BIOLOGY 3404F EVOLUTION OF PLANTS Fall 2008 Lecture 6 Tuesday October 7 Chapter 14, Fungi (part II) Symbioses.

BIOLOGY 3404FEVOLUTION OF PLANTS

Fall 2008

Lecture 6Tuesday 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

Left, Termitomyces; above, the fungus garden of an attine ant colony

www.sasionline.org/ attafldtrp/Atta0.html

www2.thu.edu.tw/~biodiver/ variety/fungus/3-29.htm

Fungal Predators of Bacteria

Photo: G.L. Barron