By Fabricio Medina-Bolívar

Editor's Note: The following article is part of an ongoing science series, written by Arkansas State University faculty members and published periodically by The Sun.

When we think of plants, the first thing that comes to our mind is what we see -- the flowers, the leaves -- and most of us will not pay attention to what is there in the underground, the roots.

Yet the roots are what give them physical support while providing the plants with a means for water and nutrient uptake, and there is a lot more.

The roots are actively interacting with the underground and manufacturing an enormous diversity of chemicals. Many of these compounds are highly complex structures and their production is still not possible in the laboratory. Thus, we can say that plant roots are indeed unique "natural chemical factories."

Many chemicals that are produced in the roots are transported to the upper part of the plant. This is the case of nicotine, the major alkaloid found in tobacco. Nicotine is actually produced in the roots and transported to the leaves where it is accumulated and believed to function in protecting the tobacco plant against insect pests.

Other root-derived chemicals are used as pharmaceutical drugs. For example, the roots of the Egyptian henbane, a plant of the same family of tobacco, produce the alkaloid hyoscyamine. Its usage dates back to antiquity: Cleopatra, Queen of Egypt, used extracts from this plant to dilate her pupils, a symbol of beauty on ancient times. Nowadays, these chemicals and their derivatives are being used as drugs used by ophthalmologists during an eye exam.

No wonder these chemicals represent a great potential for the pharmacological industry. However, studying how these different chemicals are produced in their own environment is difficult. Research at the Department of Biological Sciences at Arkansas State University has been taking advantage of a soil bacterium, Agrobacterium rhizogenes, to produce a biological system to study root-derived chemicals.

This system, called "hairy roots" originates from the transfer and integration of a piece of DNA from the bacterium into the plant's genetic code, redirecting it to produce roots. These roots are essentially programmed to grow continuously without the need of the upper parts of the plant.

The nature of these roots also represents a great potential to expand their manufacture capabilities. After all, the roots are continuously exposed to many pathogens and other stresses hence inducing the production of chemicals, many of which are antimicrobials. These inducible chemicals represent a major resource for the discovery of potential pharmaceuticals.

Experiments in my laboratory have shown that tobacco "hairy roots" can be induced to produce chemicals that are found in the leaves and even in the smoke. It is known that tobacco smoke contains more than 4000 compounds, many of them present at very low amounts. By utilizing tobacco hairy roots, now we can produce chemicals that are found in the smoke and investigate if they have any biological effect, particularly in humans.

Interestingly, some of the chemicals found in tobacco leaf and smoke may have a pharmaceutical application. For example, some researchers at ASU are studying the biological effects of nicotine in the brain cells and have been collaborating with researchers at Virginia Tech to study if some of the other chemicals in tobacco smoke and produced using the hairy root culture system could be used to control depression or in the therapy of Parkinson's disease.

For more information contact the ASU Department of Biological Sciences at biology@astate.edu.

Dr. Fabricio Medina-Bolivar is assistant professor in metabolic engineering in the Department of Biological Sciences at Arkansas State University.