ABI Research Summaries - J. Brad Murphy, Ph.D.

Dr. Murphy's research interests are focused on utilizing plants as biofactories for the production of recombinant proteins of pharmaceutical interest, and the analysis and metabolic engineering of plants for improved levels of healthful phytochemicals (neutraceuticals).

Production of Pharmaceutical Proteins in Plants.

Transgenic plants have tremendous potential for bioproduction of complex therapeutic proteins due to the ease of modification, avoidance of contamination with human pathogens and endotoxins, conservation of eukaryotic protein processing machinery, and low cost of crop production based on existing agricultural infrastructure. We are attempting to produce a number of proteins that have been identified as potential cancer markers and may have utility in diagnosis, therapy, or development as vaccines. Positive Western blots indicate the production of recombinant protein of the expected size. We have utilized an oleosin fusion system that greatly facilitates downstream purification by elimination of numerous chromatographic steps. This strategy targets the recombinant proteins to the oil bodies in oilseeds, which can be isolated by a single centrifugation step. We are also in the process of developing a strategy for targeting seed protein storage vacuoles. There exists the likelihood that tomorrow's farmers will be producers of not only food and fiber, but also a variety of medically important pharmaceutical products of high commercial value.

Analysis of carotenoid antioxidants in spinach and edible greens. Dietary carotenoid antioxidants from fresh fruit and vegetables have long been known to play an important role in human health. Dark-green leafy vegetables, such as spinach and kale, are relatively high in carotenoids, especially lutein. Lutein is of particular interest because it has a high antioxidant activity and has been directly implicated in cancer prevention and in reduction of age-related macular degeneration. An analysis of spinach commercial cultivars and UA breeding lines revealed that two UA spinach lines contained significantly higher levels of lutein. This suggests that carotenoid antioxidant levels in spinach could be further enhanced by a directed breeding program. Several lines of kale had over 50% more lutein than the highest spinach lines.

Engineering of cowpea for enhanced isoflavone content. The isoflavones, genistein and daidzein, are two important nutraceuticals, found primarily in soybean seeds. They act as phytoestrogens with a wide variety of pharmacological effects in animal cells. Dietary intake has been linked, through epidemiological and animal model studies, with a range of potential health benefits. These include chemoprevention of breast and prostate cancers, cardiovascular disease, and relief of post-menopausal ailments. Isoflavone synthase, the enzyme responsible for their synthesis, has recently been cloned; therefore, the potential now exists for producing these compounds in additional species through recombinant DNA approaches. Cowpea (Vigna unguiculata) is an important legume crop, particularly in Third World countries, and is a significant source of dietary protein there. This species, however, contains only trace amounts of isoflavones. We are attempting to metabolically engineer cowpea to increase the level of isoflavones and thus its nutritional quality.

Selected Publications:

Secks, M.E., Murphy, J.B., & Morelock,T.E. Lutein and beta-carotene levels in selections of spinach and edible greens. Hort Studies-2002. Ark. AES Res. Ser. (In press).

Hum-Musser, S.M. Targeting recombinant proteins to plant vacuoles. Ph.D. Dissertation. UAF. 2002.

Secks, M.E., Murphy, J.B., & Morelock, T.E. What's hot? What's not? Evaluation of capsaicinoids in Capsicum spp. using HPLC. Hort Studies-2001. Ark. AES Res. Ser. # 494, p. 58-60, 2002.

Huber, N. M. The production of ovarian cancer-related proteins in plants using an oleosin fusion system. M.S. Thesis. UAF. 2001.

Murphy, J.B., & Morelock, T.E. Spinach breeding program yields lines containing high levels of carotenoid antioxidants. Hort. Studies-1999. Ark. AES Res. Ser. # 475, p. 36-39, 2001.

Contact Information

J. Brad Murphy, Ph.D.
University of Arkansas-Fayetteville
Professor, Department of Horticulture
Chair, Plant Science Ph.D. Program

University of Arkansas
316 Plant Sciences
Fayetteville, AR 72701

Phone: (479) 575-2670
Fax: (479) 575-8619
E-mail: jbmurph@uark.edu