Research Areas:
My research program is focused on achieving two major objectives: increasing our understanding of the molecular signaling pathways that lead to the activation of defense pathways in plants, and applying this knowledge to improve disease resistance in cereal crops. Our work is carried out in collaboration with the other researchers of the USDA-ARS Crop Production and Pest Control Unit and the Small Grains Research Group, at Purdue, that study a range of agriculturally significant fungal, viral and insect diseases of cereals.
To achieve the first goal, my group has developed a high-throughput virus-induced gene silencing (VIGS) system to identify genes encoding functions required for disease resistance. We will then begin to investigate how the gene products function in the mechanisms of resistance, and determine if they may be useful in achieving the second objective. Our VIGS system is based on barley stripe mosaic virus (BSMV) and has proven very useful in the analysis of disease resistance pathways in hexaploid wheat. Our work employing this system to identify genes required for leaf rust resistance in wheat was recently published (Scofield et. al., 2005).
Silencing phytoene desaturase in the leaves of hexaploid wheat by BSMV-VIGS.
The first and second leaves of wheat cultivar Bobwhite were inoculated with BSMV:00 and BSMV:PDS and photographed 14
Leaf rust interactions of susceptible and resistant wheat after infection with control BSMV-VIGS constructs or constructs designed to silence genes encoding components of the Lr21-mediated resistance pathway. All plants were infected with the indicated BSMV constructs 7 days after germination and then spray inoculated with the avirulent P. triticina isolate PTRUS6 8 days after viral infection. The photographs were taken 10 days after inoculation with leaf rust and are representative of all leaves in two different experiments.
Infection with control constructs does not alter resistance or susceptibility. The infection types of the susceptible (S) cultivar Wichita (1), and the resistant (R) line WGR7 (2) inoculated with BSMV:00. The necrotic spots in (2) are sites of Lr21-dependent HR.
Leaves 3-5 come from a separate experiment from those shown in 1 and 2. Infection type of susceptible cultivar (S) inoculated with BSMV:00 (3) is shown on the left as a control. Infection with BSMV:PDS4as does not alter the infection type of the susceptible line (4) or the resistant cultivar (5).
The effects of silencing Lr21, RAR1, SGT1 and HSP90 on Lr21-mediated resistance. Ten plants resistant to PTRUS6 were inoculated with (1) BSMV:00, (2) BSMV:Lr21, (3) BSMV:RAR1, (4) BSMV:SGT1 and (5) BSMV:HSP90, 7 days after germination and sprayed with PTRUS6 8 day later.
Our approach to the second goal is to harness the power of naturally occurring disease resistance pathways, which are able to provide highly effective resistance to specific pathogens. These resistance systems have been used for decades to provide protection against particular “target” pathogens. Unfortunately, there are many significant pathogens for which no corresponding plant resistance systems are known. However, my recent work in industry, and the findings of others, demonstrate that some resistance pathways can, in fact, provide resistance to a broad-spectrum of “non-target” pathogens when they are engineered to be activated when the plant is attacked by “non-target” pathogens. To this end, we are using the tools of genetic engineering to test existing resistance pathways for the ability to provide defense against agriculturally important “non-target” pathogens, and developing strategies so that these pathways can be appropriated activated by these “non-target” pathogens.
Professional Experience:
2008-Present Research Geneticist, USDA-ARS and Adjunct Associate Professor, Department of Agronomy, Purdue University
2002-Present Research Geneticist, USDA-ARS and Adjunct Assistant Professor, Department of Agronomy, Purdue University
1997-2002 Pathogenomics Group Leader, DNA Plant Technology Corporation, Oakland, CA.
1997-1992 Assistant Research Geneticist, NSF Center for Engineering Plants for Resistance to Pathogens, University of California-Davis.
1988-1992 Post-doctoral Fellow, Sainsbury Laboratory, John Innes Centre, Norwich, UK Advisor; Jonathan Jones.
1985-1988 Post-doctoral Fellow, Plant Breeding Institute, Cambridge, UK. Advisor: Mike Bevan.
Most Significant Publications:
Scofield, SR and Nelson R. (2009) Resources for Virus-induced Gene Silencing in the Poaceae. Plant Physiology 149: 152-157.
Mudge, K., Janick J., Scofield S. and Goldschmidt E. (2009) A History of Grafting. Horticultural Reviews Volume 35: 437-487.
Held, M. Penning B., Kessans S, Yong W., Brandt, A, Scofield S., and Carpita N. (2008) Viral-induced gene silencing of cellulose synthase and cellulose synthase-like genes in barley reveals common regulatory control points involving small interfering RNAs. PNAS 105:20534-9.
Cakir, C. and Scofield, S. (2008) Evaluating the ability of the Barley stripe mosaic virus-induced gene silencing system to simultaneously silence two wheat genes. Cereal Research Communications 36: 217-222.
Sindu A, Chintamanani, S, Brandt, A.M., Zanis, M. Scofield, SR and Johal, G. (2008) A guardian of grasses: Specific origin and conservation of a unique disease resistance gene in the grass lineage. Proc. Natl. Acad. Sci. USA 105: 1762-1767. Earth and Sky Radio Interview about this article can be heard at: http://www.earthsky.org/radioshows/52377/warrior-gene-protects-grains-from-disease
Scofield, SR, Huang, L. Brandt, AS and Gill, BS (2005) Development of a virus-induced gene silencing system for hexaploid wheat and its use in functional analysis of the Lr21-mediated leaf rust resistance pathway. Plant Physiol. 138: 2165-2173, 2005.
Scofield, S.R., Tobias, C., Rathjen, J.R., Chang, J.A., Lavelle, D.T., Michelmore, R.W. and Staskawicz, B.J. (1996) The molecular basis of gene-for-gene specificity in bacterial speck disease of tomato. Science 274: 2063-2065. (Full text available at: http://www.sciencemag.org/cgi/content/full/274/5295/2063)
Salmeron, J.M., Oldroyd, G.E.D., Rommens, C.M.T., Scofield, S. R., Kim, H.S., Lavelle, D.T., Dahlbeck, D. and Staskawicz, B. J. (1996). Tomato Prf is a member of the leucine-rich repeat class of plant disease resistance genes and lies embedded within the Pto kinase cluster. Cell 86: 123-133.
Kunze, R., Kuhn, S., Jones, J. D. G., and Scofield, S. R. Somatic and germinal activities of maize Activator (Ac) transposase mutants in transgenic tobacco. (1995) Plant J. 8: 45-54.
Lawson, E. J. R., Scofield, S. R., Sjodin, C., Jones, J. D. G., and Dean, C. (1994) Modification of the 5' untranslated leader region of the maize Activator element leads to increased activity in Arabidopsis. Mol. Gen. Genet. 245: 608-615.
Scofield, S. R., English J. J., and Jones, J. D. G. (1993). High levels of Ac transposase expression inhibit excision of Ds in tobacco embryos. Cell 75: 507-517.
Scofield, S. R., Harrison, K., Nurrish, S. J. and Jones, J. D. G. (1992) Promoter fusions to the Ac transposase gene confer distinct patterns of somatic and germinal excision of Ds in tobacco. Plant Cell 4: 573-582.
Education:
A.B. Political Science, Kenyon College, Gambier, OH 1976
Ph.D. Molecular Genetics, Indiana University, 1985
Date joined staff: 2002