Transcriptome Changes in Douglas-fir (Pseudotsuga menziesii) Induced by Exposure to Diesel Emissions Generated with CeO2 Nanoparticle Fuel Additive

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; FDR ≤ 0.05). 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.