Andrew Bent was born in Springfield, OH. He obtained a B.A. degree in biology, magnum cum laude, from Oberlin College in 1983 and a Ph.D. degree from MIT in 1989. Following post-doctoral work at the University of California-Berkeley, he joined the faculty at the University of Illinois in 1994 and, in 1999, transferred to the University of Wisconsin-Madison, where he is currently professor of plant pathology. He has received multiple awards and recognition for his research and teaching, including the Pound Research Award (2002) for excellence in research at the University of Wisconsin.
Bent is an eminent authority on the molecular mechanisms underlying plant disease resistance, including pathogen recognition, signaling events leading to gene activation, and the host defenses induced. His research primarily involves Arabidopsis as a model plant, whose rapid life cycle and facile genetics facilitate discovery of general principles applicable to other plants, such as soybean, which Bent also studies. His major contributions fall essentially into five major areas as follows.
Bent, while a post-doc in the lab of Brian Staskawicz, was lead author in the work that first discovered that plant R genes can encode NB-LRR proteins (three labs did this and published on the same day in 1994), thereby clarifying the molecular basis for resistance gene function (Science 265:1856-1860). They determined the structure of the RPS2 gene in Arabidopsis that confers resistance to Pseudomonas syringae, showing that the derived amino acid sequence had a leucine-rich repeat, leucine zipper (coiled-coil), and P loop domains, suggesting specific protein functions. This was a benchmark contribution in elucidating what has subsequently proven to be the largest class of resistance proteins. Bent was also co-first author of one of the first papers (Plant Cell 3:49-59, 1991) to develop the Arabidopsis-Pseudomonas interaction as an experimental system. Many significant discoveries in plant pathology continue to emerge from use of this pathosystem.
In 1998, Clough and Bent (Plant Journal 16:735-743) investigated and improved an Agrobacterium method to transform Arabidopsis without tissue culture. Bechtold, Pelletier, and others initiated this approach but, in a much simplified version of the technique, Clough and Bent eliminated certain reagents as well as the vacuum-infiltration, uprooting, and replanting steps, and substituted a simple dipping of developing floral tissues in a 5% sucrose and surfactant solution containing the transforming bacteria. They also discovered mechanisms that underlay this method (Plant Physiology 123:895-904, 2000). The protocol proved so successful that the Clough and Bent paper achieved the rating “most highly cited paper in the field of plant and animal science” over a period 10 years (as of fall 2005) by ISI Essential Science Indicators. More importantly, the method facilitated both routine gene study in vivo and the creation of exhaustive sequence-indexed T-DNA insertion mutant collections.
Since 1998, Bent and colleagues (e.g., PNAS 95:7819-7824, 1998; PNAS 97:9323-9328, 2000; MPMI 21:1285-1296, 2008) have dissected the hypersensitive resistance response by utilizing a particular class of Arabidopsis mutants known as “defense, no death” (dnd1 and dnd2). This approach elegantly separated the phenomenon of R gene-mediated (gene-for-gene) resistance from cell death per se. This breakthrough helped to ease the dogma in plant pathology, recurrent since the discovery of the hypersensitive reaction (HR), that rapid cell death is essential to resistance (restriction of invasion). While programmed HR cell death may contribute to defense signal transduction and to resistance against some pathogens, the Bent lab’s work clarified for many that HR cell death is not a universal phenomenon and that other factors must also be involved. His group went on to show that the independently identified dnd1 and dnd2 genes both encode mutated cyclic nucleotide-gated ion channels, implying the involvement of ion channels in defense activation. Research continues to fully understand the role of these ion channels in defense.
In recent work (Sun et al. 2006, Plant Cell 18:764-779), Bent’s group investigated the defense-eliciting activity of bacterial flagellins among Xanthomonas campestris pv. campestris strains. They showed that different strains of a single pathogen can vary for this defense elicitor, analogous to what has been observed for avirulence genes. Their findings are novel and significant because, previously, plant- and animal-associated pathogen-associated molecular patterns (PAMPs, also called MAMPs) had been thought to encode relatively invariant elicitors of defense. Their paper also identified the single polymorphic amino acid within X. campestris pv. campestris flagellin that determines plant defense elicitation in Arabidopsis via the FLS2 transmembrane LRR kinase, which is broadly present in most plant species. This lays the groundwork for future work on structure/function determinants of the ligand/receptor interaction, and they are currently making progress on mechanistic dissection of host LRR-containing receptors (Plant Cell 19:3297-3231, 2007). The Sun et al. 2006 paper also showed that X. campestris pv. campestris, even when it has an eliciting flagellin, can somehow overcome host detection of that flagellin, suggesting future avenues for study.
Illustrative of his continuing applied work, Bent recently published a highly regarded paper in Crop Science (46:893-901, 2006) on field performance of ethylene-insensitive lines of soybeans. His work with Arabidopsis and soybean had previously shown roles for ethylene in disease tolerance and disease resistance. The 2006 paper is significant because it is a rare instance in which this type of host defense dissection was extended to field studies. Ethylene plays multiple regulatory roles as a plant hormone and breeders/biotechnologists have many reasons to manipulate ethylene responsiveness. The Bent group’s work showed that, to avoid negative impacts on performance traits such as disease resistance and seed yield, manipulation of ethylene responses should be targeted to specific tissues, environments, or growth stages.
In aggregate, Bent’s numerous honors and prestigious body of work establishes that he is a rigorous, highly creative scientist recognized internationally for his insightful research. Additionally, he has been lauded as an outstanding teacher and has contributed diligently to university and professional service, including multiple contributions to APS and IS-MPMI. For all of these reasons, Bent is an honorable and deserving recipient of the Noel T. Keen Award.
