Alan Collmer was born and raised in rural Upper Bucks County, Pennsylvania. He received a B.A. degree in biology from Antioch College in Yellow Springs, Ohio, in 1973. After graduation, he worked as a research technician at the Charles F. Kettering Research Laboratories for two years. In 1975, he began graduate studies at Cornell University, where he studied extracellular pectate lyases produced by Erwinia chrysanthemi. He received his Ph.D. degree in plant pathology in 1981 and spent one additional year at Cornell as a postdoctoral associate in the section of biochemistry, molecular and cell biology, where he cloned the first cellulase gene from a thermophilic actinomycete in the laboratory of D. B. Wilson. In 1982, Dr. Collmer joined the Department of Botany at the University of Maryland as an assistant professor, where he continued research on pectolytic enzymes and pathogenesis of E. chrysanthemi and initiated studies on pathogenesis of Pseudomonas syringae. He returned to Cornell University as an associate professor of plant pathology in 1988 and was subsequently promoted to professor in 1994. It is important to recognize that, as the first recipient of the Noel T. Keen Award for Research Excellence in Molecular Plant Pathology, Dr. Collmer represents a generation of molecular plant pathologists whose careers thrived because of Dr. Keen’s example and his generosity in relationships that ranged from competitor to collaborator to mentor.
Dr. Collmer’s start in molecular plant pathology began in the laboratory of D. F. Bateman at Cornell University, where he studied the regulation of pectate lyase and exopolygalacturonosidase genes in E. chrysanthemi. This early work contributed significantly to our understanding of the regulation of virulence genes in plant-pathogenic bacteria and to the characterization of a number of genes that encode pectic enzymes. Later, he developed novel mutagenesis procedures to create mutants of E. chrysanthemi that lack all of the major pectate lyases, which led to the discovery of a set of secondary pectate lyases in this bacterium. These landmark studies demonstrated the multifactorial nature of virulence and how several pectate lyases contributed incrementally to bacterial soft rot disease. During this period, he coauthored with Dr. Keen a highly cited review on the role of pectic enzymes in plant pathogenesis. His research on pathogenesis of E. chrysanthemi represented one of the first examples in which molecular tools developed in the late 1970s and early 1980s were applied to bacterial plant pathogens.
After relocating his laboratory to Cornell University, Dr. Collmer’s research interests shifted to include not only extracellular virulence proteins, but also protein secretion systems that confer the ability of a pathogen to traffic virulence proteins to plant tissues or the plant cell. In an important advance, his group cloned a functional cluster of “out” genes from E. chrysanthemi, which enabled Escherichia coli K12 to secrete pectate lyases and other related virulence proteins. Subsequently, it was demonstrated that this system was part of an emerging family of secretion systems in gram-negative bacteria, now designated type II secretion systems, which are often utilized by pathogens to secrete degradative enzymes in host tissues. His further analysis of Erwinia out and pel genes, in collaboration with Dr. Keen, identified components of the system implicated in controlling species-specific secretion in type II systems.
The growing interest of Dr. Collmer’s group in the bacterial signals or elicitors of P. syringae that allow the bacterium to produce a hypersensitive response (HR) in resistant plants led to the cloning of a functional cluster of hrp (hypersensitive response and pathogenicity) genes that conferred to E. coli the ability to elicit the HR. His research established that P. syringae hrp genes encode a protein secretion system similar to protein secretion systems in animal pathogens, which became known as the type III secretion system (TTSS). His group also demonstrated the first protein, called harpin, to be secreted via a TTSS of a plant pathogen. Subsequently, this work was extended to include avirulence proteins encoded by avr genes and led to compelling evidence that a test Avr protein was delivered into plant cells by the TTSS. This had a major impact on phytobacteriology, because it linked the hrp and avr research systems with governing roles in eliciting an HR in resistant plants. A 1996 Plant Cell review article by J. R. Alfano and Dr. Collmer proposed a new model for bacterial plant pathogenesis, in which the central event in pathogenesis is the TTSS-mediated injection of Avr-like effector proteins into plant cells, such that inside plant cells these proteins collectively promote virulence unless the presence of any one of them is recognized by R proteins that trigger plant defenses. This model focused the puzzle of bacterial plant parasitism on the identity and function of TTSS effector proteins.
Because of the importance of genomics approaches in the identification of TTSS effector genes, perhaps the largest impact that Dr. Collmer has had on molecular plant pathology occurred in 2003 with the complete sequencing of the 6.5-Mb genome of P. syringae pv. tomato DC3000 through a multi-institutional National Science Foundation Plant Genome Research Program project that he directed. DC3000 is a model pathogen of both tomato and Arabidopsis, and by using a mix of experimental and bioinformatic tools, Dr. Collmer and his collaborators have substantially enlarged the inventory of type III effectors demonstrated to travel the P. syringae TTSS, making this inventory the largest for any bacterial pathogen of plants or animals.
Dr. Collmer was named a Fellow of The American Phytopathological Society in 1996 and a Fellow of the American Academy of Microbiology in 2000. He is recognized for valuable service to his profession, including serving on the editorial boards of the Journal of Bacteriology, Annual Review of Phytopathology, and Plant Cell; as an associate editor for Molecular Plant-Microbe Interactions; as panel manager for the USDA Competitive Grants Office; and as a board member of the International Society for Molecular Plant-Microbe Interactions. At Cornell University, he has served on numerous departmental and university committees. He guided the research and academic programs of a long list of graduate students and postdoctoral associates, who have now established distinguished research programs of their own.