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Fungi Flashcards

(49 cards)

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1
Q

What are the functions of fungal spores?

A

Reproduction - asexual/sexual
Dispersal - structural adaptations
Survival - low water content, thick cell walls, pigmentation

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2
Q

What is a ‘mycelium’?

A

Complex, interconnected network of hyphae, grown from spores, 3D

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3
Q

What are germ tubes?

A

Specialised hyphae, emerge during spore germination, involved in colony establishment
Hyphal growth polarised

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4
Q

How do microtubules act in germinating spores?

A

Lengthen (polymerisation) and shorten (depolymerisation), regulated by different enzymes
Dynamic instability

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5
Q

How do motor proteins act on microtubules?

A

Transport ‘cargo’ along microtubules and actin microfilaments
Cargo = membranous organelles, vesicles, RNA, and protein complexes

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6
Q

What are the 3 types of motor proteins?

A 
Microtubule-associated:
Kinesins - 'walk' to + end
Dyenins - 'walk' to - end
Actin-associated:
Myosins

Consist of homodimer of heavy chains and some number of light chains
Heavy chain bind to microtubule
ATP hydrolysis lead to conformational changes

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7
Q

What is the dominant fungal lifestyle?

A

Filamentous fungal lifestyle

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8
Q

How does possession of hyphae demonstrate uniqueness of filamentous fungi?

A

Non-motile heterotrophic organisms
Ability to adapt to environment
Ability to undergo morphogenesis

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9
Q

What are the functions of hyphae?

A 
Exploration and resource capture
Nutrient mobilisation
Translocation of nutrients and water
Defence of occupied substratum
Reproduction
Survival
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10
Q

Why are some septal pores unplugged in peripheral growth zone of hypha?

A

Allows mass transport of protoplasm towards hyphal tip

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11
Q

What is a Spitzenkorper?

A

Concentration of vesicles as well as actin, microtubules, and other proteins
Viewed as:
Vesicle supply centre
Vesicle receiving centre
Primary response element to internal and external signals

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12
Q

What are chitosomes?

A

Located in spitzenkorper core
7 different chitin synthases
Microvesicles which can each synthesise a single chitin microfibril

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13
Q

How are sites of chitin synthesis located?

A

Miroautoradiography

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14
Q

What are hyphal walls made of?

A

2-component system - microfibrils composed of chitin, amorphous matrix composed of glucans and proteins

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15
Q

Why are microtubules important?

A

Secretory vesicle transport and tip growth

Kinesin motor proteins required to maintain polarised growth

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16
Q

What shows actin is involved in hyphal tip growth?

A

Actin microfilaments concentrated in Spitzenkorper core
Actin nucleating protein, formin, concentrated in Spitezenkorper
Myosin enriched in hyphal tips

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17
Q

What is the proposed secretory pathway in growing hyphae?

A

Short distance transport of secretory vesicles and exocytosis of apical plasma membrane via actin microfilaments and myosin
Spitzenkorper = vesicle receiving and supply centre and switching station for vesicles to ‘hop-off’ microtubules and ‘hop-on’ actin microfilaments to their final destination
Long-distance transport via microtubules and dyenin/kinesin

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18
Q

What’s the classical view of secretory pathway in fungal hypahe?

A

ER -> Golgi -> Spitzenkorper
Proteins synthesised on ER, transported to Golgi
Proteins glycosylated and packed in secretory vesicles
Secretory vesicles transported to Spitzenkorper
Secretory vesicles targeted to apical plasma membrane and exocytosed

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19
Q

What are important functions of endocytosis?

A

Recycling membrane proteins and lipids
Internalisation of proteins and lipids for degradation
Internalisation of signal molecules

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20
Q

Where is endocytosis concentrated?

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A

In a subapical ring just behind growing tip

21
Q

Where does hyphal fusion occur?

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A

In colony interior

Occurs in mature/older parts of fungal colony

22
Q

How can fungal fusion be observed?

Study These Flashcards
A

Fluorescent staining of mycelium

23
Q

How does hyphal fusion occur?

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A

Pre-contact stage - spitzenkorper forms on both hyphae
Spitzenkorper grow towards each other
Post-contact stage - adhesive glue produced and hyphae connect
Fusion of hyphae and cytoplasmic mixing

24
Q

What are ‘nuclear comets’?

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A

Dynamic aggregations of nuclei and organelles in mycelium of Neurospora
Unimpeded by septa
Only observed in central regions

25
In which direction do nuclei usually travel?
Towards growing edge of colony | Sometimes towards sites of conidia production
26
What decides velocity of nuclei?
Diameter of hyphae
27
Do all nuclei move with flow of nuclear comets?
No some show resistance | Some may be tethered by spindle pole bodies
28
What is a 'rhizomorphic' mycelium?
Aggregated hyphae in mycelium Thick strands of hyphae which have adhered Helps fungus cover area, grow quickly through, substrates and establish a feeding network Coated in melanin in thick protective layer Eg. honey fungus
29
What are the different guises of cell polarity regulation in fungi?
Initiation of cell polarity - spore germination, branch-formation, yeast-hypha dimorphism Maintenance of cell polarity - hyphal growth Re-orientation of cell polarity - hyphal growth, externally imposed polarity Loss of polarity - sporulation, infection structure formation
30
What are the mechanisms of spore liberation?
``` Water drop splash Fall of basidiospores Wind Puff ball Ascus guns Pick up by mist ```
31
What is the importance of fungi?
Parasites - plant and animal Mutualists - mycorrhizae and lichen Saprotrophs - carbon cycle, sewage disposal Fungal products - food, ripening of cheese, alcohol, bread etc.
32
What are lichens?
``` Dual organisms - fungi and algae Slow growth rates, long-lived Occupy nutrient-poor environments Resistant to desiccation and environmental extremes Sensitive to pollution Also contain yeast! ```
33
What types of mycorrhizal relationships are there?
Ectotrophic - eg basidiomycota and tree host Arbuscular - eg. glomus, obligate biotrophs Endotrphic - eg. rhizoctonia, and orchid host
34
How do basidiomycota spread spores?
Gills, pores, spines | Basidiospores released from basidia
35
What are the different types of fungal nutrition?
Saprotrophy - non-living organic material used as nutrient resource Necrotrophy - living tissue first killed then used as nutrient resource Biotrophy - living tissue used as nutrient resource
36
Where can fungi invade plant tissues?
``` Fruit and seed infection Epiphytic growth Invasion of photosynthetic tissues Local lesions Vascular wilt General systemic spread Canker Heartrot Root rot ```
37
How does 'the powdery mildew'/E. graminis (ascomycota) infect plants?
Has haustorium in plant epidermal cell Invading hypha penetrates host cell wall and forms haustorium Separated from host cell by extrahaustorial membrane across which fungus draws nutrients
38
How do 'wheat stem rust' hyphae grow?
Growth at right angles to ridges indicating surface topography induces directional growth Aim to get to stomata - increases probability Growth into grooves Appressorium penetrates stoma of plant leaf
39
How do 'bean rust' hyphae grow?
Appressorium induced bu 0.5 um ridge of guard cell | Appressorium gorw to produce haustorium in plant epidermal cell
40
How do appressorium work?
Builds up pressure by osmotic uptake of water through melanin layer Glycerol acts as solute which aids water retention Pressure pushes through cell wall
41
How do some spores stay on plants?
'Spore top mucilage' glues spores to plant leaves
42
How do plants prevent infection?
Necrosis of plant cells - hypersensitive response to prevent further infection
43
What is fluorescence?
Excitation of a substance and emission of light
44
What's an example of a fluorescent protein?
GFP - produced by jellyfish
45
Why is GFP useful?
Good for studying cell biology of living cells More FPs available now Protein/organelle labelling Non-invasive investigation of living cells
46
What is bioluminescence?
Production and emission of light from a living organism
47
What is an eg of a bioluminescent bacteria?
Photobacterium phosphoreum Marine bacteria associated with light organs on angler fish Regulated by quorum sensing Light increases at higher cell densities
48
How does firefly bioluminescence work?
Luciferase catalyses oxidation of luciferin resulting in light emission ATP dependent in fireflies Many diff types luciferins and luciferases in diff organisms
49
What is aequorin?
A luciferase that binds to a luciferin to form a single photoprotein Binding of calcium ions results in change in photoprotein structure and oxidation of the luciferin substrate results in emission of blue light Presence of GFP results in conversion to green light

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