The fungus that came in from the cold: dry rot's pre-adapted ability to invade buildings.

Many organisms benefit from being pre-adapted to niches shaped by human activity, and have successfully invaded man-made habitats. One such species is the dry rot fungus Serpula lacrymans, which has a wide distribution in buildings in temperate and boreal regions, where it decomposes coniferous construction wood. Comparative genomic analyses and growth experiments using this species and its wild relatives revealed that S. lacrymans evolved a very effective brown rot decay compared to its wild relatives, enabling an extremely rapid decay in buildings under suitable conditions. Adaptations in intracellular transport machineries promoting hyphal growth, and nutrient and water transport may explain why it is has become a successful invader of timber in houses. Further, we demonstrate that S. lacrymans has poor combative ability in our experimental setup, compared to other brown rot fungi. In sheltered indoor conditions, the dry rot fungus may have limited encounters with other wood decay fungi compared to its wild relatives. Overall, our analyses indicate that the dry rot fungus is an ecological specialist with poor combative ability against other fungi.

Interdependence of Primary Metabolism and Xenobiotic Mitigation Characterizes the Proteome of Bjerkandera adusta during Wood Decomposition.

The aim of the current work was to identify key features of the fungal proteome involved in the active decay of beechwood blocks by the white rot fungus Bjerkandera adusta at 20°C and 24°C. A combination of protein and domain analyses ensured a high level of annotation, which revealed that while the variation in the proteins identified was high between replicates, there was a considerable degree of functional conservation between the two temperatures. Further analysis revealed differences in the pathways and processes employed by the fungus at the different temperatures, particularly in relation to nutrient acquisition and xenobiotic mitigation. Key features showing temperature-dependent variation in mechanisms for both lignocellulose decomposition and sugar utilization were found, alongside differences in the enzymes involved in mitigation against damage caused by toxic phenolic compounds and oxidative stress.IMPORTANCE This work was conducted using the wood decay fungus B. adusta, grown on solid wood blocks to closely mimic the natural environment, and gives greater insight into the proteome of an important environmental fungus during active decay. We show that a change in incubation temperature from 20°C to 24°C altered the protein profile. Proteomic studies in the field of white-rotting basidiomycetes have thus far been hampered by poor annotation of protein databases, with a large proportion of proteins simply with unknown function. This study was enhanced by extensive protein domain analysis, enabling a higher level of functional assignment and greater understanding of the proteome composition. This work revealed a strong interdependence of the primary process of nutrient acquisition and specialized metabolic processes for the detoxification of plant extractives and the phenolic breakdown products of lignocellulose.

Serpula lacrymans, Wood and Buildings.

Serpula lacrymans, the causative agent of dry rot timber decay in buildings, is a Basidiomycete fungus in the Boletales clade. It owes its destructiveness to a uniquely well-developed capacity to colonize by rapid mycelial spread from sites of initial spore infection, coupled with aggressive degradation of wood cellulose. Genomic methods have recently elucidated the evolution and enzymic repertoire of the fungus, suggesting that it has a distinctive mode of brown rot wood decay. Using novel methods to image nutrient translocation, its mycelium has been modeled as a highly responsive resource-supply network. Dry rot is preventable by keeping timber dry. However, in established outbreaks, further mycelial spread can be arrested by inhibitors of translocation.

Differential expression of a putative riboflavin-aldehyde-forming enzyme (raf) gene during development and post-harvest storage and in different tissue of the sporophore in Agaricus bisporus.

Cloning and characterisation of a putative riboflavin-aldehyde-forming enzyme gene (raf) from the cultivated mushroom Agaricus bisporus and its expression during morphogenesis are described. Three cDNA clones were isolated following differential screening of cDNA libraries from rapidly expanding sporophores and post-harvest stored sporophores. The cDNA sequence and predicted translation analysis revealed an open reading frame (ORF) of 348 nucleotides encoding a polypeptide of 115 amino acids, with three introns (56-66 bases) interrupting the genomic ORF. Blast X searches of the databases with the gene sequence showed homology (40% identity and 56% similarity) to the riboflavin-aldehyde-forming enzyme gene from Schizophyllum commune. In A.bisporus, the raf gene sequence upstream of the ORF contained a large CT-rich putative regulatory element (-64 to -24 bases) found in highly expressed genes in various mushrooms, and a 6-base motif present in the 3' end of the genomic sequence, but not in the corresponding 3' non-coding part of the cDNA, was identified. The raf gene transcripts increased abundantly in rapidly developing sporophores as well in post-harvest stored sporophores. Differential expression of the raf gene transcripts in different tissues of the sporophore was also observed, with higher levels in the stipe compared with the cap and gills. The temporal and spatial expression patterns observed suggest transcriptional regulation of the raf gene during A. bisporus morphogenesis.

Cloning and postharvest expression of serine proteinase transcripts in the cultivated mushroom Agaricus bisporus.

Increases in both the levels and the activity of serine proteinase have been previously described in the senescing mushroom Agaricus bisporus. cDNA encoding serine proteinase was amplified by reverse transcriptase-polymerase chain reaction using a degenerate primer based on the N-terminal sequence of a previously isolated A. bisporus serine proteinase and then cloned. The cDNA was sequenced and shown to be homologous to those of other fungal serine proteinases. Northern analysis showed that this serine proteinase gene (Spr1) was not expressed in freshly harvested sporophores but was strongly up-regulated postharvest and found almost entirely in the stipe of the sporophore (approximately 0.08% of mRNAs 2 days after harvest). Low-level expression was detectable in the flesh (pileus trama) and gill (lamellae) tissues of the cap, but none was detected in the skin (pilei pellis). In three of the cloned cDNAs, sequence analysis showed that the poly(A) tail starts at different positions. Expression of Spr1 in Escherichia coli caused restricted colony growth.