Scientists have engineered poplar trees to not harm air quality, according to a new study.

Like palms and eucalyptus trees, poplars emit isoprene. Their leaves produce the highly volatile chemical in response to stress, like rising temperatures and drought. The chemical triggers the production of other protective compounds. Because the leaves produce so much isoprene and the molecules are so volatile, some of the isoprene escapes into the air.

Poplar stands, grown to be harvested for biofuels, toilet paper, furniture and more, now cover 36,294 square miles of lands -- double the amount of land they did 15 years ago. As a result, more isoprene is being leaked into the atmosphere.

Isoprene molecules react with sunlight to produce ozone, a respiratory irritant. It also encourages the production of atmospheric aerosols, fueling the formation of haze and boosting the greenhouse gas effect of methane.

Through lab experiments, scientists at the University of Arizona, Portland State University, Oregon State University and the Helmholtz Research Center in Munich, Germany, successfully modified the genes of poplar trees to suppress the production of isoprene.

In field tests, researchers planted and monitored the growth of the genetically engineered trees. The data, published this week in the journal PNAS, showed the lack of isoprene did not interfere with the trees' photosynthesis of biomass production rates.

Even the genetically modified trees grown in Arizona, where the climate is hot and dry, grew healthy and tall.

"The suppression of isoprene production in the leaves has triggered alternative signaling pathways that appear to compensate for the loss of stress tolerance due to isoprene," lead study author Russell Monson, a professor of ecology and evolutionary biology at the University of Arizona, said in a news release. "The trees exhibited a clever response that allowed them to work around the loss of isoprene and arrive at the same outcome, effectively tolerating high temperature and drought stress."

The research suggests isoprene emissions can be reduced without impacting biomass production among poplar tree plantations.

The genetic engineering technique deployed by the research team, called RNA interference, was developed by scientists at the Institute of Biochemical Plant Pathology, part of the Helmholtz Research Center.

"RNA interference is like a vaccination -- it triggers a natural and highly specific mechanism whereby specific targets are suppressed, be they the RNA of viruses or endogenous genes," said Helmholtz researcher Steven H. Strauss.

Researchers hypothesized that the trees didn't suffer growth reductions because poplar trees do most of their growing during the colder, wetter times of the year, when isoprene is less essential.

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