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Fungi - Chapter 28 Characteristics – Relations with humans Basic life cycle 5 groups Ecological types Mutualism, Parasitism and the evolution of virulence Fungi: Opisthokonts (Heterotrophs) Chitin is also present in Animals, illustrating the close...

Fungi - Chapter 28 Characteristics – Relations with humans Basic life cycle 5 groups Ecological types Mutualism, Parasitism and the evolution of virulence Fungi: Opisthokonts (Heterotrophs) Chitin is also present in Animals, illustrating the close relationship Image from Smithsonian Human-Fungal Relations Wine, Shoyu, Tempeh, Cheese, Miso and Bread Roquefort, with it’s Penicillium roqueforti and the cow’s milk, camembert, with P. camemberti.  Human-Fungal Relations The Death Cap: Amanita phalloides Gills - white A famously deadly mushroom has no warning (aposomatic) coloration, but may have an odor that indicates the presence of its powerful toxin. Veil or See Nature, 27 Oct. 2005, p. “skirt” 1248, for Tim Lincoln’s “The whiff of danger.” Question? Why should Cup- like mushrooms be toxic? Is the volva toxin a chemical by-product or predator deterrent?  Human-fungal relations Fungal pathogens There are relatively few human fungal diseases Usually mild skin infections Trichophyton, Epidermophyton, and Microsporum Immunosurpressed individuals can be subject to severe versions of surface infections (thrush), or fungal pneumonia  Human-fungal relations Fungal pathogens There are relatively few human fungal diseases –High body temperature may act as a ‘fungal filter’ Human body temperature is declining! –Climate change possibly contributing to less effective filter Candida auris New deadly fungal disease – known for resistance to major antifungals (azoles) – Genetically distinct strains have appeared close together in time in three different continents àMaybe global warming created environments that favored heat-tolerant fungi able to host-shift to vertebrates Figure 1—figure supplement 1.. Distribution of Protsiv M, Ley C, Lankester J, Hastie T, Parsonnet J. temperature measures (oF) for each cohort: Decreasing human body temperature in the United States UAVCW (1860–1940), NHANES I (1971–1975) since the industrial revolution. Elife. 2020 Jan 7;9:e49555. and STRIDE (2007–2017). doi: 10.7554/eLife.49555. PMID: 31908267; PMCID: PMC6946399.  Human-fungal relations Fungal pathogens There are relatively few human fungal diseases –High body temperature may act as a ‘fungal filter’ Human body temperature is declining! –Climate change possibly contributing to less effective filter Candida auris New deadly fungal disease – known for resistance to major antifungals (azoles) – Genetically distinct strains have appeared close together in time in three different continents àMaybe global warming created environments that favored heat-tolerant fungi able to host-shift to vertebrates  Proposed scheme for the emergence of C. auris. Arturo Casadevall et al. mBio 2019; doi:10.1128/mBio.01397-19  Human-fungal relations Fungal drugs Fungi are involved in the industrial processing of more than 10 of the 20 most profitable products used in medicine. Three anti-cholesterol statins, Antibiotics (Penicillin, Cephalosporins) Immunosuppressant (cyclosporin A)  Fungal parasites Sometimes severe parasites of insects and often are responsible for severe plant diseases Dutch elm disease, caused by Ceratocystis Dung fly (Scatophaga sp.) infected ulmi, carried from tree to tree by a beetle. with the parasitic fungus Entomophthora sp.  Chestnut blight Sometimes severe parasites of insects and often are responsible for severe plant diseases Castanea dentata Original range of Chestnut American Phytopathological Society; APSnet 12/2000  Chestnut blight Originally described from New York City trees in 1904 Trees imported in the late 19th century likely the carrier of blight Castanea dentata with a Cryphonectria Japanese chestnut planted in 1876, parasitica canker Old Lyme, CT American Phytopathological Society; APSnet 12/2000  Chestnut blight Originally described from New York City trees in 1904 Trees imported in the late 19th century likely the carrier of blight Japanese chestnut planted in 1876, Old Lyme, CT Shoots sprout from the base of older trees, get canker and die American Phytopathological Society; APSnet 12/2000  Chestnut blight Originally described from New York City trees in 1904 Trees imported in the late 19th century likely the carrier of blight Downloaded from http://cshperspectives.cshlp.org/ on May 21, 2019 - Published by Cold Spring Harbor Laboratory Press Pure chestnut grove after blight infection, from library of Congress, in Powell Developinget al. 2019 Blight-Tolerant American Chestnut Trees Shoots sprout from the base of older trees, get canker and die Figure 2. Example of a pure American chestnut stand a few years after the chestnut blight went through. (Photo: A ghost forest of blighted American chestnuts in Virginia provided by the Library of Congress Prints and Photo- American Phytopathological Society;graphs APSnet 12/2000 Division.)  Chestnut blight Resistant Chestnut has been crossed to native trees and back- crossed, to retain as much native genetic background as possible Ø Hybrid programs started in 1921, ended and restarted multiple times Ø Most recently 1980’s Ø This design assumes that there are two loci affecting blight resistance Ø In fact there are multiple loci, making it highly unlikely that any hybrid offspring have all the resistance genes Ø Hybrid programs also lose some of the desired native traits American Phytopathological Society; APSnet 12/2000  Transformation of American chestnut Oxalic oxidase genes to reduce necrosis from wheat, other resistance genes from grapes, Chinese chestnut Genes can be inserted into otherwise 100% American Plant Science 228 (2014) 88–97 chestnut plants Contents lists available at ScienceDirect Rapid assays with oxalic acid, longer term assays with Plant Science innoculation with blight journal homepage: www.elsevier.com/locate/plantsci https://www.esf.edu/chestnut/ Transgenic American chestnuts show enhanced blight resistance and transmit the trait to T1 progeny Andrew E. Newhouse a , Linda D. Polin-McGuigan a , Kathleen A. Baier a , Kristia E.R. Valletta a,1 , William H. Rottmann b , Timothy J. Tschaplinski c , Charles A. Maynard a , William A. Powell a,∗ a State University of New York College of Environmental Science & Forestry, 1 Forestry Drive, Syracuse, NY 13210, USA b Arborgen Inc., Ridgeville, SC 29472, USA c Oak Ridge National Lab, 1 Bethel Valley Road, Oak Ridge, TN 37831, USA  Transformation of American chestnut Resistance that is passed on to offspring Plant Science 228 (2014) 88–97 AC = American chestnut Contents lists available at ScienceDirect Dar4 = American Plant Sciencechestnut transformed with wheat oxalase journal homepage: www.elsevier.com/locate/plantsci gene CC = Chinese chestnut Transgenic American chestnuts show enhanced blight resistance and transmit the trait to T1 progeny Andrew E. inoculation Fig. 7. Stem Newhouse resultsaover , Linda D.with two years Polin-McGuigan a , Kathleen two fungal lines. CC = Chinese A.= Darling4 chestnut, Dar4 a Baiertransgenic , American chestnut, AC = sus Lines show the average growth of cankers over 14 weeks, from approximately mid-June to late August. SG2 (sections A and B) is a moderately a,1 b c Kristia EP155 E.R. (C and Valletta , William D) is a more highly H.soRottmann virulent line, , Timothy overall canker sizes are larger on J. Tschaplinski EP155 inoculations. 2013 , (B and D) was apparently an u a a,∗ Charles A. Maynard inoculations; cankers in other, experiments William(not A. shown) Powell were smaller than expected as well, even on trees known to be very susceptible to blig a State University of New York College of Environmental Science & Forestry, 1 Forestry Drive, Syracuse, NY 13210, USA b Arborgen Inc., Ridgeville, SC 29472, USA c Oak Ridge National Lab, 1 Bethel Valley Road, Oak Ridge, TN 37831, USA allow a more precise analysis of transgene insertion and inheritance not, tend to initially grow faster and straig patterns. cultured counterparts. This does not mea Several individual transgenic plants from the T1 generation propagation should be abandoned altoge  Human-Fungal Relations Fungi “Eat” Our Toys and “Treasures” After visiting Belize in Central America, a scientist found one of his CD’s discolored and unreadable. The disk's aluminum and polycarbonate layers were riddled with fungus. Geotrichu candidum, a fungus that lives on plants and animals but occasionally infects the human respiratory tract, was isolated. Fungi are known to live on organics, plastics and polymers, but this is the first report of a CD being eaten by a fungus. X. Bosch, 2001 Spores bore holes in compact disks, rendering them useless. Nature Science Update, 27 June 2001 Primary ecological value of fungi  Fossil Fungi and Living Counterparts: (A-C and E-G) Fossil hyphae and Spores From the Ordovician, (D and H) Spores Formed by Related Living Fungi. Redecker et al., Science,Vol.289 ( 5486): 1920-1921. 15 Sep 2000  Fungal from the start.. Redecker et al., Science,Vol.289 ( 5486): 1920-1921. 15 Sep 2000  Characteristics Possess cell walls almost always lacking flagellae – Cell walls made of chitin Usually found in animals Mostly multicellular – Yeasts are unicellular fungi  Characteristics Chemoheterotrophs – Decomposers – Parasites – Predators – Mutualists Typically external digestion – Powerful enzymes can be toxic, carcinogenic, medicinal, yummy – Specialized in structure for absorption - Hyphae  Hyphae septate coencytic Arthrobotrys has nematocidal hyphae Hyphae attacking bacterial colony  Some Important Terms Spore Regarding Morphology Hypha Coenocytic hypha Septa in hypha Mycelium Septate hypha Haustorium Fungal hypha Dikaryon Raven et al, 1999 Beck et al., 1991 A mycelium is a network of hyphae  Worlds largest organism Amarillaria ostoyae – Identified from area of diseased trees (infects ponderosa pine) – Collected by ‘trapping’ with tongue depressors – DNA analyzed  Worlds largest organism Amarillaria ostoyae – 3.4 miles in diameter – 2,200 acres – ~100 tons – ~2,400 years old  Fungal life cycle Asexual reproduction (in good times) – Haploid mycelium produces spores – Which develop into haploid mycelia Sexual reproduction (usually in response to stress) – Meiosis produces zoospores, not gametes – Genetically distinct mycelia producing gametangia Fungal life cycle  Sexual reproduction has two stages Fusion of cells - plasmogamy – Cells have 2 or more haploid nuclei Dikaryotic (2) or heterokaryotic (>1) cells Fusion of nuclei - karyogamy – Produces diploid nuclei – Quickly followed by haploid spores produced by meiosis Classification of the Fungi Fungal Phylogeny: Rapidly Changing Ideas Chitridomycota have flagellated gametes  Chytridiomycota (about 800 species) These were once included in the Protista. A predominantly aquatic group (some in soils) of the most ancestral fungi, with cell walls of chitin and energy storage as glycogen. Chytrid, consuming Above: diploid Euglena. sporangia Raven et al, 1999 Chytridiomycota Life Cycle Chytrids vs Oomycota Chytrids Are Implicated in the Global Decline of amphibians Daszak P, Berger L, Cunningham A, Hyatt A, Green D, Speare R. Emerging Infectious Diseases and Amphibian Population Declines. Emerg Infect Dis  Amphibian declines Several factors contribute to the decline and extinction of many species – habitat loss – environmental contaminants, – UV-B irradiation – Parasites Batrachochytrium dendrobatidis (or Bd)  Batrachochytrium dendrobatidis Some amphibian populations crashed in a single season, in undisturbed habitat B. dendrobatidis identified in 1998 – Berger L et al. (1998) PNAS USA 95: 9031-6 Koch’s postulates – Bd was isolated from sick frogs – grown in pure culture – used to re-infect other frogs that became ill with the same disease – re-isolated from those new individuals Doesn’t explain why it’s pathogenic, or where it came from http://hosts.cce.cornell.edu/mushroom_blog/?p=104  Batrachochytrium dendrobatidis ‘Out of Africa’ – Xenopus laevis - model species for developmental biology – Native to Southern Africa, exported worldwide when a pregnancy test using live Xenopus was developed in 1934 – Like Spock, it doesn’t die, but acts as a carrier Earliest ranid B. dendrobatidis infection observed on African Xenopus specimen from 1938 Emerging Infectious Diseases www.cdc.gov/eid Vol. 10, No. 12, December 2004 Batrachochytrium dendrobatidis  Fig. 1 Global distribution of chytridiomycosis-associated amphibian species declines. Ben C. Scheele et al. Science 2019;363:1459-1463 Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works  Zygomycota Includes common molds Coencytic hyphae Sporangium develops through meiosis to disperse haploid gametes The heterokaryotic stage is short  Zygomycota (1060 species) A flower fly killed by the The common bread mold, zygomycete, Rhizopus, growing on Entomothora muscae. strawberries. Raven et al., 1999 Zygomycota:Rhizopus (Bread Mold) Life Cycle  Spore Dispersal, Clever Mechanisms The zygomycete, Pilobolus, grows on dung and eventually produces a sporangiospore with a height of 5-15 mm. These are positively phototrophic, and by focusing light, osmotic pressure builds and propels the sporangia at 50 kph to a distance of 6 m. To 6 meters Raven et al., 1999  Spore Dispersal, Clever Mechanisms The zygomycete, Pilobolus, grows on dung and eventually produces a sporangiospore with a height of 5-15 mm. These are positively phototrophic, and by focusing light, osmotic pressure builds and propels the sporangia at 50 kph to a distance of 6 m.  Glomeromycota: Arbuscular Mycorrhizae Small, Ancient Group: ~ 150 species described The most common form of relationship found in most land plants, endomycorrhizae penetrate the cells of plants but also extend several centimeters into the soil. Left: Glomus versiform, an endomycorrhizae growing in a leek root; Below: Glomus etunicatum in a maple root Raven et al., 1999 Mycorrhizae  Ectomycorrhizae Most land plants have mycorrhizae Pine roots with yellow-brown Nine-month growth of pine Pisolithus (left), white seedlings with and without Rhizopagan (center) and mycorrhizae without mycorrhizal fungus Raven et al, 1999  Ectomycorrhizae Below: transverse section of Pinus root showing ectomycorrhizae penetrating between epidermal and cortical cells Ectomycorrhizae on 4 cm. pine seedling. Longitudinal section of birch root. Raven et al., 1999  Mycorrhizae Can increase surface area, absorption of nutrients, particularly phosphorus  Ascomycota: (32,300 species) Beck et al., 1991 Hemiascomycetes: Yeast, showing budding, and characteristic clumping, perhaps due to their derivation from multicellular ancestors. The common morel, Morchella esculenta, a prized edible fungus. Cup fungi Raven and Johnson, 1999  Ascomycota Life Cycle Zygote Tolypocladium niveum = inflatum and Cordyceps subsessilis The ascomycete that produces the drug cyclosporin  Ascomycota: Asexual Spores, Conidia Conidia are the characteristic asexual spores of the ascomycetes. Ergot: the Cause of St. Anthony’s Fire or Ergotism Ergots Clavipes purpurae, infecting rye grain, Secale cereale.  Claviceps purpurea Alkaloid producing, rye infecting fungus which replaces the grain with a hard mycelial mat (sclerotium, or ergot) causes the plant disease called ergot. This structure contains lysergic acid amide, a precursor of lysergic acid diethylamide (LSD). Humans or animals eating the infected grain develop a disease called ergotism, accompanied by gangrene, nervous spasms, psychotic delusions and convulsions. The Middle Ages saw widespread outbreaks and many affected individuals were accused of witchcraft. http://frost.ca.uky.edu/agripedia/ppa652/mycotlec.htm  Beauveria bassiana Entomopathogenic ascomycete – Conidia can be incorporated into bioinsecticides that are less toxic than chemical insecticides  Beauveria bassiana Conidia attach, penetrate the cuticle, and grow from within  Pseudogymnoascus destructans White-nose syndrome Fungal infection in bats first observed in 2006 Cold-loving fungus attacks hibernating bats – Many populations reduced by over 90% – Estimated to have killed over 5.7 million bats in US Raises metabolism and leads to flight and starvation  Basidiomycota (22,244 Species) The mushroom, Hygrocybe aurantiospledens, is made of densely packed mycelium. Highly toxic Amanita muscaria, the fly agaric Raven et al., 1999 Basidiomycota Life Cycle: The Basidium Basidiospores on Basidia Gills, section Four spores on each basidium, shown in mass and in close-up on the left. Raven et al., 1999 Basidiomycota: Puffballs Below: Earth Star, Geastrum saccatum, showing outer layers folding back to raise the spore mass above the ground. “Giant” puffballs can make up to 6 trillion spores – enough to circle the globe! Raven et al., 1999  Carnivorous Fungi Pleutoyus osteratus immobilizes Nematode Fungal ring nematodes with a narcotic, then invades their body with hyphae and consumes nutrients Arthrobotrys anchonia, a soil dwelling fungus catching a nematode, showing a double capture with three celled- rings that rapidly swell when stimulated. Raven and Johnson, 1999 Purves et al, 1998  Parasitic Fungi Fungal spores colonize hosts through ingestion or penetration of thin layers, such as along joints. The fungus absorbs the organic and inorganic nutrients from the insect’s body, eventually killing it, after which the fungus produces a fruiting body and new spores. This moth cadaver was photographed in Costa Rica  Other Basidiomycetes The netted stinkhorn, The white birds-nest fungus, Calostoma cinnabarina, Crucibulum laeve, showing the releases spores in a sticky, white “eggs” that contain the foul-smelling mass on the basidiospores that get splashed out top surface. Flies and scattered by raindrops. distribute spores. Raven et al., 1999  Lichens: Algae + Fungi Symbiosis British soldier, Cladonia cristatella Acarospora evolutum on rock in Arizona. “Reindeer moss,” Witches hair, Cladonia subtenuis Alectoria sarmentosa Peltigera leucophlebia http://www.lichen.com/home.html Raven et al., 1999  Lichens: Some Facts and Reproduction Lichens grow in habitats too harsh or limited for most other organisms. Lichens produce many unique biochemical compounds. Reproduction is tricky for a compound organism. Some lichens make non-sexual reproductive packages of photosynthetic and fungal cells, soredia, which are tiny projections from the surface of the lichen that can break off easily and grow into a new lichen. Most lichens are brittle when dry, and fragment  Mutualism and parasitism Symbiosis – Mutualism – Commensalism – Amensalism – Parasitism  lichens Associations of fungi and algae or cyanobacteria  lichens Trading food and possibly nitrogen for suitable environment  lichens Algae are held in place by hyphae Soredia: Asexual Reproduction of Lichens  Symbiosis between leafcutter ants and fungi Attine ants rarely eat what they forage – Tend fungal gardens of the Family Lepiotaceae Symbiosis between leafcutter ants and fungi Symbiosis between leafcutter ants and fungi A quadripartite symbiosis Leafcutter ants Fungus gardens of Lepiotaceae Escovopsis, a parasitic fungus Pseudonocardia, an actinomycete bacterium Science 2006: 311. no. 5757, pp. 81 - 83. Coevolved Crypts and Exocrine Glands Support Mutualistic Bacteria in Fungus-Growing Ants. Cameron R. Currie, Michael Poulsen, John Mendenhall, Jacobus J. Boomsma, Johan Billen  Bacterial symbiosis is ancient, shortly follows fungus gardening Genus level phylogeny of fungus-growing ants [adapted from (15, 16)] illustrating the location and modifications of the exoskeleton for maintaining the mutualistic bacteria. The origin of fungus growing by attine ants and the leaf-cutters is represented by the Lepiotaceous mushroom and the worker carrying a leaf fragment, respectively. Major groups of attine ants are depicted by colored boxes, illustrating the phylogenetically basal genera in the "paleo-attines" (red), the "lower" attine genera (brown), the "higher" attines (green), and the leaf- cutters (blue). (Column A) Photographs illustrate the location of the bacterium under the forelegs in the paleo- attines, on the propleural plates in the "lower" and "higher" attines, the presence all over the integument in the genus Acromyrmex, and absence on the cuticle in Atta. (Column B) SEM micrographs of the location of the bacterium, under the forelegs in Apterostigma and on the propleural plates in other groups. (Column C) SEM micrograph close-ups for the structures presented in (B), showing the specific structural modifications for different groups of fungus-growing ants. Presence of foveae (star) and tubercles (triangle) all over the body in some species within a genus are indicated by the corresponding symbol above the branch on the phylogeny.  Parasitism Small symbionts that harm a host - can’t kill individually, but can in aggregate Parasites can evolve rapidly Parasites may drive other kinds of rapid evolution  Parasitism Small symbionts that harm a host - can’t kill individually, but can in aggregate Parasites can evolve rapidly – Hosts need to match evolutionary adaptations in parasites – Adaptive immune system Somatic hypermutation Parasites may drive other kinds of rapid evolution – Sexual reproduction – whysex.mov on OneDrive why sex.mov Your genes can be matched with mutations for resistance Meiosis / recombination can create new combinations of genes in gametes  Virulence The harmfulness to a host – Mortality rate – Often proportional to replication rate  Virulence Myths about virulence may have contributed to covid deaths “the most virulent viruses will be more likely to kill their hosts before the virus can spread. In contrast, the milder versions of the virus will wreak less damage to their host and thus will survive over the longer time span needed to spread from one person to another. Hence the rate of transmission will trend downward, as will the severity of the virus. It is a form of natural selection. R. Epstein, Hoover Inst. 3/2020  Virulence Myths about virulence may have contributed to covid deaths In that same paper, Epstein predicted that Covid would kill a total of 500 people in the US, and also claimed that HIV evolved to a milder form in the 1990’s  Evolution of virulence Harmfulness of parasite, often due to replication rate or production of toxins Replication rate for parasites R p = SβL – S is the density of susceptible individuals – b is the transmission rate Proportion of times interactions lead to infections – L is the infectious period  Evolution of virulence Replication rate for parasites R p = SβL – S is the density of susceptible individuals – b is the transmission rate Proportion of times interactions lead to infections – L is the infectious period Infectious period depends on three quantities – Natural mortality rate – Mortality due to parasite – Length of infection  Evolution of virulence Replication rate for parasites R p = SβL – S is the density of susceptible individuals – b is the transmission rate Proportion of times interactions lead to infections – L is the infectious period Infectious period depends on three quantities – Natural mortality rate – Mortality due to parasite Virulence – Length of infection  1. A disease that is hard to transmit will.. A. Require longer infectious periods to persist B. Survive well in small populations C. Have a higher Rp R p = SβL S is the density of susceptible individuals b is the transmission rate Proportion of times interactions lead to infections L is the infectious period 2. How does an increase in population size favor or disfavor higher virulence? A. Disfavor because it’s easier to find a new host B. Favor because the infectious period can shrink due to virulence and R is still greater than 1 C. Favor because there the transmission rate will go up R p = SβL S is the density of susceptible individuals b is the transmission rate Proportion of times interactions lead to infections L is the infectious period Is virulence correlated with transmission? R p = SβL – High virulence can shorten infectious period by killing host – High virulence can lengthen infectious period by preventing ‘passing’ (eliminating) the parasite – Any process that removes transmission costs of virulence allows it to increase  (Real-Life) R is not a fixed property Depends on the population susceptible pool – Lower if more people had the disease and recovered – Lower if more people are vaccinated Depends on proportion of asymptomatic or mild cases – Increases Length of infectuous period Depends on multiple factors that are behavior dependent – How dense is the population – How frequent is contact, are people masked Oryctolagus cunniculus  myxoma virus Released in 1951, Epidemic killed 99.9% of bunnies Second epidemic only killed 70% Third only 50% Myxoma is still often lethal in Australian rabbits Take homes à Virulence evolves, BUT, parasites don’t necessarily evolve to low virulence Many diseases never evolved to low virulence Smallpox, HIV, TB Tradeoff between competition within and among hosts Too much virulence and host dies before it can infect another Too little virulence and the parasite may – Lose out in competition with other strains within a host (often virulence is often related to replication rate) – Let the host recover eliminate the parasite completely  PBS Evolution Part 4 of 7 Paul Ewald on evolution of virulence in Cholera – https://youtu.be/w122ffNceo0 (PBS series on Evolution) – Watch from 27:02 to 32:15 (whole episode is interesting tho) Waterborne diseases don’t require a healthy host to spread Different transmission patterns lead to different optimal virulence levels of transmission and virulence are coupled  Take home messages Fungi are not plants Unique sexual reproduction through plasmogamy and karyogamy Often severe plant parasites Body plan / fruiting structures define groups Value as decomposers and mutualists Kinds of symbioses Parasitism – What factors favor evolution of resistance? – What factors favor evolution of virulence?