Symbiotische Interaktionen mit freundlichen Mikroorganismen

unterstützen Wasser- und Ionenaufnahme von Wurzeln – wollen

dafür aber auch reduzierten Kohlenstoff von Pflanzen

Beneficial interaction between plants and microbes

N2fixing bacteria/legumes

nodule ↓

mycorrhiza

endomycorrhizaectomycorrhiza

↓

endophytes

bacteriafungi

roottip ↓

↓

Common feature:Promotion of plant performance

1. Colonisation of roots 2. Promotion of growth & biomass

3. Resistanz aginst abiotic & biotic stress

drought heavy metal pathogen infection

mycorrhial fungi andrhizobacteria

- few host plants

endophytesoften colonizes many hosts

- important for agriculture- easier recognition mechanisms

Pi-504 - Cellotriose

C H O

biomolecules

Myc-factor (LCO#)

C H O N S

Nod-factor (LCO#)

C H O N S

P. indica

(Sebacinales)

host range

AM fungi

(Glomeromycota)

Rhizobia

(Rhizobiales)

all planta tested

so far

P. indica

AM fungus*

Rhizobium*

microbe

moss* monocots A. thaliana* dicots

monocots dicots

legumes

[Ca]2

+c

yt(μ

M)

[Ca]2

+c

yt(μ

M)

[Ca]2

+c

yt(μ

M)

#LCO: lipochitooligosaccharide

Both partners MUST profitfrom the symbiosis.

Photosynthesis

↓

sucrosewater, soil

nutrients,

phosphate,

nitrogen

• mycorrhiza: – 450 mio years old– first land plants

• N2-fixing rhizobacterialsymbioses: – 60 mio years old– evolved from mycorrhizal symbioses

• → similar recognition and signalingpathways

Evolution

Two types ofmycorrhiza

Beneficial interaction between plants and microbes

N2fixing bacteria

/legumesnodule ↓

mycorrhiza

endomycorrhizaectomycorrhiza

↓

endophytes

bacteriafungi

roottip ↓

↓

Beneficial interaction between plants and microbes

mycorrhiza

endomycorrhizaectomycorrhiza

↓

Endo-Mycorrhiza

arbuscles

Fungal and plant cells are COMPLETELY separated.

- 80% of endomycorrhizal fungi are arbuscularmycorrhiza (VAM)

- only 6 fungal species [Glomales, Zygomycetes] form VAM

Endo-Mycorrhiza

Initiation:

- germination of spores- Hyphae form appressorium

(attachment sites)

- Formation of an extracellular hyphal system in theapoplast

Penetration:

- formation of haustorium: penetration into the plant cell

- Extracellular hyphae:

- collection of nutrients from rhizosphere

- Intracellular hyphae:

- enlargement of interaction surface- nutrient/metabolite exchange with plant cell

Life time of arbuscle: a few days

extracellularhyphae

intracellular arbuscles

Ekto-Mycorrhiza

hyphae: rhizosphere, on root surface, between root cellsdo not enter vascular tissue

fruit bodies

• many trees form ectomycorrhizas

• Hartig Net:– a net around the root (hairs) to extent access to soil

nutrients

Hartig Net

• Optimization of nutrient exchanges

• Protection against soil pathogens

• Connection of organisms in biotops– 60 km network– Support for young trees in forests– Connections between different plant species

Function of Hartig Net

Beneficial interaction between plants and microbes

N2fixing bacteria/legumes

nodule ↓

Rhizobia interacting with roots of

Legumes

Rhizobia-LegumeInteraction

• Haber-Bosch: N-fertilizer

• N2 fixation – rhizobacteria

– cyanobacteria

N2 + 8H+ + 8e- + 16 ATP = 2NH3 + H2 + 16ADP + 16 Pi

N2

fixation

rhizobia withnitrogenase

bacterialnitrogenase

Ferox

Ferred

ATP

ADP

NH4

+

N2

photosynthesis

- nitrogenase O2-sensitive

- leghaemoglobin (plant- and bacteria-encoded)

Rhizobia interacting with roots of

Legumes

Rhizobia-LegumeInteraction

Rhizobia under N limitation

alfalfa soybean

recognition