Lichens

Question 1

Which pathways are we certain that symbionts do NOT make contact with in lichens?

Answer 1

CSSP and MiSSP7

Question 2

What is the narrative surrounding lichens?

Answer 2

A fungus co-occurs with one or more algae/cyanobacteria

The alga provides sugars for use by the fungus

The fungus provides a regulated environment that optimizes algal growth

Question 3

What do real lichens look like?

Answer 3

Biophysical properties: dry = some brittle, some flexible; moist = specific torsion. elasticity, flexibility

Shape: flat, round

Water relations: ability to take up or get rid of water

Question 4

Where are yeasts in lichen typically found?

Answer 4

In the polysaccharide layer that coats the lichen

Question 5

Letharia lichens consistently contain which 3 fungi?

Answer 5

Hyphal ascomycete
Two basidiomycete yeasts

Question 6

How have the overlooked fungi been missed?

Answer 6

Primer bias
Insufficient sequencing coverage

Question 7

What is primer bias?

Answer 7

Primers are made with a priori knowledge
Can’t make a primer for something you cannot see or do not know exists

Question 8

What are fungi cemented together by in lichens?

Answer 8

An extracellular polysaccharide layer

Question 9

What is the EPS made of?

Answer 9

Ascomycetes: maybe galactomannans

Basidiomycetes: maybe GXM exo-polysaccharides

Question 10

What are the visual points of reference for polysaccharides?

Answer 10

Lectin-based localization
Direct analysis of monosaccharide profiles

Question 11

What are the GXM motifs?

Answer 11

Mannose
Glucuronic acid
Xylose
Fucose

Question 12

Which fungi produce GXM?

Answer 12

Tremellaceae like snow fungus

Question 13

What breaks down GXM in nature

Question 14

Lichens have what?

Answer 14

Numerous high-frequency symbionts that easily escape detection

Question 15

What is the most common lichen symbiont worldwide?

Answer 15

Acetobacteraceae tie with or surpass Trebouxiaceae algae as the most common

Question 16

How many bacterial families are on par with algae in frequency?

Answer 16

4

Question 17

What is the frequency of Cystobasidiomycetes?

Answer 17

They are found in at least 1/3 of Tremellomycetes and 2/3 of lichen metagenomes

Question 18

Cyanobacteria sugar assimilation?

Answer 18

Glucose assimilates into mannitol and arabitol

Question 19

Trentepohlia sugar assimilation?

Answer 19

Erythritol assimilates into erythritol

Question 20

Trebouziophyceae sugar assimilation?

Answer 20

Ribitol assimilates into mannitol and arabitol

Question 21

What are some early lichen goods exchange observations?

Answer 21

Lichens lose considerable amounts of polyols during wetting-drying cycles
Much of the cellular carbon uptake in the fungus is kept in a soluble fraction
Most lichens do not grow much

Question 22

Why are lichens not great lab models?

Answer 22

They grow extremely slow

Question 23

What mutualism arose from gene loss?

Answer 23

Saprotrophs evolved into mycorrhiza

Question 24

Almost all orphan lineages of lichens descend from what?

Answer 24

A common ancestor

Question 25

The members of the orphan lineage clade have what?

Answer 25

Some of the smallest degradative CAZyme arsenals in Ascomycota

Question 26

Lichen fungal symbionts from the Dothideomycetes have what?

Answer 26

Some of the largest degradative CAZyme arsenals

Question 27

Does symbiosis with an alga predict CAZyme and transporter arsenal size?

Answer 27

No, there is a range

Question 28

When should lichen have a genomic signal for PCWDEs?

Answer 28

If lichen fungi are getting carbon from other sources, fungal symbionts from lichens with strong organic substrate preferences should have this

Question 29

Why are non-reducing sugars Janus carbohydrates?

Answer 29

They have two uses: growth/respiration and protection

Question 30

What is the support for nutritional symbiosis?

Answer 30

CO2 exchange and CHla content are correlated in whole lichens Chla content and relative growth rate are correlated in whole lichens

Question 31

What do mycorrhizal genomes exhibit following glucose subsidy?

Answer 31

Loss of CAZymes

Question 32

What do lichen fungi exhibit a greater range of than ectomycorrhizae?

Answer 32

CAZyme arsenals

Question 33

CAZyme arsenal size varies with what?

Answer 33

The type of photobiont export

Question 34

What is the future direction for lichen research?

Answer 34

Does the duel function of polyols drive the evolution of slow growth? If the polyol pool is needed for survival, there would be costs that use this pool for growth