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Search Results: 1 - 10 of 792 matches for " Junhyun Jeon "
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Experimental Evolution Reveals Genome-Wide Spectrum and Dynamics of Mutations in the Rice Blast Fungus, Magnaporthe oryzae
Junhyun Jeon, Jaeyoung Choi, Gir-Won Lee, Ralph A. Dean, Yong-Hwan Lee
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0065416
Abstract: Knowledge on mutation processes is central to interpreting genetic analysis data as well as understanding the underlying nature of almost all evolutionary phenomena. However, studies on genome-wide mutational spectrum and dynamics in fungal pathogens are scarce, hindering our understanding of their evolution and biology. Here, we explored changes in the phenotypes and genome sequences of the rice blast fungus Magnaporthe oryzae during the forced in vitro evolution by weekly transfer of cultures on artificial media. Through combination of experimental evolution with high throughput sequencing technology, we found that mutations accumulate rapidly prior to visible phenotypic changes and that both genetic drift and selection seem to contribute to shaping mutational landscape, suggesting the buffering capacity of fungal genome against mutations. Inference of mutational effects on phenotypes through the use of T-DNA insertion mutants suggested that at least some of the DNA sequence mutations are likely associated with the observed phenotypic changes. Furthermore, our data suggest oxidative damages and UV as major sources of mutation during subcultures. Taken together, our work revealed important properties of original source of variation in the genome of the rice blast fungus. We believe that these results provide not only insights into stability of pathogenicity and genome evolution in plant pathogenic fungi but also a model in which evolution of fungal pathogens in natura can be comparatively investigated.
Regulation of Cellular Diacylglycerol through Lipid Phosphate Phosphatases Is Required for Pathogenesis of the Rice Blast Fungus, Magnaporthe oryzae
Md. Abu Sadat, Junhyun Jeon, Albely Afifa Mir, Jaeyoung Choi, Jaehyuk Choi, Yong-Hwan Lee
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0100726
Abstract: Considering implication of diacylglycerol in both metabolism and signaling pathways, maintaining proper levels of diacylglycerol (DAG) is critical to cellular homeostasis and development. Except the PIP2-PLC mediated pathway, metabolic pathways leading to generation of DAG converge on dephosphorylation of phosphatidic acid catalyzed by lipid phosphate phosphatases. Here we report the role of such enzymes in a model plant pathogenic fungus, Magnaporthe oryzae. We identified five genes encoding putative lipid phosphate phosphatases (MoLPP1 to MoLPP5). Targeted disruption of four genes (except MoLPP4) showed that MoLPP3 and MoLPP5 are required for normal progression of infection-specific development and proliferation within host plants, whereas MoLPP1 and MoLPP2 are indispensable for fungal pathogenicity. Reintroduction of MoLPP3 and MoLPP5 into individual deletion mutants restored all the defects. Furthermore, exogenous addition of saturated DAG not only restored defect in appressorium formation but also complemented reduced virulence in both mutants. Taken together, our data indicate differential roles of lipid phosphate phosphatase genes and requirement of proper regulation of cellular DAGs for fungal development and pathogenesis.
The PEX7-Mediated Peroxisomal Import System Is Required for Fungal Development and Pathogenicity in Magnaporthe oryzae
Jaeduk Goh, Junhyun Jeon, Kyoung Su Kim, Jongsun Park, Sook-Young Park, Yong-Hwan Lee
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0028220
Abstract: In eukaryotes, microbodies called peroxisomes play important roles in cellular activities during the life cycle. Previous studies indicate that peroxisomal functions are important for plant infection in many phytopathogenic fungi, but detailed relationships between fungal pathogenicity and peroxisomal function still remain unclear. Here we report the importance of peroxisomal protein import through PTS2 (Peroxisomal Targeting Signal 2) in fungal development and pathogenicity of Magnaporthe oryzae. Using an Agrobacterium tumefaciens-mediated transformation library, a pathogenicity-defective mutant was isolated from M. oryzae and identified as a T-DNA insert in the PTS2 receptor gene, MoPEX7. Gene disruption of MoPEX7 abolished peroxisomal localization of a thiolase (MoTHL1) containing PTS2, supporting its role in the peroxisomal protein import machinery. ΔMopex7 showed significantly reduced mycelial growth on media containing short-chain fatty acids as a sole carbon source. ΔMopex7 produced fewer conidiophores and conidia, but conidial germination was normal. Conidia of ΔMopex7 were able to develop appressoria, but failed to cause disease in plant cells, except after wound inoculation. Appressoria formed by ΔMopex7 showed a defect in turgor generation due to a delay in lipid degradation and increased cell wall porosity during maturation. Taken together, our results suggest that the MoPEX7-mediated peroxisomal matrix protein import system is required for fungal development and pathogenicity M. oryzae.
Deconfined criticality in bilayer graphene
Junhyun Lee,Subir Sachdev
Physics , 2014, DOI: 10.1103/PhysRevB.90.195427
Abstract: We propose that bilayer graphene can provide an experimental realization of deconfined criticality. Current experiments indicate the presence of N\'{e}el order in the presence of a moderate magnetic field. The N\'{e}el order can be destabilized by application of a transverse electric field. The resulting electric field induced state is likely to have valence bond solid order, and the transition can acquire the emergent fractionalized and gauge excitations of deconfined criticality.
Wess-Zumino-Witten Terms in Graphene Landau Levels
Junhyun Lee,Subir Sachdev
Physics , 2014, DOI: 10.1103/PhysRevLett.114.226801
Abstract: We consider the interplay between the antiferromagnetic and Kekul\'e valence bond solid orderings in the zero energy Landau levels of neutral monolayer and bilayer graphene. We establish the presence of Wess-Zumino-Witten terms between these orders: this implies that their quantum fluctuations are described by the deconfined critical theories of quantum spin systems. We present implications for experiments, including the possible presence of excitonic superfluidity in bilayer graphene.
Quantum criticality of reconstructing Fermi surfaces in antiferromagnetic metals
Junhyun Lee,Philipp Strack,Subir Sachdev
Physics , 2012, DOI: 10.1103/PhysRevB.87.045104
Abstract: We present a functional renormalization group analysis of a quantum critical point in two-dimensional metals involving Fermi surface reconstruction due to the onset of spin-density wave order. Its critical theory is controlled by a fixed point in which the order parameter and fermionic quasiparticles are strongly coupled and acquire spectral functions with a common dynamic critical exponent. We obtain results for critical exponents and for the variation in the quasiparticle spectral weight around the Fermi surface. Our analysis is implemented on a two-band variant of the spin-fermion model which will allow comparison with sign-problem-free quantum Monte Carlo simulations.
Global Expression Profiling of Transcription Factor Genes Provides New Insights into Pathogenicity and Stress Responses in the Rice Blast Fungus
Sook-Young Park,Jaeyoung Choi,Se-Eun Lim,Gir-Won Lee,Jongsun Park,Yang Kim,Sunghyung Kong,Se Ryun Kim,Hee-Sool Rho,Junhyun Jeon,Myung-Hwan Chi,Soonok Kim,Chang Hyun Khang,Seogchan Kang,Yong-Hwan Lee
PLOS Pathogens , 2013, DOI: 10.1371/journal.ppat.1003350
Abstract: Because most efforts to understand the molecular mechanisms underpinning fungal pathogenicity have focused on studying the function and role of individual genes, relatively little is known about how transcriptional machineries globally regulate and coordinate the expression of a large group of genes involved in pathogenesis. Using quantitative real-time PCR, we analyzed the expression patterns of 206 transcription factor (TF) genes in the rice blast fungus Magnaporthe oryzae under 32 conditions, including multiple infection-related developmental stages and various abiotic stresses. The resulting data, which are publicly available via an online platform, provided new insights into how these TFs are regulated and potentially work together to control cellular responses to a diverse array of stimuli. High degrees of differential TF expression were observed under the conditions tested. More than 50% of the 206 TF genes were up-regulated during conidiation and/or in conidia. Mutations in ten conidiation-specific TF genes caused defects in conidiation. Expression patterns in planta were similar to those under oxidative stress conditions. Mutants of in planta inducible genes not only exhibited sensitive to oxidative stress but also failed to infect rice. These experimental validations clearly demonstrated the value of TF expression patterns in predicting the function of individual TF genes. The regulatory network of TF genes revealed by this study provides a solid foundation for elucidating how M. oryzae regulates its pathogenesis, development, and stress responses.
Roles of NADPH oxidase 2 and 4 in endothelial cell survival and death under serum depletion  [PDF]
Hyeona Jeon, Yong Chool Boo
Advances in Biological Chemistry (ABC) , 2014, DOI: 10.4236/abc.2014.41003
Abstract: Oxidative stress and redox-signal pathways are known to be involved in endothelial apoptosis induced by serum depletion. However, the associated mechanism is not well understood and thus, was investigated in the present study focusing on NADPH oxidases (NOX). Serum removal from the culture medium led to an increase in reactive oxygen species (ROS) production and apoptotic death of human umbilical vein endothelial cells. Serum depletion also increased the gene expression of the NOX2 and NOX4 subunits. The selective suppression of NOX4 expression by small interfering RNA (siRNA) attenuated ROS production and cell death due to serum-depletion whereas siRNA for NOX2 increased cell death. Expression of exogenous NOX2 or NOX4 subunit alone had no significant effects on ROS production or cell death. Coexpression of the subunits of the NOX4 complex (NOX4 and p22phox) or the NOX2 complex (NOX2, p22phox, p47phox and p67phox) increased ROS production and cell death under serum-depleted conditions. This study suggests that endothelial cell survival and death are differentially regulated by expression levels of the subunits of NOX2 and NOX4 complexes.
Optimality Modeling in Human Evolutionary Behavioral Science
Jeon, Joonghwan
Journal of Ecology and Field Biology , 2008,
Abstract: Recently, the evolutionary study of human psychology and behavior has undergone rapid growth,diversifying into a few distinct sub-disciplines. One fundamental issue over which researchers in Human BehavioralEcology and Evolutionary Psychology (EP) have different views is the role of formal optimality modelingfor making hypotheses and deriving predictions about human adaptations. The study of EP typically rests oninformal inferences and rarely uses optimality modeling, a strategy which human behavioral ecologists haveseverely criticized. Here I argue that EP researchers have every reason to make extensive use of optimalitymodeling as its research method. I show that optimality modeling can play an integral role in identifying thefunctional organization of human psychological adaptations.
Jet Quenching in Evolving QGP Medium
Sangyong Jeon
Physics , 2009, DOI: 10.1016/j.nuclphysa.2009.10.012
Abstract: A short summary of different approaches to the parton energy loss problem is given. A particular attention is paid to the differences between various models. A possible solution to the problem of distinguishing competing approaches is discussed.
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