1. BIOLOGY 3404F EVOLUTION OF PLANTS Fall 2008
Lecture 5
Thursday October 2
Chapter 14, Fungi (part I)

2. Outline Life cycles: three types cover almost all e.g.s
Groups of fungi and fungus-like organisms and what they do
Fungus-like Protists: Myxomycota, Dictyosteliomycota, Oomycota, etc.
Five Phyla of Kingdom Fungi: Chytridiomycota, Zygomycota, Glomeromycota, Ascomycota, Basidiomycota
Unnatural groups: Deuteromycetes, Lichenomycota

3. Zygotic Meiosis, Raven et al. Fig. 12-15a

4. Gametic Meiosis, Raven et al. Fig. 12-15b

5. Sporic Meiosis, Raven et al. Fig. 12-15c

6. Which is it? (Which are we?)
Knowing Fig inside-out will make life-cycles in this course much easier to manage
We will see a lot of life cycles, but in essence there are only three kinds: recognized by ploidy of the organism
Haploid: zygotic (meiosis immediately follows formation of the diploid zygote)
Diploid: gametic (meiosis occurs in single cells of diploid individual, long after zygote formation; meiosis produces gametes, which unite to form zygote) [= delayed meiosis]
Both haploid and diploid individuals: sporic (meiosis occurs in single cells of diploid individual, long after zygote formation; meiosis produces spores, which form haploid individuals) [= delayed production of gametes]

7. But remember …
Many organisms reproduce asexually, so their life cycles do not fit in any of the three types described above.
Most asexually-reproducing organisms are derived from sexually-reproducing ones, so you can infer what type of life cycle their ancestors had
Some asexually-reproducing organisms may be “primitively asexual” - i.e., they have been around since before sex was invented

8. [Fungus-like Protists I: the slime moulds, Myxomycota and Dictyosteliomycota] – FYI only
Closely related to amoebae; spores germinate to form amoeboid stage in life cycle
Engulf food (phagocytosis) but may also have external digestion via secreted enzymes, followed by absorptive nutrition (as in Fungi)
Amoebae aggregate (cAMP) and form acellular plasmodium (Myxos) or cellular pseudoplasmodium (Dictyos): “feeding slime”

9. Slime Moulds II
Following nutritional or other environmental trigger(s), feeding slime transforms into fruiting (spore-producing) structures – very fungus-like, and very beautiful
See George Barron’s Myxo web site,
Very important as nature’s vacuum-cleaners – eating particulate organic matter, bacteria and spores, and contributing to nutrient cycling
Very common in soil and litter

10. Arcyria cinerea Dictydium cancellatum
(Photos: GL Barron)
Badhamia utricularis

11. Myxomycete life cycle, Raven et al. Fig. 15-58
Is this zygotic, gametic, or sporic meiosis?

12. Dictyostelid life cycle, Fig. 15-60

13. Fungus-like Protists II: the water moulds, Oomycota
These are closely related to Chrysophyta and others in the group sometimes called Kingdom Stramenopila (or Heterokonta)
Have motile cells (zoospores) with two flagella, one tinsel and one whiplash
Oomycota include some saprotrophs but also some important plant pathogens, such as Late Blight of Potato (Phytophthora infestans), Blue Mould of Tobacco (Peronospora destructans), and Downy Mildew of Grapes (Plasmopara viticola)

14. Late Blight of Potato, Raven et al. Fig. 15-19
Tinsel and whiplash flagella;
Kendrick 5th Kingdom

15. Oomycota life cycle, Raven et al. Fig. 15-17

16. (true) Kingdom Fungi Defined
Heterotrophic, eukaryotic organisms generally with extracellular digestion and absorptive nutrition; cell walls contain chitin and glucan/mannan, not cellulose
Most are filamentous but some are unicellular (yeasts); a few are motile
Must either live as saprotrophs (decaying dead organic matter) or symbionts (parasites or mutualists, etc., with other living organisms

17. Chytridiomycota Approximately 1000 described species
Depend on free water - flagellate
Most groups have just one flagellum, and can be recognized as chytrids by this
Some (the rumen fungi) have multiple flagella, and were considered protozoa
Synchytrium endobioticum causes potato wart disease, closed US to PEI potatoes.

18. Chytrids II
Closest to ancestral choanoflagellate, the common ancestor of both fungi and multicellular [= true] animals – Fig. 15-7
At least some have sexual and asexual phases, and also haploid and diploid phases in their life-cycle (Allomyces) – Fig

19. Allomyces life cycle, Raven et al. Fig. 14-10
Is this zygotic, gametic, or sporic meiosis?

20. Chytridiomycota Catenaria, a chytrid that attacks and consumes living
nematodes (drawing by George Barron)

21. Glomeromycota Approx. 150 described species
Thought to be M years old!
These were formerly [i.e., in your textbook] treated in Zygomycota as the Glomales
The entire group (or what we know of them) form symbioses with photoautotrophs
Entirely asexual (?) – for millions of years, but coenocytic, with different nuclei

22. Glomeromycota II
One species (Geosiphon) has an endosymbiotic cyanobacterium
The rest form mycorrhizal relations with >80% of green plants, called “endomycorrhizae” or Arbuscular Mycorrhizae (AM) – Figs , 14-44
These relations are particularly important in delivering phosphorus to herbaceous and tropical woody species in nutrient-poor soils

23. Glomeromycota III
Hyphae and a spore of a Glomales washed from soil. The spore is 1/10 mm in diameter!
[The circle beside the spore is an air bubble.] The hyphae and spores of Glomales are coenocytic. A single spore may contain several thousand nuclei, and evidence is mounting that these may be genetically different from one another! What is an individual in these fungi? As far as we know, the Glomeromycota are all asexual, and have been for millions of years.

24. Zygomycota Approximately 1,000 described species
Best known are the “bread moulds” Rhizopus and relatives (Mucorales), with tall, broad, glassy hyphae, growing on bread, fruit, and pumpkins
Broad, coenocytic hyphae, thin-walled (occasionally wall-less when growing within insects)
May have both asexual and sexual reproduction (sporangiospores and zygospores borne in zygosporangia)
May be homo- or heterothallic.

25. Zygomycota
Rhizopus

26. Zygomycota
Rhizopus
zygospores
Rhizopus hyphae and asexual spores

27. Zygomycota
Asexual spores (sporangiospores) of Cunninghamella (photo by George Barron)
Each spiny sphere is actually a sporangium containing one spore.

28. Rhizopus life cycle, Raven et al. Fig. 14-11
Is this zygotic, gametic, or sporic meiosis?

29. Ascomycota Approximately 48,000 described species
Include most yeasts, most “deuteromycota” and most “mycophycophyta” or “lichenomycota” – we will return to these fungi in lectures on “lichens”
Ascomycota include many important plant diseases, as well as diseases of humans
Saprotrophs (some may be pests) degrade incredible diversity of substrates

30. Ascomycota
Asci of a cup fungus from dung, each with eight ascospores (dark purplish brown when mature).
Photo: George Barron
Many members of the Ascomycota live most of their lives as haploids, then mate with a compatible haploid mycelium to form a short-lived dikaryon (sometimes, the union of haploids does not take place until formation of fruiting bodies, and only occurs within them). The union of the two different haploid nuclei takes place in each ascus, and is typically followed by meiosis, one mitosis, and production of eight haploid ascospores.

31. Ascomycete life cycle, Raven et al. Fig. 14-14
Is this zygotic, gametic, or sporic meiosis?

32. Ascomycota
Morels, Morchella esculenta, on a lawn in London

33. Ascomycota
“Tar spot” of maple caused by Rhytisma acerinum

34. Ascomycota Ascomata Asci
Powdery mildew of maple caused by Uncinula bicornis

35. Basidiomycota Approximately 30,000 described species
Include most mushrooms, most major wood decayers, and most mycorrhizae of boreal trees (ectomycorrhizae – more next week)
Basidiomycota include many important plant diseases, including rusts and smuts
Attine ants and termites cultivate saprotrophic mushrooms

37. Basidiomycota The “sexual cell” in Basidiomycota is the
basidium (pl. basidia).
Two different haploid
nuclei are present in
every cell – the
dikaryon, and then
fuse to form a short-lived diploid nucleus in the basidium.
Meiosis takes place in each basidium, followed by production of 4 haploid basidiospores.
Compared to Ascomycota, the dikaryon is generally more important in the life cycle of most members of the Basidiomycota. Haploid spores germinate and, usually, soon mate with mycelium derived from a compatible haploid spore to form the dikaryon that is the long-lived stage of the Basidiomycota life cycle. The mycelial individual of some mushrooms have been estimated to be several thousand years old, and occupy several hectares of soil. Basidiomycota [Club fungi], also named for meiotic cell, the basidium. Also a large and important group, for plant disease (rusts and smuts, root diseases and wood decays), few minor animal pathogens, ectomycorrhizae, and decomposition of lignocellulose (and now bioremediation). Life cycle dominated by dikaryon (vs. ascos), a few have asexual reproduction. Example of homoplasy/convergent evolution in fruiting body morphology amongst Homobasidiomycetes. Basidium form, some life cycles

38. Mushroom life cycle, Raven et al. Fig. 14-18
Skip the rust life cycle!
Is this zygotic, gametic, or sporic meiosis?

39. Clamps and dolipores

42. “Deuteromycota” – a fictitious group*
Both of these are asexual members of the Ascomycota, but some “Deuteromycota” are asexual members of the Basidiomycota: the “Deuteromycota” should be abolished as a formal taxon.
Penicillium, an asexual Ascomycete
*Your text now calls them “conidial fungi”

43. Penicillium (above) and Aspergillus (right)

44. “Lichenomycota”
Also called the Mycophycomycota, but are a completely fictitious group
Lichens (more next week) have evolved many times in many groups of Ascomycota (most) and some groups of Basidiomycota (few)