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David C. StraneyAssociate Chair of Undergraduate StudiesAssociate Professor
Ph.D., Yale University, 1987 ResearchMy interests are in the regulation of gene expression and development in response to external cues. Plant-pathogen interactions provide a wealth of systems where inter-organismal signaling determines the specificity of the interaction. The chemical nature of plant defenses and the specificity of defense chemicals used by any one plant species provides for fungal recognition of the host through recognition of these defense compounds. My lab uses the tools of molecular biology to study the components and signal pathways through which a fungal pathogen recognizes its host and triggers the expression of genes or developmental steps needed for pathogenesis. In studying plant pathogens we use a model for soilborne plant pathogenic fungi which has several well defined traits. We study the 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 (Link to picture of spore germination). 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 fungal-fungal interactions. Fungi which are antagonistic to other fungi or trigger plant defenses without causing disease are useful as biocontrol agents for protecting plants. We are studying the role of antibiotics produced by Gliocladium virens (synonym: Trichoderma 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. virens biocontrol activity through enhancement of gliotoxin production. At present I teach a Molecular Genetics lab course (BSCI415) and an introductory botany course for non- science majors (BSCI124). Current graduate students:Viji Vijayakala Recent Publications:U. Gunawardena, M. Rodriguez, D. Straney, J.T. Romeo, H.D. VanEtten, M.C. Hawes. 2005 Tissue-specific localization of pea root infection by Nectria haematococca. Mechanisms and consequences .Plant Physiol. 137: 1363-74 [Full Text] X. Wei, F. Yang, D.C. 2005 Straney Multiple Non-ribosomal Peptide Synthetase Genes Determine Peptaibol Synthesis in Trichoderma virens. Canadian Journal of Microbiology.51: 423-29[Abstract] R. Khan, R. Tan, A. Galvez Mariscal, and D. Straney. 2003 A binuclear zinc transcription factor binds a host isoflavonoid-responsive element in a fungal cytochrome P450 gene responsible for detoxification. Molecular Microbiology. 49: 117-130.[Full Text] D.C. Straney, R. Khan, R. Tan and S. Bagga 2002. Host Recognition By Pathogenic Fungi Through Plant Flavonoids. In:Flavonoids in Cell Function. Volume in the Advances in Experimental Medicine and Biology Series. Eds. J.A. Manthey and B.S. Buslig. Plenum Press pp 1-14 S.E. Wilhite , R.D. Lumsden and D.C. Straney 2001. Peptide synthetase gene in Trichoderma virens. Applied and Environmental Microbiology 67: 5055-5062 [Full Text] H.D. VanEtten, D. Straney, S. Covert, H.C. Kistler. 2001. Update on Selected Topics in the Genetics of Nectria haematococca Mating Population VI with Special Emphasis on its Conditionally Dispensable Chromosomes: A Source of Habitat Specific Genes. Pages 97-112 In: Fusarium: Paul Nelson Memorial Symposium. B.A. Summerell, J. Leslie, D. Back house,W. L. Bryden and L.W. Burgess, eds. American Phytopathological Society Press, St. Paul MN. (Link to Abstracts of papers below) Bagga, S. and D.C. Straney 2000. Modulation of cAMP and phosphodiesterase activity by flavonoids which induce spore germination of Nectria haematococca MP VI (Fusarium solani). Physiological & Molecular Plant Pathology 56: 51-61. Khan, R. and D. C. Straney 1999. Regulatory Signals Influencing Expression of the PDA1 Gene of Nectria haematococca MP VI in Culture and During Pathogenesis of Pea. Molecular Plant-Microbe Interactions. 12: 733-742 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. & 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. 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. 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. 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 vivo pisatin-responsive regulation. Current Genetics 27: 46-53. 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. 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. |
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