Project description:We examined the use of toxicogenomics data to 1) elucidate the underlying mechanisms of pulmonary responses following exposures to titanium dioxide (TiO2) nanoparticles (NPs) of different size and surface charge, and 2) determine if such responses are influenced by embedding particles in complex paint matrix. Adult C57BL/6 mice were exposed via single intratracheal instillation to three doses of free forms of NRCWE-030 (10.5 nm), NRCWE-025 (38 nm), NRCWE-001 (10 nm, neutral charge) NRCWE-002 (10 nm, positive charge) or to sanding dusts of paint consisting of NRCWE-030+NRCWE-025 or NRCWE-025 alone. Controls were exposed to dispersion medium without NPs. TiO2NPs were characterized for size, surface area, and agglomeration status in the exposure medium. Hyperspectral microscopy was performed to detect TiO2NPs in lungs and to determine the in vivo status of matrix-embedded TiO2NPs. Pulmonary gene expression profiles were generated using DNA microarrays on lung tissues collected at 24 h and 28 d post exposure time points. Bioinformatics tools were used to characterize size and surface property-pertinent effects. The data from 360 individual arrays were collapsed into 567 differentially expressed genes (False discovery rate adjusted P ≤ 0.05 and fold change ≥ 1.5 in any one condition). Unsupervised hierarchical clustering of the 567 genes revealed that TiO2NPs clustered mainly based on the post-exposure time points and then by the particle types. A meta analysis using pathway tools showed that the combination of smaller size and positive surface charge contributes to the potency of TiO2NPs. Although embedding in matrix dampens the overall toxicity of TiO2NPs, the smaller size positively influences the toxicity. Paint matrix itself did not induce any response. Finally, the observed differences in response reflected the differences in severity of the response and not the underlying mechanisms. Thus, transcriptional profiling is an effective tool to determine the important properties responsible for eliciting a response.

Project description:UnlabelledBackgroundThe recalcitrance of lignocellulosic cell wall biomass to deconstruction varies greatly in angiosperms, yet the source of this variation remains unclear. Here, in eight genotypes of short rotation coppice willow (Salix sp.) variability of the reaction wood (RW) response and the impact of this variation on cell wall recalcitrance to enzymatic saccharification was considered.ResultsA pot trial was designed to test if the 'RW response' varies between willow genotypes and contributes to the differences observed in cell wall recalcitrance to enzymatic saccharification in field-grown trees. Biomass composition was measured via wet chemistry and used with glucose release yields from enzymatic saccharification to determine cell wall recalcitrance. The levels of glucose release found for pot-grown control trees showed no significant correlation with glucose release from mature field-grown trees. However, when a RW phenotype was induced in pot-grown trees, glucose release was strongly correlated with that for mature field-grown trees. Field studies revealed a 5-fold increase in glucose release from a genotype grown at a site exposed to high wind speeds (a potentially high RW inducing environment) when compared with the same genotype grown at a more sheltered site.ConclusionsOur findings provide evidence for a new concept concerning variation in the recalcitrance to enzymatic hydrolysis of the stem biomass of different, field-grown willow genotypes (and potentially other angiosperms). Specifically, that genotypic differences in the ability to produce a response to RW inducing conditions (a 'RW response') indicate that this RW response is a primary determinant of the variation observed in cell wall glucan accessibility. The identification of the importance of this RW response trait in willows, is likely to be valuable in selective breeding strategies in willow (and other angiosperm) biofuel crops and, with further work to dissect the nature of RW variation, could provide novel targets for genetic modification for improved biofuel feedstocks.

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Physical-chemical properties of cell wall interface significantly correlated to the complex recalcitrance of corn straw.

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