Fungal Osmotrophy Flashcards
What does synapomorphy mean?
a characteristic present in an ancestral species and shared exclusively (in more or less modified form) by its evolutionary descendants.
What are some candidates for synapomorphy?
Hyphal growth
Lack of flagella
Cell wall polymers and their genes
Lysine biosynthetic pathway
Osmotrophy
Why can’t hyphal growth be used as a synapomorphic trait?
Most fungi form hyphal growth but it also happens in holozoans and oomycetes
Not all fungi are hyphal or even yeast-like
What are Laboulbeniomycetes?
Non-hyphal fungi with a determinate body plan
Has an exoskeleton and attaches itself to insects
Why can’t the lack of flagella be used as a synapomorphic trait?
Blastocladiomycota and Chytridiomycota have a flagellated life stage
What biochemical pathway isn’t found in animals but is found in fungi?
Fungi synthesize lysine via the alpha-aminoadipate pathway
Through which pathway do plants, algae, and bacteria synthesize lysine?
Diaminopimelate pathway
Why can’t the lysine synthesis pathway be used as a synapomorphic trait?
Two key alpha-aminoadipate genes are widespread in protists
Where do the particles from endocytosis localize?
In the subapical collar
What are the Golgi like in fungi?
Golgi are scattered throughout the cell in the form of small, perforated cisternae
What are among some of the fastest-growing cells?
Filamentous fungal cells
Rates up to 1 mm in 50 minutes
How many endocytotic vesicles need to be delivered to the cell tip to sustain such fast growth?
38000 vesicles
What does SPK formation involve?
Cdc42, a GTPase which interacts with several other proteins (Spa2, Bud6) to form a complex called the polarisome
What does the polarisome do?
Radiates actin filaments by means of forming (SepA and Bni1)
What are the motors that deliver vesicles?
Kinesins
Dyneins
Myosins
What does myosin-5 do?
They are outward-bound motors following actin filaments: they deliver vesicles for exocytosis as well as reinforcing the lipid rafts at the tip
Docks with exocyst protein complexes which enable vesicles to be guided to the plasma membrane
What does myosin-1 do?
Appears to support endocytosis - inward-bound
What do kinesins do?
Move cargo along microtubules to the plus end
What do dyneins do?
Move cargo to the minus end
What is the amount of dynein and kinesins necessary for hyphal tip growth?
1 dynein and 3 kinesins
What does kinesin-1 do?
Hauls vesicles for exocytosis
What does kinesin-3 do?
Forms early endosomes
What happens in the SPK?
Switch from kinesin-dependent anterograde movement of early endosomes to retrograde movement
What else is highly abundant in the SPK?
Ribosomes - mRNA may be delivered to SPK from the nucleus, perhaps by kinesin-3 for translation
What is the vesicle supply center model?
Post-Golgi vesicles are gathered in an apical vesicle supply center that regulates growth by generating a gradient of exocytosis of enzymes
Its active tip-ward movement determines hyphal shape and elongation rate
What is the steady state model?
Polar exocytosis delivers wall-forming enzymes.
Newly added wall material is noncrystalline and plastic and can be expanded by turgor pressure
The wall solidifies as it progresses towards the subapex, resisting turgor pressure and shaping the hypha
What is the amoeba-in-a-tube model?
A membrane cytoskeleton supports integrity of the tip and regulates tip extensibility
The hyphal tip expands by the force produced by the cytoskeleton
The cell wall is considered to be an extracellular matrix that confers shape to the hypha
How has loss of phagotrophy contributed to the success of fungi?
Removed the requirement for a flexible cell surface membrane, allowing fungal cells to develop rigid and structurally reinforced cellular surfaces
How has the rigid reinforcement of the cell surface contributed to the success of fungi?
Protects the cell against high turgor pressures, allowing cell function to flood the cytoplasm with high concentrations of solutes which allows for a fast metabolic rate and allows the cell to assert high force to penetrate and ramify into robust structures as part of their feeding processes
How has the evolution of rigid cells contributed to the success of fungi?
Allows for polarized growth at the hyphal tip
How has a shift to external digestion of complex compounds contributed to the success of fungi?
Coupled to active transport of processed metabolites into the cell
