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​2020 APS ​Ruth Allen Award

This award honors individuals who have made an outstanding, innovative research contribution that has changed, or has the potential to change, the direction of research in any field of plant pathology.

Nian Wang
​University of Florida

Nian Wang was born and grew up in Qufu, Shandong Province, China and obtained his BS degree in plant protection at Shandong Agricultural University in 1995, and then worked as a research assistant for the Department of Plant Protection, Tobacco Research Institute at this location until 1998. He subsequently obtained his MS degree in plant pathology from China Agricultural University in Beijing in 2001, before obtaining his PhD in plant pathology at Texas A&M University in 2005. After a short postdoctoral position at the University of California, Berkeley, he started his current position in the Department of Microbiology and Cell Science, University of Florida in 2007 and is located at the Citrus Research and Extension Center in Lake Alfred, where he currently serves as professor.

Wang has significantly contributed to our understanding of virulence mechanisms and etiology of diseases caused by several important plant pathogenic bacteria. His earlier work at Texas A&M focused on regulation of the expression of genes encoding the lipodepsipeptide phytotoxins syringomycin and syringopeptin in Pseudomonas syringae pv. syringae. Wang performed seminal research that uncovered the complex determinants of genetic regulation of expression of genes encoding this important toxin and elucidated how the expression of these toxin genes was modulated in response to various phenolic compounds and sugars found in host plants. These studies are a classic in the contextual expression of bacterial virulence traits, enabling an understanding of quantitative resistance in potential host plants.

After his move to the University of Florida, Wang has made impressive strides in our understanding of the biology and epidemiology of both Xanthomonas citri subsp. citri (Xcc) the causal agent for citrus canker disease, and Candidatus Liberibacter asiaticus (CLas) responsible for Huanglongbing disease (HLB) of citrus. Both diseases are causing devastating losses not only in Florida, but throughout the world. Wang has become the world leader in the study of Xcc, having addressed many different aspects of the physiology of this pathogen, such as cell density-dependent gene expression (quorum sensing) that modulates the expression of a wide variety of traits such as extracellular polysaccharide production, motility, and other factors that contribute to biofilm formation in host colonization and symptom development. Likewise, he has been highly successful in applying genetic and genomic tools to identify the many virulence traits employed by this pathogen in various phases of its lifecycle. In highly important publications, he has characterized a large number of effectors, most prominently PthA, that contribute to the virulence of Xcc, as well as global regulators of the type III secretion system, and thus expression of these effectors. He has also made major contributions to our genomic understanding of the population genetics of Xcc, showing how evolution of strains that differentiate between citrus species have evolved and that they are under positive selection. In perhaps his most important contribution to our understanding of bacterial pathogenesis, he has found that the type III TAL effector PthA binds to the promoter of the citrus gene LOB1, thereby activating it. The identification of LOB1 as a susceptibility gene is a major breakthrough, being one of the few such susceptibility genes yet identified. More importantly, Wang has been a leader in adapting the CRISPR/cas9 technology for site-specific gene editing in plants for disease control. His targeted gene editing of citrus species to modify the PthA effector binding elements in citrus LOB1 not only has yielded transgenic plants that are highly resistant to citrus canker, but represents a first and highly important demonstration of the power of this technology in plant disease control.

Wang also has become one of the most influential HLB researchers, having made major findings in the epidemiology, etiology, control, and physiological basis of this disease, as well as identifying many of the virulence factors employed by CLas, despite the fact this pathogen remains uncultured. The breadth of his studies on this topic is truly impressive. Not only has he published widely on practical methods of control of HLB such as by application of plant defense activators and antibiotics, but his findings of highly sensitive and selective detection of CLas by improved PCR probes enabled him to demonstrate the highly heterogeneous distribution of the pathogen throughout the plant at different scales. Wang also has revealed much about the citrus microbiome, and its linkage to the health and susceptibility of citrus to HLB. As such, his work is a classic example of the new concept of how a better definition of the phytobiome of citrus can contribute to tolerance or even resistance to infection by CLas. His work is also showing how the other microbiological components of citrus such as citrus rhizosphere bacteria can induce systemic resistance against citrus canker disease. His transcriptomic analyses of citrus gene expression changes that occur upon infection have also revealed much about both what virulence factors are being expressed by CLas, as well as their targets in the tree and thus the overall physiological changes in the plant that lead to disease symptoms. Of the many putative virulence factors that he has identified in CLas, perhaps the most noteworthy is a salicylic acid hydrolase that, by degrading host salicylic acid, suppresses plant defenses.

Already in his brief career, Wang has received considerable recognition of his research, having accepted more than 34 invited speaker opportunities at national and international meetings. He has already published 76 peer-reviewed publications, many in very high visibility journals such as PNAS as well as 9 reviews, books, and book chapters. He also has substantial service to APS, currently serving as a senior editor for Phytopathology, has previously served as senior editor for Plant Disease, and the chief editor for the volume Virulence Mechanisms of Plant Pathogenic Bacteria, published by APS PRESS. He also has chaired sessions during APS annual meetings and served as an officer in the Bacteriology Committee. In summary, Wang has made outstanding, diverse, and innovative research contributions to both fundamental and applied aspects of important bacterial diseases and is truly deserving of receiving the Ruth Allen award.​

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