A main research interest of Dr. Shih's laboratory is to introduce potential disease resistance genes into crop plants through genetic engineering techniques to increase resistance of these plants to fungal or viral infections. Currently, his laboratory is in the process of generating transgenic plants that express high levels of chitinase and beta-1,3-glucanase. Both these enzymes are hydrolytic enzymes which degrade the polysaccharides chitin and beta-1,3-glucan, respectively. Chitin and beta-1,3-glucan are major cell wall components of most fungal species.
In addition to chitinase and beta-1,3-glucanase, other plant defense proteins will also be tested for antifungal purposes. These proteins include thionin, ribosome inactivating proteins, and lytic peptides.
For increasing the resistance to viral infection, the strategies of applying the coat protein-mediated protection and production of antisense and ribozyme molecules will be tested.
Besides the transgenic/disease resistance research, Dr. Shih's laboratory is doing basic studies on the biochemical properties of protein factors involved in plant defense systems and on regulation of the genes encoding these factors. Specifically, his laboratory is currently in the process of characterizing the chitinase and the beta-1,3-glucanase activities from strawberry plants, purifying these enzymes, and preparing genomic libraries for characterization of the genes encoding these enzymes.
An additional reseach project that is currently carried out in Dr. Shih's laboratory is the identification and characterization of the enzyme(s) in tung seeds that is involved in converting linoleic acid into eleostearic acid. Eleostearic acid is an 18-C fatty acid with three conjugated double bonds, and it is the predominant fatty acid in tung oil. The final goal of this research is to use this enzyme(s) through biotechnology methods to convert linoleic acid of vegetable oils to eleostearic acid for expanding the industrial usage of vegetable oils.
Khan, A. A., Wu, J., and Shih, D. S. 1999. Cloning and sequence analysis of a class III chitinase gene ( Accession No. AF13437) from Fragaria ananasa Dutch. (PGR99-069). Plant Physiol. 120:340.
Dyer, J.M., Tang, F., Chapital, D.C., Lax, A.R., Shih, D. S., and Pepperman, A. B. 1998, Differential extraction of eleostearic acid-rich lipid-protein complex in tung seeds. J. Am. Oil Chem. Soc. 75:1687-1690
Madden,C.R., and Shih, D.S. 1996. Anlysis of the long terminal repeat from a cytopathic strain of equine infectious anemia virus. Virology225:395-399.
Dyer, J. M., Tang, F.-Q., Chapital, D. C., Lax, A,. R., Shih, D. S., and Pepperman, A. B. (1998) Differential extraction of eleostearic acid-rich lipid-protein complexes in tung seeds. J. Am. Oil Chem. Soc. 75: 1687-1690.
Khan, A. A., Wu, J.-L., and Shih, D. S. (1999) Clong and sequence analysis of a class III chitinase gene (Accession No. AF 13437) from Fragaria ananasa Dutsch. Plant Physiol. 120: 340.