01.04.08 
Southeastern biology professor publishes research that could help reduce pests in stored grain

By Southeastern University

An international, academic journal has published the findings of research by a Southeastern biology professor that could lead to significant strides in helping the food and agriculture industry reduce mealworm infestation in stored grain and stored grain products.

The paper, titled "Sequence analysis and molecular characterization of larval midgut cDNA transcripts encoding peptidases from the yellow mealworm, Tenebrio molitor L." represents four years of research for Dr. Sheila Abraham, an assistant professor of biology at Southeastern. The paper can be found in the August 2007 edition of Insect Molecular Biology, volume 16, issue IV, pages 455-468; it is published under her maiden name of Prabhakar.

Collaborating with Russian scientists through a United States Department of Agriculture project, Dr. Abraham researched the physiological and molecular processes in the digestive tract of the yellow mealworm (Tenebrio molitor) - a beetle that feeds on stored grains, including corn, rice, and wheat in bins or silos.

"Our research was to find a way to use protease inhibitors as insect control agents," Dr. Abraham said. A protease is an enzyme that insects use to digest proteins, and a protease inhibitor is something found in plants that inhibits that process. Protease inhibitors are natural ways to defend against insect attack because they interfere with the mealworm's ability to digest proteins.

Protease inhibitors stop digestive enzymes from breaking down proteins by competing with the enzyme for the binding site of the protein and preventing the mealworm from digesting the protein. They disrupt the normal digestive process and therefore hinder insect growth and development.

Dr. Abraham's research involved identifying the DNA sequence of the genes that encode the enzymes that digest proteins in the larval midgut (the middle of the digestive tube in the mealworm's larval form). She began by identifying the DNA sequence of genes and comparing the sequence she found with known genes in other creatures so she could predict the function of her unknown gene sequence.

Once she identified the function of the genes she was able to use that knowledge to find the right combination of protease inhibitors to interfere with the mealworms' digestion. The protease inhibitors she fed them are solid chemicals found naturally occurring in plants. The mealworms have learned to overcome the effects of natural protease inhibitors, but Dr. Abraham's research sought to manipulate the exact concoction they could not overcome.

When mealworms in Dr. Abraham's experiments were fed diets containing a single protease inhibitor, the mealworms were found to compensate for the effects of inhibitors and survive. But Dr. Abraham found that when fed a combination of two protease inhibitors, the mealworm's larvae grew half as much and suffered detrimental physiological effects that could keep them from developing into a mealworm.

The yellow mealworm is one of the largest pests of stored grain and results in significant economic loss to the food processing industry. Because mealworms grow so large (the larva can grow up to two centimeters long) and have a long life cycle of one year, they consume large amounts of the stored grain as well as damage the grain by leaving behind their exoskeletal remains.

Dr. Abraham said that while further research is needed, these findings hold promise for reducing mealworm infestation of stored products. Protease inhibitors would serve as a viable alternative to chemical pesticides since they are safe and eco-friendly. Using multiple, genetically engineered protease inhibitors in plants and using them in conjunction with other genes that harm the pest would be a natural and effective long-term strategy for pest management.

A native of India, Dr. Abraham earned her bachelor's degree in biology from Osmania University College for Women in Hyderabad, India, and later earned her master's degree in zoology from Osmania University, also in Hyderabad. Upon graduation from her master's program, Dr. Abraham was honored as the top academic performer in her class and received gold medals in zoology and entomology. She then moved to the United States and earned a PhD in entomology from Kansas State University in Manhattan, Kansas.

In August 2006, Dr. Abraham joined Southeastern's faculty. At the university, she has enjoyed the opportunity to integrate her study of science with her Christian faith, as well as to pursue her passion for teaching. She also met her husband since coming to Lakeland.

At Southeastern, Dr. Abraham teaches zoology, ecology, human biology, bioethics, and cell and molecular biology.