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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 . . . . . . .
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