Lecture 11 - Fungus

Question 1

Archaeplastid

Answer 1

Green plants and algae and red algae

Question 2

Ectomycorrhiza

Answer 2

Symbiosis between trees and fungi

Question 3

Basidiomycota

Answer 3

Many of the recognisable mushrooms belong to this category

Spores released from pedestals (basidia)

Question 4

Ascomycota

Answer 4

Contain many mushroom and yeast species (>60,000 species in this category)

Spores released from sacs (asci)

Question 5

Dikarya: what is it and what do they do?

Answer 5

Basidiomycetes and Ascomycetes together

During part of their life cycle they have cells with two genetically different nuclei that have not fused (separation of plasmogamy from karyogamy)

Most fungi have extensive haploid phases in their life cycle

Question 6

Glomeromycota: what are they and do they have any symbiosis?

Answer 6

Small group (~200 species) of arbuscular mycorrhizal fungi (AMF)

All are obligate symbionts (depend on plant to survive) that associate with plants soon after spore germination, and form arbuscules in plant tissue and exchange phosphorus for carbon

Question 7

Chytridiomycota: what are they, how do they reproduce, and do they have parisitic properties?

Answer 7

Aquatic fungi, single-celled with a much more basic life cycle

The only group reproducing via zoospores

Many are parasites, including Batrachochytrium dendrobatidis, the main cause of global amphibian decline

Many chytrids are non-parasitic decomposers

Question 8

Microsporidia

Answer 8

Most primitive fungi - all are single-celled parasites (causes microsporidiosis in humans, but almost all animals can be host)

Nosema sp. probably contributes to colony collapse disorder of honeybees

Question 9

Key features of fungi

Answer 9

Cell wall made of chitin, hyphae in advanced fungi, possible septae, coenocytic (multinucleated due to nuclear division without cytokinesis)

Question 10

Tip growth of hyphae

Answer 10

Like pollen, neuronal axons and root hairs

Chitin synthase specifically at the tips of hyphae

Question 11

Mycelium

Answer 11

Mass of hyphae forms mycelium

Denser mycelium forms fruiting body (mushroom)

Large surface to volume ratio facilitates absorption of nutrients

Defining feature of fungi: absorptive heterotrophy

Question 12

Saprotrophs

Answer 12

Secrete enzymes on dead organic material which produces things that are then absorbed by the fungi

Question 13

Mutualists

Answer 13

Arbuscules are highly branched hyphae in contact with root cell plasma membrane; exchange of phosphate for assimilated carbon.

Question 14

Parasites

Answer 14

Hyphae grow into plant host, manipulate it to yield more nutrients (biotrophs) or kill it and live off the remains (necrotrophs)

Question 15

Mallasezia globosa

Answer 15

Saprotrophic fungi that live on your head

Question 16

Endophytic fungi

Answer 16

Kentucky 31 is an extremely successful variety of grass (Tall Fescue, Festuca arundinacea) grown all over the US. It has high drought and heat tolerance, resistance to most pests, and is perennial, providing quality forage for cattle.

Decades after its introduction it was found that almost all the amazing properties of Tall Fescue were due to infection with an endophytic fungus.

Question 17

Mutualism

Answer 17

An interaction that increases the fitness of both species

Question 18

Parisitism

Answer 18

An antagonistic interaction that increases the fitness of one species at the expense of the other species