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A recent study of field trials in Oregon and Arizona demonstrated that poplar trees can be genetically modified to not harm the quality of the air, and that these genetic modifications do not impact their growth potential.



Technology Networks spoke with Russell Monson, Professor of Ecology and Evolutionary Biology at the University of Arizona and lead author of the study, to learn more about why the scientists adopted RNA interference and the regulations that surround genetically modified trees.



Molly Campbell (MC): Why did you choose to genetically modify poplar trees? What was the rationale behind the study?



Russell Monson (RM): Two reasons. First, we wanted to study more about why isoprene emission from trees is important to them. That it, what is the advantage of having this trait and is it necessary for their growth and vigor. Poplar trees are an easy plant system to examine these issues because the genome is well-described, it is easy to genetically modify them and they grow quickly, so we could examine growth without having to study them for too many years. Second, it is one of the trees favoured for agroforestry plantations and commercial development in the biofuel and paper-products industries. Thus, the emission of isoprene and its effects on air quality are a real-world issue that could be detrimental to the environment. We recognized that our research would have applications to helping solve this issue.



MC: Why did you choose to use RNA interference (RNAi) to genetically modify the trees?



RM: This is a technology for genetically modifying poplar trees that is well-tested. The newer technology of CRISPR will likely replace RNAi in the future, but it was not feasible six years ago when we first started our study.



MC: After genetically modifying the trees, what methods did you use to analyze the biochemical pathways in the trees to assess whether they had been altered? Why did you opt for these methods?



RM: Our RNAi treatments were intended to knock-out gene expression for the enzyme isoprene synthase, which controls the emission of isoprene to the atmosphere. We tested all of our genetically-modified lines for isoprene emission from their leaves by direct measurements using specialized isoprene detection instruments. Mainly a photon fluorescence isoprene detector from Hills Scientific.



MC: Did you encounter any challenges in the process of this research study?



RM: Oh yes, there are always challenges. One of the main ones was getting permission from the US Department of Agriculture to conduct the study. The first generation of RNAi poplar lines were produced in Germany, but we were not allowed to test lines produced outside the country using field trials within the country. So, we had to support the visit of a German post-doc to Corvallis, Oregon to work with Professor Steve Strauss to reproduce the RNAi lines in a US laboratory. We also had technical challenges with the proteomic analysis of the altered lines. This was conducted using new technologies and it took several years to get everything working well for the poplar samples that we collected.



MC: What impact could this study potentially have on climate change and fossil fuel research?



RM: If poplar plantations expand in temperate latitudes, it is likely that they will be placed near to urban or suburban communities. The mixing of plantation air with urban/suburban air has the potential to create ozone, an important greenhouse gas and primary product of automobile air pollution. Our study makes it clear that there are alternatives to these impacts, if genetic modification of trees is permitted and utilized. Our results are highly relevant to other plantation tree species, such as oil palms and eucalyptus, which are also isoprene emitters. These tree species are being used at much greater amounts in plantations in the tropics and sub-tropics. Especially with the expanded use of palm oil, the potential for palm plantations to produce isoprene and affect climate change and air quality is especially relevant to our research.



MC: What regulations exist surrounding the trees that you have genetically modified? What impact do these regulations have on your research and the progression of the research field?



RM: We must observe strictly regulated procedures in maintaining genetically modified lines in field plantings. The plantations are subjected to regular inspections by USDA staff. These regulations would indeed likely inhibit large-scale use of these types of genetic lines, as currently employed.



Russell Monson, Professor of Ecology and Evolutionary Biology at the University of Arizona, was speaking with Molly Campbell, Science Writer, Technology Networks.



Reference: Monson et al. (2020). High productivity in hybrid-poplar plantations without isoprene emission to the atmosphere. PNAS. DOI: https://doi.org/10.1073/pnas.1912327117.

