Transcript Lecture 6
BIOLOGY 3404F EVOLUTION OF PLANTS Fall 2008 Lecture 6 Tuesday October 7 Chapter 14, Fungi (part II) Symbioses Fungal Symbioses • With phototrophs: lichens, mycorrhizae, endophytes, disease [remember, symbiosis means living together, not necessarily happily for both partners] • With animals: human/veterinary diseases, “diseases” (parasitoids) of arthropods, nematodes and microfauna of soil, ant-garden and termite-garden fungi • With heterotrophic bacteria: endosymbionts, consortia, and predation Lichens • “Lichenomycota” or “Mycophycomycota”, but are a completely fictitious group • Lichens have evolved many times in at least 8 orders in 2 classes of Ascomycota (most species are Lecanorales of Lecanoromycetes) and 2 orders in Agaricomycetes of Basidiomycota (a few species in each of Agaricales and Aphyllophorales) Gargas et al. (1995) Mycorrhizae • Myco = fungus; rhiza = root; extra r as a linker • (Usually) Mutualistic symbiosis between fungi and roots or other underground organs of plants • Apparently identical fungi form associations with leaves and stems of some Bryophyta • Term mycorrhiza refers to the association or the structure, not to the fungus or the plant • We will recognize two main types: endo & ecto Endomycorrhzae (also called Arbuscular Mycorrhizae or AM; or Vesicular-A M, VAM) • • • • • These are formed by Glomeromycota in association with a great diversity of green plants, predominantly herbaceous, or tropical woody plants Fungal hyphae penetrate cell walls (but not plasmalemma) of root cortex Within root cells, form shrubby arbuscules for nutrient transfer and sometimes oily vesicles for storage/survival Form spores in soil or dead roots – no fruiting bodies Particularly important in delivery of Phosphorus Fossil endomycorrhiza from Triassic (~220 MYA) in Antarctica (when it was warmer there) Ectomycorrhizae (ECM) • These are formed by various groups of Basidiomycota (~90% are in Agaricomycetes) and a few Ascomycota, in association with predominantly temperate woody plants: e.g., Pinaceae, Betulaceae, Fagaceae • Hyphae do not (usually) penetrate cell walls of plant roots, but form a mantle over the root then a network of hyphae between cortex cells called a Hartig Net • Form large sexual fruiting bodies, above or below ground • Particularly important in delivery of Nitrogen, but also water, and in protection from root disease Plant Diseases • Billions of $ losses worldwide annually • Take Bio-318b (Mycology) or Bio-418a (Plant-Microbe Interactions) Diseases of Animals, including Humans • Many superficial skin disorders, but also major invasive infections of muscle, bone, lungs, and other organs • Some are opportunistic – taking advantage of patients exposed during surgery, and with weakened immune systems; others are aggressive pathogens • 2 of the major killers of persons with AIDS are fungal infections – of brain or lungs • Few courses on Medical Mycology, but see http://www.doctorfungus.org/ Fungus-gardening Ants & Termites • These two associations arose independently in South America and Africa • In both, the arthropods harvest organic matter (leaves, twigs, fruits) and “feed” this to the fungus, which converts it to much more nutritious food for their hosts • Neither partner can live without the other • Fungus-gardening ants are major agricultural pests in tropical America www.sasionline.org/ attafldtrp/Atta0.html www2.thu.edu.tw/~biodiver/ variety/fungus/3-29.htm Left, Termitomyces; above, the fungus garden of an attine ant colony Fungal Predators of Bacteria Photo: G.L. Barron