Deborah A. Samac is a native of Colorado. She received a B.A. degree in biology from The Colorado College in 1981 and a Ph.D. degree in plant pathology from the University of Wisconsin in 1988. After a 3-year post-doctoral associate position with Monsanto Company, she accepted a position in 1991 as a research plant pathologist with the USDA-ARS in the Plant Science Research Unit at the University of Minnesota (UMN). She serves as senior lead scientist of the five-person Forage Pathology and Utilization CRIS and is adjunct professor in the UMN’s Plant Pathology Department. Samac was also elected director of the UMN Plant Molecular Genetics Institute. She is an internationally recognized authority in the fields of forage pathology, alfalfa biotechnology, and functional genomics of Medicago truncatula host-pathogen interactions.
Samac’s early work focused on the role of plant chitinases in plant-microbe interactions. Plant chitinase enzymes were thought to be important in plant defense against pathogens because they hydrolyze chitin, a critical component of the cell wall of many plant-pathogenic fungi. However, there was little to no direct evidence for the role of chitinases in disease resistance. Samac was among the first to isolate and characterize plant chitinase genes. In addition, she showed that inoculation of Arabidopsis with fungal pathogens induced chitinase gene expression. Even more striking were experiments in which she pioneered the use of an antisense genetic construct to suppress chitinase gene expression. Suppression of Arabidopsis chitinase gene expression resulted in plants becoming more susceptible to fungal pathogens. Her chitinase studies were among the first to provide direct molecular evidence that plants induce critical enzymes to degrade the cell walls of fungal pathogens.
A hallmark of Samac’s career has been her insight in asking the relevant questions to solve important problems and then developing the tools to answer these questions. For instance, she developed a reliable genetic transformation system for alfalfa that could be used for conducting research on the genes involved in plant-microbe interactions and for advances in alfalfa biotechnology. Using an Agrobacterium tumefaciens-based transformation system for alfalfa and high-throughput PCR-based methods for identifying transgenic plants, Samac has transformed alfalfa with more than 150 gene constructs designed to test the functional importance of genes involved in many plant processes. Her biotechnology studies have had major impact. For example, she has developed transgenic alfalfa plants that have modified disease resistance, improved tolerance to abiotic stress, enhanced carbon flow for symbiotic root nodules, and the capacity to bioremediate atrazine, and that produce poly-β-hydroxybutyrate, a biodegradable plastic polymer. She is recognized as the world authority on alfalfa transformation. Evidence of her stature in this field is not only her numerous highly cited papers but also the fact that scientists throughout the world have come to her laboratory to learn gene construct development and plant transformation. Moreover, she has written many invited reviews on the transformation of alfalfa.
When forage diseases are mentioned, Samac’s name is the first to come to mind. She is an international authority on bacterial wilt of alfalfa caused by Clavibacter, Phytophthora, and brown root rots of alfalfa, spring black stem and leaf spot of alfalfa, and alfalfa root lesion nematode. Her studies include whole-plant and molecular approaches and have ranged from developing species/strain-specific PCR assays for bacterial and fungal pathogens to biological control using antibiotic-producing strains of Streptomyces. Both public and private organizations rely on Samac for pathogen identification and control recommendations. The American Phytopathological Society has recognized her outstanding role in alfalfa pathology by requesting she develop and edit a revision of the Compendium of Alfalfa Diseases. In the process of seeing the compendium through to completion Samac wrote sections on at least 15 diseases.
Most recently, Samac has become internationally recognized in legume genomics related to plant-disease interactions and host-microbe associations. Alfalfa’s outcrossing, autotetraploid genetics plus its large genome size have impeded genomic advances in the species. As a model system for alfalfa and other cool-season legumes, the legume genomics community adopted Medicago truncatula for genomic studies because of its self-compatibility, small genome, and rapid generation time. Samac produced eight cDNA libraries and sequenced more than 32,000 expressed sequence tags from pathogen-infected tissues. These sequences laid the foundation for the alfalfa gene index and first Medicago microarrays. Samac played a seminal role in developing four pathosystems for M. truncatula, which she and numerous collaborators used to evaluate gene transcript changes during pathogenesis, thereby identifying genes activated during plant disease. Furthermore, she has extended her expertise in alfalfa transformation to be applicable to M. truncatula, providing an in planta system for functional analysis of genes involved in plant-microbe interactions. She was prominent in organizing the First International Conference on Legume Genomics and Genetics held in 2002 and attended by 350 scientists. Her efforts in organizing this conference provided the underpinnings for five follow-up conferences. Her leadership with M. truncatula has been recognized with invitations to speak at many national and international conferences and to host numerous visiting scientists.
Samac’s publication and service record is exemplary. She has published some 70 refereed journal articles, 11 book chapters, and two patents. Within APS, she has served on the Centennial Planning Committee and on the Physiology, Biochemistry, and Molecular Biology Committee (chair in 1997), as senior editor of Phytopathology, and as associate editor of Plant Disease. She serves as consulting editor for the Journal of the American Society for Horticultural Science. She has played a defining role in developing the ARS national program plans for the Pasture, Forage and Rangeland Systems National Program. Nationally, Samac has served on USDA-NRICGP, NSF, and DOE grant panels. Most recently, she has been chosen to serve as the acting research leader for the Cereal Disease Laboratory in St. Paul, Minnesota.
Samac’s contributions to host-pathogen biology, biotechnology, and genomics demonstrate outstanding research creativity and productivity. Her stature is international in scope and reflects excellence on behalf of ARS, UMN, and APS. Her professional service at every level is exemplary and her mentoring of students and post-doctoral associates ensures a pipeline of plant pathologists for years to come.