Herman B. Scholthof was born in Kring van Dorth, Gorssel, the Netherlands, in 1959. He was raised on a farm, and after completing an agricultural college degree in plant research, he attended Wageningen University to obtain his B. S. and M. S. degrees in 1984 and 1986, respectively. For his dissertation research at the University of Kentucky, he investigated gene expression of caulimoviruses with Robert J. Shepherd. After completing his Ph.D. degree in 1990, he joined Andy Jackson and T. Jack Morris at the University of California-Berkeley (UC Berkeley), where he did postdoctoral work on Tomato bushy stunt virus (TBSV). In December 1994, Scholthof joined the faculty of the Department of Plant Pathology and Microbiology at Texas A&M University and was promoted to associate professor with tenure in 2000. A sabbatical leave as a visiting professor in biological chemistry and pharmacology at Harvard Medical School (2002–2003) was used to further his understanding of the physicochemistry of the TBSV-encoded P19 protein. In 2005, Scholthof was promoted to the rank of full professor.
As a Ph.D. student, Scholthof exhibited a flair for innovative thinking and experimentation. He was one of the first scientists to determine how cis- and trans-acting factors control gene expression of the polycistronic mRNA of caulimoviruses. The importance of his refined early research cannot be underestimated; some of these concepts have been applied to studying HIV and related human and animal viruses.
Scholthof had a very successful postdoctoral experience at UC Berkeley. There, he began working with TBSV and continues today to use this as a model virus to make important, conceptual, and practical contributions to our knowledge of virus–plant interactions. Scholthof showed that the capsid protein is not necessary for TBSV to systemically invade some plant hosts, and he then developed TBSV as a virus tool for expressing sequences in plants. Much of Scholthof’s work has dealt with how TBSV interacts with its host for systemic invasion and how it causes symptoms. He discovered that two TBSV proteins, P19 and P22, are expressed from the same subgenomic RNA and have different but essential roles in pathogenesis. Scholthof’s pioneering studies elegantly demonstrated the nature of the P19 protein as a pathogenicity factor and a protein that promulgated robust, systemic infections. With his creative and insightful interpretations of these roles for P19, he was an early originator of the hypothesis that the biological properties of P19 relate to its role as a suppressor of the host antiviral RNA silencing mechanism in order to protect TBSV RNA from degradation.
Scholthof is at the forefront of defining the relationships between structure and function of the P19 and P22 proteins. For instance, recent structural studies provided an explanation for earlier observations made by Scholthof on the effect of specific mutations on the structural integrity and biological activity of P19. Another example relates to his discovery that the function of P19 is dose dependent and that this is controlled by context-dependent ‘leaky scanning’ to frequently bypass the P22 start codon and initiate translation at the P19 start codon. He recently demonstrated that the high dosage of P19 is important in the regulation and efficacy of P19 as a suppressor of RNA silencing to appropriate the high levels of short-interfering RNAs (siRNAs). As a direct outcome of this, P19 has become a preferred tool of researchers in the elucidation of RNAi pathways in plants, yeast, and C. elegans. Scholthof’s scrutiny of TBSV-related interactions resulted in yet another pair of firsts: the genetic isolation and characterization of two novel host proteins that independently and specifically interact with P19 or P22. Most recently, he has shown that the ability of P19 to sequester siRNAs correlates with pathogenesis, and his group is the first to isolate an active antiviral RNA-induced silencing complex (RISC) from plants or any organism.
Scholthof recently developed the molecular tools to understand a newly recognized virus transmitted by the wheat curl mite. Wheat mosaic virus (WMoV) had proved to be an intractable problem for maize and wheat producers in the High Plains region of the United States. He reported the first partial characterization of WMoV, and his findings have proven to be important to understand the etiology of related mite-transmitted diseases.
Scholthof is an enthusiastic teacher of graduate courses in plant virology, molecular methods in plant–microbe interactions, theory of research, and virus gene vectors. He is sought after as a graduate and undergraduate student mentor, and he serves on numerous student dissertation committees. He also is a founding member of the Texas A&M intercollegiate faculty of virology.
Scholthof is widely recognized as an effective and enthusiastic collaborator. He is generous in distributing TBSV and P19 research materials, which has allowed many plant virology, C. elegans, medical, and molecular biology labs to perform experiments that would have otherwise been more difficult. Scholthof’s TBSV-based gene–vector system has been used for groundbreaking research worldwide.
Scholthof has an outstanding record of publication in peer-reviewed journals. In 2004, he was selected to give the American Society for Virology state-of-the-art lecture. Scholthof has served as an associate editor and senior editor for both Molecular-Plant Microbe Interactions and Phytopathology and is on the editorial board of Virology. He regularly organizes, cochairs, and speaks at APS symposia and brings his students to meetings to present their research.
Scholthof fulfills the spirit and intent of the Ruth Allen Award, having developed an outstanding, innovative research program that has directed and elaborated on our understanding of the roles of virus-encoded proteins. Through his influence, TBSV and its P19 protein are recognized worldwide as model experimental tools to study the elegant coordination (and outcome) of host–virus interactions.
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