Photo by S. Moll.
Intercellular colonization of radish root hairs and epidermal cells with Streptomyces turgidiscabies expressing green fluorescent protein (GFP).
Plants interact with myriad microbes with outcomes ranging from enhanced plant nutrition to devastating plant diseases. These interactions are fundamentally molecular in nature and are being investigated at the intersection of several disciplines in biology. Plant-microbe interactions are highly dynamic, and as a result of long co-evolutionary parrying, substantial portions of the genomes of plants and their microbial partners and parasites have become involved in managing these interactions. Insights into plant-microbe interactions can have broad impact in the life sciences for several reasons. Plant and animal pathogens share many virulence mechanisms; plants and animals have evolved innate immune systems with similar defense strategies; and the molecules involved in the recognition, mimicking, and subversion of each partner provide a wealth of new tools and insights into fundamental cellular processes. The research areas described below highlight overlapping clusters of activity in the Plant-Microbe Biology Program. Most laboratories in the program are engaged in all three activities.
Functional Genomics and Proteomics
The explosion in genomic resources beginning around 2000 has transformed the study of plant-microbe interactions. For example, we now use pattern-based searches of pathogen genomes to reveal complete sets of genes encoding effector proteins, biosynthetic pathways for secondary metabolites, and many other candidate virulence factors; and pathogens and their plant hosts can now be studied as complete systems involving large suites of interacting genes. Our faculty are leading genome projects involving several important phytopathogenic bacteria, including Erwinia amylovora, Pseudomonas syringae, and Streptomyces scabies. (See the Fungal and Oomycete Biology research area for more genome projects.) We are using these sequenced genomes in a variety of functional genomics projects aimed at understanding the mechanisms and regulatory signaling underlying virulence and developing more effective plant resistance. Research in this area is highly collaborative and interdisciplinary. It features extensive mentoring of newcomers to functional genomics at all levels (from high school interns to faculty), and it has the overarching goal of unifying computational and laboratory approaches, thereby enabling scientists with diverse backgrounds to explore the complex interactions of plants and microbes in the context of systems biology. The Pseudomonas syringae-tomato functional genomics project is representative.
Molecular and Cell Biology of Interaction Molecules
Interactions between microbe and host molecules (and associated cell structures) ultimately determine whether an encounter between organisms results in disease, resistance, or symbiosis. Our investigations of these molecular events focus on key virulence molecules such as toxins, siderophores, hormones, quorum-sensing molecules, degradative enzymes, and effector proteins, as well as important plant molecules such as antimicrobial compounds, receptor proteins, and cell wall polymers. We are also exploring the respective secretion and vesicle trafficking pathways that deliver these microbe and plant molecules. Our molecular/cellular research utilizes state-of-the art approaches in structural biology, chemistry, and biological imaging; and it features collaborations with other researchers across campus, including those in: the Department of Chemistry and Chemical Biology; the Department of Biochemistry, Molecular and Cell Biology; the Department of Plant Biology; the Cornell Theory Center; the Cornell Developmental Resource for Biophysical Imaging Opto-Electronics; and the Cornell High Energy Synchrotron Source.
Plant Signaling in Response to Symbionts and Pathogens
An increasingly important focus of our research is the signaling underlying the responses of plants to symbiotic partners and pathogens. This research is potentiated by the use of model plant species – Medicago truncatula for the study of symbiotic interactions and Arabidopsis and tomato for the study of pathogenic interactions. Our current research addresses four areas: the plant role during symbiosis with mycorrhizal fungi, plant disease resistance signaling, plant disease susceptibility mechanisms, and molecular approaches to the development of crop varieties with increased disease resistance. Work on resistance signaling addresses systemic acquired resistance, basal innate immunity, and defenses mediated by resistance genes. Work on mechanisms of plant susceptibility emphasizes the characterization of plant factors targeted by pathogens. An overarching goal of our research on plant responses to pathogens is to unravel and understand the layered nature and variety of plant defenses and to convert that knowledge into improved disease resistance.
Plant-Microbe Biology faculty research programs
Steven Beer—Molecular genetics and mechanisms of pathogenicity of Erwinia amylovora; biological control of fire blight and other diseases by bacteria.
Gary Bergstrom—Biology, epidemiology, and integrated management of diseases of wheat, corn, soybean, forage legumes, and biofuel feedstock crops.
Samuel Cartinhour—Analysis of regulatory mechanisms and gene expression networks in Pseudomonas syringae.
Alan Collmer—Molecular phytobacteriology and microbial genomics.
Candace Collmer—Microbial genome annotation---specifically, the development and use of Gene Ontology (GO) terms describing microbe-host interactions. (Adjunct faculty, Wells College)
William Fry—Biology of oomycetes and management of disease they cause (with emphasis on Phytophthora infestans).
Stewart Gray—The biology of plant virus - insect vector interactions, virus diseases of potato and grain crops, virus disease management and epidemiology.
Maria Harrison—The arbuscular mycorrhizal symbiosis and phosphate acquisition in plants. (Adjunct faculty, BTI)
Dan Klessig—Plant immunity: molecular mechanisms of pathogen recognition and defense signal transduction. (Adjunct faculty,BTI)
Sondra Lazarowitz—Molecular mechanisms in virus-host interactions; molecular genetics of plant-virus movement and host resistance to virus infection; intra- and intercellular communications in plants.
Kwangwon Lee—Characterizing light and clock regulations in fungi and their roles in pathogenic plant-microbe interactions using genomics, quantitative genetics and molecular biology tools.
Rosemary Loria—Host-pathogen interactions; molecular genetic analysis of pathogenicity determinants.
Gregory Martin—Elucidation of the molecular basis of recognition specificity displayed by disease resistance gene products and bacterial avirulence proteins
Michael Milgroom—Population biology and evolution of plant pathogens; the integration of population biology and plant disease epidemiology.
Peter Moffett— Plant-virus interactions; molecular mechanisms of disease resistance. (Adjunct faculty, BTI)
Eric Nelson—Ecology and development of oomycetes in the spermosphere and rhizosphere with special emphasis on plant pathogenic Pythium species. Of special interest is understanding how microbial interactions and plant associations influence Pythium development and pathogenesis.
Rebecca Nelson—The genetics of quantitative disease resistance; international agriculture. We currently focus on two diseases of maize that are important both in the US and in Africa: northern corn leaf blight and gray leaf spot.
P.F. Palukaitis—Adjunct faculty
Teresa Pawlowska—Biology and evolution of arbuscular mycorrhizal (AM) fungi (phylum Glomeromycota)
Keith Perry—Cucumber mosaic virus and its vector transmission, pathogen diagnostics technologies, and potato viruses; Director of the NYS Foundation Potato Seed Program and the Uihlein Laboratory and Farm
David Schneider—Adjunct faculty, USDA-ARS
Gillian Turgeon—Genetics and molecular biology of fungal pathogens.
Xiaohong Wang—Molecular basis of plant-nematode interactions, host resistance to the potato cyst nematodes.