The Laccaria genome: a symbiont blueprint decoded.
The first genomic sequence for a representative of symbiotic fungi, the ectomycorrhizal basidiomycete Laccaria bicolor, has been published. The unravelling of this genome provides tantalizing hints about differences between this symbiotic fungus and its saprotrophic and pathogenic relatives. An expansion of several multigene families occurred in L. bicolor, suggesting that adaptation to symbiosis proceeded by gene duplication. Within lineage-specific genes those coding for symbiosis-regulated secreted proteins showed an up-regulated expression in ectomycorrhizas. L. bicolor is lacking enzymes involved in the degradation of plant cell wall components (cellulose, hemicellulose, pectins and pectates), preventing the symbiont from degrading host cells. By contrast, L. bicolor possesses expanded multigene families associated with hydrolysis of bacterial and microfauna polysaccharides and proteins. The genome analysis revealed the dual saprotrophic and biotrophic lifestyle of the mycorrhizal fungus that enables it to grow within both soil and living plant roots. The next stages will involve finer-scale investigation of gene networks to reveal the details of the general patterns now uncovered at the genomic level. The acceptance of L. bicolor as a model organism for symbiosis genetics will, however, depend strongly on the availability of additional genetic, genomic and molecular biological resources, such as gene inactivation procedures.
Martin
Francis
F
UMR1136 INRA-Nancy Université Interactions Arbres/Micro-organismes, IFR110, Centre de Nancy, 54280 Champenoux, France.
Selosse
Marc-André
MA
UMR5175, Centre d'Ecologie Fonctionnelle et Evolutive, Equipe Interactions Biotiques, 1919 Route de Mende, 34 293 Montpellier cedex 5, France.
D004251:DNA Transposable Elements; D015966:Gene Expression Regulation, Fungal; D005828:Genetics, Population; D016681:Genome, Fungal; D055399:Laccaria / Q000235:genetics*; D005810:Multigene Family; D038821:Mycorrhizae / Q000235:genetics*; D018517:Plant Roots / Q000382:microbiology; D032107:Populus / Q000382:microbiology; D012098:Reproduction; D015398:Signal Transduction; D013559:Symbiosis / Q000235:genetics
D004251:DNA Transposable Elements