Source: PENNSYLVANIA STATE UNIVERSITY submitted to
MOLECULAR BASIS OF FUSARIUM WILT
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0193358
Grant No.
2002-35319-12638
Project No.
PEN03913
Proposal No.
2002-02367
Multistate No.
(N/A)
Program Code
51.8
Project Start Date
Sep 1, 2002
Project End Date
Jun 30, 2006
Grant Year
2002
Project Director
Kang, S.
Recipient Organization
PENNSYLVANIA STATE UNIVERSITY
208 MUELLER LABORATORY
UNIVERSITY PARK,PA 16802
Performing Department
PLANT PATHOLOGY
Non Technical Summary
Although the persistence of soilborne fungi, compounded by the limited number of available control strategies, continuously threatens the sustainability of many crops, soilborne fungal pathogens have only received limited attention relative to those causing foliar diseases. We hope to enhance our understanding of the molecular and cellular basis of soilborne fungal diseases through the use of a new model system based around Arabidopsis thaliana, a model plant with rich resources, and Fusarium oxysporum, an important vascular wilt pathogen. This understanding will advance our efforts to control soilborne fungal diseases. The ability to manipulate both A. thaliana and F. oxysporum using tools of molecular genetics, molecular cytology and genomics will greatly facilitate the characterization of the mechanisms at play from both sides of the interaction and will permit us to study how changes in F. oxysporum influence responses by A. thaliana and vice versa. We will focus on determining whether proper regulation of phosphorus and nitrogen acquisition and metabolism is necessary for F. oxysporum to successfully infect and colonize A. thaliana. We will study how A. thaliana responds to F. oxysporum infection at the molecular and cellular levels by employing defense-related mutants of A. thaliana and a large-scale gene expression analysis. In addition to establishing a model for soilborne diseases, this work will contribute to our understanding of other fungal diseases by providing powerful research tools for characterizing the molecular and cellular basis of their interactions.
Animal Health Component
20%
Research Effort Categories
Basic
80%
Applied
20%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2122420103010%
2122420104030%
2122420116010%
2124020103010%
2124020104030%
2124020116010%
Goals / Objectives
The main objective of this collaborative project is to study the nature and mechanisms of interaction between Arabidopsis thaliana and Fusarium oxysporum using tools of molecular genetics, molecular cytology and genomics. Being able to manipulate genes in both A. thaliana and F. oxysporum will significantly facilitate the characterization of changes at play from both sides of the interaction. In addition, this system will permit us to study how changes in F. oxysporum influence defense responses by A. thaliana and vice versa. In contrast to A. thaliana, available knowledge and resources for F. oxysporum are rather limited. Consequently, as a preliminary step, we have focused our efforts on developing tools for efficient manipulation of F. oxysporum genes and characterizing the molecular and cellular basis of Fusarium wilt using these tools. This proposal is an extension of our on-going work and aims to identify genes and signaling pathways of F. oxysporum and A. thaliana that might play important roles in pathogenicity and defense, respectively. Specifically, we will test whether proper regulation of phosphorus and nitrogen acquisition and metabolism is necessary for F. oxysporum to successfully infect and colonize its hosts. We propose to mutagenize selected regulatory genes involved in phosphorus or nitrogen acquisition and metabolism. Pathogenicity of resulting mutants will be evaluated. If their virulence is significantly reduced from that of wild-type F. oxysporum strain, we will mutagenize the remaining regulatory genes. Further characterization of the defense signaling pathways in A. thaliana will also be conducted. The proposed experiments will include (i) molecular cytological analysis of the infection process by F. oxysporum and the temporal and spatial patterns of pathogenesis-related gene expression in A. thaliana, (ii) comparative infection assays with selected Arabidopsis mutants to identify genes important for defense against F. oxysporum (iii) identification of additional A. thaliana genes that are differentially expressed upon F. oxysporum infection using a microarray technique. In addition to enhancing our understanding of the molecular and cellular basis of Fusarium wilt, this project will facilitate the characterization of the molecular and cellular basis of other fungal diseases by providing various molecular and cytological tools.
Project Methods
As a first step to test the hypothesis that proper regulation of phosphorus and nitrogen acquisition and metabolism is important for F. oxysporum pathogenicity, we plan to isolate all the major regulatory genes controlling these activities from F. oxysporum by screening a F. oxysporum genomic DNA library with their homologues in F. verticillioides as probes. To mutagenize these genes, we will employ a highly efficient gene knockout system, which is based on the in vitro transposon-mediated mutagenesis of the target gene followed by gene replacement via Agrobacterium tumefaciens-mediated transformation (ATMT). Putative gene knockout mutants and some ectopic transformants generated using ATMT will be purified through monoconidiation and confirmed by Southern analysis. Two Arabidopsis ecotypes and a cabbage variety that are highly susceptible to F. oxysporum will be used for comparing the virulence of each mutant with wild-type controls. In addition to the visual evaluation of their virulence, since all these mutants express a fluorescence reporter gene (ECFP, DsREd, or EGFP), we will also compare the growth of these mutants with that of wild type controls in planta using a confocal/multiphoton microscope. To test the hypothesize that certain defects in pathogenicity might be complemented by defects in the host defense machinery, those mutants with reduced virulence will be used to infect those A. thaliana mutants that exhibited reduced resistance to F. oxysporum. To determine the significance of salicylic acid (SA) for defense against F. oxysporum, we will determine whether an application of BTH (SA analog) to leaves or roots of nahG and ndr1 restores their resistance to the level comparable to ecotype Col-0. We will also determine if the application of BTH or SA can increase the resistance of other highly susceptible hosts. The PR-1, GST1, Thi2.1 and PDF1.2 genes in A. thaliana are differentially regulated in certain ecotypes in response to F. oxysporum infection. We will use transgenic lines of A. thaliana, expressing green fluorescence protein (GFP) under the control of the PR-1, Thi2.1 and PDF1.2 promoters to monitor at the cellular level when and where each of these genes is expressed relative to fluorescent hyphae/spore of F. oxysporum (labeled with ECFP or DsRed fluorescence protein). Global gene expression changes in A. thaliana upon infection by F. oxysporum will be characterized using a microarray technique.

Progress 09/01/02 to 06/30/06

Outputs
To elucidate the molecular and cellular mechanisms underpinning Fusarium wilt, interactions between Arabidopsis thaliana and Fusarium oxysporum have been studied using various approaches. One approach is targeted mutagenesis of putative pathogenicity genes in F. oxysporum using a newly developed method, termed ATMT-DS (Agrobacterium tumefaciens-mediated transformation via double selection). This project demonstrated that ATMT-DS is an efficient functional genomic tool not only for F. oxysporum but also for other filamentous fungi. A large number of vectors have been constructed to facilitate fungal gene manipulation via ATMT-DS. Four F. oxysporum genes have been mutagenized via ATMT-DS, and their roles in pathogenicity have been studied. Disruption of the FoSNF1 gene, controlling carbon catabolite repression and the production of cell-wall degrading enzymes resulted in reduced expression of several genes encoding cell-wall degrading enzymes and poor growth on certain carbon sources. Progression of disease symptoms in A. thaliana and cabbage plants infected by fosnf1 mutants was considerably delayed compared to that in plants infected by a wild-type strain. Disruption of the gene encoding cAMP-dependent protein kinase caused loss of pathogenicity and also affected fungal growth and differentiation. Two genes involved in phosphorus and iron metabolisms, respectively were also disrupted, and resulting mutants are currently being characterized. With fungal strains expressing a fluorescent protein (green, cyan, and red), colonization sequences of A. thaliana roots by F. oxysporum were visualized through multi-photon/confocal imaging. Using two A. thaliana ecotypes, Cvi-0 (susceptible) and Gre-0 (resistant), that differentially interact with F. oxysporum, three-dimensional, time-resolved data from individual infection sites were obtained over a several day period without physical manipulation of infected plants. Initial penetration occurred primarily in the meristematic region of primary and lateral roots. It appeared that a mycelial mass on either the root tip or lateral root was required to initiate the penetration process. The technique allowed direct measurement of fungal growth rates within the vascular tissue and observation of changes in root cells in response to fungal growth. The fungus appears to produce a phytotoxin or other small molecule that could effectively move to nearby cells and affect vacuolar membrane integrity and potentially induce cell death. To further expand this molecular cytological approach, a number of in vivo sensors of key signaling molecules such as calicium and pH have been developed and tested in both A. thaliana and F. oxysporum. Spore germination rates in the rhizosphere of Cvi-0 and Gre-0 were compared using a hydroponic system. Spore germination in the rhizosphere of Gre-0 was significantly inhibited relative to that in the rhizosphere of Cvi-0, suggesting that Gre-0 roots secrete metabolites inhibitory to spore germination as part of its root exudate. Chromatographic separation and structural identification of metabolites is currently being conducted. Patent Application No. 10/777,405; February, 2004

Impacts
This research addressed both practical and scientific needs. Although the persistence of soilborne fungi, compounded by the limited number of effective control strategies, continuously threatens the sustainability of many crops, soilborne fungal diseases have only received limited scientific attention relative to those causing foliar diseases. Molecular genetics and cytological tools have significantly facilitated the characterization of the mechanisms at play from both sides of the interaction between A. thaliana and F. oxysporum. In addition to enhancing our understanding of the molecular and cellular basis of soilborne fungal diseases, research tools from this project also contribute to studying other diseases of economic significance. For example, this molecular cytological approach will allow the visualization of the dynamic interactions between plant and pathogen in four dimensions from both sides. The ATMT-DS significantly enhances our ability to manipulate genes in other fungi. Besides the value of Fusarium wilt as an experimental model system, this disease is a serious threat to over 100 cultivated plant species, including tomato, potato, sugarcane, conifers, cotton, bean, peas, date and oil palm, as well as cooking and dessert bananas. This disease nearly eliminated the banana export trade in Central America during a 1950s outbreak. A better understanding of fungal pathogenicity and the corresponding plant defense mechanisms underpinning this disease will contribute to our efforts of controlling Fusarium wilt, as well as other soilborne fungal diseases.

Publications

  • 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. In: K. Wang (ed.) Agrobacterium Protocols. Humana Press, Totowa. PP.403-420,


Progress 09/01/02 to 02/28/05

Outputs
A novel method was developed for in planta 3-D time-lapse documentation of root fungal pathogenesis in Arabidopsis thaliana using confocal and multi-photon microscopy. Arabidopsis plants were grown on either Murashige and Skoog agar or a soil mixture in commercially available coverslip-bottomed chambers. Documentation of fungal ingress, in vivo, was facilitated by transformation of F. oxysporum for constitutive cytoplasmic expression of the reef coral fluorescent protein ZsGreen. Data from individual encounter sites could be acquired repeatedly over a several-day period without physical manipulation and/or retrieval from the growth chamber. Ecotypes Cape Verde Islands (Cvi-0) and Greenville (Gre-0) recorded a differential response to F. oxysporum strain O-685, expressing susceptible and resistant phenotypes, respectively. Disease severity in ecotype Col-0 was between those of Cvi-0 and Gre-0. Irrespective of the growth media selected for experiments and the degree of resistance to F. oxysporum, many aspects of the early infection process were similar for the three ecotypes (Cvi-0, Col-0, and Gre-0) and transgenic Col-0 expressing HDEL-GFP used in this study. Initial penetration occurred primarily in the meristematic region of primary and lateral roots. It appeared that a mycelial mass on either the root tip or lateral root was required to initiate the penetration process. In A. thaliana, two distinct forms of autofluorescence were analyzed for changes in physical and temporal appearance. Blue autofluorescence (produced by UV excitation via multiphoton excitation) was always present in cortex cell vacuoles. Surprisingly, unpenetrated cortex cells lost their autofluorescent vacuolar contents as nearby vascular hyphae approached even though still physically separated by an uninfected endodermis, suggesting that F. oxysporum produced a phytotoxin or other small molecule that could effectively move to nearby cells and affect vacuolar membrane integrity and potentially induce cell death. The loss of vacuolar fluorescence was swift but not instantaneous (within 6 minutes). During early stages of infection red autofluorescence only appeared in specific infected areas and was possibly generated by the production of defense-related molecules associated with salicylic acid or phenolic compound production. Fortunately, the uninfected A. thaliana root tip was virtually non-autofluorescent at this portion of the visible spectrum, which made detection of the relatively weak cell wall signals possible. The technique also allowed us to make direct measurement of fungal growth rates within the vascular tissue, and to observe alteration of plant endoplasmic reticulum distribution and loss of vacuolar content in adjacent uninfected cells during vascular ramification. The data demonstrated that this novel approach was essential for visualizing the dynamic interactions between F. oxysporum and A. thaliana in four dimensions from the perspective of both the host and pathogen.

Impacts
Although the persistence of soilborne fungal pathogens, compounded by the limited number of effective control strategies, continuously threatens the sustainability of many crops, soilborne fungal diseases have only received limited attention relative to those causing foliar diseases. The main objective of this project is to enhance our understanding of the molecular and cellular basis of soilborne fungal diseases through the use of Arabidopsis thaliana, a model plant with rich genetic resources, and F. oxysporum, an important vascular wilt pathogen. Such an understanding will advance our efforts to control soilborne fungal diseases. The ability to manipulate both A. thaliana and F. oxysporum using tools of molecular genetics, molecular cytology and genomics will significantly facilitate the characterization of the mechanisms at play from both sides of the interaction and will permit us to study how changes in F. oxysporum influence responses by A. thaliana and vice versa. As summarized in the research progress, the molecular cytology technique we developed has tremendous potential to elucidate details of root development, bio-competition, symbiosis and pathogenesis between genetically-altered hosts and pathogens.

Publications

  • 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.


Progress 01/01/04 to 12/31/04

Outputs
During this period, we focused on charactering how Fusarium oxysporum colonizes Arabidopsis thaliana. The use of fluorescent proteins as vital markers has permitted the visualization of fungal colonization sequences through multi-photon/confocal imaging without the requirement for exogenous substrates. In addition, three-dimensional, time-resolved data from infection sites were obtained. We generated green fluorescent transformants of F. oxysporum strain O-685. One such transformant, labeled FO5, was used to monitor its root infection processes in multiple Arabidopsis ecotypes with an emphasis on the ecotypes CV (susceptible) and GRE (resistant). A number of patterns have emerged from the microscopic observations of infection processes: (i) in all ecotypes, the fungus preferentially colonizes emerging primodia of the lateral root and the elongation zone of the primary root, (ii) fungal colonization leads to the growth arrest and subsequent physical collapse of the primodia of the lateral root and the elongation zone of the primary root, probably caused by toxin(s) secreted by the fungus, (iii) the fungus enters to the vascular system through these collapsed tissues, (iv) in the vascular system, the fungus appears to colonizes all the vessels, not limited to xylem, and (v) the fungus also appears to secrete toxin(s) inside the vascular system. We also compared spore germination rates in the rhizosphere of CV and GRE using a hydroponic system. Spore germination in the rhizosphere of GRE was significantly inhibited (less than 2% germination in 24 hours), whereas in the rhizosphere of CV, 30% of the spores germinated in 24 hours. This result suggests that GRE secretes metabolites inhibitory to spore germination through its root exudates. Chromatographic separation and structural identification of such metabolites is currently being conducted. We developed an efficient targeted gene knock-out (TGK) method that can potentially be applied to a broad spectrum of fungi. This method, termed ATMT-PNS, is based on Agrobacterium tumefaciens-mediated transformation (ATMT) with a mutant allele of the target gene flanked by a conditional negative selection marker, the herpes simplex virus thymidine kinase gene. A dual (positive and negative) selection of transformants permitted the enrichment of target mutants. During this period, we evaluated factors affecting the efficiency of TGK via ATMT-PNS using Magnaporthe grisea and F. oxysporum. In addition, to facilitate TGK via ATMT-PNS, we constructed a series of new binary vectors that allow for convenient cloning of a mutant allele. Several putative pathogenicity genes in F. oxysporum are currently being mutagenized using ATMT-PNS to determine their role in pathogenicity.

Impacts
Although the persistence of soilborne fungi, compounded by the limited number of effective control strategies, continuously threatens the sustainability of many crops, soilborne fungal diseases have only received limited attention relative to those causing foliar diseases. The main objective of this project is to enhance our understanding of the molecular and cellular basis of soilborne fungal diseases through the use of Arabidopsis thaliana, a model plant with rich genetic resources, and F. oxysporum, an important vascular wilt pathogen. Such an understanding will advance our efforts to control soilborne fungal diseases. The ability to manipulate both A. thaliana and F. oxysporum using tools of molecular genetics, molecular cytology and genomics will significantly facilitate the characterization of the mechanisms at play from both sides of the interaction and will permit us to study how changes in F. oxysporum influence responses by A. thaliana and vice versa. In many fungi, a major barrier in studying fungal biology through targeted gene knock-out is the low efficiency of homologous recombination. The ATMT-PNS method developed here will significantly enhance our ability to manipulate fungal genes. A better understanding of fungal biology will facilitate judicious use of beneficial fungi and will also advance our efforts to control pathogenic fungi.

Publications

  • Kang, S., and Dobinson, K. 2004. Molecular and genetic basis of plant-fungal pathogen interactions. IN Fungal Genomics. D. K. Arora and G. G. Khachatourians, eds. Elsevier Science, Dordrecht pp. 59-97.
  • 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.
  • Khang, C., Park, S., Lee, Y., Kang, S. 2004. A dual selection based, targeted gene knock-out method for fungi. Phytopathology 4:S51 (Abstract).


Progress 01/01/03 to 12/31/03

Outputs
We have isolated a number of putative pathogenicity genes from Fusarium oxysporum. During this period, we focused on charactering one such gene in detail. Pathogenesis by F. oxysporum is believed to require the activity of cell-wall degrading enzymes. Production of this group of enzymes in fungi is subject to carbon catabolite repression, a process that in yeast is mostly controlled by the SNF1 (sucrose non-fermenting 1) gene. To elucidate the role of cell-wall degrading enzymes in F. oxysporum pathogenicity, we cloned and disrupted its SNF1 homolog (FoSNF1). The fosnf1 mutants had reduced expression of several genes encoding cell-wall degrading enzymes and grew poorly on certain carbon sources. Infection assays on Arabidopsis thaliana and Brassica oleracea revealed that progression of wilt symptoms in plants infected by fosnf1 mutants was considerably delayed compared to those infected by a wild-type strain. In conclusion, mutations in FoSNF1 prevent F. oxysporum from properly derepressing the production of cell-wall degrading enzymes, compromise the utilization of certain carbon sources, and reduce its virulence on A. thaliana and B. oleracea. In most filamentous fungi, transformation results from the integration of the transforming DNA into the fungal genome by either illegitimate or homologous recombination. Homologous integration permits targeted gene disruption. However, for fungi that exhibit low frequencies of homologous integration, identification of the desired gene disruptants may require that a large number of transformants be generated and screened. To circumvent this time-consuming process, we have developed and tested a new mutagenesis method (termed ATMT-PNS), which is based on Agrobacterium tumefaciens-mediated transformation (ATMT) and a subsequent positive-negative selection (PNS) to identify desired mutants. Employing Magnaporthe grisea and F. oxysporum, we evaluated the potential of this method as an efficient functional genomic tool for filamentous fungi. A number of vectors for have been constructed to facilitate fungal gene manipulation via ATMT-PNS. Several putative pathogenicity genes in F. oxysporum are currently being characterized for their role in pathogenicity using this technique.

Impacts
Although the persistence of soilborne fungi, compounded by the limited number of available control strategies, continuously threatens the sustainability of many crops, soilborne fungal pathogens have only received limited attention relative to those causing foliar diseases. The main objective of this project is to enhance our understanding of the molecular and cellular basis of soilborne fungal diseases through the use of a new pathosystem based on Arabidopsis thaliana, a model plant with rich resources, and F. oxysporum, an important vascular wilt pathogen. Such an understanding will advance our efforts to control soilborne fungal diseases. The importance of A. thaliana as a model plant for probing the molecular mechanisms underpinning plant-pathogen interactions continues to increase, yet only a limited number of pathogens have been employed to characterize its defense mechanisms. Fusarium oxysporum will allow us to study how A. thaliana responds to soilborne pathogens. The ability to manipulate both A. thaliana and F. oxysporum using tools of molecular genetics, molecular cytology and genomics will significantly facilitate the characterization of the mechanisms at play from both sides of the interaction and will permit us to study how changes in F. oxysporum influence responses by A. thaliana and vice versa. The highly efficient gene manipulation method developed here will contribute to studying other fungal pathogens by providing an efficient tool for studying gene function.

Publications

  • Kim, H.J., Khang, C.H., Moorman, G., Kang, S,, Lynch, J.P. and Brown, K.M. 2003. Disease development in ethylene insensitive etr1-1 petunia infected by Thielaviopsis basicola under low phosphorus stress. Phytopathology 93: S45.
  • 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.


Progress 01/01/02 to 12/31/02

Outputs
To test the hypothesis that proper regulation of phosphorus and nitrogen acquisition and metabolism is important for Fusarium oxysporum pathogenicity, we plan to isolate all the major regulatory genes controlling these activities from F. oxysporum by screening a F. oxysporum genomic DNA library with their homologues in F. verticillioides as probes. We obtained F. verticillioides genomic and cDNA clones corresponding to the target genes from DuPont/Pioneer and completely sequenced them. We are currently screening a F. oxysporum genomic DNA library with individual probes. To facilitate the mutagenesis of these F. oxysporum genes, we have developed a highly efficient gene knockout system, which is based on Agrobacterium tumefaciens-mediated transformation (ATMT). We are currently testing the system in a number of fungi. As part of our goal in understanding the molecular mechanisms of Fusarium wilt, molecular cytology approaches using fluorescent proteins as reporters have been applied to monitor the infection process of F. oxysporum and the host responses at both the cellular and molecular levels. Using a F. oxysporum strain labeled with EGFP, we have studied its infection process in multiples Arabidopsis ecotypes that exhibit differential disease resistance to F. oxysporum. On Blh-1, a resistant ecotype, very few fungal hyphae were growing parallel and associated with root in the elongation zone. It looked as if the fungus did not even seem to notice the presence of its roots. In contrast, root tips of CV, a highly susceptible ecotype, were heavily colonized and showed evidence of both intercellular and intracellular invasion. Col-0, an ecotype exhibiting an intermediate resistance, was also heavily colonized. Direct penetration of cells, but no obvious appresorial-like penetration structure, was observed. Fungal strains were also successfully transformed using EYFP, ECFP and ZsGreen as reporters. Transformants with ZsGreen were much brighter than those generated with EGFP, and future cytological experiments will be carried out using ZsGreen transformants. The expression patterns of PR-1, PDF1.2 and Thi2.1 in Arabidopsis infected by F. oxysporum raised many interesting questions about how the SA- and JA/ETH-dependent signaling pathways operate in response to the fungus. To further characterize when and where each of these genes become activated in response to F. oxysporum infection, we constructed a series of reporter systems by cloning the EGFP and EYFP genes under the control of the PR-1, PDF1.2 and Thi2.1 promoters and the nopaline synthase (nos) terminator in a binary vector for Arabidopsis transformation. Transgenic lines of Col-0 with individual reporter constructs have been generated. We are currently screening the second generation of transformants for those lines carrying a single copy of the reporter and properly expressing EGFP in response to SA, JA, and ETH.

Impacts
Although the persistence of soilborne fungi, compounded by the limited number of available control strategies, continuously threatens the sustainability of many crops, soilborne fungal pathogens have only received limited attention relative to those causing foliar diseases. The long-term objective of this project is to enhance our understanding of the molecular and cellular basis of soilborne fungal diseases through the use of a new pathosystem based on Arabidopsis thaliana, a model plant with rich resources, and F. oxysporum, an important vascular wilt pathogen. Such an understanding will advance our efforts to control soilborne fungal diseases. The importance of A. thaliana as a model plant for probing the molecular mechanisms underpinning plant-pathogen interactions continues to increase, yet only a limited number of pathogens have been employed to characterize its defense mechanisms. Fusarium oxysporum will allow us to study how A. thaliana responds to soilborne pathogens. The ability to manipulate both A. thaliana and F. oxysporum using tools of molecular genetics, molecular cytology and genomics will significantly facilitate the characterization of the mechanisms at play from both sides of the interaction and will permit us to study how changes in F. oxysporum influence responses by A. thaliana and vice versa. In addition to establishing a model for soilborne diseases, this work will contribute to our understanding of other fungal diseases by providing powerful research tools for characterizing the molecular and cellular basis of their interactions.

Publications

  • Mullins, E. M., Rauyaree, P., Ospina-Giraldo, M., Raina, R., Czymmek, K. Bhat, R., Subbarao, K., Dobinson, K. and Kang, S. 2002. Comparative analysis of fungal pathogenicity using Arabidopsis thaliana as a host. Phytopathology 92:S103 (Abstract).