Thomas J. Baum was born in Bingen, Germany. He began his agricultural sciences curriculum at the University of Bonn in 1983. After a 1-year internship on farms in Germany, he transferred to the Technical University of Munich, where he conducted research under the guidance of G. M. Hoffman and J.-A. Verreet and graduated in 1989. Baum continued his education as a Ph.D. graduate student (plant pathology) at Clemson University, where he investigated root-knot nematodes under the guidance of Stephen Lewis, Bruce Fortnum, and Ralph Dean. Baum graduated in 1993 and, following post-doctoral work at the University of Georgia with R. S. Hussey, in 1995, he joined the faculty at Iowa State University, where he currently is in his third term as chair (2005–present) of the Department of Plant Pathology and Microbiology.
Throughout Baum’s exemplary career, he has made many significant pioneering contributions that have greatly advanced our understanding and knowledge of the molecular interactions of nematodes with their host plants. His initial molecular biology studies involved the production of plantibodies to a secreted nematode effector in tobacco as a means of interfering with compatible nematode–plant interactions (MPMI, 1996). These early studies were followed by an extensive series of outstanding contributions on the identification, characterization, and functional analyses of effectors produced by nematodes. The Baum lab had the leadership role in expressed sequence tag generation and informatics to identify the majority of known phytonematode parasitism genes that encode secreted effector proteins (APS Ruth Allen Co-Awardee, 2006). The Baum lab has also paved the way in functional studies of nematode effectors. His lab was the first to demonstrate that nematode effectors that contained nuclear localization signals could be imported into the nuclei of host cells for potential direct regulatory activity to promote parasitism (International Journal of Parasitology, 2007). Baum’s lab recently published the first research report on CLAVATA3/ESR-related effector peptides in root-knot nematodes (Phytopathology, 2014). While the effector research originally focused on the Heterodera glycines (SCN)–soybean interaction, Baum was the first to extend effector research to a model system of Arabidopsis thaliana–Heterodera schachtii. This approach provided the advantage of a wealth of available Arabidopsis genetic resources because H. schachtii has nearly identical effector genes as H. glycines (MPMI, 2000; Journal of Nematology, 2000). Using this system, Baum’s research group made many significant advances on cyst nematode effector functions. For example, a secreted cellulose binding protein was shown to directly interact with a host pectin methylesterase (PME3), which altered this enzyme’s activity and aided cyst nematode parasitism by allowing cell wall modifications (Plant Cell, 2008). In another study, Baum’s group showed that a nematode effector altered polyamine signaling by targeting a plant spermidine synthase protein, which increased the plant antioxidant machinery (Plant Physiology, 2010). Additional research on plant defenses against nematodes included the use of a VIGS system in soybean to confirm the function of the cloned soybean rhg4 SCN resistance gene with a collaborating team (Nature, 2012). Baum’s research team also has made many major contributions in the molecular analyses of the plant side of the model system of A. thaliana–H. schachtii. They implemented a high-throughput system, taking advantage of Arabidopsis microarrays to study plant gene expression during nematode infection (Plant Journal, 2003). In a series of research reports, they were able to demonstrate that susceptibility of Arabidopsis to H. schachtii is modulated by the ethylene signal transduction pathway (MPMI, 2001, 2002; Plant Journal, 2004). Many plant endogenous small RNAs (sRNAs), including microRNAs (miRNAs) and small interfering RNAs (siRNAs), are known to play an important role in gene expression. In a pioneering study with his associate Tarek Hewezi, Baum’s group was the first to show that miRNAs and siRNAs differentially accumulate in Arabidopsis roots during H. schachtii parasitism, presenting the exciting possibility that host cell gene-silencing mechanisms play an important role during cyst nematode parasitism (MPMI, 2008). In elegant follow-up studies, they demonstrated that miR396 is differentially expressed in the cyst nematode feeding cell and that this miRNA functions as an important master switch in syncytium formation by targeting host Growth Regulating Factor (GRF) genes (Plant Physiology, 2012; Plant Signaling and Behavior, 2012). Genome-wide expression profiling revealed that the miR396–GRF regulatory system can alter the expression of 44% of the more than 7,000 genes reported to change expression in the Arabidopsis syncytium, implicating miR396 as a key regulator for reprogramming of root cells.
Baum’s team also developed innovative methods that have significantly contributed to nematode effector research, including an mRNA in situ hybridization technique that allowed the confirmation of expression of putative effector genes in nematode esophageal gland cells and now is used in virtually all phytonematode effector studies (Journal of Nematology, 1998). More recently, his lab developed a method to directly isolate whole nematode esophageal gland cells for transcriptomic analyses that will allow for the first time the identification of effector repertoires and their variability from nematodes with different modes of parasitism (MPMI, 2013). His group also demonstrated the utility of virus-induced gene silencing by Bean pod mottle virus in various soybean tissues for molecular analyses of infection by nematodes and other pathogens (Molecular Plant Pathology, 2012). Other seminal studies using the Arabidopsis–H. schachtii pathosystem have been published in a broad range of research journals (18 different journals), including many top-tier journals (PNAS, Nature, Plant Physiology, The Plant Journal, The Plant Cell, Journal of Experimental Botany, New Phytologist, BCM Genomics, Plant Molecular Biology, Genome Biology) outside traditional disciplinary journals, thereby providing important exposure of plant nematology to wider audiences. The pioneering investigations from Baum’s program have led the way for research in molecular plant-nematode interactions for almost two decades. As an established leader in molecular nematology, he is regularly sought to participate in national and international symposia, to present seminars, and to write review articles on his areas of research interest. Baum remains a true pioneer and leader in the field of molecular plant nematology and is a very worthy recipient of the Noel T. Keen Award from APS.