Citation:

Reichman, Jay R, P. Rygiewicz, Mark G Johnson, Michael A Bollman, Bonnie M Smith, Q Todd Krantz, Charly J King, K. Kovalcik, AND Christian P Andersen. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) Transcriptome Profile Changes Induced by Diesel Emissions Generated with CeO2 Nanoparticle Fuel Borne Catalyst. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 52(17):10067-10077, (2018). https://doi.org/10.1021/acs.est.8b02169

Impact/Purpose:

Engineered nanoparticles (ENMs) have been recognized as valuable components of new technologies and are currently being used in a variety of consumer products due to their unique physical, chemical, and electrical properties. The properties that make these particles functionally unique also may influence their toxicity to organisms in ecosystems. CSS’s Emerging Materials research is designed to identify potential adverse effects of these materials in the environment, including identification of molecular initiating events (MIE) that may lead to predictable downstream effects and subsequent adverse outcome pathway (AOP) development. The vast majority of studies characterizing the effects of ENMs have used native particles, which may not reflect the toxicity associated with particle release through product use. In this study, we examined changes in gene expression in Douglas-fir seedlings exposed to diesel exhaust with and without nCeO2 as a fuel-added catalyst. After two weeks of exposure, there was deposition and binding of Ce in the needles of seedlings exposed to diesel exhaust containing nCeO2, and the elevated Ce was associated with altered gene expression patterns. Nearly 94% of the significantly down-regulated genes associated with nCeO2-diesel exhaust were unique. Affected genes included 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. Analyses also identified RNA regulation of transcription, protein degradation, and lipid metabolism pathways that were enriched with down-regulated transcripts. Even though diesel exhaust without nCeO2 affected expression of more total genes than exhaust containing nCeO2, the unique transcriptome profiles indicated that the addition of nCeO2 to diesel fuel may uniquely affect plant physiology and development. These findings raise important questions on the effects of compounds released into the environment from products containing engineered nanomaterials, and may lead to sensitive earlier indicators of ENM exposure in some plant species.

Description:

It is important to understand molecular effects on plants exposed to compounds released from use of products containing engineered nanomaterials. Here, we present mRNA sequencing data on transcriptome impacts to Douglas-fir following 2 weeks of sublethal exposure to 30:1 diluted airborne emissions released from combustion of diesel fuel containing engineered CeO2 nanoparticle catalysts (DECe). Our hypothesis was that chamber exposure to DECe would induce distinct transcriptome changes in seedling needles compared with responses to conventional diesel exhaust (DE) or filtered DECe Gas Phase. Significantly increased uptake/binding of Ce in needles of DECe treated seedlings was 2.7X above background levels and was associated with altered gene expression patterns. All 225 Blast2GO gene ontologies (GOs) enriched by up-regulated DECe transcripts were nested within GOs for DE, however, 29 of 31 enriched GOs for down-regulated DECe transcripts were unique. MapMan analysis also identified three pathways enriched with DECe down-regulated transcripts. There was prominent representation of genes with attenuated expression in transferase, transporter, RNA regulation and protein degradation GOs and pathways. CeO2 nanoparticle additive decreased and shifted molecular impact of diesel emissions. Wide-spread use of such products and chronic environmental exposure to DECe may adversely affect plant physiology and development.

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