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[edit] Secondary Metabolites of Fungi

[edit] Definitions

  • Primary metabolite: a metabolite synthesized in a step in primary metabolism (www.medilexicon.com)
  • Secondary metabolite: a metabolite synthesized in a step in secondary metabolism (www.medilexicon.com)
  • Primary metabolism: metabolic processes central to most cells, biosynthesis of macromolecules, energy production, turnover (www.medilexicon.com)
  • Secondary metabolism: metabolic processes in which substances (such as pigments, alkaloids, or terpenes) are only synthesized in certain types of tissues or cells or are only synthesized under certain conditions (www.medilexicon.com)
  • Intermediate: A metabolic intermediate is a sub product produced at a certain step in the pathway that is used at a later time in the same pathway or a different pathway (Moore et al 2011)
  • Transporter: A transporter is an molecule that binds to a substrate in order to move it to another location (Moore et al 2011)
  • Antibiotic: A soluble substance derived from a mold or bacterium that kills or inhibits the growth of other microorganisms (www.medilexicon.com)
  • Evolutionary advantage: Having a trait/characteristic that competing species do not have that causes favoritism by selection (Bergstrom et al 2012)
  • Natural Pigment: A naturally occurring colored compound; absorbs light in the visible range of the electromagnetic spectrum (www.medilexicon.com)
  • Bacteriophage/phage:A virus with specific affinity for bacteria (www.medilexicon.com)
  • Steroid: Biological regulator that can act various hormones, D vitamins. Steroid have unique structure with four cycilic rings that is derived from perhydrocyclopentanophenanthrene ring.(Solomons et al,

2011)

  • Sterols: Hydroxylated steroids that retain some or all of the carbon atoms of squalene in the side chain. It is commonly found in cell membranes (Akoh & Min, 2008)
  • Terpenes: Technically, terpene is a hydrocarbon molecule that is made of 9 carbon and 16 hydrogen. However, the term can be generally be refered as 10-carbon isporenoids, which can occurs in chained or cyclic form.(Moore et al., 2011)
  • Pentaketide Pathway: The route to cell wall melanization among these agents of chromoblastomycosis and phaeohyphomycosis (Taylor et al, 1987)
  • Lyse: To cause dissolution or destruction of cells (www.thefreedictionary.com)
  • Nephrotoxicity: The quality or state of being toxic to kidney cells (www.medilexicon.com)
  • Cyclosporin: A cyclic oligopeptide immunosuppressant produced by the fungus Tolypocladium inflatum Gams; used to inhibit organ transplant rejection (www.medilexicon.com)
  • Immunosuppression: Prevention or interference with the development of immunologic response; may reflect natural immunologic unresponsiveness (tolerance), may be artificially induced by chemical, biologic, or physical agents, or may be caused by disease (www.medilexicon.com)
  • Keratin: Collective name for a group of proteins that form the intermediate filaments in epithelial cells (www.medilexicon.com)
  • Mitosis: The usual process of somatic reproduction of cells consisting of a sequence of modifications of the nucleus (prophase, prometaphase, metaphase, anaphase, telophase) that result in the formation of two daughter cells with exactly the same chromosome and nuclear DNA content as that of the original cell (www.medilexicon.com)
  • Dermatophyte: A fungus that causes superficial infections of the skin, hair, and/or nails, keratinized tissues (www.medilexicon.com)

[edit] Introduction

Fungi produce two types of metabolites; those that are required for survival and those that are not required but have evolutionary advantages (Moore et al, 2011). These are labeled primary metabolites and secondary metabolites and can occur at the same time using similar intermediates(Moore et al, 2011). Secondary metabolites are often smaller molecules that are often present after food sources are depleted (Keller et al, 2005 & Moore et al, 2011). Few secondary metabolites are present during primary metabolism as additional transporters of intermediates, however many are bioactive(Keller et al, 2005). Many secondary metabolites are used in medicine as antibiotics and industry (fungal biology 2004). Secondary metabolism occurs as growth rate declines and during the stationary phase, and often is associated with differentiation and sporulation (Carlile, 2001). The production of secondary metabolites tend to be restricted to one or a few organisms (Carlile, 2001).

[edit] Biosynthesis of Secondary Metabolites

Interrelationships of metabolic pathways in primary and secondary metabolism (Griffin, 1993)
Interrelationships of metabolic pathways in primary and secondary metabolism (Griffin, 1993)

Secondary metabolites originate as derivatives from many different intermediates in primary metabolism. Although there are some exceptions, most of them can be classified according to five main metabolic sources. The sources are glucose, the shikimic acid pathway for the biosynthesis of aromatic amino acids, the polyketide biosynthetic pathway from acetyl coenzyme A (CoA), the mevolonic amino acids pathway for the acetyl CoA, and amino acids (Griffin, 1993). Glucose from primary metabolism is directly used for synthesis of sugar alcohols and polysaccharides. The shikimic acid is a precursor of aromatic amino acid and many of them are toxic. Tryptophan is also made from this pathway which brings psilocybin and other compound that are found in 'magic mushroom' (Moore et al,2011). Acetyl CoA is used to make polyketides and phenolics. They are commonly found in mycotoxins. Acetyl CoA also derives mevalonic acid. Mevalonic acid can be converted to carotenoids, steroids and terpenes. The pathway dealing with amino acid are found from pyruvate, during the TCA cycles. Amino acid from pyruvate becomes penicillin which is important for antibiotics (Griffin, 1993).

[edit] Pigments

Fungal pigmentation usually occurs from the metabolism of light. A common metabolic effect of light is the induction of carotenoid biosynthesis (Carlile, 2001). Mycelium of Neurospora crassa, Fursarium aquaeductuum and other fungi result in being an orange pigment when grown in the light, but colourless if cultured in the dark (Carlile, 2001). The amounts of carotenoid are increased when exposed to light. The photoreceptor that is usually involved is known as flavin (Carlile, 2001). Black pigment is also stimulated by light. Black or dark brown pigment in fungi is usually melanin or melanoprotein (Durán et al, 2002). In the Dematiaceae, both hyphae and conidia are heavily pigmented (Ibid). Many Ascomycetes and imperfect fungi appear to produce melanin by the pentaketide pathway while Basidiomycetes employ a different route; special substrates are used for the phenoloxidase system that leads to the formation of melanin (Ibid). Melanin is important for the resistance of damage from high environmental temperature, ezymatic and chemical attack (Carlile, 2001). A protective role in desiccation and irradiation has also been suggested, where melanin is deposited in the cell (Ibid). Melanin is deposited as either an extracellular polymer in the medium around cells, or directly in the cell wall (Bell et al, 1986). Below are examples of the different pigments fungi may obtain.

Figure 2. Exidia glandulosa is a jelly fungus that has a black pigmentation.

Figure 3. Tremella fuciformis is a mushroom displaying a bright yellow pigmentation.

Figure 4. The fungus Mycena clarkeana shows a purple pigmentation.

Figure 5. Hygrocybe psittacina, also known as parrot toadstool, shows a green pigmentation.

Figure 6. Clavariaceae, also known as coral fungi, displays a pink pigmentation.

Figure 7. A mushroom trametes versicolor, also know as turkey tail, displays a blue pigmentation.

[edit] Carotenoids

Carotenoids are naturally occurring terpenoid pigments, and are the most common (Bhosale, 2004). Acetyl CoA is the precursor secreted that stimulates production. It is first converted to HMG-CoA (3-hydroxy-3-methyl glutaryl), which is then converted to mevalonic acid (Bhosale, 2004). Mevalonic acid, or MVA, is the precursor of terpenoic biosynthesis. MVA is phosphorylated by a kinase, becoming isopentyl pyrophosphate (IPP) (Bhosale, 2004). The is then desaturated to form lycopene, which acts as a precursor for cyclic carotenoids (Bhosale, 2004).

[edit] Cell Wall Bound Melanin

Most melanized fungi have two layers in the conidial, hyphal and sclerotial walls, one which is electron translucent, and one that contains electron dense granules (Bell et al, 1986). Chlamydospores have a third layer which occurs as a second primary wall (Bell et al, 1986). Species such as Thielaviopsis contain electron granules throughout all layers, which other species such as Verticillium only contain these granules in the outer wall (Bell et al, 1986). The melanin is either seen as a well defined outer layer, or as granules included in the fibrillar matrix (Langfelder et al, 2003). Formation occurs from melanin precursors which are secreted onto the cell wall by the cytoplasm, stimulating production (Langfelder et al, 2003).

[edit] Extracellular Melanin

This type of melanin is formed in two different ways. The first and most common manner is by release of phenolxidase into the culture fluid, which oxidizes some of the proteins and other culture components to produce pigment (Langfelder et al, 2003). The second manner occurs through the release of other phenol compounds into the medium. In the presence of catechol or L-DOPA, the melanins may bind to the cell wall, giving a false impression of being cell wall bound (Langfelder et al, 2003).

[edit] Bioluminescence

Bioluminescence is the production of light from a living organism. This occurs through the oxidation of luciferin by the enzyme luciferase (dictionary.com). In the fruiting body, luminescence aids in spore dispersal by attracting insects, while in the rhizomorphs and mycelia, luminescence is responsible for DNA repair (Carlile, 2001). Some species involved in the production of bioluminescent compounds are Basidiomycetes, Panellus and Mycena (Carlile, 2001).

Figure 8. An example of bioluminescent fungus.

[edit] Fungal Pigments in the Food Industry

There are a variety of other pigments of fungi being studied for the use of natural dyes in foods (Durán et al, 2002). Natural pigments in foodstuff has increased over the years because synthetic pigments were causing concerns about the harmful effects they may have on consumers (Mapari et al, 2006). An example of a synthetic dye would be “fast green dye” which was causing harmful effects of the immune system (Ibid). An example of a natural dye would be β-Carotene that comes from the fungus Blakeslea, which is completely safe and produces a red-orange pigment (Ibid).

Most of the available literature about pigment-producing fungi for food use points toward Monascus, which produces pigments that are good food colorants because they are stable in the pH range of 2−10 (Ibid). Besides Monascus pigments, several characteristic noncarotenoid pigments are produced by filamentous fungi that exhibit a unique structural and chemical diversity with an extraordinary ranges of colors (Ibid).

Developing pigments from fungi is an easily renewable resource that can be produced in high amounts. Current pigments that are used in foods have several drawbacks relating to their usability, such as the compound curcumin which is has a strong, spicy flavour and therefore limits the amount of products it can be used in (Mapari et al, 2005). Other pigments that are derived from fruits and other raw materials depend on availability of the source material, which becomes a problem when droughts occur (Mapari et al, 2005). This is also be a useful resource in the search for all natural and/or vegan colorants.

[edit] Volatiles

Fungal volatiles give an advantagous edge by allowing the ability to approach another organism with a gas phase. This is especially imperative for fungi that grow some of their mycelium and fruiting structures in the air above wet or liquid substrates. Volatility leads to escape from observation[1]. Because the substances are active as gases, they are relatively simple molecules with low boiling points and high vapor pressure at room temperature.

[edit] Health Concerns

Molds are the most primary candidate for augmenting the quality of indoor air. They are very adaptable and can colonize dead and decaying organic matter like textiles, leather, wood or paper. If organic nutrients are available on substrate or in the air (like dust or soil), molds are able to grow on inorganic substances like bare concrete or glass surfaces.Black mold inside the home can lead to breathing problems and allergies. Some people are severly sensitive to mold volatile, and others develop a resistance to the toxicity. It also leads to eye, nose and throat irritation and is responsible for triggering severe asthma symptoms for those who have it. (health canada)

[edit] Other Uses of Volatiles

Many different species of fungus can produce a multitude of different volatiles, and can be used for many different, often unorthodox things. Some example include Muscodor vitigensis, Penicillium casefulvum, and Trichoderma spp. Trichoderma spp, produce volatiles that can digest the volatiles of other hosts. Specifically, it produces volatiles that decarboxylate sorbic and cinnamic acid produced by the cinnamon tree[2]. Penicillium casefulvum makes a wide range of intense aromatic volatiles. These are used as cultures in the production of dairy products like yogurt, or brie cheese[3]. Finally, Muscodor spp, can produce naphthalene as a volatile[4]. It does this to deter insects, but as you may know, naphthalene is also a common gas used as fuel for camping stoves, and other outdoor equipment. Common volatiles are 2-methyl-1-propanol, 3-methyl-1-butanol, 1-octen-3-ol, 3-octanone, 3-methylfuran, ethyl acetate, and the malodorous 2-methyl-isoborneol and geosmin. Volatile sesquiterpenes can be used for taxonomic classification and species identification in Penicillium, as well as to indicate mycotoxin formation in Fusarium and Aspergillus. Volatile compound mappers, also known as electroniic noses, detect volatile compounds and produce electical signals. The signals are used to detect the presence of molds, levels of ergosterol and fungal colony-forming units in cereal and grain. This is very imperative when deducing the levels of mycotoxin contamination of food and animal feeds. (Shurer,1999)


Image:Cladiosporum.png

Figure 9: Cladiosporum

[edit] Antibiotics

The ability of a fungus to produce antibiotics as a secondary metabolite allows for it to have an evolutionary advantage since it can inhibit the growth of competitors (Moore et al, 2011).

[edit] Penicillin

Penicillin production as a secondary metabolite is a characteristic of species in the Penicillium genus (Moore et al, 2011). See the video below to learn more about individuals in this genus.

Penicillin was the first broad spectra antibiotic to be identified (Keller et al, 2005). It was first identified by Alexander Fleming in 1929 in the species Penicillium notatum(Díez et al, 2001 & Keller et al, 2005). However penicillin was not purified enough to fully determine its effects on microorganisms until 1939 (Díez et al, 2001 & Keller et al, 2005). Shortly after that methods for greater production were developed such as selecting for individuals with greater production of penicillin (Keller et al, 2005). More recent methods of improving production include duplicating the genes that code for penicillin can using a phage to introduce them (Díez et al, 2001).

Image:penicillin.jpg

Penicillin acts as a antibiotic by restricting the gene responsible for the cross linking component of many bacterial walls from transcription and causing cell lysis(Díez et al, 2001).

[edit] Griseofulvin

Griseofulvin is an antifungal drug which is used both in animals and humans to treat fungal infections of the skin and nails and taken orally. (Barnes et al, 1961) The most common skin infection is the ringworm. It was first isolated from Penicillium griseofulvum in 1939.(Jessup et al, 2000)

The drug disrupts the mitotic spindle through interacting with polymerized microtubules where inhibiting the mitosis. (Barnes et al, 1961) The cells get resistant to fungal infections when it binds to keratin in keratin precursor cells. (Barnes et al, 1961) The drug reaches its site of action only when the hair or skin is replaced by the keratin griseofulvin complex. (Barnes et al, 1961) Then the drug will bind to fungal microtubules by entering the dermatophyte through energy dependent transport process. (Barnes et al, 1961) Therefore, the process of mitosis changes and the original information for deposition of fungal cell walls. (Barnes et al, 1961)

Image:griseofulvin.jpg

Griseofulvin can also be a potential treatment for cancer. (Jessup et al, 2000)They use an unusual mechanism to confirm the correct genetic material is present within each of the resulting tumor cells when cancer cells divide in undergoing mitosis. (Jessup et al, 2000) The most common side effects are nausea, diarrhea, headache, skin eruptions and photosensitivity. Hepatotoxicity and neurological side effects hardly occur. (MedicineNet, Inc. 1996-2013)

[edit] Immune-suppressants

Fungi are fruitful sources of potent pharmacologically active molecules, such as the immunosuppresive cyclosporin (Carlile, 2001). Cyclosporin was originally discovered in an antifungal screen, that showed great potency for immunosuppresive agents (Carlile, 2001). Cyclosporin inhibits T-cell activation, which belongs to a group of white blood cells that are involved with immunity.

Soil fungi produce macrolides, which have immunosuppressant properties. They will help with the treatment of inflammatory dermatoses (Marsland, 2002). Cyclosporin, and macrolides tacrolimus and pimecrolimus, regulate immune-cell function by stopping the process calcineurin-dependent dephosphorylation-activation, thus preventing transcription of pro-inflammatory cytokines (Marsland, 2002). The macrolide rapamycin acts by aboloshing the target of Rapamycin, a protein that controls activation of proteins by signals which direct progression of the cell cycle in response to pro-inflammatory cytokines (Marsland, 2002). The use of systemic cyclosporin must be limited because there can be harmful effects such as nephrotoxicity and hypertension (Marsland, 2002). Tpoical cyclosporin is not very effective because it does not penetrate the skin well, while tacrolimus is a more improved topical substance that can penetrate through the skin easily(Marsland, 2002).

[edit] Toxins

Toxins derived from fungi are grouped as mycotixins (toxinology, 2010). Mycotoxin contamination has affected humans since before recorded history. Festivals were described in the 7th and 8th century, by the Romans, to ward off rust and mold to stop poisoning from crops.Ergotism outbreaks were even described in the middle ages. Only in the last approximate fourty years have scientists been able to isolate specific toxins from selected fungi. These methods are being continuously revisited and revised (R. Brambl, 2009). The reason as to why fungi produce mycotoxins is widely debated and not entirely understood. Common theroy speculates that they are used for a sort of "chemical warefare" to create an advantage for survival in a variety of environments (toxinology, 2010).

[edit] Magic Mushrooms

A commonly known toxic effect of some fungi in pop culture is that of psilocybin; a commonly occuring chemical found in "magic mushrooms". Psilocybin is a hallucinogen.As such it has the capacity to alter perception. All five senses are affect as one may see, hear, smell, taste or feel sensations that are not occuring. It's effects can be felt within a few minutes if desolved into tea or after 30 minutes if consumed by eating mushrooms. The effects typically last within range of three to six hours; however some records have indicated hallucinations up to four days after consumption (Health Canada, 2009).

Psilocybin(4-phosphoryloxy-N,N-dimethyltryp-tamine)is a substituted indolealkylamine. It mainly stimulates the sympathetic nervous system and increases beta activity in the neo-cortex.Throughout the brain there is strong evidence of stimulation. Aside from the cortex, basal ganglia, occipital-cortex and sensorimotor regions are greatly stimulated (Passie et al, 2002).

Psilocybin interacts mainly via serotonergic neurotransmission. Ergo it interacts greatly with serotonin release and binding(Passie et al, 2002). Serotonin is a chemical transmitter which is greatly attributed to creating feelings of well-being and happieness (Young, 2007) . It does not affect dopamine release or absorbtion. With high seratonin release, feedback loops between the cortex and thalamus are altered. This opens the thalamic filter for greatly increased sensory imput(Passie et al, 2002).

[edit] Human Poison

The chart illustrated below indicates some toxins produced by Fungi and their effects on humans.

Image:Poopty_pewpty_pants.png

(D.W.Gover, 2006)

See also: Amanita phalloides

[edit] Terpenes & Steroids

[edit] Introduction

Terpenes and steroids are widely distributed in the nature and many of the end-products have chemical structures which are unique to fungal metabolism. They have five carbon atoms arranged as in the hydrocarbon isoprene. (Moore et al, 2011) They are widely used by fungi since they have hormonal, regulatory and structural roles in fungi. It could also have pathogenesis and disease resistances (Hendrix, 1970). Each steroids have specific structures which enables to have various functions. They are synthesized from the metabolism of glucose through complex chemical pathways.

[edit] Processes involved

[edit] Steroid Synthesis
Cyclisation of squalene oxide creates different types of sterols (Moore et al, 2011)
Cyclisation of squalene oxide creates different types of sterols (Moore et al, 2011)

Steroid synthesis happens through the complex biosynthetic pathways. The steroids are derived from the mevalonic acid pathway in the metabolic pathway in primary and secondary metabolism (Griffin, 1993). Acetyl-CoA made from pyruvate after EMP pathway is used for steroids synthesis along with other secondary metabolites (Griffin, 1993). Acetyl-CoA is converted to 3-hydroxy 3-methylglutaryl-CoA (HMG-CoA) by HMG-CoA synthase. HMG-CoA reductase converts HMG-CoA into mevalonic acid. This acid is then converted to isopentenyl pyrophospate which is precursor to various steroids. This acid is then converted to isopentenyl pyrophospate and to squalene. Squalene is a significant precursor that derives differences in each sterols. The sterols are derived by cyclisation of squalene oxide. Some of the examples of sterols are fructosol that leads to the production of oogoniol or antheridiol with different R-groups. It can also produce lanosterol which becomes ergosterol.

Steroid synthesis pathway (Konstantinopoulos,2007)
Steroid synthesis pathway (Konstantinopoulos,2007)
[edit] Terpene synthesis
Terpene synthesis pathway (Moore et al, 2011)
Terpene synthesis pathway (Moore et al, 2011)

Terpene synthesis is derived from precursor of isoprene unit. The Isoprene unit precursor is shown in the top box. This isoprene precursor condensate and also bind with Acetyl Coenzyme A to form mevalonate, a single unit of terpene.(Moore et al, 2011) This terpene unit can bind with other terpene units to form a long chain. Each terpene unit contains 5 carbons. For 10 carbon terpene chain, 15 carbon terpene chain, and 20 carbon terpene chain are called isoterpene, sesquiterpene, and diterpene respectively.

[edit] Species Involved

[edit] Alchyla bisexualis and Alchlya ambisexualis: Reproductive hormones

Steroids take a role as reproductive hormones. John Raper found two hormones and the mechanism in 1940 (McMorris,1978). Alchyla bisexualis and Alchlya ambisexualis produces steroid sex hormones to perform heterothallic reproduction. This means that when two compatible mycelia meet, one produces male and the other one produces female structure. Their mycelium do not form any sexual structure. However, they contain either 'female' strain or 'male' strain. Female strain produces hormone A or antheridiol that is active at low concentrations. This hormone affects the male strain to develop antheridial initials. This development makes male strain to produce another hormone called hormone B or oogoniol. This hormone induces formation of oogonial initials in the female strain. Antheridial initials grow towards oogonia by chemotropism for fertilization (Carlile, 2001).

A.Antheridiol B.Oogoniols (Carlile, 2001)
A.Antheridiol B.Oogoniols (Carlile, 2001)
[edit] Neuraspora crassa and Saccharomyces cerevisiae: Ergosterol

Ergosterol is important sterol which gives architectural component. The name came from ergot fungus because it was first isolated from the ergot fungus. It also influences the permeability characteristics of the membrane. This sterol is only found in fungi. Other sterols, such as cholesterol, occurs commonly in other fungi. (Walker, 1998) For example, they are found in Neuraspora crassa and Saccharomyces cerevisiae. Ergosterol synthesis is a potential target for antifungal agents. This is because ergosterol is only found in fungi and it can specifically attack them. When the biosynthetic pathway of ergosterol is disrupted, it also disturbs the yeast membrane function (Walker, 1998). It is synthesized from the lanosterol.

[edit] Gibberella fujikuroi: Gibberellic acid
Gibberellic Acid Synthesis Pathway (Tuzynski, 2005)
Gibberellic Acid Synthesis Pathway (Tuzynski, 2005)

Gibberellic acid(GA) is a diterpene (20 carbon) molecule that are produced by a plant pathogen, Gibberella fujikuroi.(Moore et al, 2011) Gibberella fujikuroi was discovered in Japanese rice farmer. The symptom of Gibberella fujikuroi infected rice plant were extremely tall stem, and dark rices with inability to produce seeds.(Taiz & Zeiger, 2010) In 1930, the underlying compound of this symptom was determined and named giberellin A, aka gibberellic acid. Originally, Gibberellic acid is a plant hormone that promotes seed germination, juvenile to adult phase regulation, initiation of fruit growth, seed development, and most importantly, plant stem elongation.(Taiz & Zeiger, 2010) Gibberellic acid is well regulated hormone within a healthy plant.(Taiz & Zeiger, 2010) However, imbalance of gibberellic acid can cause damage to the plants. For gibberella fujikuroi, the gibberellin secretion to the host plant result overgrowth of stem, causing etiolation, chlorosis, and eventually death.(Moore et al, 2011) There has more than 20 GA identified that are mostly produced inactive or intermediate diterpene (Taiz & Zeiger, 2010). The Gibberellic acid synthesis of Gibberella fujikuroi starts with a molecule called, Geranylgeranylpyrophosphate(GGPP) (Tuzynski, 2005). The plant host and Gibberella fujikuroi shares similar Gibberellic acid synthesis pathway until GA12 (Tuzynski, 2005). Fungal enzyme catalyzes the reaction different pathway than host depends on the environmental stress that the fungal pathogen expreience (Tuzynski, 2005). Enzyme P450-1 takes place for clustering gene for rapid rate of GA production than host (Tuzynski, 2005). The end product GA1 and GA3 is the active GA that cause pathogenic symptoms.(Taiz & Zeiger 2010)

[edit] Gliocladium virens: Viridiol

Gilocladium virens is a destructive mycoparasite that infects on other fungal organisms such as Sclerotinia sclerotiorum.(Tu, 1980) G.virens produces a steroidal secondary metabolites called viridiol.(Howell & Stipanovic, 1984) Viridiol's chemical structure is similar to a well known anti fungal compound called viridin (Howell & Stipanovic, 1984) . In fact, viridian can be derived from viridin with a slight change of its functions from viridin(Howell & Stipanovic, 1984) . Unlike viridin, viridiol does not cause mycotoxic effect against other fungi organisms(Howell & Stipanovic, 1984) . Depends on the condition of the viridiol applied , viridiol's phytotoxicity appears, or diminishes(Howell & Stipanovic, 1984) . When purified dry viridiol is applied to a plant it prevents germination of plants seed. Also, It is suspected that viridiol have a necrotic effect on plant's outer tissue (Andersson, 2012).

[edit] Other


[edit] References

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Andersson, P.F. (2012). Secondary metabolites associated with plant disease, plant defense and biocontrol. (Doctoral dissertation).

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