Morphogenesis, physiology and genetics of development of fungal

fruit bodies - plus some holiday snaps

David MooreSchool of Biological Sciences

The University of Manchester

Fungal mycelium has a number of alternative developmental

pathways open to it

• continuation of hyphal growth

• production of asexual structures

• progress into the sexual cycle

These are not strict alternatives

• a culture may express all of these possibilities

• so, genetic control must be local

Classic genetic approaches are:

• identification of variant strains

• complementation tests to establish functional cistrons

• heterokaryons to determine dominance

• epistatic relationships in heterokaryons (to indicate the sequence of gene expression)

hyphal tu ftsfru it body in itials

E nvironm entalstim uli

hap-5 & hap-6

hap-7 & hap-8

hap-1

fru it bodyin itials

maturefru it body

monokaryoticfru iting

hyphalfusion

dikaryotic fru iting

genefi fb

fru it bodyin itials

m aturefru it body

genem ating typefactors

hap-2, -3 & hap-4

hyphal tu ftsfru it body in itials

E nvironm entalstim uli

hap-5 & hap-6

hap-7 & hap-8

hap-1

fru it bodyin itials

maturefru it body

monokaryoticfru iting

hyphalfusion

dikaryotic fru iting

genefi fb

fru it bodyin itials

m aturefru it body

genem ating typefactors

hap-2, -3 & hap-4

Sclerotiumin itial

I n itiation ofaggregatedgrow th

C apexpan sion

H ymenophored ifferen tiation

H ymen iumd ifferen tiation

M eiosis andsporu lationC ap

dem arcationFru it bod y

in itial

R in d p igm en tationM edu lla d ifferen tiation

Sclerotiummatu ration

Stemd ifferen tiation

Stemexpan sion

Stemdem arcation

Sclerotiumin itial

I n itiation ofaggregatedgrow th

C apexpan sion

H ymenophored ifferen tiation

H ymen iumd ifferen tiation

M eiosis andsporu lationC ap

dem arcationFru it bod y

in itial

R in d p igm en tationM edu lla d ifferen tiation

Sclerotiummatu ration

Stemd ifferen tiation

Stemexpan sion

Stemdem arcation

Normal morphogenesis is made up of developmental subroutines

• subroutines for hymenophore, hymenium, stem, cap, etc.

• subroutines can be put into operation independently of one another

• under separate genetic control

• under separate physiological control

Control of fungal morphogenesis

Molecular models which might account for these features are:

• translational triggering

• feedback fixation

Translational triggering isa mechanism which can relate morphogenesis to physiological

preparation (‘competence’), and to response to environmental

signals

Translational triggering

• illumination• temperature shock• nutritional crisis• injury• edge encounter• extracellular matrix signal• other factors

The ‘trigger’ might be caused by

Feedback fixation

• reinforces expression of the whole regulatory pathway to make it independent of the external environmental cues which initiated it

• results in developmental determination in the classic embryological sense

For thefull story ...

And now … the holiday snaps