COLLEGE OF AGRICULTURE AND LIFE SCIENCES

	Ralph Dewey Professor of Crop Science, Plant Molecular Biology specialty	CROP SCIENCE PERSONNEL
	Campus Box 8009 212 Partners III-Centennial Campus Raleigh, NC 27695-8009	CURRICULUM VITAE
	Phone: (919) 515-2705 FAX: (919) 515-7959 ralph_dewey@ncsu.edu

Dr. Dewey received his graduate training in Plant Molecular Biology at North Carolina State University with Dr. C. S. Levings III and Dr. David Timothy as his mentors. Funded by an NSF postdoctoral fellowship, Dr. Dewey received additional experience at the Waksman Institute, Rutgers University under the direction of Dr. Daniel F. Klessig. Since 1991, Dr. Dewey has applied the techniques of molecular biology toward the identification and characterization of genes of potential agronomic value as a faculty member in the Department of Crop Science, NCSU. He team teaches the course Molecular Biology in Plant Breeding (CS/GN/HS 720) together with Dr. Rongda Qu.

Research Projects

Identifying the Molecular Basis of Soybean Lines Displaying Useful Oil Phenotypes.

Although soybean seeds are the predominant source of plant vegetable oils worldwide, the quality and versatility of soybean oil could be greatly improved if one were able to modify its fatty acid composition in a directed, reliable fashion. Our efforts are focused towards utilizing our understanding of the biochemistry and molecular biology of plant lipid biosynthesis to identify the specific molecular mutations that give rise to a desirable oil phenotype within soybean germplasm developed by plant breeders. After obtaining this information, we subsequently develop facile, specific molecular markers that can accelerate the introgression of these modified oil traits into elite varieties using marker-assisted selection.

To date we have been successful in identifying the molecular basis of several novel oil phenotypes found in soybeans. Specifically, we have characterized mutations and developed corresponding molecular markers for genes that mediate low palmitic acid (16:0) phenotypes, elevated palmitic acid accumulation, low linolenic acid (18:3) content and increased in the stearic acid (18:0) accumulation in the seed oil. The information and markers developed will enable breeders to quickly transfer either individual or complex combinations of genes specific to a desired oil end product into elite cultivars for the generation of new, high value soybean varieties.

Reducing Nornicotine Synthesis and Accumulation in Tobacco.

Nornicotine is a secondary tobacco alkaloid that is produced via the enzymatic demethylation of nicotine. Lowering nornicotine levels in tobacco is desirable because this alkaloid serves as a precursor to the well documented carcinogen N’-nitrosonornicotine. Keeping nornicotine levels low has been a chronic problem in Burley tobaccos because of an unstable mutation in these varieties that gives rise to progeny producing high levels of this secondary alkaloid.

We utilized a microarray-based transcript profiling strategy to screen thousands of genes isolated from senescing leaf cDNA libraries in an attempt to identify genes that are differentially regulated between tobacco plants that produce high versus low levels of nornicotine. These efforts lead to the identification of a gene designated CYP82E4, whose product is responsible for catalyzing the enzymatic demethylation of nicotine to form nornicotine. Using RNAi-based antisense constructs that target CYP82E4 transcripts for degradation, we have produced transgenic tobacco lines that accumulate much lower amounts of nornicotine than what is currently observed in commercial varieties. Application of this technology holds the promise of providing a convenient, inexpensive means of ensuring low nornicotine levels (and thus low N’-nitrosonornicotine formation) in cultivated tobacco.

Characterization of a Novel Hyperosmotic Stress Signaling Pathway.

Phosphatidylinositol (PI) transfer proteins have recently been shown to play critical roles in secretory and signaling pathways of yeast and mammals. By genetic complementation of a yeast strain lacking a functional PI transfer protein (known as SEC14p), we have isolated two distinct soybean cDNAs that encode SEC14p-like proteins. Our investigations have shown that one of these, designated Ssh1p, serves as a very early intermediate in an osmosensory signal transduction pathway.

Within minutes after the exposure of plant cells to osmotic stress, Ssh1p is phosphorylated by an activated protein kinase termed SPK1. Our current results suggest that the phosphorylation of Ssh1p modifies that plant's ability to synthesize polyphosphoinositides, important signaling molecules. Further study of the SPK1/Ssh1p pathway promises to reveal new information with regard to the mechanisms by which plants perceive water stresses and how the cognate signal is relayed to the nucleus to establish a new profile of gene expression that enables the plant to adapt to the stress.