Trees and fungi have constructed a close relationship with the passing
of the ages. Fungi like to grow between the roots of trees and the
arrangement is beneficial to both partners. Their delicate balance is now
being revealed for the very first time. VIB researchers at Ghent University
in collaboration with an international team have succeeded in unraveling the
genetic code of the Laccaria bicolor fungus. This new information is crucial
to our knowledge. It will lead to a better understanding of how fungi help
trees to grow and how together they can be indicators of climate change.
Trees and fungi live happily together
Trees are the lungs of the earth. They draw CO2 from the atmosphere
and convert it into sugars, which then become a source of energy. In the
process they breathe O2 back into the atmosphere. This "green" production of
biomass ? trees account for 90% of the planet's land-based biomass ? is a
major influence on the health of our planet.

Trees grow better and faster when certain specialized micro-organisms
occur in their root systems. One such organism is the Laccaria bicolor
fungus. The symbiotic relationship of the fungus and the tree root systems
is advantageous to both. The fungus facilitates the uptake of scarce
nutrients such as phosphates and nitrogen and protects the roots against
parasites in the soil. In return they are able to draw on the sugars in the
roots. 85% of all plants and trees are dependent on symbiotic processes of
this kind for their growth.

Genetic code of symbiotic fungus yields up first secrets
An international collaborative project was set up to characterize the
genome of the soil fungus Laccaria bicolor . VIB scientists Pierre Rouzé and
Yves Van de Peer, working with France's renowned INRA and JGI of the US,
have sequenced the DNA of the fungus. They have been able to identify 20,000
genes in the fungal genome. Their analyses immediately resulted in new
knowledge, including the discovery of an arsenal of small proteins known as
SSPs (small secreted proteins), which are only made at those places where
the fungus and the tree root come into contact. The genome study also
revealed that the fungus is unable to break down plant cells but does affect
the cell walls of pathogens. This could explain how these fungi protect
their symbiotic partners. Additionally the researchers identified genes
which play a role in communicating with all the players in the surroundings
of the roots of the host tree during growth.

Fungi: barometers of climate change?
A better understanding of the genetic secrets of this fungus does not
just hold out the prospect of being able to optimize biomass production;
research into the delicate balance between fungus and tree may also yield
important information that could be used to monitor climate change. Not only
has the genome of the Laccaria bicolor been fully sequenced, that of the
poplar, one of the trees with which it forms a relationship, is also fully
known. This will make it possible to find out exactly how tree and fungus
cooperate and react to stress factors such as drought or extreme
temperatures resulting from climate change. The hope exists that the
assembled information will result in concrete applications in which trees
and fungi can be deployed to the benefit of both people and the environment.

Yves Van de Peer leads the group of Bioinformatics and Evolutionary
Genomics in the VIB Departement of Plant Systems Biology, UGent ? under
direction of Dirk Inzé. (more info:
www.vib.be/Research/EN/Research+Departments/Department+of+Plant+Systems+Biology/Yves+Van+de+Peer/)

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