IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Session Details: Wednesday 30 November 2011
Plenary Session 5
0900 - 1030
Authors: Erik Limpens 1 , Sergey Ivanov 1 , Evgenia Ovchinnikova 1,2 , Alexey Borisov 2 , Rik op den
Camp 1 , Stephane de Mita 3 , René Geurts 1 , Elena Fedorova 1,4 , Ton Bisseling 1
1 Laboratory of Molecular Biology, Wageningen University, The Netherlands.
2 All-Russia Research Institute for Agricultural Microbiology, Laboratory of Genetics of
Plant-Microbe Interactions, St. Petersburg, Russia.
3 Plant Diversity and Adaptation, Institute for Research and Development, Montpellier,
France.
4 Timiryazev Institute of Plant Physiology RAS, Moscow, Russia.
Presentation Title: Formation of a symbiotic interface in rhizobial and mycorrhizal symbioses
Presentation Time: 0930 – 1000
In both the rhizobium-legume symbiosis and the arbuscular mycorrhizal symbiosis the microbes are hosted
intracellularly in a novel, specialized membrane compartment that forms a symbiotic interface. The formation of
this interface is at the heart of symbiosis. In the case of rhizobia they are accommodated as novel nitrogen-fixing
organelles, called symbiosomes, inside infected cells of the root nodule. Arbuscular mycorrhizal (AM) fungi form
highly branched hyphal structures, called arbuscules, in infected root cortical cells. In both cases the microbial
symbiont is surrounded by a plant derived membrane that has a special plasma membrane identity and where
generally a structured plant cell wall is lacking. It has recently become clear that the signaling molecules and
signaling pathway that trigger these different symbioses are strikingly similar. We show that this signaling
pathway also controls the formation of the symbiotic interfaces in both symbioses. The observed plasma
membrane identity of both interface membranes indicates a major role for exocytotic vesicle traffic. By studying
plasma membrane (PM) SNARE proteins we show that knock-down of specific PM SNARE members blocks the
release of the bacteria from cell wall bound infection threads and/or subsequent symbiosome development.
Furthermore, two specific SNARE proteins required for symbiosome formation are also essential for arbuscule
formation by AM fungi. These results suggest that in evolution the ability to produce Nod factors gave rhizobia
the ability to use the ancient AM machinery to recruit a specific exocytotic pathway for the establishment of a
symbiotic interface.
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