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It was with great sadness that we learned that our respected colleague, Tom Guilfoyle, died unexpectedly on April 30, 2017.

Tom Guilfoyle was born in Mendota, Illinois on January 13, 1946, to Lawrence and Marguerite Guilfoyle. He attended Holy Cross School, Mendota High School, and in 1968 he earned his B.Sc. degree from Illinois State University. From there, he entered graduate school at the University of Illinois where he worked on plant RNA polymerases with John (Jack) Hanson. However, his graduate studies were interrupted by the draft and he served two years in the U.S. Army. He took his M.Sc. (1969) before leaving and then returned and finished his Ph.D. (1974). He did postdoctoral work with Joe Key at the University of Georgia, Athens, before joining the Department of Botany at the University of Minnesota, St. Paul in 1976. He rose to the rank of professor at Minnesota where he also held an adjunct appointment in Biochemistry. In 1986, he moved his lab to the University of Missouri, where he joined the Department of Biochemistry and the Interdisciplinary Plant Group.

Guilfoyle and his colleagues proved that auxin rapidly regulates expression of specific genes and also identified regulatory proteins and DNA sequences. Their research identified auxin response elements (AuxRE) in the promoters of auxin responsive genes, which allowed development of the synthetic auxin-responsive promoter, called DR5, which is widely used in auxin studies by researchers around the world. He and his colleagues used the AuxRE’s DNA sequences to isolate a family of transcription factors called Auxin Response Factors (ARFs) that have made it possible to study the molecular details of auxin-regulated gene expression. The resulting paradigm—that auxin acts to stimulate gene expression by removing repressor proteins that interact with DNA bound ARFs, thus allowing for transcriptional induction of auxin response genes—has been characterized as a “triumph” of plant biology.

Guilfoyle published 113 articles in leading scientific journals, including Science, Nature, and The Proceedings of the National Academy of Science, in addition to 32 chapters in edited collections. In 2007, he was elected a Fellow of the American Association for the Advancement of Science in recognition of his distinguished contributions. Of Guilfoyle’s science, Joe Key shared, “Tom was technically outstanding along with his keen intellect which allowed him to commence an outstanding scientific career, which focused on the regulation of gene expression, a quest for knowledge of the influence of auxin on gene expression, and the overlap of these endeavors.”

Guilfoyle was an active, long-time member of the American Society of Plant Biology. He generously contributed his time and expertise in various ways, including as co-editor of The Plant Cell for over a decade. His editorial work was an expression of how much he cared for the scientific enterprise and its values. Guilfoyle’s scientific discoveries and service to plant biology were recognized by three of ASPB’s most prestigious awards: the Lawrence Bogorad Award for Excellence in Plant Biology in 2014, the Charles Reid Barnes Life Membership Award in 2009, and the Fellow of the ASPB Award in 2007. The Barnes Life Membership Award was given jointly with Guilfoyle’s long-time partner in life and science, Gretchen Hagen. This is the only time this award has been given jointly.

Over his career, Guilfoyle mentored 12 graduate students and 24 postdoctoral fellows. Many of his students have gone on to hold prestigious academic and industry positions throughout the world. As a mentor, he had a reputation for setting high standards for scientific rigor and hard work while cultivating independence in his students and postdocs. I did my doctoral work with Guilfoyle and Hagen in the 1980s. These were some of the best years of my life. We worked crazy hard, and Tom set the standard. He did not tell students and postdocs how to do science, he showed us. I believe Guilfoyle himself would point with greatest pride to the extent that he fostered our independence and question-driven approach to science. Others have had similar recollections:

“Tom's lab was a stimulating and exciting place. He set a good example for all of us with his high standards for scientific quality and integrity as well as his personal work habits. He loved discussing and debating ideas and encouraged it in others. He treated his graduate students and postdocs as colleagues and encouraged us to be independent and develop our own ideas and research approaches. My time in Tom’s lab was one of the best times in my life,” shared Professor Neil Olszewski, who completed his doctoral work with Guilfoyle in the 1980s.

“The years I spent [in Tom’s lab] undoubtedly represent the best time of my life, filled with excitement of scientific discovery and constant quest for new knowledge and unbiased answers. Tom was undoubtedly my best mentor. He expected greatness. He demanded independence, creativity and critical thinking. And, above all, he wanted to see or hear something that was new and exciting,” wrote Tim Ulmasov, a postdoctoral fellow in Guilfoyle’s lab in the 1990s.

During his graduate studies at the University of Illinois, Guilfoyle met Gretchen Hagen, who would later become his wife and research partner. In the lab, they shared their passion, talents, energy, and creativity working to understand the auxin response. Long time friend and colleague University of Florida Professor Bill Gurley shared that their discoveries “established trails of investigative inquiry that will be followed for years to come.” Outside the lab, they enjoyed good wine, cooking, jazz, and the company of their stalwart cat, Junior. They hosted memorable costume Halloween parties at their home for 35 years. Guilfoyle retired in October 2016 and looked forward to life without faculty meetings and classes. Still, his passion “to hear something that was new and exciting” never abated. MU Biochemistry Chair Jerry Hazelbauer noted that Guilfoyle’s intense engagement with his science kept bringing him into his office almost every day.

To many, the loss of Guilfoyle is deeply felt.

“Tom epitomized (in his research and questioning) the scientific rigour that is a hallmark of his generation of U.S. scientist….He was a true giant in the plant molecular biology field, whose shoulders both I and others have had the privilege to stand upon. He will be greatly missed.” Malcom Bennett, University of Nottingham.

“Tom was a great colleague, a friend for life, and one who will remain in my heart forever, and be sorely missed by all who knew him.” Joe Key.

“No matter how worried or concerned I may have been, Tom would always respond in a jovial, calming tone. He cut through the [colorful term] like no one else – with a smile or witty remark. Tom was truly one a kind and will be missed by everyone who had the pleasure to get to know him. Jay Thelen, MU.

As for me, Tom’s deep voice will always be with me, pushing me to be better. Tom is well known for his contributions to science. His friends know he also loved just plain fun. I’ll miss him, but as long as he is remembered, as I do, he is not gone.

Bruce McClure