EBIO 3400 1st Edition Lecture 13Outline of Last Lecture I. FungiOutline of Current Lecture II. BasidiomycotaIII. Importance of Mycorrhizal fungiIV. EctomycorrhizaeV. GlomeromycotaVI. AscomycotaVII. Endophytic FungiCurrent LectureI. BasidiomycotaTypes: MushroomsShelf fungiPuffballsJelly fungi‘Death Cap’ Amanita phalloides‘Destroying Angel’ Amanita virosa Life cycle: involves transitions among n, n + n, and 2n. The underground secondary mycelia of some mushrooms form mycorrhizae with tree rootsII. Importance of Mycorrhizal fungiAlmost all plants form root-fungus associations (mycorrhizae) that are mutualistic symbiosesThis is a mutualism:1) The plant gives the fungus organic molecules and the fungus takes up nutrients (e.g. P and N) for the plant and protects it from some pathogens2) The basic idea behind mycorrhizae = increase in surface area and zone of exploitation (hyphae can extend much further than root hairs) to take up nutrients. Also increased enzymatic abilitiesA. The two different kinds are observed: 1. Ectomycorrhizae: colonize the rhizoplaneThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Fungal mycelia don’t penetrate root cells2. Endomycorrhizae: form more intimate association in which fungi penetrate plantcells- Form an arbuscle within a root cell- Vesicular-arbuscular mycorrhizae (VAM) Mycorrhizae greatly enhance the plant’s uptake of water and minerals- Also help distribute organic substances among different plantsIII. Ectomycorrhizae- Ectomycorrhizal fungi are mostly Basidiomycetes (the rest are Ascomycetes). Many of the large mushrooms in forests are the sexual stage of ectomycorrhizal fungi….- All gymnosperms (pines, spruce etc…) form ectomycorrhizal relationships- Many deciduous trees do as well (e.g. Oaks, Beech etc…)- Some smaller plants such as sedges form ectomycorrhizae also- Most ectomycorrhizal fungi can be grown in pure culture away from their plant hosts. - Most have saprotrophic abilities and are able to breakdown proteins etc. obtaining N for themselves and their host plants. Two main functions are to:1. Increase surface area and enzymatic abilities for nutrient uptake2. Protect the root and increase its longevity IV. Glomeromycota Mostly arbuscular mycorrhizae (AM) = “endomycorrhizae”- Intimate mutualistic networks of connections with plant roots, exchanging minerals for plant sugars Arbuscular Mycorrhizae (AM) are Glomeromycota and are associated with over 70% of land plants - also called “Endomychorrizae” (because arbuscules are intracellular)Found in most plant families, but rare in weedy groups like the mustards Why can’t AM fungi be grown in pure culture?Co-evolved with their host plants for 100+ million years - probably have lost some physiological (saprophytic) functions. Were not thought until recently to be able to breakdown soil organic matterV. AscomycotaFood moldsMildewsCup fungiMorelsMany types of yeastSome mychorrizae- Hyphae are septate (cells separated by crosswalls)- Characteristic sexual structure = Ascus- Very common in soils- Many forms have never been grown in lab- Several large new groups (at the class and sub-phylum level) of fungi discovered VI. Endophytic FungiEndophytic fungi are “non-mycorrhizal” fungi that live in almost all plants that have been examined (roots and tops)…. Most are AscomycetesMost endophytic fungi are thought to be mutualistic or mildly parasitic; best studied in grasses and sedges. They help the plant by: 1) Increasing drought and heat tolerance, 2) Increasing vegetative growth, and 3) Producing toxins that inhibit herbivores (including cows*, sheep*, humans* and insects)*Grazing animals (and humans) are adversely affected because of #3 (e.g. fescue toxicosis in cows and ryegrass staggers in sheep). Defensive endophytes can affect humans when they eat the seeds (grain) of grasses infected with endophytes. We call this disease, but to the grass it is a beneficial relationship- Example of a “disease” caused by fungal endophytes: Ergot, Claviceps purpurea (Ascomycete)- Ergot has played a notorious role in human history. Endophyte of grasses such as wheat, barley, oats, but most readily attacks rye and triticale. It often totally replaces the grain (seed) with seed-shaped sclerotia (thick masses of hyphae and spores)- Ergot symptoms: burning sensation in feet and hands, convulsions, gangrene, delirium, hallucinations, bizarre behavior, induction of labor in pregnant women- -Hallucinogens (alkaloids related to lysergic acid) constricts blood vessels and increase contraction of uterus- More often afflicts livestock these days - feeding spoiled grain to
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