Announcements Next week – no lab Wednesday evening –Lab closes 5pm for Biol 203 exam –Lab will be open Tuesday 5-10 pm Biol 204 notes – –Biology –Class notes -- Biol 204 – kaminskyj –2004 lectures

Cytoplasmic migration in tip growth

Fungal cell walls Thin Fiber reinforced –Taxonomically relevant Plastic/extensible at tip Elastic/inextensible at maturity

Wall vesicle exocytosis at Saprolegnia hyphal tip

Hydrophobins Without hydrophobins, hyphae cannot break through the surface tension of water Hydrophobins are essential for mold sporulation and mushroom formation

Hydrophobin rodlets

Diverse features of Protista (P), Chromista (C), Eumycota (F) Walls in vegetative phase –Lacking (P) –Having (C, F)

Diverse features of Protista (P), Chromista (C), Eumycota (F) Walls in vegetative phase Mode of nutrition (always heterotrophic) –Ingestive (P) –Absorptive (C, F)

Protistan fungi – three taxa Myxomycota – “acellular” slime molds

Dictyosteliomycota – cellular slime molds

Plasmodiophoromycota – endoparasitic slime molds

Common features of Protistan fungi Nutrition by ingestion –Possible because vegetative stages do not have walls

Common features of Protistan fungi Nutrition by ingestion Lifestyle –Individual cells or colonies –Dictyosteliomycota -> Alternating individual and colonial stges

Common features of Protistan fungi Nutrition by ingestion Lifestyle –Individual cells or colonies –Alternating individual and colonial stges (Dictyosteliomycota) Sexual reproduction by spore formation –Only walled stage –Fibrils of peptidoglycan, cellulose, chitin

Myxomycete plasmodia

Physarum – nuclear behaviour

Myxomycete plasmodia can distinguish nonself and self

Physarum on heterogeneous substrate – food preference

Myxomycete spores in sporangia Physarum Stemonitis

Myxomycete spore walls contain peptidoglycan

Dictyosteliomycota – “cellular” slime molds

Dictyostelium Aggregation of amoebae uses chemical signals

Dictyostelium cell differentiation model system www2.mrc-lmb.cam.ac.uk

Dictyostelium spore walls contain cellulose niko.unl.edu

Plasmodiophoromycota – endoparasitic slime molds

Plasmodiophora in cabbage root hair

Plasmodiophora resting spores

Chromistan fungi – Oomycetes Saprobes, parasites/pathogens

Chromistan fungi – Oomycetes Saprobes, parasites/pathogens Obligate parasites – must have a living host to complete life cycle – aggressive Facultative parasites – parasitism is optional – less aggressive

Saprophytes and facultative parasites Asexual zoospores of Achlya biusexualis

Attachment, infection, colonization In nature, infective stage is motile flagellated zoospores – primary and secondary Heterokont flagella Zoospores find a food source by chemotaxis

Attachment, infection, colonization In nature, infective stage is motile flagellated zoospores – primary and secondary Heterokont flagella Zoospores locate a food source by chemotaxis

Attachment, infection, colonization In nature, infective stage is motile flagellated zoospores – primary and secondary Zoospores find food a source by chemotaxis Attachment is followed by shedding flagella Infection requires growth of a penetrating hypha

Saprophyte attachment and germination

1° zoospore 1° cyst 2° zoospore 2° cyst germination and infection Morphology and parasitic aggressiveness

Parasitism The joy of slime

Oomycetes as plant pathogens Phytophthora infestans chapter1/epidemic.htm

Understanding late blight disease attributed to –excess water in the plants, –effects of the newly introduced steam locomotives Reverend M.J. Berkeley –Early 1850’s –Fungal pathogen

Phytophthora sporangia and zoospores Drier soils -> direct germination Wet soils -> zoospores

Social consequences of Phytophthora infestans riots, eviction, emigration

Sexual spores of oomycetes Major significance in genetic recombination -> development of new pathotypes

Next time: it’s not easy being green