Host-induced gene silencing by RNAi in fungal and oomycete pathogens for healthier and safer food – DsRNAguard

Crop yield and the quality of plant products are affected by a plethora of plant diseases. The agronomically most important losses are caused by fungal and oomycete pathogens. These diseases are mostly controlled by the use of partially resistant cultivars and phytopharmaceutical compounds. However, these crop-protection strategies have important limitations such as breaking of dominant plant resistance genes by virulent pathogen races, or tolerance of fungi and oomycetes towards chemical control agents. Gene technology offers an important alternative for efficient and durable crop protection, as demonstrated by the success of insect-resistant maize and cotton cultivars carrying Bt toxin. Members of this consortium recently discovered that silencing of key fungal transcripts by plantexpressed RNAi constructs provides protection against important pathogens such as powdery mildew, rice blast or Fusarium sp. This discovery has an enormous application potential for the production of healthier and safer food without the need of chemical disease control, and has been protected by patent applications from Bayer Crop Science (BCS) and the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK). The aim of the RNAguard consortium is to study the mechanisms of host-induced gene silencing (HIGS) in major fungal and oomycete diseases of mono- and dicots, and to develop and optimize the technology for its future application in agricultural practice. The consortium will follow a broad approach to explore the agronomic potential of HIGS, including major crop plants such as wheat, maize, potato and tomato, and important fungal and oomycete pathogens such as Fusarium, Colletotrichum, and Phytophthora. In three overlapping phases of the project we propose to identify new HIGS targets in these pathogens by genome-wide transcript profiling during in planta growth, by Agrobacterium-mediated targeted as well as random mutagenesis, and by a hypothesis-driven approach. Potential targets will be initially validated in transient gene silencing assays. In the second phase of the project, transgenic events will be generated in all four crop plants, based on newly identified top target candidates plus first pre-existing (at partners), validated candidates. The transgenic lines will by challenged by different pathogens in the greenhouse and molecularly characterized. We also propose to test novel approaches to target multiple diseases by double or triple RNAi constructs, or to enhance the transgene effect by simultaneously targeting multiple genes in a single pathogen. During the third phase of the project, we will conduct field trials in wheat and maize with the four most promising events in Germany and/or Spain, and in the USA. The expected results of the project will be: - A better understanding of pathogenicity and virulence factors in major crop pathogens. - A better understanding of the mechanism(s) underlying the HIGS phenomenon. - A solid validation of the agronomic potential of HIGS as novel crop-protection strategy. - Transgenic lead events for the direct development of new cultivars by backcrossing into elite material. - Additional intellectual property (IP) for lead events.