pathogenesis Talbot et al., 1996 . Howard et al. 1991 used solutions of polyethylene...

General Features Of Pathogenesis

Phytopathogens Fungi Stomata

Once fungi were recognized as a pathogen, it was understood that disease is a state of altered metabolism of cells and tissues resulting from a reciprocal interaction of a parasite and host, each of which is individually influenced by the environment. The example of a biotrophic fungus for example, a rust fungus can be used to understand what is conveyed by the above diagram and to point to some generic features of pathogenesis. After arriving on the leaf surface, the urediospore germinates if...

Homologous Vs Ectopic Integration Oftransgene

In contrast to yeast, where the transforming DNA molecule commonly integrates at the related sequence by cross over homologous recombination , integration in the filamentous fungi occurs commonly at unrelated sequences heterologous or ectopic recombination . As an example, Figure 9.2 shows the partial restriction map of a circular plasmid carrying Figure 9.2 a Map of plasmid used to obtain HygR transformants of Ascobolus immersus. Black thick lines correspond to hph genes, dotted lines are...

Classes Of Plant Pathogenic Fungi 431 Necrotrophic and Biotrophic Fungi

Plant parasitic fungi may be broadly classified as necrotrophic or biotrophic fungi based on their modes of nutrition. Necrotrophic fungi are destructive parasites and derive their organic nutrients from the dead cells they have killed. Their effects vary from local discrete lesions, as seen in some leaf spot diseases, to massive tissue destruction, as seen in fruit rots. Upon infection, the hyphae produce polygalacturonases and pectate lyase enzymes which act on pectic substances of the middle...

Nuclear Migration

A process as fundamental as nuclear migration can be expected to have common components in different organisms. In fungi, nuclei must migrate at specific times and in predetermined directions for growth of hypha to occur, for spores to be formed and for mating to take place. Nuclei divide in the hyphal tip King and Alexander, 1969 and migrate through septal pores into hyphal compartments. The fungal hypha is therefore an excellent material for studying the rates and mechanisms of long distance...

Mycorrhiza

Root Anatomy Mycorrhizal Aquatic Plants

Land plants never had an independence from fungi for if they had, they could never have colonized land. KA. Pirozynski and D.W. Malloch 1975 About 90 of all terrestrial plants have underground fungal partners known as mycorrhiza, which means fungus-root or a root colonized by a symbiotic fungus. The fungus invades tree roots and obtains nourishment by tapping into the plant's vascular system. The hyphae enmesh the root and extend into the soil particles or leaf-litter, tapping a larger volume...

Cellcell Recognition 821 Mating Types

The fungi grouped in Basidiomycotina are remarkable for having thousands of potential mating partners or mating types. It is of interest to learn how these fungi select a mating partner in the absence of any morphological differentiation. They are remarkable too for having a life cycle in which the nuclei of opposite mating types divide synchronously and remain in close proximity as an n n pair by a special type of hyphal growth called a clamp connection, in which a short hyphal branch grows...

Qk603m34 2005

Taylor amp Francis Group is the Academic Division of T amp F Informa plc. Visit the Taylor amp Francis Web site at http www.taylorandfrancis.com and the CRC Press Web site at http www.crcpress.com Fungi are organisms generally composed of tubes that are invisible to the naked eye. The cells of these tubes are multinucleate and in cytoplasmic continuity. Fungi are among the oldest and largest living organisms, rivaling the mass of a California redwood tree or a blue whale. As the chief agents of...

Cell Wall

Thermophilic Cell Structure

The tubular form of the hypha is an ideal structure for forcing entry into living tissues, for extending through soil or for growing erect to produce propagules and disseminate them into the air. For carrying out these functions, the hypha must generate enormous turgor pressure and have strong cell walls to contain it. If the cell wall is digested by microbial cell wall lytic enzymes, round protoplasts are released. This suggests that the tubular shape of the hypha is due to the rigid cell...

Thermophilic Fungi Eukaryotic Life at High Temperature

It is of interest to study the systematics, distribution, and physiological adaptations of organisms which have been successful in colonizing high temperature environments in order to examine the limits to which evolution can be pushed. From an ecological point of view, high temperature environments usually have relatively simple species composition and short food chains, which make a study of productivity, trophodynam-ics, population fluctuation, and species interaction more simple. From the...

Habitat Life Style And Life Cycle

Neurospora Life Cycle

Neurospora Figure 5.1 is frequently seen growing on stubbles of sugar cane after the canes have been harvested for milling and the agricultural field is burnt Pandit and Maheshwari, 1996 to clear the trash of the cut leaves. In addition to the pink-orange type, a yellow-colored N. intermedia is found in Asia on maize cobs which have been discarded on road-sides, parks or railway tracks after the roasted kernels are eaten by residents. Another species, N. discreta a species thought to be...

Mapping Transcription Network

In the early 1960s, bacterial genetics laid the concept of regulatory circuits controlling expression of genes. In its simplest form, circuits are turned on or off' by the binding of transcription factors or repressors to the upstream regulatory sequences of genes respectively. Expression analysis by microarrays described in the earlier section revealed the co-regulated expression and repression of sometimes hundreds of genes during specific cellular Figure 6.14 A schematic representation of a...

Distribution In Soil

Thermophilic fungi have been isolated from almost any soil, even in the temperate zones, prompting the remark the ubiquitous distribution of organisms, whose minimal temperature for growth exceeds the temperature obtainable in the natural environment from whence they were isolated, still stands as a 'perfect crime' story in the library of biological systems Tendler et al., 1967 . Whether their presence in soil is because of their growth therein or a consequence of dissemination of their spores...

Self Heating of Stored Agricultural Products

Thermophilic Fungi

Thermophilic fungi were discovered as chance contaminants of bread or potato that had been inoculated with garden soil see Cooney and Emerson, 1964 Maheshwari et al., 2000 . Their habitats and growth conditions were discovered when Hugo Miehe 1907 of Germany was drawn to investigate the cause of self-heating and the spontaneous combustion of damp stacks of hay. He studied the role of microbial flora in thermogenesis. From the self-heating haystacks, Miehe isolated several microorganisms,...

Guayule Rets

During the years of the Second World War, the need for finding alternate sources of rubber led to studies of the latex-bearing guayule plant Parthenium argentatum as a potential source. The extractability and quality of rubber improved if, before milling, this shrub was chopped and stored in a mass rets that self-heated to temperatures between 65 and 70 C. From the guayule rets, Paul J. Allen and Ralph Emerson 1949 isolated some ten species of thermophilic fungi with temperature limits up to 60...

Heterothallism Vs Homothallism

Heterothallism Homothallism

The processes leading to fertilization and production of progeny are quite variable in fungi. In the early twentieth century, A.F. Blakeslee found that a large number of morphologically indistinguishable single spore-derived cultures of a species belonging to Mucorales Zygomycotina could be sorted into two types, which he called plus and minus - since the strains could not be morphologically distinguished as male or female. If a plus colony was grown with another plus strain in a petri dish, or...

Meiotic Events

Genetic Recombination Fungi

Lindegren perceived Neurospora as a marvelous organism for genetic analysis as the four products of a single meiosis are packaged as ascospores in a single row in the order of their formation in ascus usually called a tetrad, although in Neurospora the meiotic division is followed by a mitotic division hence, each of the four meiotically produced ascospores are duplicated as sister ascospores, thus an octad . The ascospores are large enough, measuring approximately 29 X 15...

Proteomics And System Biology Modeling

A cell continuously senses environmental stimuli and relays that information inside across membranes to trigger a response. The process of signal transduction occurs by sequential transfer of information via protein-protein interaction. Take the example of a yeast cell growing in a glucose-rich environment suddenly encountering galactose. It senses the change in composition of the carbon source, shuts off the expression of genes required for glucose metabolism and turns on the genes required...

Part I

Giant Mycelium Diagram

Fungi are composed of microscopic, tube-like structures called hyphae singular hypha which grow on substrates such as leaf litter, fallen timber and herbivore dung. The hypha has the shape of a cylindrical tube of even diameter with a tapering tip that branches subapically, with each branch having a tip of its own. By iteration of this modular unit comprising of a tip and a subapical branch Figure 1.1 , a radiating system of hypha called the mycelium is formed Carlile, 1995 . At places, hyphae...

Mycobiont and Photobiont

The mycobiont is mostly an Ascomycotina. The fungus is the dominant member of the partnership and determines the morphology of the lichen. Based on the chlorophyll content of alga, it was estimated that the alga Nostoc comprises about 5 of the lichen Peltigera. Beneath the algal layer is fungal medulla 400 to 1000 m thick. Electron microscopy shows that alga and fungus are in intimate contact but there is no penetration of algal cells by fungus. Lichen fungi are not specific to their algal...