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The Power of Trees: Keys to Fuel, Pharmaceutical and Climate Challenges

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Chung-Jui (CJ) Tsai in her lab.
Credit: Marsha Walton

College students who excel in science often gravitate toward careers in medicine. In outreach programs and workshops, plant biologist Chung-Jui (CJ) Tsai opens up other possibilities for students who want to explore microbiology, biotechnology, and emerging fields such as CRISPR genome editing.

“You can do everything you do as a medical doctor, but your patients won’t run from you, they won’t bleed on you,” she said. “We have a lot of natural resource issues that we can address, too.”

From wood and paper to energy and pharmaceuticals, everyday life depends on trees and the ecological services they provide. Tsai’s research involves understanding and improving on what trees offer.

Tsai, the Winfred N. Haynes Professor in Forest Biotechnology at the University of Georgia in Athens, said her passion for trees developed somewhat by chance. With the rigid higher education structure in her native Taiwan, Tsai did not have full control over what she would study when she started university.

“My first choice was psychology. I got into forestry college by accident. I thought for a while I might switch. But then I started to do forest soil, forest genetics, and it started being interesting to me,” she said.

When a professor taught her how to look for Mycorrhizae fungi spores, a Ph.D. student in that lab warned her that she would soon be dreaming of spores.

“That really happened! After a few days as soon as you close your eyes, I was seeing all the spores,” said Tsai.

The intense effort paid off.

“I think I did really well,” she said. “I apparently helped the professor identify new Mycorrhizae spore species. At the time I did not really quite know what the big picture was. But it was an interesting job, to see how the information in the classroom could be related to the real world. So then I worked my way into a tissue culture lab, and I became hooked. That’s really how I got into biotechnology and molecular biology, and genomics.”

She remembers the cooperation and encouragement she got from older students and dedicated mentors at Taiwan University in Taipei. That’s why Tsai said now, when she teaches, she explains to students that even if they are doing repetitive, technical work, they need to understand how the information may be applied later, whether for improving crop yields or making biofuels more efficient.

Climate change, biofuels production, and invasive diseases are among the long-term challenges in her field.

Tsai believes the evolutionary hardiness of trees makes them one of the best models for studying climate change. A better understanding of how trees, with their longevity, cope with stresses — from drought to high temperatures, to insect infestations – could help facilitate answers to many global warming threats.

In 2008, Tsai moved her lab from Michigan Technological University to the University of Georgia in the deep south, known as the “wood basket” of the country. It’s a region where the lumber and paper industries have been economic drivers for centuries. The genomic technology used by her team, added to the hands-on knowledge of generations of tree farmers, brings benefits and new avenues for agricultural innovation.

“Genetic improvement is already ingrained into plantation forests. It’s not really such a big jump to think about CRISPR, (a genome editing tool) identifying suitable genetic material with more precision and in a much quicker manner,” she said.

“This is also an area where a very intensive tree breeding program has been going on, especially with pines. But it is hopelessly slow. I think people already have this idea that you can improve the germplasm, improve the genetic material, make it more beneficial,” she said.

While scientists can learn a great deal from a tree’s longevity, a tree’s lifespan of decades or even centuries makes traditional multi-generational studies impossible. That’s why gene editing techniques have become such an important tool for tree biologists.

TREE’S MYSTERIOUS POLYMER: LIGNIN

One plant component with qualities that continue to baffle plant biologists, farmers and biofuels researchers is lignin, a biopolymer that makes wood strong and durable.

“Lignin, I think it is a mysterious polymer, but also a really fantastic polymer,” said Tsai. Coming from the pulp and paper industry’s perspective, lignin is a troublemaker. In biofuels, lignin is also a troublemaker.

The search is on now to find ways to take advantage of its strength, and to use its sometimes unwieldy parts in as many ways as possible.

“So the main thinking is to perhaps utilize lignin in a biological manner that you could potentially harvest your cellulosic materials for bio based industry, but then also recycle, or re-use, extract, or partition lignin for other applications,” she said.

Researchers are seeking new methods of reducing the complexity of lignin with processes that are a lot more environmentally friendly, and that generate less pollution. Efforts are underway, for example, to produce carbon nanotubes from lignin. (Carbon nanotubes, with their unusual electronic, magnetic and mechanical properties, are opening new doors in materials science. Nanotube fibers can be used to strengthen almost any type of material.) Another use is for biomedical materials for medicinal applications.

Tsai said understanding these complex polymers is still a slow process. While some of its properties are better understood than they were a few years ago, researchers have also uncovered more types of lignin units, and learned about lignin in different tissues and different tree species.

NEW AVENUES FOR PLANTS AS FUEL

While humans have used wood as fuel for millennia, experts are looking for answers to make it a lot more efficient than just throwing another log on the fire.

In 2000, Tsai joined the bioenergy research center, based at Oak Ridge National Laboratory in Tennessee. She said about 200 principle investigators are part of the team, from specialists in lignin chemistry, lignin polymers, to the microbial side, focused on improving genetic materials to use biomass more efficiently.

For this aspect of her research, she is working on the CRISPR engineering of poplar trees. CRISPR is a very precise and efficient method of editing genes by cutting DNA.

“This is really how perhaps bioenergy research is heading; an integrated approach with large teams, and specialized expertise including life cycle analyses,” she said.

Tsai’s current research also includes the mapping of the dogwood tree genome; studying a group of genes responsible for sucrose transport, and understanding the role of salicylic acid in growth and disease resistance.

MEDICINAL QUALITIES OF TREES

Certain types of tree bark have been used as medicine for centuries. Perhaps the best known is willow bark, which contains the compound salicylic acid, the active ingredient in aspirin. Tsai’s lab studies those phenolic compounds in tree bark and leaves, used by the trees for disease resistance.

“Salicylic acid provides important defensive compounds in poplars and willows. We know the chemical structure, but we don’t really know how they are synthesized; or in what genes,” said Tsai.

In humans, aspirin is good at reducing fever but may upset the stomach. In plants, spraying salicylic acid on them can give them better disease resistance, but too much can be toxic.

And in some species, increasing salicylic acid for better disease resistance stunts the growth of the tree.

Tsai and her colleagues have identified multiple mechanisms involved in using salicylic acid to help plants improve their disease resistance without jeopardizing growth or yield.

Tsai gets continuous input on new approaches to research from a graduate course she teaches in functional genomics.

“So it evolves over time but focuses on emerging technologies, new twists from the fundamental principles that students learn in foundation classes. It is an opportunity to introduce how biology and engineering, how some of those concepts actually come together, along with the technological improvements for biological research,” she said.

Students in the class have a variety of majors spanning the schools of agriculture, forestry, ecology, and engineering.

Tsai said from the wood, paper, energy, fruits, nuts and pharmaceuticals that they produce, to less tangible things such as carbon sequestration and wildlife habitat, our everyday life depends on trees.

“Trees are under-appreciated,” said Tsai.

And there’s a constant challenge to convince governments and policymakers that certain types of research are critical, even though it may be years or decades before answers are reached.

“It is difficult, it is a pressure we all face,” she said.

She stresses to students that there is intrigue and satisfaction in plant biology, as well as many career options, from academia, to the traditional lumber and paper industry, to organic farming and alternative fuels.

And whether or not someone is making trees their life’s work, they can enjoy the benefits they provide. Perhaps when communities are designed, she said, beyond incorporating necessities like water, power and sewer systems, city planners could add trees to the list of essentials.

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Marsha Walton