This project fuses genetic, evolutionary, and functional approaches to understand the co-evolution of plants and pathogens at the molecular level. Protein-protein interactions will be analyzed in yeast and in plants to build an interaction network of receptor (NBS-LRR) proteins, plant signaling components, and virulence effector proteins from bacterial and oomycete pathogens. The functional significance of these interactions to disease will be studied by a variety of cell biology and disease assays. The project will reveal whether targets of effectors represent a limited number of points of weakness in the plant that are exploited by multiple effectors and pathogens and whether protein complexes that determine the infection phenotype co-evolve. Libraries of genes encoding NBS-LRR proteins and their domains as well as signaling proteins that are candidate plant targets of effectors studied will be distributed through the Arabidopsis Biological Resource Center. The global approach will generate large amounts of data that will impact many labs focused on understanding the molecular basis of disease resistance in plants as well as contribute to the functional characterization of numerous genes in Arabidopsis. Data from the project will be broadly disseminated through the project web site (http://niblrrs.ucdavis.edu ) and through The Arabidopsis Information Resource. Deciphering the molecular determinants of resistance has practical importance as well as fundamental interest. A greater understanding of the mechanisms of perception and responses will provide new possibilities for developing disease resistant plants. Consequently, this project will expand the options available to plant breeders to achieve more durable resistance. Researchers involved in the project will benefit from inter-disciplinary training that includes the molecular genetics and cell biology of the defense response components and protein-protein interactions involved in pathogen-host interactions. Outreach efforts will include dissemination of genomics approaches to high schools through curriculum development, workshops and internships.
Our long term goal is to understand the mechanism(s) of plant resistance to pathogens. This project was aimed at understanding how plants recognize that they are being attacked by pathogens and how they respond to such attacks. To achieve this, we utilized the model plant Arabidopsis because it is easy to manipulate experimentally, is well characterized at the genetic and molecular level, and has many experimental tools available. Pathogens inject proteins into host plant cells in order to suppress plant defenses as well as alter the plant cell to the pathogen's advantage. However, plants have evolved counter measures to detect and repel pathogens that involve recognition of these pathogen-derived proteins and the elicitation of a defense response. We conducted a large-scale screen to detect physical interactions between proteins injected into plants by pathogens and two groups of plant proteins: proteins that are potentially targeted by pathogen-derived proteins and proteins that potentially recognize the pathogen proteins and initiate the resistance response. Genes encoding proteins were derived from several types of pathogens including bacteria and fungi. The initial large-scale screens were made in yeast so as to be able to test hundreds of thousands for pair-wise combinations. A subset of interactions identified in yeast were confirmed and studied in detail in whole plants. These studies identified many interactions between proteins. Some were expected; others were novel. This allowed us to generate a network of interacting proteins and confirmed that diverse pathogens manipulate similar proteins and target similar points of vulnerability in the plant. Analysis of the variation in these proteins provided insights as to how pathogens and their hosts co-evolve through antagonistic cycles of selection for increased virulence in the pathogen and increased resistance in the host plant. The ability of Arabidopsis to recognize proteins from non-pathogens also helped explain why diseases of plants are the exception rather than being more common. Our large-scale approach generated large amounts of data that will be useful to numerous labs who are studying disease resistance in plants as well as contribute to the further development of Arabidopsis as an experimental model plant. Deciphering the molecular determinants of disease resistance has practical importance as well as scientific interest. A greater understanding of the mechanisms of pathogen perception by plants and resistance responses provides new possibilities for developing disease resistance plants. Consequently, these results will expand the options available to plant breeders to achieve more durable disease resistance. Researchers involved in the project benefited from inter-disciplinary training that included the molecular genetics and cell biology of the defense response. Outreach activities included dissemination of genomics approaches to high schools through curriculum development, workshops, and internships. The internships provided hands-on experience in research labs and helped inspire high school and undergraduate students to embark on a scientific career.
