David Glenn Gilchrist
David Glenn Gilchrist was born in Lincoln, IL, and raised on a farm. He graduated from the University of Illinois with a B.S. degree in biological science and an M.S. degree in agronomy. He received his Ph.D. degree in genetics from the University of Nebraska. He joined the Department of Plant Pathology at the University of California, Davis, as a NIH postdoctoral fellow and was appointed to the faculty in 1975.
Gilchrist’s research program emphasizes two areas within thegeneral subject of plant diseases and plant–microbe interactions: (i) role and mechanisms of programmed cell death (PCD), or apoptosis, in plant disease; and (ii) genetic regulation and biochemical response of plants to infection. A unifying element across these focus areas is the role of lipid-based signaling and PCD in disease, with particular emphasis on ceramide-related signals as determinants of cellular homeostasis. Gilchrist’s research is highly interdisciplinary in scope, requiring an understanding of many rapidly emerging areas in the biology of both plants and animals. He has established productive collaborations with investigators in a variety of biological disciplines, including both plants and animals, fostered in part during his service as associate director of the NSF-supported Center for Engineering Plants for Resistance Against Pathogens (CEPRAP; 1991–2002). The collaborations forged over the years have enabled Gilchrist to expand his research on apoptosis into animal and human biology, with synergies that have enhanced our capabilities for studies of the role of PCD in plant disease susceptibility.
Gilchrist’s research on plant–microbe interaction spans 3 decades. He was one of the early proponents of selecting model systems with a solid genetic basis to understand causal mechanisms in plant disease. His training in biochemical genetics, coupled with his postdoctoral research on the regulation of aromatic amino acid metabolism in plants, established a foundation that has guided his pioneering research on the interaction of tomato with Alternaria alternata f. sp. lycopersici (Alternaria stem canker) and other diseases. Key discoveries include purification and characterization of the host-selective AAL toxin and its congeners, development of sensitive toxin detection methods, characterization of the biochemical and physiological effects of toxin on host tissue, and genetic analyses of toxin action and host response. Gilchrist’s research on AAL toxin and the closely related fumonisins produced by Fusarium verticillioides are broadly relevant to issues concerning contamination of food products with these mycotoxins in addition to basic research on PCD in plants and animals triggered by toxins. Other important research endeavors have included studies on the genetics, physiology, and biochemistry of diseases of alfalfa, notably characterization of the interaction of alfalfa with Stemphylium botryosum and a toxin secreted by this pathogen. Related to these basic studies were collaborative efforts with breeders to identify and introgress genetic resistance to diseases of tomato, alfalfa, and wheat into commercial germplasm. These projects resulted in the release of spring wheat cultivars with resistance to Septoria leaf blotch and the release of several germplasm lines with high levels of resistance to Stemphylium leaf spot and Stagonospora crown rot in alfalfa. His efforts included the identification of the Asc gene in tomato conferring resistance to Alternaria stem canker, a disease that initially threatened the fresh-market tomato industry in California. Nearly all fresh-market tomato lines grown in California now carry the Asc gene and have been free of Alternaria stem canker for more than 2 decades.
A seminal contribution is the discovery by Gilchrist and his colleagues demonstrating PCD with hallmark features of apoptosis in plants, a process extensively studied and documented in animals. AAL toxin, fumonisin, pathogens, and certain chemical agents were shown to kill plant cells by the PCD process, providing the first evidence that apoptosis was functionally conserved across the two kingdoms as a basic process fundamental to both disease and development in plants.
The research also pointed to the participation of a ceramide-linked signaling pathway in the triggering of PCD, a first in plant biology, and revealed that these same toxins could trigger the equivalent process leading to death in animal cells. This research provided strong evidence for a general role for PCD in plant disease, which has profoundly influenced thinking about plant pathogenesis, particularly in necrotrophic interactions. The research is provocative in that it suggests opportunities for engineered disease resistance by targeting PCD. Gilchrist has challenged traditional views on the functional role of cell death in resistance as observed in the hypersensitive response, an issue articulated in reviews and opinion papers. He is now applying principles and screening methods developed in the tomato model to identify genes in grape that block disease symptoms of Pierce’s disease caused by Xylella fastidiosa.
Gilchrist’s research accomplishments are well recognized. He was honored as a distinguished scholar at Vriji Universiteit, Amsterdam (1993); the E.S. Luttrell Memorial Lecturer, University of Georgia (1997); the Rosie Perez Memorial Lecturer, North Carolina State University (1999); a fellow, American Association for the Advancement of Science (AAAS, 2001); and a distinguished scientist, University of Western Australia (2002).
Gilchrist has contributed extensively in teaching, service, and outreach, including substantive contributions to APS directly or through programs that impact APS and its membership. He has been the APS affiliate representative to AAAS from 2001 to 2007. He is highly regarded as a teacher and has mentored a number of graduate students in plant pathology and other disciplines who have gone on to successful careers. He is an accomplished speaker with a knack for capturing the essence of an issue in a clever phrase that helps his audience identify and retain the salient points. His outreach efforts deserve special note. As director of the NSF-funded Partnership for Plant Genomics Education (PPGE), he and his staff have developed novel educational software for introducing biotechnology to high school biology students, with an overall national contact of more than 5,000 schools in the past 10 years. PPGE also developed and supports a widely recognized “Biotechnology in the Classroom” curriculum and laboratory kit loan program. Over the past decade, 30,000 northern California area students have used these hands-on biotechnology exercises not otherwise accessible at the local school level.