Ph.D. 1987, Yale University
Telephone: (301) 405-1622
Fax: (301) 314-9082
E-mail: straney@umail.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, a plant genetics and molecular biology course a graduate course on plant-microbe interactions at the cellular and molecular levels.
Khan, R., & D.C. Straney. 1999. Regulatory signals influencing expression of the PDA1 gene of Nectria haematococca MPVI in culture and during pathogenesis of pea. Molec. Plant-Microbe Interact. 12: in press
He, Y., Y. Ruan & D.C. Straney. 1996. Analysis of determinants of binding and transcriptional activation of the pisatin-responsive DNA-binding factor of Nectria haematococca. Molec. Plant-Microbe Interact. 9: 171-179.
Ruan, Y., V. Kotraiah & D.C. Straney. 1995. Flavonoids stimulate spore germination in Fusarium solani pathogenic on legumes in a manner sensitive to inhibitors of cAMP-dependent kinase. Molec. Plant-Microbe Interactions 8: 929-938.
Ruan, Y. & D.C. Straney. 1994a. PCR-based construction of promoter/Gfree templates for in vitro transcription analysis allows selection of plasmids with optimal activity in homologous extracts. Gene 146: 227-232.
Ruan, Y. & D.C. Straney. 1994b. In vitro transcription from the Nectria haematococca PDA1 promoter in a homologous extract reflects in vivopisatin-responsive regulation. Current Genetics 27: 46-53.
Ruan, Y. & D.C Straney. 1996 . Identification of elements in the PDA1 promoter of Nectria haematococca necessary for a high level of transcription in vitro. Molec. Gen. Genetics 250: 29-38.
Straney, D., Y. Ruan & J. He. 1994. In vitro transcription and binding analysis of promoter regulation by a host-specific signal in a phytopathogenic fungus. Antonie van Leeuwenhoek 65: 183-189
Straney, D. & H.D. Van Etten. 1994. Characterization of the PDA1 promoter of Nectria haematococca and identification of a region which binds a pisatin- responsive DNA binding factor. Molec. Plant-Microbe Interact. 7: 256-266.
Suleman, P., A.M. Tohamy, A. Saleh, M. Madkour & D.C. Straney. 1996. Variation in sensitivity to tomatine and rishitin among isolates of Fusarium oxysporum f.sp. lycopersici and strains not pathogenic on tomato. Physiol. Molec. Plant Pathol. 48: 131-144.
Wilhite, S.E., R.D. Lumsden & D.C. Straney. 1994. Mutational analysis of gliotoxin production by the biocontrol fungus Gliocladium virens in relation to suppression of Pythium damping-off. Phytopathology 84: 816-821.
Wilhite, S.E. & D.C. Straney. 1996. Timing of gliotoxin biosynthesis in the fungal biological control agent Gliocladium virens (Trichoderma virens) Appl. Microbiol. Biotechnol. 45: 513-518.