RNA-sequencing analysis of Douglas-fir transcriptome responses to diesel emissions generated with CeO2 nanoparticle additive

Transcriptome changes of Douglas-fir seedlings were analyzed to investigate molecular impacts of exposure to airborne emissions released from combustion of diesel fuel containing engineered cerium dioxide (CeO2) nanoparticle catalysts (DECe). We analyzed mRNA-sequencing data from exposed one-year-old needles. Our hypothesis is that 2-week chamber exposure to DECe would induce certain distinct transcriptome changes in the needles compared with responses to conventional diesel exhaust (DE) or filtered DECe Gas Phase. Blast2GO gene ontologies (GOs) enriched by significantly up-regulated DECe transcripts were nested within the GOs for DE, however, 93.5% of enriched GOs for significantly down-regulated DECe transcripts were unique. DECe attenuated expression of genes that affect functions of transferases, kinases, transmembrane transporters, transcription factors, diester hydrolases and RNA polymerase III; processes of protein phosphorylation, responses to stimuli, hormones and chemicals, carbohydrate transport, RNA polymerase III transcription, and cellular anion homeostasis; plus, components of the plasma membrane. MapMan analysis also identified RNA regulation of transcription, protein degradation, and lipid metabolism pathways that were enriched with DECe down-regulated transcripts. Divergent DECe treatment effects were associated with significantly elevated needle uptake of cerium. DE affected expression of more genes than DECe. Nevertheless, unique transcriptome profile changes suggest that chronic DECe exposure may adversely affect plant growth and development.