Antoine Le Quéré, Kasper Astrup Eriksen, Balaji Rajashekar, Andres Schützendübel, Björn Canbäck, Tomas Johansson and Anders Tunlid
Screening for rapidly evolving genes in the ectomycorrhizal fungus Paxillus involutus using cDNA microarrays.
Molecular Ecology 15, 535 (2006)
Abstract: We have examined the variations in gene
content and sequence divergence that could be associated with
symbiotic adaptations in the ectomycorrhizal fungus Paxillus
involutus and the closely related species Paxillus
filamentosus. Strains with various abilities to form
mycorrhizae were analysed by comparative genomic
hybridizations using a cDNA microarray containing 1076
putative unique genes of P. involutus. To screen for genes
diverging at an enhanced and presumably non-neutral rate, we
implemented a simple rate test using information from both
the variations in hybridizations signal and data on sequence
divergence of the arrayed genes relative to the genome of
Coprinus cinereus. C. cinereus is a free-living saprophyte
and is the closest evolutionary relative to P. involutus that
has been fully sequenced. Approximately 17% of the genes
investigated were detected as rapidly diverging within
Paxillus. Furthermore, 6% of the genes varied in copy numbers
between the analysed strains. Genome rearrangements
associated with this variation including duplications and
deletions may also play a role in adaptive evolution. The
cohort of divergent and duplicated genes showed an
over-representation of either orphans, genes whose products
are located at membranes, or genes encoding for components of
stress/defence reactions. Some of the identified genomic
changes may be associated with the variation in host
specificity of ectomycorrhizal fungi. The proposed procedure
could be generally applicable to screen for rapidly evolving
genes in closely related strains or species where at least
one has been sequenced or characterized by expressed sequence
tag analysis.
LU TP 05-08