How we study diversity: phylogenetic tree. Fungi vs. Animals. Fungi vs. Plants 3/8/18

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1 Ya Yang How we study diversity: phylogenetic tree Office Hours: Monday AM 714 Biological Sciences Center Fungi are eukaryotic organisms that are more closely related to animals than to plants Fungi vs. Animals Red algae Green plants Brown algae Both are chemoheterotrophs: obtain both energy and carbon from organic material Animals eat their food and digest it, and absorb nutrients from the gut Fungi live in their food. Some fungi obtain nutrition from living organisms such as mycorrhizae and lichens. Others are saprobes - organisms that feed on dead organic material. Because fungi have a rigid cell wall, that cannot engulf food as animal cells can. They secrete digestive enzymes and transport the products (sugars, amino acids, peptides) through the plasma membrane. All Living Organisms Fungi vs. Plants Most fungi develop branching filaments known as hyphae. Both have cell walls but the fungi use chitin (polymer of acetylglucosamine) for cell walls while plants use cellulose (polymer of glucose) Septate (has partitions) Aseptate (lacking partitions) Mycelium - branching network of hyphae Plants are photoautotropic, fungi are chemoheterotrophic Very high surface-to-volume ratio 1

2 Hyphae allow the fungus to grow towards food sources by chemotropism (remember that a tropism is oriented growth in response to a directional signal). Hyphae grow by tip growth Red color indicates Chitin synthase Fungi are diverse 0.15 million described species. Estimated 1.5 million total species Dashed line indicates uncertainty on branching pattern Life cycle Life cycle of fungi Haploid: 1n, having one set of chromosomes. Diploid: 2n Two key points in life cycle Fertilization 1n à 2n Meiosis 2n à 1n Some fungi can reproduce asexually Spore: a reproductive cell, usually unicellular, capable of developing into an adult without fusion with another cell Fungi can reproduce both sexually and asexually Fertilization consists of two stages: plasmogamy and karyogamy Alternatively, by budding or fragmentation 2

3 Microsporidia are highly reduced, parasitic fungi Obligate intracellular parasites of many animal species, including human ~1,500 species Among the smallest eukaryotes known. Polar tube used to infect host Chytrids: fungi with swimming reproductive cells; mostly aquatic mitospores (zoospores) mitosporangium asexual loop meiospores (zoospores) Karyogamy (fusion of nuclei) and meiosis gametes Plasmogamy zygote resting meiosporangium Chytrids are diverse ~1,000 named species Aseptate Amphibian diseases caused by chytrids Phylum Zygomycota 1,100 zygomycete species, including the black bread mold Phylum Zygomycota - fungi with zygospores, aseptate hyphae, mitosporangia and lack of swimming cells. Zygomyces vs. chytrids Smilarity: both meiospores and mitospores are made in sporangia the meiosporagium is a resting phase both make aseptate hyphae Differences: in the Zygomycota neither meiospores nor mitospores are motile Swimming gametes fuse in the chytrids but is replaced by fusing hypha in the Zygomycota 3

4 Phylum Glomeromycota Arbuscular mycorrhizal fungi form symbioses with plants Phylum Glomeromycota cortex root tissues epidermis < 200 described species. All aseptate % of plants make symbiotic mycorrhizal interactions with glomeromycetes vesicle root hair soil spore form endomycorrhizae - fungal interactions within the cell arbuscules - little trees, hyphal proliferations within the cell wall of plant cells but not within the plasma membrane arbuscule hypha The fungus contributes water, nutrients such as phosphate to the plant and may make other - yet to be discovered - contributions. Sexual reproduction is unknown in glomeromycetes, they make huge asexual mitospores (up to 1mm). cortex cell fungal mycelium ascospores in asci Phyla (continued) Ascomycota - fungi that produce sexual spores in asci, and they spread primarily by releasing asexual mitospores. >30,000 species. Both Ascomycota and Basidiomycota have septate hyphae and there is a dikaryotic stage in sexual reproduction Basidiomycota - all members extrude myospores from a basidium (a stalk). >20,000 species. basidium Both Ascomycota and Basidiomycota have septate hyphae and there is a dikaryotic stage in sexual reproduction Ascomycota Many human diseases: athelete s foot, jock itch, ringworm Many plant diseases: apple scab, corn leaf blight, Dutch elm disease, powdery mildew Many benefits to humans also: bread, wine, beer, penicillin, morels (Morchella), truffles (Tuber), soy sauce, bleu cheese. 4

5 Some Ascomycota species live as single cells (yeasts) Some are dimorphic consisting of hyphae or single cell Budding (asexual reproduction) Most fungi produce asexual spores to multiply, such as these mitospores from Penicillium yeasts Ascomycota The vast majority of lichens are composed of an ascomycete + either a cyanobacteria or an algae. algal layer filamentous fungal layer Common lichen growth forms leaflike Most lichens reproduce asexually by releasing soredia (singular is soredium). Soredia are a few hyphae wrapped around photosynthetic cells. branching flat and crusty 5

6 Lichens also reproduce asexually through isidia (singular is isidium). The symbiotic relationship enables lichens to survive in harsh conditions such as in Antarctica isidia are fragments of lichens isidia Photo by Richard Droker Phylum Basidiomycota Stinkhorns Phylum Basidiomycota Mushrooms Shelf fungi Coral fungi Phylum Basidiomycota Puff balls Phylum Basidiomycota Basidiomycota contains smuts and rusts that do not make large fruiting structures. These include some of the most destructive fungal pathogens. Corn smut 6

7 Six major groups of fungi Group Representative Hyphae Asexual Sexual Spore Reproduction Microsporidia Unicellular Nonmotile spores Nonmotile spores Chytrids Aseptate Zoospores Zoospores Zygomycetes Black bread mold Aseptate Nonmotile spores Zygospores Glomeromycota Endomycorrhizal fungi Aseptate Nonmotile spores Unknown Ascomycota Basidiomycota Morels, truffles, yeasts, Penicillum Mushrooms, stinkhorns, puffballs, shelf fungi, rusts, smuts Septate or unicellular Septate Budding, nonmotile spores, fragmentation Budding, nonmotile spores, fragmentation Ascospores Basidiospores Lecture 15 Study Guide Definition of heterotrophic. Definition of saprobe give an example of a fungus that is not a saprobe. Differences between plants and fungi (cell wall and source of carbon) What is a fungal septa? What is the analogous structure in plants? The six major groups of fungi we discussed in class - you need to know their names (Microsporidia, Chytrids, Zygomycota, Glomeromycota, Ascomycota, and Basidiomycota) and the distinguishing characteristics of each phyla. Hyphae direction of growth is controlled by chemotropism. Define chemotropism Fungi and bacteria often compete for the same resources. What strategies do fungi use to compete successfully with bacteria? Define plasmogamy and karyogamy. If septate fungal hyphae underwent plasmogamy but not karyogamy then the resulting hyphae would be. After karyogamy the fungal hyphae would be. How is chitrids lifecycle different from the lifecycle of every other major groups of fungi? Name the two phyla with aseptate hyphae. Which phyla of fungi form endomycorrhizae interactions with plants? Name a human disease caused by an ascomycete fungi. Name one food that depends on ascomycete fungi. What is an arbuscule? In the Ascomycete lifecycle is the ascoma haploid, diploid, or dikaryotic? In the Ascomycete lifecycle where does meiosis take place? Name examples of ascomycete fruiting bodies. Ascomycetes are part of the lichen symbiosis, what is the other part? Lichens reproduce asexually using which structures? In the Basidiomycota, plasmogamy occurs between two. In the Basidiomycota spores are always haploid or diploid? In the Basidiomycota, where does meiosis take place? 7