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Announcements

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 www.usask.ca Biology Class notes -- Biol 204 – kaminskyj 2004 lectures. Cytoplasmic migration in tip growth. Fungal cell walls. Thin Fiber reinforced

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Announcements

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  1. 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 • www.usask.ca • Biology • Class notes -- Biol 204 – kaminskyj • 2004 lectures

  2. Cytoplasmic migrationin tip growth

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

  4. Wall vesicle exocytosis at Saprolegniahyphal tip

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

  6. Hydrophobin rodlets

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

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

  9. Protistan fungi – three taxa • Myxomycota – “acellular” slime molds

  10. Dictyosteliomycota – cellular slime molds

  11. Plasmodiophoromycota – endoparasitic slime molds

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

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

  14. 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

  15. Myxomycete plasmodia

  16. Physarum – nuclear behaviour

  17. Myxomycete plasmodia can distinguish nonself and self

  18. Physarum on heterogeneous substrate – food preference

  19. Myxomycete spores in sporangia Physarum Stemonitis

  20. Myxomycete spore walls contain peptidoglycan

  21. Dictyosteliomycota – “cellular” slime molds

  22. Dictyostelium Aggregation of amoebae uses chemical signals

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

  24. Dictyostelium spore walls contain cellulose niko.unl.edu

  25. Plasmodiophoromycota – endoparasitic slime molds

  26. Plasmodiophora in cabbage root hair

  27. Plasmodiophora resting spores

  28. Chromistan fungi – Oomycetes • Saprobes, parasites/pathogens

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

  30. Saprophytes and facultative parasites Asexual zoospores of Achlya biusexualis

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

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

  33. 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

  34. Saprophyte attachment and germination

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

  36. Parasitism The joy of slime

  37. Oomycetes as plant pathogens Phytophthora infestans www.scisoc.org/feature/lateblit/ chapter1/epidemic.htm

  38. 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

  39. Phytophthora sporangia and zoospores Wet soils -> zoospores Drier soils -> direct germination www.scisoc.org/feature/lateblit/chapter1/epidemic.htm

  40. Social consequences of Phytophthora infestans riots, eviction, emigration

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

  42. Next time:it’s not easy being green

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