Youfu 'Frank' Zhao

1. Transcriptome of Erwinia amylovora signal transduction networks

Fire blight, caused by Erwinia amylovora, is a particularly devastating disease for the apple and pear fruit industry, in part because of lack of effective control measures driven by the development of resistance to streptomycin in the bacterial pathogen population. Our long-term goal is to comprehensively characterize two-component signal transduction systems (TCSTs) and to reconstruct gene regulatory networks (GRNs) in E. amylovora, thus allowing a better understanding of the basic mechanisms of pathogenicity and biology of E. amylovora. We are currently studying a group of TCST genes, including HrpXY, RcsBCD, GrrSA, and EnvZ/OmpR, in E. amylovora, which play important roles in virulence and survival. We will genetically characterize these genes, identify target genes or regulon using microarray, and establish GRNs using computational modeling. Critical target genes and their functions will then be characterized and compared in both E. amylovora and Escherichia coli, thus extending our knowledge to two closely-related plant and mammalian microorganisms.

2. IGMSC Fire Blight (Integrated genomics and management systems for control of fire blight - Evaluate and assess virulence inhibitors against Erwinia amylovora)

Type III secretion system (T3SS) is a universal target for developing novel antibacterial agents -Recent advances in studying bacterial virulence factors provide mounting evidence that, the T3SS system is a potent virulence mechanism shared by a broad spectrum of pathogenic Gram negative bacteria that infect both plant and mammalian hosts by injecting effector proteins into host cells. Thus, the T3SS apparatus is essential for bacteria to evade the host immune defense. It is likely that agents that inhibit type III expression or effector secretion and translocation can result in antibacterial responses without actually killing the bacteria. Based on this hypothesis, recent publications have described screening of small molecular inhibitors targeting T3SSs. These screens have identified several classes of synthetic compounds as well as natural products as active T3SS inhibitors in a wide range Gram-negative bacterial pathogens, including E. coli, Salmonella, Yersinia, Shigella, and Chlamydia. We are currently evaluating and assessing virulence inhibitors against Erwinia amylovora. Project website: http://fireblight.nres.uiuc.edu/index.html

3. Genome sequencing and comparative genomics of Pseudomonas savastanoi pv. glycinea, and identification of new resistance sources of soybean against race 4

Soybean(Glycine max (L.)), one of the world’s largest providers of protein and oil, is a major crop in the United States, which accounts for about 40% of the soybeans produced in the world. Bacterial blight, caused by Pseudomonas savastanoi pv. glycinea (Psg), is a common bacterial disease of soybean and occurs in most soybean grown areas. Yield losses due to bacterial blight disease of soybean estimated at 4 to 40% in the U.S. Our recent studies have shown that field isolates of Psg are predominantly race 4, which infect all cultivars currently available. However, resistant cultivars have not been identified for Psg race 4. Identification of new resistance sources for breeding against Psg race 4 will provide us another means of control. Furthermore, genomic sequences of bacterial pathogens have greatly increased the understanding of host-pathogen interactions. Elucidation of molecular mechanisms of disease and resistance interactions between microbial plant pathogens and their host plants will lead to the development of improved disease management strategies. We are sequencing genomes of two Psg strains, race 4 and B076, using next generation sequencing technology. In silico subtractive hybridization-based comparative genomic analyses with other sequenced phytopathogenic pseudomonads will also be conducted. Genome link: http://www.ncbi.nlm.nih.gov/nuccore/320326756; http://www.ncbi.nlm.nih.gov/nuccore/320332072; and http://www.pseudomonas-syringae.org/

Khan, M.A., Zhao, Y.F., and Korban, S.S. 2012. Molecular mechanisms of pathogenesis and resistance to the bacterial pathogen Erwinia amylovora, causal agent of fire blight disease in Rosaceae. Plant Mol. Biol. Rep. 30:247-260. (invited review)

Wang, D. P., Qi, M. S., Calla, B., Korban, S. S., Clough, S. J., Cock, P., Sundin, G. W., Toth, I., and Zhao, Y. F. 2012. Genome-wide identification of genes regulated by the Rcs phosphorelay system in Erwinia amylovora. Mol. Plant-Microbe Interact. 25:6-17.