Rik Op den Camp, Arend Streng, Stephanie De Mita,
Quingpin Cao, Elisa Polone, Wei Liu, Jetty S. S. Ammiraju,
Dave Kudrna, Rod Wing, Andreas Untergasser, Ton
Bisseling, Rene Geurts
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Rik Op den Camp
◦ PhD student Molecular Biology at Wageningen
University
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Arend Streng
◦ PhD researcher at Wageningen University
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STEPHANE DE MITA
◦ Ph.D, molecular evolutionist
◦ Do mutually beneficial symbioses cause strong selective pressures
and represent an evolutionary driving force comparable to hostpathogen relationships?
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Focused on the independent evolution of the
recognition of the rhizobial signal that starts
the symbiotic interaction...The nod factor
Identify the genetic constraints which caused
such Nod Factor signaling
◦ Compare it to the Myc Factor
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Soil bacteria that help
to fix nitrogen after
entering into the root
nodule of a plant cell.
Usually unique for
legumes
◦ However, it has been
found that Parasponia,
a non legume has a
rhizobia nodule
symbiosis.
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***Symbiosis is
induced for all by
specific Nod factors
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Plant
◦ nitrogen in a usable form because of nitrogen
fixation
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Rhizobia
◦ Reduced carbon
◦ Protective environment
Legume
Non legume
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 Parasponia
Key: Both have symbiosis with
bacteria to fix nitrogen.
Fabaceae
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-Lipochitooligosaccharides
-Nod factors are perceived
by specific Lys M receptor
kinases
-Activate a signaling
cascade
-Results in the
introduction of a dominant
active form of
calcium/calmodulindependent kinase (CCaMK)
Allow for rhizobia to enter
plant cell
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Signal to allow for the response of
a plant cell to be penetrated by a
fungus
Induces a Calcium spike
Part of symbiosis between plant
and fungi
Lipochito-oligosaccharides
Myc Factor receptors, like Nod
factor receptors are presumed to
activate a common pathway to
initiate this symbiosis. Thus,
before these to differentiated
maybe a DUAL PURPOSE RECEPTOR
existed!
This experiment sought to prove,
if not find its existence.
Parasponia andersonii = a plant
member of the non-legume,
nitrogen fixing, group
Sinorhizobium = a broadly
occurring bacteria used to
illustrate Nod factor use
Medicago truncatula MtCCaMK=
a dominant active kinase that
spontaneously forms nodules in
both legumes and Parasponia
They introduced a normal strain of Sinorhizobium to P. andersonii
and a mutant strain
to a different batch of P. andersonii.
The Mutant bacteria had the Nod factor disabled and NO nodules
formed.
The Normal bacteria produced healthy, nitrogen fixing nodules.
By using an extremely dominant and fast acting kinase, Medicago
truncatula MtCCaMK,
nodules were able to spontaneously form on both the legume and P.
andersonii.
-There is a common signaling pathway used
between two organisms in order to gain
functioning nodules
- This pathway is activated upon a Nod Factor
Perception
- Legumes have two factors to initiate the
common pathway, we hope to find that P.
andersonii only has one!
-The only one capable of the mechanisms
needed is the MtNFP/LjNFR5 factor
What does this mean?
They need to find the gene(s) that
code for this and compare it to
relative species in order to varify its
unique properties
Method to Identify Gene:
Southern Blotting and Sequencing (Very Similar to PCR)
MtNFP/LjNFR5- like receptor named PaNFP
Fulfills Dual Function of intracellular lifestyle:
both the Arbuscular Mycorrhiza and rhizobium.
Unique to Parasponia as only having this one receptor!
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Favor: Mycorrhizal signaling
pathway including the Myc
receptor being recruited by
the legumes to make a
common signaling pathway
Nod factors then have
emerged then by gene
duplication
Support:
Chitooligosaccharides which
is the backbone of the Nod
factor is a fungal
characteristic
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Strength
◦ Detailed evidence to prove their interpretation of
the data
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Weakness
◦ Does not disprove the second way in which states
the recognition of the Nod factor was created
without the Myc factor involved
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How does a plant then clarify whether it is a fungi or
a bacteria making the symbiosis?
◦ Look at the differences in the spike of Calcium to see if
large enough difference can verify the symbiosis.