Research Topics
Department of Crop Sciences
Ph.D. (1995) University of California, Davis
Research Topics
Research Interests
My laboratory studies the molecular biology and biochemistry of plant parasitic nematodes. We use a combination of molecular and cell biology techniques to study these animals. Such methods include, construction of cDNA libraries from single cells, gene discovery using differential screening, RNA in situ hybridization, immunofluorescence microscopy, and the generation of transgenic plants.
We are interested in many aspects of nematode biology, but all projects have the ultimate goal of trying to exploit key points in the nematode life cycle to control agronomically damaging nematode species, such as the root-knot and the soybean cyst nematodes. Current projects involve cloning and characterization of secreted nematode proteins that allow the nematode to parasitize the plant. Secreted proteins in nematodes are often only produced in one or a few gland cells. We use surgical techniques to remove these cells and to construct cDNA libraries. These libraries are then differentially screened to identify gland-specific genes and the clones are sequenced to generate a targeted EST database. Bioinfomatic analysis of the gland-specific clones determines if they are potentially secreted and if they have conserved functional domains. RNA in situ hybridization and immunoflurescence methods are then used to determine if the genes are expressed in the glands and to determine if they encode secreted proteins. For key nematode proteins transgenic plants are produced, using either Agrobacterium or plant viral vectors, to ascertain the potential function of the nematode protein in the plant. Finally, we are attempting to develop and express inhibitors of these essential nematode proteins in transgenic plants to generate novel nematode resistance genes.
We currently are studying two classes of secreted nematode proteins, a pectate lyase-like protein and a chorismate mutase. The nematode pectate lyase-like protein most likely is involved in digesting or binding to the plant cell wall to allow the nematode to penetrate its host root. The chorismate mutase, on the other hand, appears to be microinjected into the plant cell cytosol where it probably modifies the metabolism of the plant aromatic amino acids. The modification of plant aromatic amino acid biosynthesis can have a dramatic effect on the plant growth and development and may be involved in the generation plant giant cells, which the nematode feeds on during its parasitic phase of life.
Other projects in the lab involve the identification and analysis of secreted nematode proteins not directly involved in plant parasitism. We have recently initiated a project to clone nematode intestine and endocrine gland genes in the hopes of identify important genes that could be targets for disrupting the nematode life cycle. Such essential nematode genes are ideal targets for the development of engineered nematode resistance genes.
Key Words Recombinant DNA, Plant Nematodes, Gene Expression, Microscopy, Transgenic
Plants, Secreted Proteins
Current Research Funding
USDA-NRI,
C-FAR