Lecture 17. Fungi1. How do fungi fit onto the eukaryotic tree?- Opistokonts: monophyletic group: the unplaced fungi have been shown to root to a common ancestor that gave rise to the remaining fungal bodes, while the protist lineage share a common acncestor with the all eukaryotes.- Common ancestor is a single cell eukaryote.- Fungus is more closely related to animals than plants2. “Unifying” fungal traits- A number of different cell types:o Unicellular (yeast) or multicellular (most)o Multicellular all has unicellular stages (Earth star fungus)o Hyphae (filamentous) -> Septate (Septa) or Coenocytic (no septa) - Cell walls with chitino The same material to the bug-crust-body and crab shell body -> closer related to the animal than the plant.o Give structure to fungus. - Dikaryon stage (only in septate fungi)o Hyphae that has two haploid nuclei.o Dikaryons form from the fusion of two haploid mating strains. (during sexual reproduction)o Many sexually reproducing fungi undergo a stage in whichtwo haploid nuclei coexist in a single cell; dikaryon for some period of time before fusing to make a diploid nucleus. o Rare difference between male & female: mating type (+), (-); same type doesn’t mate.- Nuclear mitosiso The nucleus replicates and forms two copies, but the cell remains a single unit; not cell division.o Mitosis divides the nucleus but not the hyphae itself. o The nuclear membrane does not split apart in process of mitosis. Instead, mitosis takes place in nucleus.- Sexual & asexual reproductiono Fungi use sexual & asexual reproduction (most asexual, sexual reproduction is fast.) o Sexual stages are used to identify fungus, making it hard to finalize the fungal phylogeny.o Plasmogany: fusion of cytoplasm from different individualso Karyogamy: nuclei fusion: zygote- Heterotrophs: Fungal digestiono External digestiono Creep digestive enzyme. After the enzyme digested the food, fungus absorbs this nutritious enzyme.o Reflect fungal body plan Unicellular fungi have the largest surface of the volume ration of any fungus. They maximize the surface for absorbing the nutrition. Multicellular fungi: mass of hyphae (mycelium), the nutrition need to be dissolved in water to be absorbed: Fungi is the early plant completely dependent on water. 3. Fungal bodyA. Hyphae (singular hypha)- Long, slender filaments: may be packed together to form complex structure, such as a mushroom.- Cytoplasm moves throughout hyphae: fungal hyphae may grow very rapidly.B. Septa (singular septum)- Not complete barrier: it’s single long large multi-nuclei.- Long chains of cells joined end-to-end and divided by cross-walls.(1) Septate fungi: many divisions by septa.(2) Coenocytic fungi: no septa at all: cell separation is not important in fungus. It allow fungus to grow rapidly with water: because of movement of cytoplasm.C. Mycelium (Group hyphae)- Mass of connected hyphae joined together.- Can form different functional group.- Digestive structure + reproductive structure.4. Mutualists- Exchange of good. - Both benefit- With photobacterial species: fungi provide home for bacteria andabsorb nutrient. The photosynthetic bacteria produce sugar to feed fungus.- Ex) Micorrhizal fungi5. Saprophytes- Eat dead: decomposers.- Cleans up: digest wood.- Eat things what hard to digest; cellulose6. Parasites- Eat living things.- Ex) Athletes foot, ringworm, chestnut blight- Hard to treat: host cell is damaged as well.7. Fungi TreeA. Microsporidia (parasite in insect and fish)- Small eukaryotes found on earth- Inside animal cells.- Tend to lead to chronic wasting disease; weight loss, decreased life span.- Host cells are penetrated when microsporidia injects in its polar tube into the host cell. After injection, the host cell reproduces the microsporidia, like virus.- Lack true mitochondria: early branch of eukaryotic tree- DNA free structure: mitosome: membrane identical of mitochondria. Derived from the ancestor to mitochondria. -> they don’t need mitochondria because they are parasitic.B. Chytrids- Paraphyletic- Aquatic with unicellular flagellated stages.- Coenocytic- Chitin- Do not have dikaryotic stage- Parasitic (killing amphibians) or mutualistic: auatic zoospore on amphibian skin.- Produce haploid gametes in sexual reproduction or diploid zoospores (motile spore) in asexual reproduction.C. Zygomycetes- Paraphyletic- Terrestrial fungi: saprophytes or parasites- Grow on bread- Coenocytic.- Asexual reproduction is more common, but production of zygospore from sexual reproduction unifies this group.D. Glomeromycetes- Mycorrhizae: mutualistic relationship with plants. Hyphae grows inside of root cell (arbuscular mycorrhizae)- Coenocytic: no mycellium- Monophyletic, even though there is no evidence of sexual reproduction- Lack zygosporesE. Ascomycetes (septate group)- 75% of known species- Economically important: cup fungi, yeast, common molds (including penicillin), truffles, morels, cheese molds, plant pathogens (chestnut blight and dutch elm disease).- Cup fungi- Truffle - Morels- Attributes to production of wine, beer, bread. - Forms ascospores (from asus= basidiopspore/ basidia) by sexual production.- Goes through asexual reproduction as well: yeast within this group generally reproduce asexually by budding (self division) and break glucose down to carbon dioxide.- Dikaryon stages: short- Bear their spore in cup structures.F. Basidiomycetes (septate group)- Wild, edible Mushroom - Exception: Truffles, and morels; they are ascomycetes.- Ex) Puffballs, Mushroom, Bracket fungus: a secondary (dikaryotic) mycelium.- Spores arise underneath a basidiocarp.- 40 million spores in a hour.- Largest fungus species. * Ascomycetes and basidiomycetes are distinguished by whethersexual spores born out of cups or
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