The MYSTERYof the altered GENEProfessor Peter M Gresshoff

p.gresshoff@uq.edu.au

www.cilr.uq.edu.au

NODULE FORMATION and

NITROGEN FIXATION

Professor Peter M Gresshoff

p.gresshoff@uq.edu.au

www.cilr.uq.edu.au

Nodules

Sucrose

1 mmNitrogen Gas

Ammonium Amino acids/protein/DNA/RNA

LEGUMES form NODULES

N2 + 16 ATP + 8 e- + 8 H+

2 NH3 + 16 ADP + H2

ENERGY:Solar (photosynthesis) or fossil (Haber-Bosch process)????

ENERGY:Solar (photosynthesis) or fossil (Haber-Bosch process)????

Protein-rich Seeds Protein-rich Seeds Cell Division Cell Division

Nitrogen Fixation Nitrogen Fixation

Endosymbiosis Endosymbiosis Colonisation Colonisation

Nodule induction Nodule induction

Root hairdeformation and curling Root hair

deformation and curling

Nodulation and nitrogen fixation are key processes for food, feed, and fuel

Nodulation and nitrogen fixation are key processes for food, feed, and fuel

Nod factors

Rhizobium

FLAVONES

Nod genes

Legume Root

RECEPTIONNFR1/5

Root hairsRhizobia

Curling root Curling root hairhair

Infection thread

Cell walls

Infection pocket

Inner cortex cells dividing

Cell nuclei

Vascular bundle

Rhizobia in cortex

Infection thread

Nodule Nodule primordiumprimordium

CortexCortexXylemXylem

PhloemPhloem

EpidermisEpidermis

Bacteroids

Vasculature

NucleusNodule cortex

Rhizobium cells (25,000)

The NODULATION processallows the conversion of atmospheric nitrogen gas to ammonia- which is a fertiliser for all plants

The NODULATION processallows the conversion of atmospheric nitrogen gas to ammonia- which is a fertiliser for all plants

Bacteroid withina legume nodule cells, engulfed by a plant membrane controlling nutrient and ammonia transport

Bacteroid withina legume nodule cells, engulfed by a plant membrane controlling nutrient and ammonia transport

malate

ammonia

aminoacids

N2 + 16 ATP + 8 e- + 8 H+

2 NH3 + 16 ADP + H2

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