Plant's Defenses Used Against Them

April 13, 1997

San Francisco, Calif. -- With their roots stuck in the ground, the only way plants can attract pollinators or deter predators is to produce chemicals that entice beneficial organisms and repel or destroy dangerous ones, according to a Penn State researcher.

Defense compounds, colors and flavors have commercial uses, but the plants or plant cells must be coerced into producing in reliable and sufficient quantities in manufacturing settings. These potential products include vanilla, morphine, taxol, quinine, ginseng and shikonen -- a red dye.

"Plants or plant cells only produce these secondary metabolites when they need them, and manufacturers would like a reliable way of producing these chemicals in the factory," says Dr. Gurmeet Singh, assistant professor of chemical engineering. "What we are trying to due is bluff the plant into thinking it is being attacked," Singh told attendees at the American Chemical Society meeting today (April 13) in San Francisco.

Singh's approach, called elicitation, is to grow plant cells in nutrient solutions and to force the cells to produce secondary metabolites by adding dead, cell wall fragments of fungus. If live fungi were used, they would kill the plants.

"The fungi fragments turn on the secondary metabolite pathways," says Singh. "With this type of prodding we can increase production as much as 500 fold."

Singh notes that it is not just the defensive chemicals that react to the invasion of fungus, but that flavor and color chemicals are also produced. These same chemical pathways are also turned on if a plant is physically wounded.

In the manufacturing environment, producers want to use just the right amount of fungus fragments to optimize chemical production.

"If manufacturers add too much, they would waste expensive fungus and risk damaging the plant cells, but if they add too little, they might under exploit the cells," says Singh.

The Penn State scientist is looking at the fungus concentration in the liquid and the complicated interaction of this elicitor with the cells to come up with commercially useful formulas for elicitor addition.

He is also looking at a natural plant compound, methyljasmonate, and its interaction with fungal elicitors. Methyljasmonate is a chemical produced by most plants and is thought to be used to signal other plants. A very volatile compound, methyljasmonate quickly diffuses through the air where it can be sensed by other plants. The exact information conveyed is unknown.

"However, when methyljasmonate is mixed with the fungal elicitor, the amount of elicitor needed decreases dramatically," says Singh. "Since methyljasmonate is much less expensive than fungal elicitors, this could help manufacturers."

Singh does not know the mechanism involved in methyljasmonate's enhancement of fungal elicitors, but he does know that methyljasmonate by itself, does not elicit production of secondary metabolites.

**aem**

EDITOR: Dr. Singh may be reached at (814) 865-1628 or gxs11@psuvm.psu.edu

Penn State

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