PI: Dan Nettleton (Iowa State University)
Senior Personnel: Roger Wise (USDA-ARS), Adam Bogdanove (Cornell University), Roger Innes (Indiana University), Fredy Altpeter (University of Florida), Adah Leshem (Iowa State University) and Jaquelyn Jackson (Tuskegee University)
ERA-CAPS Collaborators: Patrick Schweizer [Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Germany] and Pietro Spanu (Imperial College, United Kingdom)
Crop loss caused by disease remains one of the greatest agricultural challenges in both developed and developing countries. Obligate fungal pathogens, i.e., pathogens that require their host to survive, are a major threat to crop production worldwide. Effector proteins secreted by these pathogens suppress host defenses to promote nutrient acquisition and colonization. However, the molecular mechanisms by which these effectors manipulate these processes are poorly understood. This project aims to fill this knowledge gap by identifying the networks of interacting host and pathogen proteins in the well-characterized barley-powdery mildew, host-microbe system. Previous joint NSF-BBSRC funded research identified a collection of novel effectors secreted by the powdery mildew fungus, Blumeria graminis f. sp. hordei, that contribute to pathogen virulence. This group of effectors will be used to identify host target proteins, using yeast two-hybrid screens, with the goal of identifying proteins that are targeted by multiple effectors. These host targets, as well as key effectors, will be evaluated for their roles in host immunity by silencing via RNA interference (RNAi) and by overexpression in a bacterial type III delivery system. Those that impact host immune regulation will be further characterized using TAL effector nuclease (TALEN) mutagenesis or RNAi-mediated gene silencing in stable barley transgenics. Among the fungal effectors identified and characterized thus far is a predicted metalloprotease (BEC1019) that is required for virulence, suppresses host defenses and is evolutionarily conserved among at least 96 other diverse fungi, including economically important plant pathogens, animal pathogens, and free-living non-pathogens. As a proof of concept, barley will be engineered with a newly discovered system that will activate defense responses upon detection of BEC1019 activity, which is predicted to confer resistance to a wide range of fungal pathogens.
Deciphering the molecular functions of evolutionarily conserved fungal effectors and understanding the host genes that respond will elucidate plant defense mechanisms and promote broadly applicable disease control strategies. All research objectives will be incorporated into training and mentoring opportunities for undergraduate and graduate students, postdocs, and K-12 teachers. International research exchanges with the European ERA-CAPS (www.eracaps.org/) companion project, "Functional characterization and validation of nonhost components in Triticeae species for durable resistance against fungal diseases (DURESTrit)", will enhance the training of students and postdocs. An inquiry-based Research Experience for Teachers on "Inheritance of Traits and Genes in Barley" (iTAG Barley) will be disseminated to serve underrepresented groups in secondary schools, community colleges, and 1890 land-grant institutions, providing hands-on training in genetics as it applies to agriculture and human health. Public access to project data will be fostered through a project website, the PLEXdb (www.plexdb.org) on-line database for gene expression for plants and plant pathogens, as well as NCBI-GEO (www.ncbi.nlm.nih.gov/geo/), Ensembl Genomes (http://ensemblgenomes.org/), and GrainGenes (wheat.pw.usda.gov). Thus, this project will promote research, education, and dissemination to a broad audience, while developing a new generation of agricultural and computational scientists.
