David C. Straney
Associate Chair of Undergraduate Studies
Ph.D., Yale University, 1987
Telephone: (301) 405-1622
Fax: (301) 314-9082
My 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
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
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
Current graduate students:
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
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:
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.
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:
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.
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:
Wilhite, S.E. & D.C. Straney. 1996. Timing
of gliotoxin biosynthesis in the fungal biological control agent
Gliocladium virens (Trichoderma virens) Appl. Microbiol. Biotechnol.
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
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.