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Transcriptome Changes in Douglas-fir (Pseudotsuga menziesii) Induced by Exposure to Diesel Emissions Generated with CeO2 Nanoparticle Fuel Additive
Citation:
Reichman, J., P. Rygiewicz, Mike Bollman, B. Smith, Todd Krantz, C. King, AND C. Andersen. Transcriptome Changes in Douglas-fir (Pseudotsuga menziesii) Induced by Exposure to Diesel Emissions Generated with CeO2 Nanoparticle Fuel Additive. International PAG XXIV - Plant and Animal Genome 2016, San Diego, CA, January 09 - 13, 2016.
Impact/Purpose:
Metals are sometimes added to fuels to improve engine combustion efficiencies and reduce pollutant emissions. Formulations including CeO2 nanoparticles have become commercially available for addition to diesel fuels. When CeO2 nanoparticles are added to diesel fuel, the emissions (DECe) have characteristics that differ from conventional diesel exhaust (DE). Previous EPA research demonstrated that DECe induces more adverse pulmonary effects in rats on a mass basis than DE, which raises human health concerns. In addition to investigating the human health effects associated with CeO2 nanoparticle fuel additives, EPA is interested in understanding their possible impacts on terrestrial ecosystems. Effects of DECe on plants have not been studied. Here we report gene expression changes in Douglas-fir seedlings exposed to DECe that are distinct from DE or the DECe gas phase. Interesting examples of biological processes altered included response to cadmium ion, response to cold, response to abscisic acid and mRNA methylation. The gene expression changes documented here point to potential molecular initiating events and downstream adverse outcomes in plants exposed to DECe. The use of actual combustion products provides a real-world exposure of CeO2 nanoparticles to plants, unlike previous studies using native particles.
Description:
When cerium oxide nanoparticles are added to diesel fuel, fuel burning efficiency increases, producing emissions (DECe) with characteristics that differ from conventional diesel exhaust (DE). It has previously been shown that DECe induces more adverse pulmonary effects in rats on a mass basis than DE, which raises human health concerns. However, effects of DECe on plants have not been studied. We examined if 2 weeks of chamber exposure to DECe would induce transcriptome responses in Douglas-fir seedlings that are distinct from response to DE or the DECe gas phase. RNA-seq data were collected for 1-year old needles from 25 seedlings (DECe N = 7; DE N = 7; DECe gas phase N = 5; Air Control N = 6). Contigs for each sample were assembled using the 199,623 sequence psme_transcriptome_v202 as the template. There were 519, 1672 and 1051 significantly regulated transcripts in DECe, DE and DECe Gas phase compared to controls, respectively, based on ≥2-fold change and 95% confidence. Transcriptome changes under DECe treatment were unique regarding sequence identity of regulated genes, ratio of up to down-regulated transcripts, and significantly enriched gene ontologies (P ≤ 0.05). Interesting examples of biological process enrichment by up-regulated transcripts included responses to cadmium ion, cold, abscisic acid, and mRNA methylation. The differential gene expression documented here points to potential molecular initiating events and downstream adverse outcomes in plants exposed to DECe. Impacts to of DECe on plant development and reproduction remain to be determined. These results provide a frame of reference for future studies to compare responses across plant species and to evaluate effects of various exposure regimes.