Research Topics
Departments of Plant Biology and Biochemistry
Ph.D. (1981) Cornell University
Research Topics
Research Interests
One focus of the research in my laboratory is aimed at understanding the factors that influence the removal of introns from pre-mRNAs in plant nuclei and defining the mechanism for intron recognition and excision. Although it might be logical to assume that plants and animals share common mechanisms for this process, many studies have demonstrated that the splicing machineries are not interchangeable between plants and animals or, for that matter, between dicot and monocot plants. My laboratory utilizes a variety of biochemical and molecular genetic approaches to define the RNA and protein factors influencing intron recognition and splicing in plant nuclei. Site-directed mutagenesis of intron and exon sequences has allowed us to demonstrate that plant intron recognition depends on changes in adenosine and uridine content between introns and exons as well as on the sequences at the 5' and 3' splice sites. Splicing proteins involved in the recognition of the AU-rich intron elements and in the general splicing process are being characterized by molecular genetic analysis using overexpression and underexpression strategies in the model plant Arabidopsis thaliana. These molecular approaches should, in the long run, help define the optimal sequences needed for expression of heterologous genes and proteins in transgenic plants.
The second major focus in my laboratory is aimed at defining the transcriptional elements regulating expression of plant and insect cytochrome P450 monooxygenase genes. In both plants and insects, these genes encode enzymes critical for synthesis of an array of hormones and defense compounds as well as the metabolism of hydroxylated products such as herbicides and insecticides. Because of this, their transcriptional regulatory cascades respond to natural and synthetic compounds, predators and pathogens in the environment. A variety of RT-PCR and microarray strategies are being used to define the range of plant (Arabidopsis thaliana, Zea mays) P450 genes induced in response to chemical and environmental stresses and the range of insect (Papilio polyxenes, Helicoverpa zea) P450 genes induced in response to plant signaling molecules and toxins. The elements regulating transcription are being identified using promoter:reporter gene fusions (CAT, LUC, GFP) in transgenic plants and in transfected insect cell cultures.
The third focus in my laboratory is aimed at developing molecular models of the catalytic sites in insect P450s metabolizing plant toxins and insecticides and in plant P450s synthesizing an array of secondary products. A variety of protein expression strategies using yeast and baculovirus systems and site-directed changes in catalytic site residues are being used to refine our molecular models and to predict alternate substrates for each of these P450s.
Key Words
Pre-mRNA Splicing, Insect P450 Monooxygenases, Plant P450 Monooxygenases,
Functional Genomics
Current Research Funding
NIH, NSF, USDA