Project description:White-rot fungi (WRF), considered the most efficient organisms at degrading organic carbon in the biosphere, are found in plant cell wall lignin biopolymer. We employ multi-omics to demonstrate that Trametes versicolor and Gelatoporia subvermispora funnel lignin-derived aromatic compounds into central carbon metabolism via intracellular catabolic pathways. These results provide insights into global carbon cycling in soil ecosystems.
Project description:Many trees form ectomycorrhizal symbiosis with fungi. During symbiosis, the tree roots supply sugar to the fungi in exchange for nitrogen, and this process is critical for the nitrogen and carbon cycles in forest ecosystems. However, the extents to which ectomycorrhizal fungi can liberate nitrogen and modify the soil organic matter and the mechanisms by which they do so remain unclear since they have lost many enzymes for litter decomposition that were present in their free-living, saprotrophic ancestors. Using time-series spectroscopy and transcriptomics, we examined the ability of two ectomycorrhizal fungi from two independently evolved ectomycorrhizal lineages to mobilize soil organic nitrogen. Both species oxidized the organic matter and accessed the organic nitrogen. The expression of those events was controlled by the availability of glucose and inorganic nitrogen. Despite those similarities, the decomposition mechanisms, including the type of genes involved as well as the patterns of their expression, differed markedly between the two species. Our results suggest that in agreement with their diverse evolutionary origins, ectomycorrhizal fungi use different decomposition mechanisms to access organic nitrogen entrapped in soil organic matter. The timing and magnitude of the expression of the decomposition activity can be controlled by the below-ground nitrogen quality and the above-ground carbon supply.
Project description:Decomposition of soil organic matter in forest soils is thought to be controlled by the activity of saprotrophic fungi, while biotrophic fungi including ectomycorrhizal fungi act as vectors for input of plant carbon. The limited decomposing ability of ectomycorrhizal fungi is supported by recent findings showing that they have lost many of the genes that encode hydrolytic plant cell-wall degrading enzymes in their saprophytic ancestors. Nevertheless, here we demonstrate that ectomycorrhizal fungi representing at least four origins of symbiosis have retained significant capacity to degrade humus-rich litter amended with glucose. Spectroscopy showed that this decomposition involves an oxidative mechanism and that the extent of oxidation varies with the phylogeny and ecology of the species. RNA-Seq analyses revealed that the genome-wide set of expressed transcripts during litter decomposition has diverged over evolutionary time. Each species expressed a unique set of enzymes that are involved in oxidative lignocellulose degradation by saprotrophic fungi. A comparison of closely related species within the Boletales showed that ectomycorrhizal fungi oxidized litter material as efficiently as brown-rot saprotrophs. The ectomycorrhizal species within this clade exhibited more similar decomposing mechanisms than expected from the species phylogeny in concordance with adaptive evolution occurring as a result of similar selection pressures. Our data shows that ectomycorrhizal fungi are potential organic matter decomposers, yet not saprotrophs. We suggest that the primary function of this decomposing activity is to mobilize nutrients embedded in organic matter complexes and that the activity is driven by host carbon supply. Comparative transcriptomics of ectomycorrhizal (ECM) versus brown-rot (BR) fungi while degrading soil-organic matter
Project description:The photosynthetic model marine diatom Phaeodactylum tricornutum was cultured with varying nitrogen sources and availability to elicit shifts in the proteome. Cells were grown to mid-exponential phase on ammonium (880 uM), collected by centrifugation and resuspended in N-free media for 2 hrs, and spiked with nitrate (150 uM) for 90 min. Cells were again collected by centrifugation, washed in N-free media, and resuspended in experimental treatments with no nitrogen (N-) and a nitrogen source (300 uM) provided as ammonium, nitrite, or nitrate. Each experimental treatment was sampled after 15 min, 45 min, and 18 hr.
Project description:Cytochrome P450 enzymes play an important role in bioactivating or detoxifying polycyclic aromatic hydrocarbons (PAHs). We exposed mice to doses of benzo[a]pyrene (BaP) or a mixture of PAHs to characterize dose- and time-response relationships of specific cytochrome P450s. Mice exposed to the highest PAH exposures exhibited 1.7-5-fold higher intrinsic clearance rates for BaP, compared to controls, and higher Vmax values, indicating higher amounts of enzymes capable of metabolizing BaP. This study demonstrates that PAHs induce enzymes in dose- and time-dependent patterns in animal models at exposure levels researchers use to characterize hazards and at relevant human exposure levels to PAH mixtures found at Superfund sites. Accounting for these potential changes in enzyme profiles, relative rates of PAH bioactivation and detoxification, and resulting risk will help reduce uncertainty and improve risk assessments for PAHs at contaminated sites.
Project description:Proteomic data from dengue virus infected U-937 cells. PVD_C samples were infected via antibody-mediated or DC-SIGN receptor mediated entry routes with wild-type DENV-4 or mock inoculum; time points 2, 8, 16, and 24 hours; 5 biological replicates. PVD_L samples were infected via antibody-mediated or DC-SIGN receptor mediated entry routes with wild-type DENV-1 or mock inoculum; time points 2, 6, 10, 18, 24, and 30 hours; 5 biological replicates.
Project description:The photosynthetic model marine diatom Phaeodactylum tricornutum was cultured under conditions varying nitrogen content and availability, or varying iron concentrations over diel cycles to elicit shifts in the proteome and phosphoproteome. For the nitrogen experiments, cells were grown to mid-exponential phase on ammonium (880 uM), collected by centrifugation and resuspended in N-free media for 2 hrs, and spiked with nitrate (150 uM) for 90 min. Cells were again collected by centrifugation, washed in N-free media, and resuspended in experimental treatments with no nitrogen (N-) and a nitrogen source (300 uM) provided as ammonium, nitrite, or nitrate. Each experimental treatment was sampled after 15 min, 45 min, and 18 hr. For iron experiments, steady-state axenic cultures were maintained under a diel cycle of 12h light: 12h darkness and at three different concentrations of Fe' (Fe' is the sum of all Fe species not complexed to EDTA): a low concentration (20 pM Fe'), intermediate concentration (40 pM Fe') and at Fe-replete levels (400 pM Fe'). Samples were taken every four hours.