Quiz 2: Ascomycetes

Ascomycete role

Agricultural pathogen
Abruscular mycorryhizal
Human pathogens
spoilage /toxins and preservatives in food
Secondary products in industrialand food enzymes and pharmaceuticals

Ascomycota Characterisitcs

Chitin in cell walls, septate hyphae, conidia in asexual repro, sexual repro has various gametes that give rise to ascospores, usually haploid

Sexual/Asexual Life Cycle

types of plasmogomy

gametangio-gametangiogamy, gameto-gametangiogamy, somatogamy

gametangio-gametangiogamy

Female looks different from male
Initially looks similar oomycetes

gameto-gametangiogamy

Has spermatium - small unicellular male that fuses with femal ascogonium

somatogamy

No recongizable sexual structures with undifferentiated hyphae

Ascogenous (secondary) hyphae

Formed from an ascogonium
Branch repeatedly
Each cell contains several nuclei
Results in production of crozier cell

Ascus Formation

A: crozier cell forms from a hooj in the tup of the ascogenous hyphar
B: two dikaryotic nyckeu divide simultaneously
C: septa delimit the pentulitmte cell from the stalk
Karyogamy occurs
D: diploid nucelus in the ascus intial
Only diploid stage in life cycle and new crozier is developing alongside first
E: meiosis
F: mitosis in 4 haploid nuclei results in 8
G: ascospores are formed froma scus cytoplasm

types of ascocarp

apothecium
cleistothecium
perithecium
loculate

Apothecium

Shaped like cup or saucer
Asci discharge simultaneously
Distinct structural layers
-Hymenium
-Subhymeinum
-Excipulum
Development
-Sterile hyphae intertwined with ascogenous hyphae
-Paraphyses appear before asci
-Crozier cells form at base of paraphyses
-Hymenium may be celistohymenial (closed) or gymnohymenial (exposed)

Cleistothecium

Totally encoled by wall of sterile hyphae (peridium)
Asci are released after the wall breaks down from weathering
Chemical attractants encourage dispersal by animals

Perithecium

Flask shaped, can be globular
pore/slit for ascospore release
Ascospore discharge from nlyone or a few asci at a time
Neck length varies
Can be
-Embedded in host
-On surface of host
-Embedded ina s troma
Sterile filaments throughout
-Paraphyses - apical ends free
-Pseudoparaphyses - grow from the top down
-Periphyses - short hairs within the neck

Loculate

Form asci in cavities (locules) within strom but DONT have a distinct wall
One or several within each strom
Hard to distunguis from perithecia
Ascospore discharge perithecia

Ascus types

Unitunicate-operculate,Unitunicate-inoperculate, Protunicate, Bitunicate

Unitunicate-operculate

Single functional wall
Wall doesnt separate during ascospore discharge
Built in lid (operculum) at the tip
Found only in apothecial ascomata

Unitunicate-inoperculate

No operculum (lid)
Elastic ring mechanism in the tip
Found in mostly perithecial ascomata and some apothecial

Protunicate

No active spore dispersal
Usually round
Wall dissolves/ruptured at maturity
Found in several ascomycete orders

Bitunicate

Ascus wall separates during discharge
At maturity rigid outerwall splits
Elastic inner wall absorbs water and expands
Asci stretch to the ascoma necka nd shoots spores
Produced by pseudothecial ascocrps

hyphomycetes

asexual fungi tht produce conidia freely or on a sporodochium or synnema
-Dematiaceous: Produce dark brown conidia, green-black or black colonies
-Hyaline: Colonies are hyaline or brightly colored, not dark pigmented

Coelomycetes

asexual fungi that produce pycnidia or acervuli

stages of conidial production

Conidial initiation
Maturation
Delimitation - secondary septa formation
Secession - separation from condidiogenous cells
Proliferation to form further conidia

blastic conidia

Condiia are formed by blowing out the cell wall usually from hyphal tip

holoblastic conidia

All wall layers of the conidiogenous cell contribute to the wall of the conidium

enteroblastic conidia

Wall of the conidiiogenous cell is rigid and breaks open
Conidium is pushed through the opening surrounded by a newly formed wall

phialidic enteroblastic conidia

Initially holoblastic
Phialide wall breaks at the tip
First conidium cut off by a septum
Second adn third conidia develop beneath first
Lower part of the phialide wall persists as a collarette

annellidic enteroblastic conidia

Initially holoblastic
First conidium cut off by a septum
Second conidium develops beneath first
Septum cuts off second cindiia beyond the point of the first
The development of more conidia results in further annellations

holothallic conidia

Terminal hyphal segment cut off by septum
A second septum is formed near the first cutting off the separating cell
The terminal cell enlarges
The separating cell collapses and the condiia release

Thallic-arthic conidia

Terminal hyphal segment cut off by a septum
Septa divide the segment into several sections
The septa each divide into two layers
The daughter cells separate