KINGDOM EUMYCOTA Phylum 3 - DIKARYOMYCOTA Subphylum ...

KINGDOM EUMYCOTA 

Phylum 3 - DIKARYOMYCOTA 

Subphylum 2 - BASIDIOMYCOTINA 

There are 3 Classes of Basidiomycotina: 

Holobasidiomycetes (one-celled basidia; 

“Hymenomycetes” and “Gasteromycetes”) 

Phragmobasidiomycetes (jelly fungi with multicelled basidia) 

Teliomycetes (rusts and smuts - plant and human parasites 

with teliospores that germinate to form multicelled basidia) 

Images from TEXT 

1-celled basidium 

Rust Corn smut 

Summary from Lecture 6: Jelly fungi in the 

Holobasidiomycetes and Phragmobasidiomycetes: 

4-celled basidium 

Not all jelly fungi have multicelled basidia: the Dacrymycetales has 

One-celled, tuning fork shaped basidia. Also carotenoid pigments. 

Jelly fungi with multicelled basidia include the Tremellales and 

Auriculariales.These orders and the Dacrymycetales have forcible 

basidiospore discharge. They also produce asexual mitospores 

(termed conidia). 

Septobasidiales are insect parasites. 

If the meiotic spindle is perpendicular to the main axis of the 

basidium, septa in the basidium will be which, transverse or 

longitudinal? What if the spindle is parallel to the main axis? 

The Tulasnellales and Ceratobasidiales have septa at the base of 

their sterigmata, but not in the basidium. Rhizoctonia is a genus of 

asexual species whose sexual states are in these orders; Rhizoctonia 

can be a plant pathogen or a mycorrhizal symbiont.

Lecture 7: Teliomycetes I– Smuts 

Reading: Text, Chapter 5, http://tolweb.org/Basidiomycota/20520 

And http://tolweb.org/Ustilaginomycotina/20530 

Objectives: Ustilaginales (class Teliomycetes). Know what a teliospore 

is. Interpret the relationship between haploid yeast, dikaryotic 

mycelial and teliospore forms of smut with phases in the disease 

process 

Corn smut Teliospores 

http://tolweb.org/tree?group=Basidiomycota&contgroup=Fungi 

Exobasidium forms no fruitbodies 

http://tolweb.org/Ustilaginomycotina/20530 

The Ustilaginomycetes (1400 species in 70 

genera) are ecologically characterized by 

being parasites of vascular plants. 

None parasitize orchids – a family with 

20,000 species. 

Features of the Ustilaginomycetes: 

Plant parasitism – with cellular interaction by means of interactive vesicles, 

Cell wall carbohydrate composition - dominance of glucose and no xylose, 

5S rRNA secondary structure of type B, 

Septal pores without parenthesomes, but with 3-part membrane caps, 

Life cycle with parasitic dikaryon phase and a saprophytic haploid phase.

3 characteristics of Ustilaginales (= Ustilaginomycetes):(1) haustoria 

and interactive vesicles; (2) simple septum with 2 caps; (3) saprobicparasitic 

alternation in life cycle. 

Primary interactive vesicles. 

Scale bar = 0.2 µm. 

Type 1 

long n+n phase. 

Typical for 

Basidiomycetes. 

local interaction zone (arrows) 

between fungus (lower cell) and its 

host (upper cell). Interaction 

structure(arrows) and deposit at host 

cell. Scale = 0.5 µm. 

Generalized life cycle of the Ustilaginomycetes. 

© R. Bauer and F. Oberwinkler 1997 

http://www.botany.hawaii.edu/faculty/wong/Bot201/Basi 

diomycota/Ustomycetes/Ustomycetes.htm 

http://botit.botany.wisc.edu/toms_fungi/march98.html 

Enlarged interaction zone 

between enlarged interaction 

zone between fungus and 

host. Haustorium (h). 

Scale = 2 µm 

http://tolweb.org/tree?group=Ustilaginomycetes&contgroup=Basidiomycota#cycle 

Transmission electron micrograph 

showing Ustilaginomycetes simple 

septal pore with two membrane caps. 

Scale = 0.1 µm. © R. Bauer 1997 

Symptom of corn smut is “tumor” - each ovary of female flower 

(collectively comprising the corn “cob” or “ear” undergoes increase in 

both cell size and cell number, termed hyperplasia.

Ustilago maydis (corn smut) shows an alternation between a saprophytic 

yeast phase and a parasitic (obligately!) filamentous phase. 

Casselton, LA and Olesnickcy, NS 1998 Microbiology and Molecular Biology Reviews 62: 55-70.

Key points: 

-Corn smut is caused by Ustilago maydis 

-A promycelium = a 4 celled smut basidium 

-The monokaryon is a haploid saprophyte yeast 

(yeast cells are here called sporidia). 

-Not until mating and the formation of dikaryon 

does this fungus become a obligate parasite on 

corn. There are 2 mating type loci, each with 

different “jobs”. 

-Dimorphism means two forms: yeast + hyphae 

-The haploid dikaryon is the obligate, biotrophic 

parasitic phase. It is filamentous hyphae. 

- To reproduce, a diploid forms that in turn 

forms teliospores. 

-Teliospores form basidia (= promycelia). 

Switch from saprophytic growth by budding to 

filamentous and pathogenic development 

regulated by the multi-allelic b-mating type locus 

that encodes 2 unrelated homeodomain proteins 

bE and bW. The combination of the alleles forms 

heterodimer that controls pathogenicity genes as 

a transcriptional regulator. 

- Bolker M. 2001. Microbiology 147:1395-1401. 

- Steinberg, G. and Perez-Martin, J. (2008) Ustilago 

maydis, a new fungal model system for cell biology. 

Trends Cell Biol., 18, 61-67.

Microbotryum, which causes anther smut disease on 

members of the plant family Caryophyllaceae. 

http://www.people.virginia.edu/%7Emeh2s/labhome/idnp.htm 

Janis Antonovics 

Anther smut as a sexual disease: 

•Epidemiology, e.g short and long term dynamics 

•Host shifts 

•Virulence, e.g.,Multiple infections and competition on a single plant 

•Think about the plant equivalent of social systems, mating systems, and habitat use. 

Text recognizes two families in the Ustilaginales in class 

Teliomycetes, Ustilaginaceae and Tilletiaceae; based on DNA, the Tree 

of Life puts these families in two different classes of phylum 

Ustilaginomycotina 

Family Tilletiaceae. karyogamy, meiosis and mitosis all happen inside the teliospore. 

Resulting basidium produces a cluster of slender, parallel basidiospores from its apex. 

These soon copulate in pairs to restore the dikaryon. 

Tilletia caries, the cause of `bunt' or stinking smut of wheat, is just as important an 

economic problem as stem rust, because it has so far proved impossible to breed strains of 

wheat resistant to this fungus. 

Symptoms of Karnal Bunt (Tilletia indica) 

Infection on wheat seed. 

This disease was first noted in India, then Iraq, Nepal, Pakistan, Afghanstan, introduced 

to Mexico, now is in SW USA. 

Major trade issue for US export of wheat. (Quarantines/trade restrictions have been 

costly and controversial. 

1. Healthy wheat seed. 2. "Tip" infection. 3. More advanced tip infection. 4. Advanced infection. 

5. "Canoe" symptom hollowing out interrior of seed. – Infected wheat stinks and cannot be used for 

flour! http://www.aphis.usda.gov/oa/pubs/karnel.html 

http://tolweb.org/Ustilaginomycotina/20530

KINGDOM EUMYCOTA Phylum 3 - DIKARYOMYCOTA Subphylum ...

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