Ph.D. - Yale University, 1987

Associate Professor

Department of Cell Biology and Molecular Genetics

University of Maryland

College Park, MD 20742

Telephone: (301)-405-1622

Fax: (301)-314-9082

E-mail: straney@umd.edu

Fungi have a major impact on agriculture, some cause plant diseases while others act as disease-suppressing (biocontrol)agents. My lab uses the tools of molecular biology to study the molecular determinants in these fungi which allow pathogenic or disease- suppressing ability.

In studying plant pathogens, we are interested in the regulation of pathogenicity/virulence gene expression in response to plant-derived signal molecules. A model for plant-induced gene expression is the plant-pathogen interaction between garden pea (Pisum sativum) and the fungus Nectria haematococca MPVI (anamorph: Fusarium solani), the causal agent of pea stem and root rot. Infection, wounding, or other stresses induce pea to make an isoflavanoid antibiotic, pisatin. Nectria haematococca uses pisatin as a signal to induce synthesis of pisatin demethylase, a cytochrome P-450 monooxygenase which detoxifies pisatin. We are studying this pisatin regulation of the pisatin demethylase promoter. We have used the cloned pisatin demethylase gene to apply in vitro methods for defining protein-protein, protein-DNA and protein/small molecule interactions in this signaling pathway, and in studying their role in function through homologous in vitro transcription analysis; in vivo methods, such as fungal transformation of promoter/GUS gene constructs, are used to evaluate the role of these molecular interactions in signaling and disease. We are also studying a second pisatin response in this fungus - that of stimulation of germination by pisatin and related plant flavonoids. This response may be a critical step in the plant- pathogen interaction since, like many soilborne pathogens, the fungal spores remain dormant in the soil until the appearance of a potential host. Flavonoids present an intriguing signal for vegetative growth since their exudation from legume roots are required for initiating plant-Rhizobium interactions which lead to symbiosis and nitrogen fixation. Thus the fungal pathogen and bacterial symbiont appear to utilize the same signal to initiate interaction with the plant. Our goals are to determine the genetic components which determine this response, and the differences in flavonoid specificity which we see between F. solani isolates which specialize on different leguminous hosts. A second focus in the lab studies the role of antibiotics produced by Gliocladium virens in its ability to suppress damping-off disease caused by Pythium ultimum. Gliotoxin is one antibiotic made by this biocontrol agent. Through mutational analysis, we have demonstrated that this antibiotic does contribute to biocontrol activity. We are presently cloning the genes required for gliotoxin biosynthesis to study the regulation of its biosynthesis. Ultimately, we hope to improve the range and effectiveness of G. virensbiocontrol activity through enhancement of gliotoxin production.

At present I teach an introductory botany course for non- science majors and two graduate courses on pathogenic microorganisms which concentrate on plant-microbe interactions at the organismal, cellular and molecular levels.