MycorrhizaA universal plant-fungal

symbiosis

Rasmus KjøllerMikrobiologisk Afdeling Københavns Universitet

Mycorrhiza - a universal plant-fungus symbiosis

• The basic princible• Three different mycorrhizal types

– Nutrition of plants– Carbon cycling in ecosystems

• Identification

• Mycorrhiza is a mutualistic symbiosisbetween plants and fungi

• Mycorrhiza means fungal root

Basic princible - nutrients taken up from the soil are exchanged with sugar...

CO2

Roots and mycorrhiza

sugar

Soil nutrientsphosphorusammonium

nitrate aminoacids

Mycorrhizas have a root contact zone where nutrients are exchanged and an external phase in the soil

external mycelia

root contakt

Common for all mykorrhizal types:

• Increase of the soil volume searchablefor nutrients by the plant

• Hyphae may enter smaller soilparticles than roots

Mycorrhizasa universal symbiosis

• Over 90 % of all plant species forms mycorrhiza

• Mycorrhizas are integrated parts of major ecosystems e.g. boreal, temperate and tropical forets, grasslands, agricultural ecosystems ...

• Plants do not have roots, they have mycorrhizas

MycorrhizasThree dominating types

Mycorrhizal dominating types

• Ectomycorrhiza is mainly found ontrees e.g. spruce, pine, birch, beech, oak, hazel …

• Arbuscular mycorrhiza is typical in herbs and bushes but ash, maple and many tropical trees forms AM

• Ericoid mycorrhiza are found on manyplant species within Ericales

ARBUSCULAR MYCORRHIZA

external mycelia

internal mycelia

The arbuscule

Arbuscular mycorrhizas: small plants big plants

Untreated soil Fumigated soil Fumigated and AM re-inoculated soil

Increased uptake of phosphorus oftenexplains the growth response

50

70

90

110

130

0 100 200 300 400

Superfosfat (kg P/ha)

Høs

tudb

ytte

(g /

2m ræ

kke)

Experimentwith flax. Plants withmycorrhiza (●) or withoutmycorrhiza (o).

depletionzone

External mycelium

spore

External mycelium

Phosphate

rootphosphate concentration in soil is often very low (1% of total P) and diffusion is relatively low

- Aphanomyces +Aphanomyces

0 GI GC 0 GI GC

AM can protect plants against soil borne

pathogens e.g. peas against Aphanomyces

euteiches

- Aphanomyces +Aphanomyces

0 GI GC 0 GI GC

Ectomycorrhizas:

Ectomycorrhizason beech

Ectomycorrhizal diversity

Peziziales sp.

Cortinarius sp.

Cenococcum geophilum

Rhizopogon sp.

Four different ”exploration” types

Ectomycorrhizal fungi constitutes a significant part of the micobial biomass of forest soils and are responsible for a large volume of the CO2 respired from forests.

In a large scale experiment in Northern Sweeden, 9 plots 30x30 m the supply of current photosynthates to roots and mycorrhizas were terminated by tree-girdling

There were about 120 trees in each plot!

Trees were girdled early (June) and late (August) in the season and soil respiration were measured at nine occations

From Högberg et al. (2001)

control: filled circles

early girdled: triangles

late girdled: open circles

Calculated root/mycorrhizaland heterotrophic respiration

open triangles: heterotrophicrespiration (early girdled plots)

filled triangles: root/mycorrhizal respiration (control – early girdled)

From Högberg et al. (2001)

Girdling reduced soil respiration to about 50%

Soil respiration are to a large extent driven by currentassimilates

Soil microbial C decreased 23 and 41 % in early and lategirdled plots

ectomycorrhizal mycelia is a major component of forestsoils

Ectomycorrhizas• increases the soil

volume explored• small diameter of

the hyphae• uptake kinetics

may differ from plant roots

• access to nutrients from SOM

birchseedlingscolonized

with Paxilusinvolutus

trays withbeech, pine

and birchlitter

tray with pine pollen

tray withnematodes to the right

beech tray

From: Read, Perez-Moreno New Phytologist 157 (3)

ERICHOID-MYKORRHIZA

From Smith & Read 1997 External mycelia

Transverse sectionLongitutionalsection

ERICHOID-MYKORRHIZA

Inspired by Table 1 in: Smith, S. E. and D. J. Read (1997). Mycorrhizal symbiosis.

yesyesnoProduction of extracellular enzymes

fewOver 5000Ca 150Fungal species

few3% of seed plants90% of vascular plants

Plant species

EricalesGymnospermsAngiosperms

BryophytaPteridophytaGymnospermsAngiosperms

Plant taxa

clade within Helotiales(Asco)

BasidiemycotaAscomycotaGlomeromycotaFungal taxa

noyesnoHartig net

noyesnoFungal mantle surrounds root

yesnoyesIntracellular colonization

septaseptano septaHyphae

ericoidectoarbuscular

Comparison of mycorrhizal types

Mycorhizal excretion of enzymes

From: Read, Perez-Moreno New Phytologist 157 (3)

LignaseLigninHydrolysis of lignin

Catechol oxidase

Laccase

Polyphenoloxidase

PolyphenolsOxidation of phenolicacids and tannins

1;3 glucanase

L-arabinosidase

D-galactosidase

D-mannosidase

Xylosidase

XylanaseHemicellulose

CellobiohydrolaseCellobiose

CellulaseCellulose

PolygalacturonasePectinPlant cell walldegradation

Extra cellular enzymes* known to be produced by ericoid mycorrhizal fungi

From: Read, Perez-Moreno New Phytologist 157 (3)

Lignin Peroxidase

Manganeseperoxidase

LigninHydrolysis of lignin

Laccase

Peroxidase

Polyphenol oxidasePolyphenols

TyrosinaseMonophenolsOxidation of phenolicacids and tannins

XylanaseHemicellulose

CellobiohydrolaseCellobiose

CellulaseCellulose

PolygalacturonasePectinPlant cell walldegradation

Fatty Acid EsteraseCutin, Lipid, Waxes

Cuticle degradation

Extra cellular enzymes* known to be produced by ectomycorrhizal fungi

*acid proteases are also excretedby both mycorrhizal types

Plant

Roots withmycorrhiza

Mycelia

Soil detritus: litter, mycelia, animals, pollen, phenolic acids

sugar Nutrients (N, P)

enzymes

Dissolvednutrients

mineralization

Mycorrhizas providesacces to organicbound nutrients

Remember that the mycorrhizas carbonare supplied by their hosts

CO2

Roots and mycorrhiza

Soil Organic Matter

sugars

amino acids amino-sugars

nucleotides etc

enzymes

Orchids and Monotropoid plantsalso forms ”mycorrhiza”

Nutrients includingcarbon are directedfrom the fungus to the plant or from a tree via a shared fungal partner to the plant

Cullings et al 1996 Nature 379

Mycorrhizal communities are extremely diverse

a n t a l j o r d p r ø v e r ( u d a f 1 5 6 )0 5 1 0 1 5 2 0 2 5 3 0 3 5

P e z iz a le s s p . 6C o r t in a r iu s c f i l l i o p o d iu s

R u s s u la b r u n n e o v io la c e aT o m e n t e l la s p . 1 4

C o r t in a r iu s s p . 6P e z iz a le s s p . 1 0

T o m e n t e l la s p . 1 5I n o c y b e g la b r ip e s

C o r t in a r iu s c f . l i v id o o c h r a c e u sS e b a c in o id s p . 4

B y s s o c o r t ic iu m a t r o v i r e n sI n o c y b e s p . 6

T r ic h o lo m a la s c iv u mI n o c y b e s p . 5H e lv e l la s p . 2

T o m e n t e l la s p . 1 3C o r t in a r iu s c f p r a e s t ig o s u s

C r a t e r e l lu s t u b a e f o r m isI n o c y b e s p . 3

T o m e n t e l la s p . 1 0c a n t h a r e l lo id s p . 4

B o le t u s b a d iu sT o m e n t e l la s p . 5

I n o c y b e s p . 1H e lo t ia c e a e s p . 1T o m e n t e l la s p . 9S e b a c in o id s p . 2P e z iz a le s s p . 1 1

I n o c y b e s p . 2T o m e n t e l la a t r o a r e n ic o lo r

P e z iz a le s s p . 9I n o c y b e a s t e r o s p o r a

P i lo d e r m a s p . 2C o r t in a r iu s d ia s e m o s p e r m u s

A m a n i t a s p is s aR u s s u la v e t e r n o s a

T o m e n t e l la s u b s t e s t a c e aA m a n i t a r u b e s c e n s

T o m e n t e l la s p . 1c a n t h a r e l lo id s p . 2

b o le t o id s p . 2S e b a c in o id s p . 1

c a n t h a r e l lo id s p . 3S e b a c in o id s p . 3T o m e n t e l la s p . 6

P e z iz a le s s p . 1T u b e r p u b e r u lu m

P e z iz a le s s p . 4P e z iz a le s s p . 5

E la p h o m y c e s s p . 1T o m e n t e l la b a d ia

T o m e n t e l la t e r r e s t r isL a c c a r ia s p . 1

P e z iz a le s s p . 3P i lo d e r m a s p . 1

L a c t a r iu s b le n n iu sT o m e n t e l la b r y o p h i la

C o r t in a r iu s c f . d e c ip ie n sC o r t in a r iu s c f s e r t ip e sL a c c a r ia a m a t h y s t in a

T o m e n t e l la s p . 4R u s s u la f e l le a

B o le t u s p r u in a t u sL a c t a r iu s c a m p h o r a t u s

C o r t in a r iu s c a s im i r iR u s s u la o c h r o le u c a

C e n o c o c c u m g e o p h i lu mP e z iz a le s s p . 2

C o r t in a r iu s a n o m a lu sR u s s u la m a i r e i

C la v u l in a c r is t a t aI n o c y b e p e t ig in o s a

T o m e n t e l la s p . 7c a n t h a r e l lo id s p . 1

R u s s u la v e s c aR u s s u la n ig r i c a n s

L a c t a r iu s s u b d u lc is

In Lille Bøgeskov 15x15 m:• On average 3 species

in each sample = 50 ml (in some up to 8 species

• Within 5 x 5 meter onaverage 26 species

• 77 species identifiedfrom root tips

• 4 more species from mycelia

• 3 more species from sporocarps

• Totally: 84 species

sporocarps -identification? PCR

morphotypes -

identification?

RFLP

RFLP types -identification?

DNA sequences

sequencetypes –identification?

Mycorrhizal fungi can be identified in the environment by molecular methods

Comparison between Russulamycorrhiza and fruitbody sequences

Russula fellea basidiocarp G T C G C T G A C - T T T T T - - - - G T C G T G C A C G C C C G A G T G C T CRf mycorrhiza 1-3-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Rf mycorrhiza 8-19-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Russula mairei basidiocarp . . . . . . . . . C . . . . C . . . G . . . . . . . . . . . . . A . . . . . . .Rm mycorrhiza 4-3-1 . . . . . . . . . C . . . . C . . . G . . . . . . . . . . . . . A . . . . . . .Rm mycorrhiza 5-2-2 . . . . . . . . . C . . . . C . . . G . . . . . . . . . . . . . A . . . . . . .Russula ochroleuca basidiocarp . . . . . . . . . C C - - - G A A A G . . . . . . . . . . . . . . . . . . . C .Ro mycorrhiza 6-6-1 . . . . . . . . . C C - - - G A A A G . . . . . . . . . . . . . . . . . . . C .Ro mycorrhiza 8-6-3 . . . . . . . . . C C - - - G A A A G . . . . . . . . . . . . . . . . . . . C .Rus sp.1 mycorrhiza 1-20-7 . . . . . . . . . C . . . - A A A A G . . T . . . . . . . . . . A . . . . . . .Rus sp.1 mycorrhiza 1-26-5 . . . . . . . . . C . . . - A A A A G . . T . . . . . . . . . . A . . . . . . .