Filamentous fungi -a background

Lecture 1 and 2 What are they?

What are they doing?

Fungi are important in natureFungi 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 agaricFly agaric(flugsvamp)(flugsvamp)

Ergot of rye• Caused by Claviceps

purpurea.• Cause of ergotism:

“Holy Fire” or “St. Anthony’s Fire”.

• Sclerotia are dangerous.

• Witch hunts.• Caused low fertility

and death in 14th-18th century Europe.

Other toxins made by fungi• Endophytic fungi (Acremonium) in grasses

can be toxic to cattle (fescue toxicosis)• Other mycotoxins:

– Ochratoxins

– Aflatoxins - carcinogenic

– Fumonosins - blind stagger of horses

– Patulin - bleeding in lungs and brain, kidney damage, cancer

Medicines that come from fungi

• Penicillin. Penicillium chrysogenum. Alexander Fleming, 1928.

• Cephalosporin• Cyclosporin

Fungal diseases of humans - mycoses• Trichophyton rubrum. Causal agent of athlete’s

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 Examples of symptoms caused by fungi:caused by fungi:

CankersStorage rots of fruits and vegetablesRust, mildewsLeaf spots

Pathogen life styles

Necrotrophs - kill Necrotrophs - kill host cells with host cells with toxins and toxins and hydrolytic enzymes.hydrolytic enzymes.Ex: Ex: Botrytis cinereaBotrytis cinerea..

Biotrophs - specialize Biotrophs - specialize on a living host.on a living host.Ex. Powdery Ex. Powdery mildews and rusts.mildews and rusts.

Hemibiotrophs - start out Hemibiotrophs - start out biotrophic. Then, they kill the host biotrophic. Then, they kill the host cells. Ex. cells. Ex. Phytophthora infestansPhytophthora infestans..

Botrytis cinereaBotrytis cinerea - a fungus -causes - a fungus -causes grey moldgrey mold

Grey mould of strawberries

Characteristics of grey moldCharacteristics of grey mold

• B. 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.

scleriotiascleriotia

In the field, blossom blight often precede the fruit rots

The fungus enters the fruit The fungus enters the fruit through the dead flower petals.through the dead flower petals.

The fungus Botrytis cinerea

Develops grey Develops grey mycelium with long, mycelium with long, branched branched conidiophores with conidiophores with clusters of one-celled, clusters of one-celled, ovoid conidia.ovoid conidia.

The conidiophores and The conidiophores and conidia resemble a conidia resemble a grapelike cluster.grapelike cluster.

Botrytis cinerea of tomato

Botrytis cinerea of tomatoSpots on fruits are from spores that have landedSpots on fruits are from spores that have landed

Attack on fruit originated in the flowerAttack on fruit originated in the flower

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

Life cycle of Botrytis cinerea

Powdery mildew on rosePowdery mildew on rose

• Sphaerotheca 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 (rönn)

Rust of raspberry

Rust of rose

Four phyla of fungiFour phyla of fungi

o Chytridiomycota - no sexual sporeo Zygomycota - zygosporeo Ascomycota - ascosporeo Basidiomycota - basidiospore

Characteristics of fungiCharacteristics of fungi

Fungi have hyphae. A mass of hyphae is a mycelium. The hyphae may be septate or aseptate.

Specialized hyphae, haustoria are feeding structures.

Fungal reproductionFungal reproductionAsexually, by forming conidia

Sexually (three steps):•Plasmogami (dikaryon)•Karyogami (zygote forms)•Meiosis (sexual spore forms):

•ZygosporeZygospore•AscosporeAscospore•BasidiosporeBasidiospore

Incompatibility systemsIncompatibility systemsFungi (ascomycetes) have Fungi (ascomycetes) have mating typesmating types. . They are designated MATa and They are designated MATa and MATMAT(yeast), MATA and MAT(yeast), MATA and MAT ((NeurosporaNeurospora) or MAT1-1 and MAT1-2. ) or MAT1-1 and MAT1-2. Sexual reproduction in a Sexual reproduction in a heterothallicheterothallic ascomycete requires the participation of ascomycete requires the participation of different mating types. In a different mating types. In a homothallichomothallic strain the fusing individuals are of the strain the fusing individuals are of the same mating type. The inability of two same mating type. The inability of two individuals of the same mating type to individuals of the same mating type to fuse is called fuse is called vegetative incompatibilityvegetative incompatibility..

ChytridiomycotaChytridiomycota

ZygomycotaZygomycota

Gametangia fuse to produce a Gametangia fuse to produce a zygospore (zygospore (Rhizopus stoloniferRhizopus stolonifer))

AscomycotaAscomycota

PenicilliumPenicillium and and AspergillusAspergillus

Examples of Examples of conidiophores of other conidiophores of other

imperfect fungi or imperfect fungi or DeuteromycetesDeuteromycetes