Wood is a major pool of organic carbon that is highly resistant to decay, owing largely to the presence of lignin. The only organisms capable of substantial lignin decay are white rot fungi in the Agaricomycetes, which also contains non–lignin-degrading brown rot and ectomycorrhizal species. Comparative analyses of 31 fungal genomes (12 generated for this study) suggest that lignin-degrading peroxidases expanded in the lineage leading to the ancestor of the Agaricomycetes, which is reconstructed as a white rot species, and then contracted in parallel lineages leading to brown rot and mycorrhizal species. Molecular clock analyses suggest that the origin of lignin degradation might have coincided with the sharp decrease in the rate of organic carbon burial around the end of the Carboniferous period.
Incompatibility systems in which individuals bearing identical alleles reject each other favor the maintenance of a diversity of alleles. Mushroom mating type loci (MAT) encode for dozens or hundreds of incompatibility alleles whose loss from the population is greatly restricted through negative frequency selection, leading to a system of alleles with highly divergent sequences. Here we use DNA sequences of homeodomain (HD) encoding genes the MAT locus of five closely related species of the root rot basidiomycete Heterobasidion annosum sensu lato to show that the extended coalescence time of MAT alleles greatly predates speciation in the group, contrasting loci outside of MAT that show allele divergences largely consistent with the species phylogeny with those of MAT which show rampant trans-species polymorphism. We observe a roughly six-fold greater genealogical depth and polymorphism of MAT compared to non-MAT which argues for the maintenance of balanced polymorphism for a minimum duration of 24 million years based on a molecular-clock calibrated species phylogeny. As with other basidiomycete HD genes, balancing selection appears to be concentrated at the specificity-determining region in the N-terminus of the protein based on identification of codons under selection and the absence of recombination within the region. However, the elevated polymorphism extends into the non-specificity determining regions as well as a neighboring non-MAT gene, the mitochondrial intermediate peptidase (MIP). In doing so, increased divergence should decrease recombination among alleles and as a by-product create incompatibilities in the functional domains not involved in allele recognition but in regulating sexual development.
Tree rusts are fungal diseases causing dusty orange or brown spots (pustules) on the leaves of poplar, willow, birch, plum and five-needled pine.
Tree rusts cause eye-catching infections on the leaves of some trees, particularly Populus spp. (poplar), Salix spp. (willow), Betula spp. (birch), plum and Pinus spp. (five-needled pines). Tree rusts may be seen from spring until autumn for trees that lose their leaves in winter (deciduous) and all year on evergreens.
These are the rust fungi involved:
> Poplar rust is caused by several species of Melampsora
> Willow rust is also caused by several species of Melampsora, but not the same as those infecting poplars
> Birch rust is caused by Melampsoridium betulinumPlum rust is caused by Tranzschelia pruni-spinosae var. discolor
> Five-needled pines are infected by white pine blister rust, caused by Cronartium ribicola
Brown rot decay removes cellulose and hemicellulose from wood—residual lignin contributing up to 30% of forest soil carbon—and is derived from an ancestral white rot saprotrophy in which both lignin and cellulose are decomposed. Comparative and functional genomics of the “dry rot” fungus Serpula lacrymans, derived from forest ancestors, demonstrated that the evolution of both ectomycorrhizal biotrophy and brown rot saprotrophy were accompanied by reductions and losses in specific protein families, suggesting adaptation to an intercellular interaction with plant tissue. Transcriptome and proteome analysis also identified differences in wood decomposition in S. lacrymans relative to the brown rot Postia placenta. Furthermore, fungal nutritional mode diversification suggests that the boreal forest biome originated via genetic coevolution of above- and below-ground biota.
RNA interference (RNAi) refers to a mechanism in which cells control gene expression, protect the genome against mobile repetitive DNA sequences, retro elements and transposons, and defend themself against viruses. Two core components, dicer and argonaute, are central in the RNAi machinery. In this study the evolution of argonaute and dicer genes were analyzed, with the focus on Basidiomycota, using 43 fungal genomes. Argonaute and dicer genes are widely represented in Basidiomycota as well as in other fungal groups but the number of copies of them vary. However, in certain lineages, argonaute or dicer is missing. Our results suggest an ancient duplication of dicer and argonaute genes concurrently with early diversification of the Basidiomycota followed by additional species specific duplications and losses of more recent origin. Several distinct RNAi pathways exist in fungi, based on structural similarity and phylogenetic relationship, our results indicate that quelling possibly exist in most Basidiomycota, while we could not find any evidence for the MSUD (meiotic silencing) pathway in Basidiomycota. RNAi has been developed to an important tool for reverse genetics studies. Since both argonaute and dicer are present in almost all Basidiomycota our results indicate that it should be possible to develope RNAi as a tool for functional studies of genes in most Basidiomycota species.
This meeting will focus on the scientific work currently investigating the many pest and disease threats to our woodlands. As well as talks on a wide range of relevant topics there will also be opportunities to discuss issues on a more informal basis. Presentations at the meeting will be selected from abstracts submitted by delegates.
Abstracts must be submitted online by 16th July 2013. Please use the abstract upload function when registering.
UKPSF has just launched a new website that collates the latest information on ash dieback. The site will be updated regularly with news on relevant research findings, funding opportunities, meetings and policy developments. You can sign up to receive email updates by subscribing via the homepage.
The button mushroom occupies a prominent place in our diet and in the grocery store where it boasts a tasty multibillion-dollar niche, while in nature, Agaricus bisporus is known to decay leaf matter on the forest floor. Now, owing to an international collaboration of two-dozen institutions led by the French National Institute for Agricultural Research (INRA) and the U.S. Department of Energy Joint Genome Institute (DOE JGI), the full repertoire of A. bisporus genes has been determined. In particular, new work shows how its genes are actually deployed not only in leaf decay but also wood decay and in the development of fruiting bodies (the above ground part of the mushroom harvested for food). The work also suggests how such processes have major implications for forest carbon management. The analysis of the inner workings of the world’s most cultivated mushroom was published online the week of October 8 in the journal, the Proceedings of the National Academy of Sciences (PNAS).
Scientists are reporting new evidence that a white rot fungus shows promise in the search for a way to use waste corn stalks, cobs and leaves – rather than corn itself – to produce ethanol to extend supplies of gasoline.
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