Filamentous fungi -a backgroundLecture 1 and 2 What are they?What are they doing?

Fungi are important in nature

As decomposersAs pathogens of plants, animals and humans, and in food spoilageAs producers of secondary metabolites, e. g. penicillinIn cheese, bread and wine making

Fly agaric(flugsvamp)

Ergot of ryeCaused by Claviceps purpurea.Cause of ergotism: Holy Fire or St. Anthonys Fire.Sclerotia are dangerous.Witch hunts.Caused low fertility and death in 14th-18th century Europe.

Other toxins made by fungiEndophytic fungi (Acremonium) in grasses can be toxic to cattle (fescue toxicosis)Other mycotoxins:OchratoxinsAflatoxins - carcinogenicFumonosins - blind stagger of horsesPatulin - bleeding in lungs and brain, kidney damage, cancer

Medicines that come from fungiPenicillin. Penicillium chrysogenum. Alexander Fleming, 1928.CephalosporinCyclosporin

Fungal diseases of humans - mycosesTrichophyton rubrum. Causal agent of athletes foot. Came from tropics.Candida albicans. Causes candidiasis = yeast infections. Around genitalia. Disease of mouth and throat.Blastomycosis, Cryptococcosis, Histoplasmosis, Aspergillosis are other diseases.

Smut infection of a wheat field inEastern Washington (1956)

Ustilago maydis - the corn smut fungus

Ustilago maydisis a popular fooddelicacy in Mexico

Examples of symptoms caused by fungi:CankersStorage rots of fruits and vegetablesRust, mildewsLeaf spots

Pathogen life stylesNecrotrophs - kill host cells with toxins and hydrolytic enzymes.Ex: Botrytis cinerea.Biotrophs - specialize on a living host.Ex. Powdery mildews and rusts.Hemibiotrophs - start out biotrophic. Then, they kill the host cells. Ex. Phytophthora infestans.

Botrytis cinerea - a fungus -causes grey mold

Grey mould of strawberries

Characteristics of grey moldB. cinerea is a necrotroph, entering the plant through dead or dying tissue.It is a pathogen that attacks almost any known plant species. It invades healthy tissue through dead petals or leaves or dying wood.

Botrytis cinerea causes rots on fruits and vegetables, blossom blights, damping off, stem cankers, leaf spots and bulb rots.scleriotia

In the field, blossom blight often precede the fruit rotsThe fungus enters the fruit through the dead flower petals.

The fungus Botrytis cinereaDevelops grey mycelium with long, branched conidiophores with clusters of one-celled, ovoid conidia.The conidiophores and conidia resemble a grapelike cluster.

Botrytis cinerea of tomato

Botrytis cinerea of tomatoSpots on fruits are from spores that have landedAttack on fruit originated in the flower

Grey mould - continuedB. cinerea overwinters as mycelium in decaying plant debris or as sclerotia - black, hard resting structures.It also attacks fruit and vegetables during storage. The fruits rot internally (often from the flower end) and a soft mycelial mat develops on the surface. The fungus does most damage when it is very humid and damp.

Life cycle of Botrytis cinerea

Powdery mildew on roseSphaerotheca pannosa is the causal agent of powdery mildew on roses. It is an example of a biotroph: It grows only in living plant tissue.The white, powdery appearance is due to conidiophores/conidia

Powdery mildew on Poinsettia

Powdery mildew on squash

Powdery mildew on cucumber

Life cycle of powdery mildew

Rust of roen (rnn)

Rust of raspberry

Rust of rose

Four phyla of fungiChytridiomycota - no sexual sporeZygomycota - zygosporeAscomycota - ascosporeBasidiomycota - basidiospore

Characteristics of fungiFungi have hyphae. A mass of hyphae is a mycelium. The hyphae may be septate or aseptate.Specialized hyphae, haustoria are feeding structures.

Fungal reproductionAsexually, by forming conidiaSexually (three steps):Plasmogami (dikaryon)Karyogami (zygote forms)Meiosis (sexual spore forms):ZygosporeAscosporeBasidiospore

Incompatibility systemsFungi (ascomycetes) have mating types. They are designated MATa and MATa (yeast), MATA and MATa (Neurospora) or MAT1-1 and MAT1-2. Sexual reproduction in a heterothallic ascomycete requires the participation of different mating types. In a homothallic strain the fusing individuals are of the same mating type. The inability of two individuals of the same mating type to fuse is called vegetative incompatibility.

Chytridiomycota

Zygomycota

Gametangia fuse to produce a zygospore (Rhizopus stolonifer)

Ascomycota

Penicillium and Aspergillus

Examples of conidiophores of other imperfect fungi or Deuteromycetes