Plant Pathology Faculty Pages: Seogchan Kang

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Arabidopsis ecotypes infected with Fusarium oxysporum (WT) and a fosnf1 mutant.

GFP-labeled F. oxysporum colonizing the root xylem of Arabidopsis.

SEOGCHAN KANG
Associate Professor of Plant Pathology

311 Buckhout Laboratory
University Park, PA 16802-4508
Phone: 814-863-3846
E-mail: sxk55@psu.edu

Areas of Interests:
	Plant-fungal pathogen interactions; Fungal genomics and informatics; Plant pathogen databases

Education | Program Interests | Publications | PowerPoint Presentation

Education:

B.S., Seoul National University Chemistry
M.S., Seoul National University Chemistry
Ph.D., University of Wisconsin Physiological Chemistry

Program Interests:

The goal of my research program is to study plant- pathogen interactions at multiple levels, ranging from genes to ecosystems.

(A) Root pathogenesis/defense using Arabidopsis thaliana as a host: Because much of our current knowledge on the molecular basis of plant-fungal pathogen interactions has been derived from studies based on foliar pathogens, our understanding of soil-borne diseases lags considerably behind. My approach is to employ a diverse array of pathogens representing different infection strategies and tissue specificity so as to identify both general and pathogen-specific defense mechanisms in A. thaliana. Two soil-borne pathogens, Fusarium oxysporum and Verticillium dahliae, have been utilized in these studies. Members of the F. oxysporum species complex are the most common fungi in soil and consist of numerous pathogenic and non-pathogenic forms. Pathogenic members can be divided into many host specific forms (i.e., forma specialis = f. sp.) and collectively cause vascular wilt, damping-off, and root rot diseases in over 100 cultivated plant species. Rich strain resources (>1,000 isolates) in combination with well-established phylogenetic relationships within the species complex, nicely support studies on the evolutionary mechanisms underpinning host specialization. Verticillium dahliae also has a broad host range and causes vascular wilt, but unlike F. oxysporum , many isolates do not exhibit clear host specificity. The broad host ranges of F. oxysporum and V. dahliae make it possible to compare pathogenicity and defense mechanisms in diverse plant species.

We identified eight F. oxysporum isolates pathogenic to A. thaliana. Among 48 ecotypes infected with two of the isolates, substantial variation in resistance both within and between isolates was observed. Mechanisms of their interactions have been characterized using a combination of cytological, genetic, and metabolomics tools. Using two A. thaliana ecotypes, Cvi-0 (susceptible) and Gre-0 (resistant), three-dimensional, time-resolved data from individual infection sites by fluorescently-labeled fungal strains were obtained over several days without physical manipulation of infected plants (in collaboration with Dr. Kirk Czymmek at the University of Delaware). This technique allowed monitoring of fungal growth on the root surface and within the vascular tissue and observation of changes in root cells in response to fungal growth. Initial penetration occurred primarily in the meristematic region of primary and lateral roots and seems to require a mycelial mass for penetration (similar to quorum sensing in bacterial pathogens). The fungus appears to produce phytotoxin(s) that could effectively move to nearby cells and affect vacuolar membrane integrity and potentially induce host cell death.

(B) Rice blast: Worldwide, this disease, caused by Magnaporthe oryzae, is the biggest threat to rice cultivation. Besides its economic significance, rice blast presents many advantages as an experimental model. Unlike most plant–fungal pathogen systems, the genome sequences of both M. oryzae and rice are available, providing a unique opportunity to study their interactions from both sides using functional genomics tools. Two areas of my research on rice blast include the genetic mechanisms underpinning the breakdown of resistance in the field and the molecular and cellular basis of pathogenesis/defense. Although resistance ( R ) gene-mediated resistance is highly effective once triggered, such resistance frequently loses its effectiveness in the field due to the emergence of new races. Considering the importance of utilizing R genes to control various diseases, especially in many developing countries where chemical control is economically impractical, answering the questions of how new races arise and how gene-for-gene interactions are controlled is crucial for sustainable disease management. I have been pursuing these questions at multiple levels, ranging from genes to field populations. Specifically, I have focused on the evolution, function and variation of the PWL and AVR-Pita avirulence (AVR ) gene families in M. oryzae. Certain members of these gene families are specifically expressed in planta and seem to be transported to host cytoplasm via a vesicle-like structure (termed Effector Secretion Bodies) on infection hyphae (Fig. 1). Fungal genes controlling the expression and function of these gene families are currently being isolated.

Fig. 1 . Localization of the AVR-Pita1-GFP fusion protein in infection hyphae. (A) Bright field image of infection hyphae inside rice epidermal cells at 24h post inoculation. (B) Hypha in (A) visualized with the GFP filter. An effector secretion body (ESB) is denoted by an arrow. This work has been conducted in collaboration with Dr. Barbara Valent at KSU.

By taking advantage of genome sequences from M. oryzae , Dr. Yong-Hwan Lee at SNU and I have conducted a genome-wide search for pathogenicity genes, resulting in the identification of ~200 such genes. Functional characterization of these genes is in progress. Interactions between Arabidopsis thaliana and M. oryzae are currently being studied to dissect nonhost resistance. The fungus infects certain ecotypes, but the required factors for A. thaliana infection are different from those for rice infection.

(C) Cyber-infrastructure for Plant Pathogens (CiPP): The goals of CiPP are to integrate existing genotypic and phenotypic information on plant pathogens with important environmental variables, and to engage the global community of plant pathologists to use state-of-the-art data mining and visualization tools for the advancement of science, education, and outreach (Fig. 2). Our first and foremost reason for building CiPP is to collect and catalog biological information and materials for present and future use. Properly archiving accumulated data and materials in a format that can maximally support future research is as important as generating new data and materials. Because science builds on existing knowledge, failure to establish proper links between what has been done and what will be done is a poor scientific practice and frequently forces us to ‘reinvent the wheel.' Pathogen cultures often form the primary link that connects discoveries of the present with established knowledge of the past, facilitate comparisons of findings in different areas, and support pathogen forensics. The second motivation came from the realization that the full potential of pathogen genomics as a foundation for understanding and managing disease dynamics, hinges on how effectively we use genome sequence data to gain a comprehensive understanding of the evolutionary and pathological potential and mechanisms within species.

Fig. 2 . Organization and functionality of CiPP. The CiPP weaves together (i) Phytophthora Database; (ii) detailed global distribution maps of Phytophthora ; (iii) versatile molecular diagnostic tools; (iv) IT tools supporting the use of archived data for Phytophthora detection and identification; (v) GIS tools for visualizing the distribution and change of Phytophthora in environmental and geospatial contexts; and (vi) a globally-linked network of scientists working together in monitoring Phytophthora diseases.

The Phytophthora Database ( www.phytophthoradb.org ) is the first fruit of CiPP. Database for other groups of pathogens are in progress. Given increasing movements of pathogens via global agricultural trade, a pathogen monitoring system focused primarily on the United States would not be adequate. In collaboration with scientists in many parts of the world, we are building a global atlas of Phytophthora. In the long run, the database will support integration and utilization of data from diverse areas of research on Phytophthora, ranging from genomics, phylogenetics and population biology to epidemiology.

(D) Development of research tools and resources: During the last 3-4 years, we have developed experimental tools and resources that will help us study dynamic changes underlying plant-pathogen interactions at multiple levels, ranging from genes to whole organisms. One resource is the genome sequences of several fungal pathogens that, in combination with the genome sequences of host plants, will facilitate studies on their interactions from both the plant and pathogen sides. I am a coPI of two genome sequencing projects (funded by the USDA Microbial Genome Sequencing program), one for F. oxysporum and F. verticilliodes and the other for V. dahliae and V. albo-atrum. The former project is completed, and the latter project is in progress. Another area of investment is the development of cytological tools for both plants and pathogens to study cell-to-cell communications within and between plant and pathogen throughout the disease cycle. These tools include FRET-based biosensors for Ca and cAMP, pH-sensitive GFP and an array of fluorescent markers for labeling fungi and plants. Transformants of A. thaliana , F. oxysporum , and M. oryzae with some of these sensors have been generated, which are currently being used to map cell-to-cell communications during various stages of pathogenesis/defense. A third resource is fungal gene manipulation tools via the use of Agrobacterium tumefaciens.

Publications

Park, J., Park, J., Jang, S., Kim, S., Kong, S., Choi, J., Ahn, K., Kim, J., Lee, S., Kim, S., Park, B., Jung, K., Kim, S., Kang, S. and Lee, L. (2008) FTFD: An informatics pipeline supporting phylogenomic analysis of fungal transcription factors. Bioinformatics in press.

Balci, Y., Balci, S., Blair, J.E., Park, S., Kang, S., and MacDonald, W. (2008) Phytophthora quercetorum sp. nov., a novel species isolated from eastern and north-central US oak forest soils. Mycological Research in press.

Park, J., Park, B., Veeraraghavan, N., Blair, J.E., Geiser, D.M., Isard, S., Mansfield, M.A., Nikolaeva, E., Park, S.-Y., Russo, J., Kim, S.H., Greene, M., Ivors, K.L., Balci, Y., Peiman, M., Erwin, D.C., Coffey, M.D., Jung, K., Lee, Y.-H., Rossman, A., Farr, D., Cline, E., Grünwald, N.J., Luster, D.G., Schrandt, J., Martin, F., Ribeiro, O.K., Makalowska, I., and Kang, S. (2008) Phytophthora Database: A forensic database supporting the identification and monitoring of Phytophthora. Plant Disease 92: .

Khang, C., Park, S., Lee, Y., Valent, B., and Kang, S. (2008) Genome organization and evolution of the AVR-Pita avirulence gene family in the Magnaporthe grisea species complex. Mol. Plant-Microbe Interact. 21: 658-670.

Park, J., Park, B., Jung, J., Jang , S., Yu, K., Kong, S., Park, S., Kim, S., Choi, J., Kim, H., Kim, S., Blair, J.E., Lee, K., Kang, S. and Lee, Y. (2008) CFGP: a Web-based, Comparative Fungal Genomics Platform. Nucleic Acid Research 36: D74-D81.

Park, S., Milgroom, M. G., Han, S. S., Kang, S., and Lee, Y. (2008) Genetic differentiation of Magnaporthe oryzae populations from scouting plots and commercial rice fields in Korea. Phytopathology 98: 436-442 .

Blair, J.E., Coffey, M.D., Park, S.-Y., Geiser, D.M., and Kang, S. (2008) A multi-locus phylogeny for Phytophthora utilizing markers derived from complete pathogen genomes. Fungal Genet. Biol. 45:266-277.

Choi, J., Park, J., Jeon, J., Chi, M., Goh, J., Yoo, S., Park, J., Jung, K., Kim, H., Park, S., Rho , H., Kim, S., Kim, K., Han, S., Kang, S., and Lee, Y. (2007) Genome-wide analysis of T-DNA integration into the chromosomes of Magnaporthe oryzae. Molecular Microbiology 66: 371–382.

Czymmek, K., Fogg, M., Powell, D., Sweigard, J., Park, S., and Kang, S. (2007) Method for in vivo time-lapse documentation of Arabidopsis root-fungal pathogen interactions. Fungal Genetics & Biology 44: 1011-1023.

Irish, B., Goenaga, R., Park, S, and Kang, S. (2007) First Report of Phytophthora palmivora , Causal Agent of Black Pod, on Cacao in Puerto Rico. Plant Disease (Note). 91: 1051.

Jeon, J., Park, S., Chi, M., Choi, J., Park, J., Rho, H., Kim, S., Goh, J., Yoo, S., Choi, J., Park, J., Yi, M., Yang, S., Kwon, M., Han, S., Kim, B., Khang, C., Park, B., Lim, S., Jung, K., Kong, S., Karunakaran, M., Oh, H., Kim, H., Kim, S., Park, J., Kang, S., Choi, W., Kang, S., and Lee, Y. (2007) Genome-wide functional analysis of pathogenicity genes in rice blast fungus. Nature Genetics 39: 561-565.

Tosa, Y., Uddin, W., Viji, G., Kang, S., and Mayama, S. (2007) Comparative genetic analysis of Magnaporthe grisea isolates causing gray leaf spot of perennial ryegrass turf in the United States and Japan. Plant Disease 91:517-524.

Kang, S ., Blair, J. E., Geiser, D. M., Khang, C., Park, S., Gahegan, M., O'Donnell, K., Luster, D. G., Ivors, K. I., Kim, S. H., Lee, Y., Lee, Y., Grünwald, N. J., Martin, F. M., Coffey, M. D., Veeraraghavan, N. , and Makalowska, I. (2006) Plant pathogen culture collections: It takes a village to preserve these resources vital to the advancement of agricultural security and plant pathology. Phytopathology 96: 920-925.

Khang, C., Park, S., Rho , H., Lee, Y., and Kang, S. (2006) Agrobacterium tumefaciens -mediated transformation and mutagenesis of filamentous fungi Magnaporthe grisea and Fusarium oxysporum. PP. 403-420, In: K. Wang (ed.) Agrobacterium Protocols. Humana Press, Totowa.

Ahn I. , Kim, S., Kang, S. , and Lee, Y. (2005) Rice defense mechanisms against Cochliobolus miyabeanus and Magnaporthe grisea are distinct. Phytopathology 95:1248-1255.

Rauyaree, P., Bhat, R. G., Ospina-Giraldo, M. D., Grant, S. J., Dobinson, K. F., Subbarao, K. V., and Kang , S. (2005) Mutations in VMK1, a mitogen-activated protein kinase gene, affect colony morphology, microsclerotia formation and pathogenicity in Verticillium dahliae. Current Genetics 48: 109-116.

Khang, C., Park, S., Lee, Y., and Kang, S. (2005) A dual selection based, targeted gene replacement tool for Magnaporthe grisea and Fusarium oxysporum. Fungal Genetics & Biology 42: 483-492.

Geiser, D. M., Jiménez-Gasco, M., Kang, S. , Makalowska, I., Veeraraghavan, N., Ward, T. J., Zhang, N., Kuldau, G. A., and O'Donnell, K. (2004) FUSARIUM-ID v.1.0: A DNA sequence database for identifying Fusarium. European J. Plant Pathology 110: 473-479.

Dobinson, K. F., Grant, S. J., and Kang, S. (2004) Cloning and targeted disruption, via Agrobacterium tumefaciens -mediated transformation, of a trypsin protease gene from the vascular wilt fungus Verticillium dahliae . Current Genetics 45:104-110.

Kang, S ., and Dobinson, K. (2003) Molecular and cellular basis of plant-fungal pathogen interactions. pp. 59-97 In: D. K. Arora and G. G. Khachatourians (eds.) Fungal Genomic and Bioinformatics. Elsevier Science, Dordrecht

Park, S., Milgroom, M. G., Han, S. S., Kang, S., and Lee, Y.-H. (2003) Diversity of pathotypes and DNA fingerprint haplotypes in populations of Magnaporthe grisea in Korea over two decades. Phytopathology 93: 1378-1385.

Ospina-Giraldo, M. D., Mullins, E. M., and Kang, S. (2003) Loss of function of the Fusarium oxysporum SNF1 gene reduces virulence on cabbage and Arabidopsis. Current Genetics 44: 49-57.

Gao, W., Khang, C., Park, S., Lee, Y., and Kang, S. (2002) Evolution and organization of a highly dynamic, subtelomeric helicase gene family in the rice blast fungus Magnaporthe grisea. Genetics 162: 103-112.

Moorman, G. W., Kang , S. , Geiser, D. M., and Kim, S. (2002) Identification and characterization of Pythium species associated with greenhouse floral crops in Pennsylvania. Plant Disease 86: 1227-1231.

Ivors, K., Beyer, D., Wuest, P. J., and Kang, S. (2002) Survey of fungal diversity in mushroom compost using sequences of PCR-amplified genes encoding 18S ribosomal RNA. pp. 18-24 In: H. Insam, J. Feurle, S. Klammer, and N. Riddech (eds). Proceedings of the 1st Microbiology of Composting Symposium. Springer-Verlag, Heidelberg.

Kang, S ., Ayers, J. E., DeWolf, E. D., Geiser, D. M., Kuldau, G, Moorman, G. W., Mullins, E., Uddin, W., Correll, J. C., Deckert, G., Lee, Y. -H., Lee, Y. -W., Martin, F. N., and Subbarao, K. (2002) The Internet-based fungal pathogen database: A proposed model. Phytopathology 92: 232-236.

Kang, S . (2001) Organization and distribution pattern of MGLR-3, a novel retrotransposon in the rice blast fungus Magnaporthe grisea. Fungal Genet. Biol. 32: 11-19.

Mullins, E., Romaine, P., Chen, X., Geiser, D. M., Raina, R., and Kang, S. (2001) Agrobacterium tumefaciens -mediated transformation of Fusarium oxysporum: An efficient tool for insertional mutagenesis and gene transfer. Phytopathology 91: 173-180.

Kang, S ., Lebrun, M.-H., Farrall, L., and Valent, B. (2001) Gain of virulence caused by insertion of a Pot3 transposon in a Magnaporthe grisea avirulence gene. Mol. Plant-Microbe Interact. 14: 671-674.

Viji, G. A., Wu, B., Kang , S. , Uddin, W., and Huff, D. R. (2001) Pyricularia grisea causing gray leaf spot (blast) of perennial ryegrass turf: Population structure and host specificity. Plant Dis. 85: 817-826.

Rho , H., Kang , S ., and Y. Lee (2001) Agrobacterium tumefaciens -mediated transformation of the plant pathogenic fungus Magnaporthe grisea . Mol. Cells 12: 407-411.

Mullins, E. D., and Kang, S. (2001) Transformation: A tool for studying fungal pathogens of plants. Cell. Mol. Life Sci. 58: 2043-2052.

Ivors, K., Collopy, P., Beyer, D., and Kang, S. (2000) Identification of microorganisms in mushroom compost using ribosomal RNA sequence. Compost Sci. Utiliz. 8: 247-253.

Kang, S. and Y. Lee (2000) Population structure and race variation of the rice blast fungus. Plant Pathol. J. 16: 1-8.

Kang, S ., Mullins, E., DeZwaan, T. M., and Orbach, M. J. (2000) Molecular and cellular basis of pathogenesis in the rice blast fungus, Magnaporthe grisea , pp. 195-235. In: J. W. Kronstad (ed.) Fungal Pathology. Kluwer Academic Publishers, Dordrecht.

Ivors, K., Beyer, D., and Kang, S. (2000) Identification of microorganisms in mushroom compost using ribosomal RNA sequence, pp. 493-506. In: P. R. Warman and B. R. Taylor (eds) Proceedings of the 15th International Composting Symposium. CBA Press Inc., Truro, Nova Scotia.

Ivors, K., Beyer, D., Wuest, P. J., and S. Kang , S. (2000) Survey of microbial diversity within mushroom substrate using molecular techniques, pp. 401-407. In: L. J. L. D. Van Griensven (ed.) Science and Cultivation of Edible Fungi. Barkema Publisher, Rotterdam.

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