The genome of Laccaria bicolor provides insights into mycorrhizal symbiosis
Author
Summary, in English
Mycorrhizal symbioses -- the union of roots and soil fungi -- are universal in terrestrial ecosystems and
may have been fundamental to land colonization by plants1,2. Boreal, temperate, and montane forests all
depend upon ectomycorrhizae1. Identification of the primary factors that regulate symbiotic
development and metabolic activity will therefore open the door to understanding the role of
2
ectomycorrhizae in plant development and physiology, allowing the full ecological significance of this
symbiosis to be explored. Here, we report the genome sequence of the ectomycorrhizal basidiomycete
Laccaria bicolor (Fig. 1) and highlight gene sets involved in rhizosphere colonization and symbiosis. This
65-million-base genome assembly contains ~ 20,000 predicted protein-encoding genes and a very large
number of transposons and repeated sequences. We detected unexpected genomic features most notably
a battery of effector-type small secreted proteins (SSP) with unknown function, several of which are only
expressed in symbiotic tissues. The most highly expressed SSP accumulates in the proliferating hyphae
colonizing the host root. The ectomycorrhizae-specific proteins likely play a decisive role in the
establishment of the symbiosis. The unexpected observation that the genome of L. bicolor lacks
carbohydrate-active enzymes involved in degradation of plant cell walls, but maintains the ability to
degrade non-plant cell walls, reveals the dual saprotrophic and biotrophic lifestyle of the mycorrhizal
fungus which enables it to grow within both soil and living plant roots. The predicted gene inventory of
the L. bicolor genome, therefore, points to previously unknown mechanisms of symbiosis operating in
biotrophic mycorrhizal fungi. The availability of this genome provides an unparalleled opportunity to
develop a deeper understanding of the processes by which symbionts interact with plants within their
ecosystem in order to perform vital functions in the carbon and nitrogen cycles that are fundamental to
sustainable plant productivity.
may have been fundamental to land colonization by plants1,2. Boreal, temperate, and montane forests all
depend upon ectomycorrhizae1. Identification of the primary factors that regulate symbiotic
development and metabolic activity will therefore open the door to understanding the role of
2
ectomycorrhizae in plant development and physiology, allowing the full ecological significance of this
symbiosis to be explored. Here, we report the genome sequence of the ectomycorrhizal basidiomycete
Laccaria bicolor (Fig. 1) and highlight gene sets involved in rhizosphere colonization and symbiosis. This
65-million-base genome assembly contains ~ 20,000 predicted protein-encoding genes and a very large
number of transposons and repeated sequences. We detected unexpected genomic features most notably
a battery of effector-type small secreted proteins (SSP) with unknown function, several of which are only
expressed in symbiotic tissues. The most highly expressed SSP accumulates in the proliferating hyphae
colonizing the host root. The ectomycorrhizae-specific proteins likely play a decisive role in the
establishment of the symbiosis. The unexpected observation that the genome of L. bicolor lacks
carbohydrate-active enzymes involved in degradation of plant cell walls, but maintains the ability to
degrade non-plant cell walls, reveals the dual saprotrophic and biotrophic lifestyle of the mycorrhizal
fungus which enables it to grow within both soil and living plant roots. The predicted gene inventory of
the L. bicolor genome, therefore, points to previously unknown mechanisms of symbiosis operating in
biotrophic mycorrhizal fungi. The availability of this genome provides an unparalleled opportunity to
develop a deeper understanding of the processes by which symbionts interact with plants within their
ecosystem in order to perform vital functions in the carbon and nitrogen cycles that are fundamental to
sustainable plant productivity.
Department/s
Publishing year
2008
Language
English
Pages
7-88
Publication/Series
Nature
Volume
452
Issue
7183
Document type
Journal article (letter)
Publisher
Nature Publishing Group
Topic
- Biological Sciences
Status
Published
Project
- Mobilization of organic nitrogen by ectomycorrhizal fungi
Research group
- Microbial Ecology
ISBN/ISSN/Other
- ISSN: 0028-0836