Basidiomycota

1. Basidiomycota Mushrooms, bracket fungi, puffballs, rusts and smuts

2. Basidiomycota • Large phylum – 16,000 spp of higher fungi • All produce a basidium – club shaped structure (site of karyogamy & meiosis) that produces haploid basidiospores

3. Basidia • Basidia divided into two types depending on whether they are septate • Septate basidia – phragmobasidia • Septa can be transverse or longitudinal • Aseptate basidia - holobasidia

4. Hyphae • Hyphae are regularly septate • Specialized type of pore can occur – dolipore septum with parenthosome • Allows cytoplasmic movement but prevents nuclear migration from one compartment to the next

5. Basidiomycota • Three classes • Basidiomycetes – produce a basidioma, (multicellular fruiting body), includes the mushrooms, brackets, puffballs, jelly fungi, stinkhorns • Uredinomycetes – no basidioma, teliospore produces basidia, obligate plant parasites, the rusts • Ustomycetes – no basidioma, teliospore produces basidia, facultative plant parasites, the smuts

6. Class - Basidiomycetes • Produce macroscopic basidiomata • Most produce holobasidia, phragmobasidia produced by some jelly fungi • Large and diverse class • In life cycle, dikaryotic mycelium becomes the major vegetative mycelium – dikaryotic phase is extended over the Ascomycota

7. Life cycle • Haploid basidiospores germinate to produce haploid mycelium = primary mycelium • In some species, the primary mycelium contains one nucleus in each compartment, in others, there may be multiple nuclei/compartment – also called monokaryon since it contains nuclei of one genotype • Primary mycelium exhibits limited growth

8. Life cycle • Plasmogamy occurs shortly after basidiospore germination • Most Basidiomycetes are heterothallic • Plasmogamy occurs between two compatible hyphae (somatogamy) – no specialized sex cells • Plasmogamy initiates dikaryotic phase or the secondary mycelium (dikaryon) • After plasmogamy, nuclei migrate into monokaryotic cells to establish dikaryotic condition

9. Dikaryon • As mycelium grows, nuclei divide conjugately to maintain dikaryotic condition in cells • Dolipore septum prevents nuclear migration so that each compartment contains two nuclei, pore is 0.1-0.2 μm in diameter • Under certain conditions (e.g. after plasmogamy), dolipore septum breaks down to allow nuclear migration

10. Dikaryon • Secondary mycelium is the major vegetative phase of Basidiomycota • Many Basidiomycetes also form clamp connections (formation is reminiscent of crozier formation in Ascomycota)

11. Clamp connections • Branch that grows back

12. Clamp connections • Thought to be a mechanism to maintain dikaryotic condition • Only found in dikaryotic hyphae, but not all dikaryotic hyphae form them

13. Dikaryon • Dikaryon grows – may reproduce asexually, but asexual reproduction is not widespread in Basidiomycetes • Favorable environmental conditions stimulate formation of basidiomata • Multiple basidiomata can be produced from mycelium - one plasmogamy

14. Basidioma • Composed entirely of dikaryotic hyphae (unlike ascoma) • May be considerable tissue differentiation • Typically macroscopic, forms button then expands

15. Basidioma • Within the basidioma, cells in fertile regions – the hymenium - will develop into basidia and produce basidiospores • As the basidium develops, karyogamy and meiosis take place meiosis karyogamy

16. Basidium • Sterigma (pl. –mata) – projections from basidium to basidiospores • Basidia may or may not produce sterigmata

17. Basidioma • Basidia are produced in hymenia – fertile regions in the basidioma (will discuss position in different basidiomata)

18. Basidia • Basidia with sterigmata can actively discharge basidiospores • Basidiospores are positioned at a 45 angle • 5-10 seconds before discharge a droplet forms

19. Basidia • Thought that force to discharge spore comes from droplet flowing around the spore form a hydrophobic region to a wettable region • Change in center of mass of spore rapidly is thought to provide the force to discharge it • Drop of fluid accompanies the spore

20. Basidia • Spore is discharged less than a mm, then drops straight down • Hymenia must be vertical with respect of gravity

21. Basidioma • Many basidiomata exhibit geotropism • Hymenium exhibits positive geotropism • Basidioma exhibits negative geotropism

22. Basidioma • Basidiospores fall out of basidioma, into turbulent air current and are carried away

23. Basidioma • Composed entirely of dikaryotic hyphae • Basidioma is generally divided into 3 zones • Hymenium – layer of basidia with basidiospores • Subhymenium – distinct area that gives rise to hymenium • Trama – comprises the bulk of the basidioma, separates hymenia • May also have cuticle – skin like layer on surface of some

24. Overall life cycle

25. Representative Basidiomycetes • Jelly Fungi - Basidiomycetes that can be grouped into the “jelly fungi” belong to 6 orders • Basidioma of these fungi is typically gelatinous – during development hyphae in some tissues disintegrate and leave a gelatinous mass

26. Jelly fungi • Most are saprotrophic on wood, some may be parasitic • Most of little economic value • Some used as food – wood ear • Shape of basidiomata varies – cushion shaped, ear shaped • May dry out to a hard, horny texture and then become rewetted to become gelatinous again • Most produce phragmobasidia, those that produce holobasidia have a unique morphology

27. Auricularia– ear fungus, wood ear • Hymenium on surface of basidoma

28. Tremella • cushion shaped basidioma that can vary in color (white, yellow, brown, black)

29. Dacrymyces • cushion shaped basidiomata that are frequently bright yellow

30. Aphyllophorales • Large order - ~2000 spp. • Includes species that primarily produce dry, woody, corky basidiomata (some may be fleshy) • Produce holobasidia • Hymenium is on the surface of the basidioma in some; surface may be smooth, ridged or spiny • Hymenium may line tubes or gills – if the hymenium lines tubes or gills then the basidioma is always woody, never fleshy

31. Wood decomposition • White rots – lignin preferentially decomposed • Brown rots – cellulose preferentially decomposed

32. Corticium • Simplest type of basidioma – thin, flattened, resupinate basidiomata that are on the surface of wood or bark • Hymenium is flat and covers the surface of the basidioma (resembles paint)

33. Clavaria – coral fungi • Produce club shaped or branched basidiomata • Hymenium covers surface of branches except at base • Resemble coral, brightly colored, yellow, orange, violet

34. Coral fungi • Other species

35. Toothed or hedgehog fungi • Hymenium formed on surface of spines or teeth like projections that point down

36. Toothed fungi • Others

37. Chanterelles • Form a funnel shaped basidioma with hymenium on ridges on lower surface

38. Chanterelles

39. Polypores – bracket fungi • Hymenium lines the surface of pores in woody basidiomata • Some may be perennial

41. Polypores • Bracket fungi

42. Polypores

43. Agaricales • Large order - ~5000 spp • Hymenium lines surfaces of tubes or gills in fleshy basidiomata • Includes the mushrooms and boletes • Primarily saprotrophs in soil, litter or wood • Many are biotrophic – form mycorrhizal associations with trees • Economically important as cultivated mushrooms and mycorrhizae (used in forestry)

44. Agaricales • Basidiomata arise from extensive perennial mycelia • Overall structure of basidioma

45. Basidioma structure • Basidia produced in hymenia on gills – flat plate like structures • Cystidia extend out from hymenia • In many, the gills are geotropic – parallel to force of gravity so that basidiospores can fall out once they leave the basidia

46. Gills • Increased surface area for greater number of basidia

47. Basidioma development • Hemiangiocarpic development – button is surrounded by a layer of tissue, the universal veil (forms the volva and scales) , also contains a partial veil (forms the annulus and cortina)

48. Basidioma development • Pseudoangiocarpic development – button has only a partial veil (forms annulus and cortina)

49. Gymnocarpic development

50. Gasteroid Basidiomycetes • Many Basidiomycetes bear their basidiospores internally – gasteroid • May or may not form a hymenium • If a hymenium is formed, the basidioma remains closed until basidia form basidiospores • All produce holobasidia