Korea-U.S. economic relationship with or without an FTA

행사명 : Academic Symposiu

Loss of FlhE in the flagellar Type III secretion system allows proton influx into Salmonella and Escherichia coli

textflhE belongs to the flhBAE flagellar operon in Enterobacteria, whose first two members function in Type III secretion (T3S). In Salmonella enterica, absence of FlhE affects swarming but not swimming motility. Based on a chance observation of a ‘green’ colony phenotype of flhE mutants on pH indicator plates containing glucose, I have established that this phenotype is associated with lysis of flagellated cells in an acidic environment created by glucose metabolism. The flhE mutant phenotype of Escherichia coli is similar overall to that of S. enterica, but is seen in the absence of glucose and unlike in S. enterica, causes a substantial growth defect. flhE mutants have a lowered cytoplasmic pH in both bacteria, indicative of a proton leak. GFP reporter assays indicate that the leak is dependent on the flagellar system, is present before the T3S system switches to secretion of late substrates, but gets worse after the switch and upon filament assembly, leading to cell lysis. I show that FlhE is a periplasmic protein, which co-purifies with flagellar basal bodies. Also, co-localization of fluorescent fusion proteins suggests a plausible interaction between FlhE and FlhA, implicated in channeling protons for PMF-driven secretion. These results imply that FlhE may act as a plug or a chaperone to regulate proton flow through the flagellar T3S system. I have obtained crystals of the FlhE protein. X-ray data show that the FlhE crystal belongs to space group P212121 and is diffracted to 2.02 Å. Completion of this study will contribute to a better understanding of the proposed role of FlhE.Microbiolog

DEVELOPMENT OF MOLECULAR DETECTION SYSTEM FOR SDHI FUNGICIDE RESISTANCE AND FIELD ASSESSMENT OF SDHI FUNGICIDES ON SCLEROTINIA HOMOEOCARPA POPULATION INOCULATED WITH SDHI-RESISTANT ISOLATES

Dollar spot, caused by the causal agent Clarireedia spp. (formerly, Sclerotinia homoeocarpa), is one of the most economically challenging turfgrass diseases in North America. To maintain acceptable quality of amenity turfgrasses, multiple fungicide applications are required. Since the launching of boscalid in 2003, succinate dehydrogenase inhibitors (SDHI) have been frequently used, becoming one of the most important fungicide classes not only for dollar spot control but for other plant pathogenic fungal diseases. However, repeated application of fungicides often lead to fungicide resistance. SDHI fungicide resistance has proven to be more complex than the resistance of other fungicide classes, with differential patterns of cross-resistance to five SDHI ingredients dependent on specific mutations to the succinate dehydrogenase (SDH) enzyme. Since 2016, our lab has received samples from several golf courses and one university research plot that experienced SDHI field failure against dollar spot. Through in vitro assays and DNA sequencing, our previous studies identified and profiled four mutations conferring differential SDHI sensitivity in Clarireedia spp.; an amino acid substitution H267Y and a silent mutation (CTT to CTC) at amino acid position 181 in SDHB subunit, and amino acid substitution G91R and G150R in SDHC subunit. In this project, through in vitro assays and DNA sequencing, we identified and profiled two additional mutations conferring differential sensitivity; H267R in SDHB subunit and P80L in SDHC subunit. However, in vitro sensitivity assays alone can present numerous challenges and can sometimes provide inconclusive results. Therefore, in order to fully understand the complicated mechanisms of SDHI resistance, it is important to understand the association between in vitro assays and field efficacy. Further, the ability to quickly detect SDHI resistance using molecular tools could prove useful for providing fast and accurate recommendations for resistance management to practitioners. The first objective of this research was the development of a molecular detection system for SDHI resistance using molecular markers. Using cleaved amplified polymorphic sequence (CAPS) and derived CAPS (dCAPS) molecular markers, different types of mutations in SDHI-resistant isolates were clearly identified. The second objective was an investigation of the association between in vitro SDHI sensitivity and field efficacy. Following inoculation of turf research plots with the identified SDHI-resistant isolates, similar patterns of differential sensitivity that had already been profiled via in vitro assays were validated. In summary, it is important to monitor the distribution of resistance to SDHIs using both in vitro assay and molecular markers, to understand cross-resistance relationship among SDHIs including new chemistries to be registered, and to better understand the resistance mechanism for development of SDHI resistance management strategies

Mending the Wound or Pulling It Apart? New Proposals for International Investment Courts and Fragmentation of International Investment Law

Robust discussions on standing investment courts are currently taking place at various fora. In particular, negotiations to include bilateral investment courts in IIAs are in full swing and leading to the creation of such courts. On the other hand, negotiation for a multilateral investment court has yet to start. Even if negotiation begins, it is not clear how long it will take and whether it will indeed lead to a successful conclusion. As such, for a significant amount of time in the future, it is bilateral investment courts that states administer to resolve investment disputes. Bilateral investment courts, however, will further deepen the already existing fragmentation of international investment law. They will be unable to issue harmonized and consistent jurisprudence for similar or essentially the same legal issues. In addition, they will more easily stoke sovereignty infringement claims by domestic critics. If legitimacy enhancement is the ultimate objective of the present ISDS reform discussions, it will only be achieved through a multilateral court. This is the only alternative to address the basic concern that has prompted the ISDS reform debates in general and the court proposals in particular. Global efforts should be mobilized to initiate and conclude negotiations for the establishment of a multilateral court as promptly as possible. In the interim, current negotiations to create and adopt bilateral courts should be suspended

Phase Transformation of Two-Dimensional Transition Metal Dichalcogenides

Transition metal dichalcogenide (TMD) materials have distinctive structures in comparison with other two-dimensional materials. TMD materials??? structure is held together by van der Waals and covalent intralayer interactions; consequently, TMDs exhibit multiple phases and properties depending on their structure. This article reviews some of the research currently being undertaken to control TMD phases to utilize their different properties. This review introduces some trials for changing the phase of TMDs