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The brown rot fungus Fomitopsis pinicola efficiently depolymerizes wood cellulose via the combined activities of oxidative and hydrolytic enzymes. Mass spectrometric analyses of culture filtrates identified specific proteins, many of which were differentially regulated in response to substrate composition.

Wood-decaying fungi tend to have characteristic substrate ranges that partly define their ecological niche. Fomitopsis pinicola is a brown rot species of Polyporales that is reported on 82 species of softwoods and 42 species of hardwoods. We analyzed gene expression levels of F. pinicola from submerged cultures with ground wood powder (sampled at 5 days) or solid wood wafers (sampled at 10 and 30 days), using aspen, pine, and spruce substrates (aspen was used only in submerged cultures). Fomitopsis pinicola expressed similar sets of wood-degrading enzymes typical of brown rot fungi across all culture conditions and time points. Nevertheless, differential gene expression was observed across all pairwise comparisons of substrates and time points. Genes exhibiting differential expression encode diverse enzymes with known or potential function in brown rot decay, including laccase, benzoquinone reductase, aryl alcohol oxidase, cytochrome P450s, and various glycoside hydrolases. Comparing transcriptomes from submerged cultures and wood wafers, we found that culture conditions had a greater impact on global expression profiles than substrate wood species. These findings highlight the need for standardization of culture conditions in studies of gene expression in wood-decaying fungi.IMPORTANCE All species of wood-decaying fungi occur on a characteristic range of substrates (host plants), which may be broad or narrow. Understanding the mechanisms that allow fungi to grow on particular substrates is important for both fungal ecology and applied uses of different feedstocks in industrial processes. We grew the wood-decaying polypore Fomitopsis pinicola on three different wood species—aspen, pine, and spruce—under various culture conditions. We found that F. pinicola is able to modify gene expression (transcription levels) across different substrate species and culture conditions. Many of the genes involved encode enzymes with known or predicted functions in wood decay. This study provides clues to how wood-decaying fungi may adjust their arsenal of decay enzymes to accommodate different host substrates.

The emerald ash borer (EAB) is an invasive beetle that has killed hundreds of millions of ash trees throughout North America since its arrival. The use of entomopathogenic fungi as part of integrated pest management approaches is considered effective against a wide range of insect pests. The aim of this study was to screen and select locally adapted EAB-associated entomopathogenic fungi with ovicidal effect on EAB eggs under laboratory conditions. The pathogenicity of nine fungal strains, previously isolated from EAB galleries, and the commercial Beauveria bassiana strain GHA was tested. Three of these, Akanthomyces muscarius 48-27, Lecanicillium longisporum 66-14 Lecanicillium psalliotae 59-2, and GHA B. bassiana strain consistently showed significant ovicidal effects and a high percentage of inoculum recovery both from eggs and neonate larvae. The high levels of inoculum recovery from neonate larvae demonstrate that, even after emergence, larvae were infected. The possibility of disrupting EAB's life cycle at the egg stage through microbial control represents a potential management opportunity that should be explored in future field studies. Future work should also study the effect of EPF on neonate larvae survival and performance. To our knowledge, this is the first study to evaluate the effect of entomopathogenic fungi against the egg stage of EAB. [ABSTRACT FROM AUTHOR]

Basidiomycota (basidiomycetes) make up 32percent of the described fungi and include most wood decaying species, as well as pathogens and mutualistic symbionts. Wood-decaying basidiomycetes have typically been classified as either white rot or brown rot, based on the ability (in white rot only) to degrade lignin along with cellulose and hemicellulose. Prior genomic comparisons suggested that the two decay modes can be distinguished based on the presence or absence of ligninolytic class II peroxidases (PODs), as well as the abundance of enzymes acting directly on crystalline cellulose (reduced in brown rot). To assess the generality of the white rot/brown rot classification paradigm we compared the genomes of 33 basidiomycetes, including four newly sequenced wood decayers, and performed phylogenetically-informed Principal Components Analysis (PCA) of a broad range of gene families encoding plant biomass-degrading enzymes. The newly sequenced Botryobasidium botryosum and Jaapia argillacea genomes lack PODs, but possess diverse enzymes acting on crystalline cellulose, and they group close to the model white rot species Phanerochaete chrysosporium in the PCA. Furthermore, laboratory assays showed that both B. botryosum and J. argillacea can degrade all polymeric components of woody plant cell walls, a characteristic of white rot. We also found expansions in reducing polyketide synthase genes specific to the brown rot fungi. Our results suggest a continuum rather than a dichotomy between the white rot and brown rot modes of wooddecay. A more nuanced categorization of rot types is needed, based on an improved understanding of the genomics and biochemistry of wood decay.

Fungi of the phylum Basidiomycota (basidiomycetes), make up some 37percent of the described fungi, and are important in forestry, agriculture, medicine, and bioenergy. This diverse phylum includes symbionts, pathogens, and saprotrophs including the majority of wood decaying and ectomycorrhizal species. To better understand the genetic diversity of this phylum we compared the genomes of 35 basidiomycetes including 6 newly sequenced genomes. These genomes span extremes of genome size, gene number, and repeat content. Analysis of core genes reveals that some 48percent of basidiomycete proteins are unique to the phylum with nearly half of those (22percent) found in only one organism. Correlations between lifestyle and certain gene families are evident. Phylogenetic patterns of plant biomass-degrading genes in Agaricomycotina suggest a continuum rather than a dichotomy between the white rot and brown rot modes of wood decay. Based on phylogenetically-informed PCA analysis of wood decay genes, we predict that that Botryobasidium botryosum and Jaapia argillacea have properties similar to white rot species, although neither has typical ligninolytic class II fungal peroxidases (PODs). This prediction is supported by growth assays in which both fungi exhibit wood decay with white rot-like characteristics. Based on this, we suggest that the white/brown rot dichotomy may be inadequate to describe the full range of wood decaying fungi. Analysis of the rate of discovery of proteins with no or few homologs suggests the value of continued sequencing of basidiomycete fungi.

Fungi of the phylum Basidiomycota (basidiomycetes), make up some 37percent of the described fungi, and are important in forestry, agriculture, medicine, and bioenergy. This diverse phylum includes symbionts, pathogens, and saprobes including wood decaying fungi. To better understand the diversity of this phylum we compared the genomes of 35 basidiomycete fungi including 6 newly sequenced genomes. The genomes of basidiomycetes span extremes of genome size, gene number, and repeat content. A phylogenetic tree of Basidiomycota was generated using the Phyldog software, which uses all available protein sequence data to simultaneously infer gene and species trees. Analysis of core genes reveals that some 48percent of basidiomycete proteins are unique to the phylum with nearly half of those (22percent) comprising proteins found in only one organism. Phylogenetic patterns of plant biomass-degrading genes suggest a continuum rather than a sharp dichotomy between the white rot and brown rot modes of wood decay among the members of Agaricomycotina subphylum. There is a correlation of the profile of certain gene families to nutritional mode in Agaricomycotina. Based on phylogenetically-informed PCA analysis of such profiles, we predict that that Botryobasidium botryosum and Jaapia argillacea have properties similar to white rot species, although neither has liginolytic class II fungal peroxidases. Furthermore, we find that both fungi exhibit wood decay with white rot-like characteristics in growth assays. Analysis of the rate of discovery of proteins with no or few homologs suggests the high value of continued sequencing of basidiomycete fungi.

Efficient lignin depolymerization is unique to the wood decay basidiomycetes, collectively referred to as white rot fungi. Phanerochaete chrysosporium simultaneously degrades lignin and cellulose, whereas the closely related species, Ceriporiopsis subvermispora, also depolymerizes lignin but may do so with relatively little cellulose degradation. To investigate the basis for selective ligninolysis, we conducted comparative genome analysis of C. subvermispora and P. chrysosporium. Genes encoding manganese peroxidase numbered 13 and five in C. subvermispora and P. chrysosporium, respectively. In addition, the C. subvermispora genome contains at least seven genes predicted to encode laccases, whereas the P. chrysosporium genome contains none. We also observed expansion of the number of C. subvermispora desaturase-encoding genes putatively involved in lipid metabolism. Microarray-based transcriptome analysis showed substantial up-regulation of several desaturase and MnP genes in wood-containing medium. MS identified MnP proteins in C. subvermispora culture filtrates, but none in P. chrysosporium cultures. These results support the importance of MnP and a lignin degradation mechanism whereby cleavage of the dominant nonphenolic structures is mediated by lipid peroxidation products. Two C. subvermispora genes were predicted to encode peroxidases structurally similar to P. chrysosporium lignin peroxidase and, following heterologous expression in Escherichia coli, the enzymes were shown to oxidize high redox potential substrates, but not Mn2. Apart from oxidative lignin degradation, we also examined cellulolytic and hemicellulolytic systems in both fungi. In summary, the C. subvermispora genetic inventory and expression patterns exhibit increased oxidoreductase potential and diminished cellulolytic capability relative to P. chrysosporium.

Raffaelea lauricola causes laurel wilt of avocado, Persea americana. Host X pathogen interactions were examined with light and scanning electron microscopy. The susceptible avocado cultivar 'Simmonds' was inoculated and examined 5 cm above the inoculation site 3, 7, 14, 21, and 42 days after inoculation (dai). No external symptoms were observed at 3 and 7 dai, and there were no anatomical differences when compared with the mock-inoculated plants. By 14 dai, external symptoms were present and dark discoloration had developed in sapwood. Tylose development increased significantly by 14 dai, and was positivity correlated with disease severity (P < 0.05). By 14 dai, gels formed in xylem vessels, fibers, and adjacent parenchyma cells; they were associated with xylem blockage and composed of phenols, pectin, and lipids, as suggested by, respectively, toluidine blue O, ruthenium red, and Sudan III stains. With a chitin-specific stain, fluorescein-conjugated wheat germ agglutinin, infrequent mycelia, and conidia of R. lauricola were visualized within xylem lumena and fibers, regardless of sample date. Understanding how avocado responds to the presence of this pathogen could assist the development of laurel wilt-resistant avocado genotypes and inform efforts to manage this disease with other measures. Key words: avocado, laurel wilt, Raffaelea lauricola, Xyleborus glabratus, ambrosia beetle. Le Raffaelea lauricola cause la fletrissure du laurier chez l'avocat. Les auteurs ont examine les interactions hote x pathogene a l'aide de la microscopie photonique et electronique par balayage. Ils ont inocule le cultivar d'avocat 'Simmonds' susceptible, et ont examine la partie situee a 5 cm au dessus du site d'inoculation, 3, 7, 14, 21, et 42 jours apres l'inoculation (jai) On n'observe aucun symptome aux jai 3 et 7, et il n'y a pas de differences anatomiques lorsque que l'on compare avec les plants inocules a blanc. Vers le jai 14, on observe des symptomes externes montrant une decoloration foncee se developpant dans l'aubier. Le developpement des thylles augmente significativement vers le jai 14 et montre une correlation avec la severite de la maladie (P < 0,05). Vers le jai 14, des gels se forment dans les vaisseaux du xyleme, les fibres et les cellules de parenchymes adjacentes; ils sont associes au blocage du xyleme et sont composes de phenols, pectine et lipides, tel que suggere par les colorations au bleu de toluidine O, au rouge de ruthenium, et au Soudan III. Independamment de la date d'echantillonnage, on observe a l'aide d'un colorant specifique a la chitine, une fluoresceine conjuguee al'agglutinine du germe de ble, une presence peu frequente de myceliums et de conidies du R. lauricola dans les lumens du xyleme et des fibres. Une meilleure comprehension des reactions de l'avocat a la presence de ce champignon pathogene pourrait aider a developper des genotypes d'avocat resistants a cette fletrissure et orienter les efforts d'amenagement de la maladie vers d'autres directions. Mots-cles : avocat, fletrissure du laurier, Raffaelea lauricola, Xyleborus glabratus, scolyte du bois. [Traduit par la Redaction], Introduction Laurel wilt affects American members of the Lauraceae plant family, including the important fruit crop avocado (Persea americana Mill.) and native trees in the southeastern USA, such as redbay [...]